Add UnsetAttr

Fully address #20

.editorconfig

@@ -0,0 +1,12 @@
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+indent_style = tab
+indent_size = 8
+charset = utf-8
+
+[*.md]
+indent_style = space
+indent_size = 2

README.md

@@ -1,6 +1,8 @@
 # tomo
 
-WIP rewrite of tomo.
+[![Go Reference](https://pkg.go.dev/badge/git.tebibyte.media/tomo/tomo.svg)](https://pkg.go.dev/git.tebibyte.media/tomo/tomo)
 
-This module will serve as a wafer-thin collection of interfaces and glue code so
-that plugins will be an actual viable concept.
+Tomo is a lightweight GUI toolkit written in pure Go. This repository defines
+the API that other components of the toolkit agree upon. In order to use Tomo in
+an application, use [Nasin](https://git.tebibyte.media/tomo/nasin), which builds
+an application framework on top of Tomo.

attribute.go

@@ -0,0 +1,306 @@
+package tomo
+
+import "image"
+import "image/color"
+import "golang.org/x/image/font"
+import "git.tebibyte.media/tomo/tomo/canvas"
+
+// AttrSet is a set of attributes wherein only one/zero of each attribute type
+// can exist. It is keyed by the AttrKind of each attribute and must not be
+// modified directly.
+type AttrSet map[AttrKind] Attr
+
+// AS builds an AttrSet out of a vararg list of Attr values. If multiple Attrs
+// of the same kind are specified, the last one will override the others.
+func AS (attrs ...Attr) AttrSet {
+	set := AttrSet { }
+	set.Add(attrs...)
+	return set
+}
+
+// Add adds attributes to the set.
+func (this AttrSet) Add (attrs ...Attr) {
+	for _, attr := range attrs {
+		this[attr.Kind()] = attr
+	}
+}
+
+// MergeUnder takes attributes from another set and adds them if they don't
+// already exist in this one.
+func (this AttrSet) MergeUnder (other AttrSet) {
+	if other == nil { return }
+	for _, attr := range other {
+		if _, exists := this[attr.Kind()]; !exists {
+			this.Add(attr)
+		}
+	}
+}
+
+// MergeOver takes attributes from another set and adds them, overriding this
+// one.
+func (this AttrSet) MergeOver (other AttrSet) {
+	if other == nil { return }
+	for _, attr := range other {
+		this.Add(attr)
+	}
+}
+
+// Attr modifies one thing about a box's style.
+type Attr interface {
+	// Equals returns true if both attributes can reasonably be declared
+	// equal.
+	Equals (Attr) bool
+	Kind   () AttrKind
+	attr   ()
+}
+
+type AttrKind int; const (
+	AttrKindColor AttrKind = iota
+	AttrKindTexture
+	AttrKindTextureMode
+	AttrKindBorder
+	AttrKindMinimumSize
+	AttrKindPadding
+	AttrKindGap
+	AttrKindTextColor
+	AttrKindDotColor
+	AttrKindFace
+	AttrKindWrap
+	AttrKindAlign
+	AttrKindOverflow
+	AttrKindLayout
+)
+
+// AttrColor sets the background color of a box.
+type AttrColor struct { color.Color }
+// AttrTexture sets the texture of a box to a named texture.
+type AttrTexture struct { canvas.Texture }
+// AttrTextureMode sets the rendering mode of a box's texture.
+type AttrTextureMode TextureMode
+// AttrBorder sets the border of a box.
+type AttrBorder []Border
+// AttrMinimumSize sets the minimum size of a box.
+type AttrMinimumSize image.Point
+// AttrPadding sets the inner padding of a box.
+type AttrPadding Inset
+// AttrGap sets the gap between child boxes, if the box is a ContainerBox.
+type AttrGap image.Point
+// AttrTextColor sets the text color, if the box is a TextBox.
+type AttrTextColor struct { color.Color }
+// AttrDotColor sets the text selection color, if the box is a TextBox.
+type AttrDotColor struct { color.Color }
+// AttrFace sets the font face, if the box is a TextBox.
+type AttrFace struct { font.Face }
+// AttrWrap sets if the text wraps, if the box is a TextBox.
+type AttrWrap bool
+// AttrAlign sets the alignment, if the box is a ContentBox.
+type AttrAlign struct { X, Y Align }
+// AttrOverflow sets the overflow, if the box is a ContentBox.
+type AttrOverflow struct { X, Y bool }
+// AttrLayout sets the layout, if the box is a ContentBox.
+type AttrLayout struct { Layout }
+
+// AColor is a convenience constructor for the color attribute.
+func AColor (col color.Color) AttrColor {
+	return AttrColor { Color: col }
+}
+// ATexture is a convenience constructor for the texture attribute.
+func ATexture (texture canvas.Texture) AttrTexture {
+	return AttrTexture { Texture: texture }
+}
+// ATextureMode is a convenience constructor for the texture mode attribute.
+func ATextureMode (mode TextureMode) AttrTextureMode {
+	return AttrTextureMode(mode)
+}
+// ABorder is a convenience constructor for the border attribute.
+func ABorder (borders ...Border) AttrBorder {
+	return AttrBorder(borders)
+}
+// AMinimumSize is a convenience constructor for the minimum size attribute.
+func AMinimumSize (x, y int) AttrMinimumSize {
+	return AttrMinimumSize(image.Pt(x, y))
+}
+// APadding is a convenience constructor for the padding attribute.
+func APadding (sides ...int) AttrPadding {
+	return AttrPadding(I(sides...))
+}
+// AGap is a convenience constructor for the gap attribute.
+func AGap (x, y int) AttrGap {
+	return AttrGap(image.Pt(x, y))
+}
+// ATextColor is a convenience constructor for the text color attribute.
+func ATextColor (col color.Color) AttrTextColor {
+	return AttrTextColor { Color: col }
+}
+// ADotColor is a convenience constructor for the dot color attribute.
+func ADotColor (col color.Color) AttrDotColor {
+	return AttrDotColor { Color: col }
+}
+// AFace is a convenience constructor for the face attribute.
+func AFace (face font.Face) AttrFace {
+	return AttrFace { Face: face }
+}
+// AWrap is a convenience constructor for the wrap attribute.
+func AWrap (wrap bool) AttrWrap {
+	return AttrWrap(wrap)
+}
+// AAlign is a convenience constructor for the align attribute.
+func AAlign (x, y Align) AttrAlign {
+	return AttrAlign { X: x, Y: y }
+}
+// AOverflow is a convenience constructor for the overflow attribute.
+func AOverflow (x, y bool) AttrOverflow {
+	return AttrOverflow { X: x, Y: y }
+}
+// ALayout is a convenience constructor for the overflow attribute.
+func ALayout (layout Layout) AttrLayout {
+	return AttrLayout { Layout: layout }
+}
+
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrColor) Equals (other Attr) bool {
+	if other, ok := other.(AttrColor); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrTexture) Equals (other Attr) bool {
+	if other, ok := other.(AttrTexture); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrTextureMode) Equals (other Attr) bool {
+	if other, ok := other.(AttrTextureMode); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrBorder) Equals (other Attr) bool {
+	if other, ok := other.(AttrBorder); ok {
+		if len(this) != len(other) { return false }
+		for index := range this {
+			thisBorder  := this[index]
+			otherBorder := other[index]
+			if thisBorder != otherBorder { return false }
+		}
+		return true
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrMinimumSize) Equals (other Attr) bool {
+	if other, ok := other.(AttrMinimumSize); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrPadding) Equals (other Attr) bool {
+	if other, ok := other.(AttrPadding); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrGap) Equals (other Attr) bool {
+	if other, ok := other.(AttrGap); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrTextColor) Equals (other Attr) bool {
+	if other, ok := other.(AttrTextColor); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrDotColor) Equals (other Attr) bool {
+	if other, ok := other.(AttrDotColor); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrFace) Equals (other Attr) bool {
+	if other, ok := other.(AttrFace); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrWrap) Equals (other Attr) bool {
+	if other, ok := other.(AttrWrap); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrAlign) Equals (other Attr) bool {
+	if other, ok := other.(AttrAlign); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrOverflow) Equals (other Attr) bool {
+	if other, ok := other.(AttrOverflow); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrLayout) Equals (other Attr) bool {
+	// for some goofy reason if we try to compare two AttrLayouts we get a
+	// fucking runtime error????? its probably for the best anyways because
+	// two layouts cannot "reasonably" be declared equal
+	return false
+}
+
+func (AttrColor)       Kind () AttrKind { return AttrKindColor }
+func (AttrTexture)     Kind () AttrKind { return AttrKindTexture }
+func (AttrTextureMode) Kind () AttrKind { return AttrKindTextureMode }
+func (AttrBorder)      Kind () AttrKind { return AttrKindBorder }
+func (AttrMinimumSize) Kind () AttrKind { return AttrKindMinimumSize }
+func (AttrPadding)     Kind () AttrKind { return AttrKindPadding }
+func (AttrGap)         Kind () AttrKind { return AttrKindGap }
+func (AttrTextColor)   Kind () AttrKind { return AttrKindTextColor }
+func (AttrDotColor)    Kind () AttrKind { return AttrKindDotColor }
+func (AttrFace)        Kind () AttrKind { return AttrKindFace }
+func (AttrWrap)        Kind () AttrKind { return AttrKindWrap }
+func (AttrAlign)       Kind () AttrKind { return AttrKindAlign }
+func (AttrOverflow)    Kind () AttrKind { return AttrKindOverflow }
+func (AttrLayout)      Kind () AttrKind { return AttrKindLayout }
+
+func (AttrColor)       attr () { }
+func (AttrTexture)     attr () { }
+func (AttrTextureMode) attr () { }
+func (AttrBorder)      attr () { }
+func (AttrMinimumSize) attr () { }
+func (AttrPadding)     attr () { }
+func (AttrGap)         attr () { }
+func (AttrTextColor)   attr () { }
+func (AttrDotColor)    attr () { }
+func (AttrFace)        attr () { }
+func (AttrWrap)        attr () { }
+func (AttrAlign)       attr () { }
+func (AttrOverflow)    attr () { }
+func (AttrLayout)      attr () { }

backend.go

@@ -11,15 +11,38 @@ import "git.tebibyte.media/tomo/tomo/canvas"
 type Backend interface {
 	// These methods create new objects. The backend must reject any object
 	// that was not made by it.
-	NewWindow       (image.Rectangle) (MainWindow, error)
 	NewBox          () Box
 	NewTextBox      () TextBox
 	NewCanvasBox    () CanvasBox
+	NewSurfaceBox   () (SurfaceBox, error)
 	NewContainerBox () ContainerBox
 
+	// NewWindow creates a normal Window and returns it.
+	NewWindow (image.Rectangle) (Window, error)
+
+	// NewPlainWindow creates an undecorated window that does not appear in
+	// window lists and returns it. This is intended for making things like
+	// panels, docks, etc.
+	NewPlainWindow (image.Rectangle) (Window, error)
+
 	// NewTexture creates a new texture from an image. The backend must
 	// reject any texture that was not made by it.
-	NewTexture (image.Image) canvas.Texture
+	NewTexture (image.Image) canvas.TextureCloser
+
+	// NewCanvas creates a new canvas with the specified bounds. The backend
+	// must reject any canvas that was not made by it.
+	NewCanvas (image.Rectangle) canvas.CanvasCloser
+
+	// SetStyle sets the style that will be used on objects. The backend is
+	// in charge of applying the style to objects. When this method is
+	// called, it must propagate a StyleChange event to all boxes it is
+	// keeping track of.
+	SetStyle (*Style)
+
+	// SetIconSet sets the icon set that icons will be pulled from. When
+	// this method is called, it must propagate an IconChange event to all
+	// boxes it is keeping track of.
+	SetIconSet (IconSet)
 
 	// Run runs the event loop until Stop() is called, or the backend
 	// experiences a fatal error.
@@ -52,11 +75,11 @@ func Register (priority int, factory Factory) {
 	})
 }
 
-// Initialize instantiates a backend. The first backend (sorted by priority)
+// initialize instantiates a backend. The first backend (sorted by priority)
 // that does not throw an error when initialized is used. If no backend could be
 // instantiated, this function returns an error. This function should be called
 // only once.
-func Initialize () (Backend, error) {
+func initialize () (Backend, error) {
 	backend, err := instantiate()
 	if err != nil { return nil, err }
 	return backend, err

canvas/canvas.go

@@ -2,15 +2,16 @@
 // primitives.
 package canvas
 
+import "io"
 import "image"
 import "image/draw"
 import "image/color"
 
 // Cap represents a stroke cap type.
 type Cap int; const (
-	CapButt Cap = iota // Square cap that ends at the point
-	CapRound           // Round cap that surrounds the point
-	CapSquare          // square cap that surrounds the point
+	CapRound Cap = iota // Round cap that surrounds the point
+	CapSquare           // Square cap that surrounds the point
+	CapButt             // Square cap that ends at the point
 )
 
 // Joint represents a stroke joint type.
@@ -30,23 +31,38 @@ type StrokeAlign int; const (
 
 // Pen represents a drawing context that is linked to a canvas. Each canvas can
 // have multiple pens associated with it, each maintaining their own drawing
-// context.
+// state.
 type Pen interface {
-	// Rectangle draws a rectangle
+	// Rectangle draws a rectangle.
 	Rectangle (image.Rectangle)
 
-	// Path draws a path
+	// Path draws a path, which is a series of connected points.
 	Path (points ...image.Point)
 
-	Closed       (bool)        // if the path is closed
-	Cap          (Cap)         // line cap stype
-	Joint        (Joint)       // line joint style
-	StrokeWeight (int)         // how thick the stroke is
-	StrokeAlign  (StrokeAlign) // where the stroke is drawn
+	// StrokeWeight sets how thick the stroke is. The default value is zero.
+	StrokeWeight (int)
+	// SetClosed sets whether the path is a closed shape, or has an open
+	// side. This only applies if the stroke weight is greater than zero.
+	Closed (bool)
+	// Cap sets how the ends of the stroke look. This only applies if the
+	// stroke weight is greater than zero, and if the path is not closed.
+	// The default value is CapRound.
+	Cap (Cap)
+	// Joint sets how bend points in the stroke look. This only applies if
+	// the stroke weight is greater than zero. The default value is
+	// JointRound.
+	Joint (Joint)
+	// StrokeAlign sets where the stroke is drawn in relation to the path.
+	// This only applies if the stroke weight is greater than zero. The
+	// default value is StrokeAlignCenter.
+	StrokeAlign (StrokeAlign)
 
-	Stroke  (color.Color) // Sets the stroke to a solid color
-	Fill    (color.Color) // Sets the fill to a solid color
-	Texture (Texture)     // Overlaps a texture onto the fill color
+	// Stroke sets the stroke to a solid color.
+	Stroke (color.Color)
+	// Fill sets the fill to a solid color.
+	Fill (color.Color)
+	// Texture overlaps a texture onto the fill color.
+	Texture (Texture)
 }
 
 // Canvas is an image that supports drawing paths.
@@ -56,11 +72,20 @@ type Canvas interface {
 	// Pen returns a new pen for this canvas.
 	Pen () Pen
 
-	// Clip returns a new canvas that points to a specific area of this one.
-	Clip (image.Rectangle) Canvas
+	// SubCanvas returns a returns a Canvas representing the portion of this
+	// Canvas visible and drawable through a rectangle. The returned value
+	// shares pixels with the original Canvas.
+	SubCanvas (image.Rectangle) Canvas
 }
 
-// Drawer is an object that can draw to a canvas.
+// CanvasCloser is a canvas that can be closed. Anything that receives a
+// CanvasCloser must close it after use.
+type CanvasCloser interface {
+	Canvas
+	io.Closer
+}
+
+// Drawer can draw to a canvas.
 type Drawer interface {
 	// Draw draws to the given canvas.
 	Draw (Canvas)

canvas/texture.go

@@ -5,25 +5,17 @@ import "image"
 
 // Texture is a handle that points to a 2D raster image managed by the backend.
 type Texture interface {
-	io.Closer
+	image.Image
 
-	// Clip returns a smaller section of this texture, pointing to the same
-	// internal data. Becaue of this, closing a clipped section will close
-	// the original texture as well.
-	Clip (image.Rectangle) Texture
+	// SubTexture returns a returns a Texture representing the portion of
+	// this Texture visible through a rectangle. The returned value shares
+	// pixels with the original Texture.
+	SubTexture (image.Rectangle) Texture
 }
 
-type protectedTexture struct {
+// TextureCloser is a texture that can be closed. Anything that receives a
+// TextureCloser must close it after use.
+type TextureCloser interface {
 	Texture
-}
-
-func (protectedTexture) Close () error {
-	return nil
-}
-
-// Protect makes the Close() method of a texture do nothing. This is useful if
-// several of the same texture are given out to different objects, but only one
-// has the responsibility of closing it.
-func Protect (texture Texture) Texture {
-	return protectedTexture { Texture: texture }
+	io.Closer
 }

data/data.go

@@ -3,57 +3,127 @@ package data
 
 import "io"
 import "bytes"
+import "strings"
 
 // Data represents arbitrary polymorphic data that can be used for data transfer
 // between applications.
-type Data map[Mime] io.ReadSeekCloser
+type Data interface {
+	// Convert converts the data to the specified MIME type and returns it.
+	// If the type is not supported, this behavior will return nil, and
+	// false for ok. Note that Convert may be called multiple times for the
+	// same MIME type, so it must not return the same reader.
+	Convert (Mime) (reader io.ReadSeekCloser, ok bool)
+
+	// Supported returns a slice of MIME types that Convert can accept.
+	Supported () []Mime
+}
 
 // Mime represents a MIME type.
 type Mime struct {
 	// Type is the first half of the MIME type, and Subtype is the second
 	// half. The separating slash is not included in either. For example,
 	// text/html becomes:
-	// Mime { Type: "text", Subtype: "html" }
+	//   Mime { Type: "text", Subtype: "html" }
+	// The subtype is stored here including the tree and the suffix.
 	Type, Subtype string
+
+	// Charset is an optional field applicable to text types that specifies
+	// the character encoding of the data. If empty, UTF-8 is conventionally
+	// assumed because it's the only text encoding worth using.
+	Charset string
 }
 
 // M is shorthand for creating a MIME type.
 func M (ty, subtype string) Mime {
-	return Mime { ty, subtype }
+	return Mime {
+		Type: strings.ToLower(ty),
+		Subtype: strings.ToLower(subtype),
+	}
 }
 
-// String returns the string representation of the MIME type.
-func (mime Mime) String () string {
-	return mime.Type + "/" + mime.Subtype
+// ParseMime parses a MIME type from text.
+func ParseMime (text string) Mime {
+	ty, subty, _ := strings.Cut(text, "/")
+	subty, parameters, _ := strings.Cut(subty, ";")
+	mime := M(ty, subty)
+	for _, parameter := range strings.Split(parameters, " ") {
+		if parameter == "" { continue }
+		key, val, _ := strings.Cut(parameter, "=")
+		// TODO handle things like quoted values
+		val = strings.TrimSpace(val)
+		switch strings.TrimSpace(strings.ToLower(key)) {
+		case "charset":
+			mime.Charset = val
+		}
+	}
+	return mime
 }
 
 // MimePlain returns the MIME type of plain text.
-func MimePlain () Mime { return Mime { "text", "plain"    } }
+func MimePlain () Mime { return Mime { Type: "text", Subtype: "plain"    } }
 
 // MimeFile returns the MIME type of a file path/URI.
-func MimeFile  () Mime { return Mime { "text", "uri-list" } }
+func MimeFile  () Mime { return Mime { Type: "text", Subtype: "uri-list" } }
+
+// String returns the string representation of the MIME type.
+func (mime Mime) String () string {
+	out := mime.Type + "/" + mime.Subtype
+	if mime.Charset != "" {
+		out += "; charset=" + mime.Charset
+	}
+	return out
+}
+
+// FromText returns plain text Data given a string.
+func FromText (text string) Data {
+	return FromBytes(MimePlain(), []byte(text))
+}
 
 type byteReadCloser struct { *bytes.Reader }
 func (byteReadCloser) Close () error { return nil }
 
-// Text returns plain text Data given a string.
-func Text (text string) Data {
-	return Bytes(MimePlain(), []byte(text))
+type bytesData struct {
+	mime   Mime
+	buffer []byte
 }
 
-// Bytes constructs a Data given a buffer and a mime type.
-func Bytes (mime Mime, buffer []byte) Data {
-	return Data {
-		mime: byteReadCloser { bytes.NewReader(buffer) },
+// FromBytes constructs a Data given a buffer and a mime type.
+func FromBytes (mime Mime, buffer []byte) Data {
+	return bytesData {
+		mime:   mime,
+		buffer: buffer,
 	}
 }
 
-// Merge combines several Datas together. If multiple Datas provide a reader for
-// the same mime type, the ones further on in the list will take precedence.
-func Merge (individual ...Data) (combined Data) {
-	for _, data := range individual {
-	for mime, reader := range data {
-		combined[mime] = reader
-	}}
-	return
+func (bytesDat bytesData) Convert (mime Mime) (io.ReadSeekCloser, bool) {
+	if mime != bytesDat.mime { return nil, false }
+	return byteReadCloser { bytes.NewReader(bytesDat.buffer) }, true
+}
+
+func (bytesDat bytesData) Supported () []Mime {
+	return []Mime { bytesDat.mime }
+}
+
+type mergedData []Data
+
+func (merged mergedData) Convert (mime Mime) (io.ReadSeekCloser, bool) {
+	for _, individual := range merged {
+		if reader, ok := individual.Convert(mime); ok {
+			return reader, ok
+		}
+	}
+	return nil, false
+}
+
+func (merged mergedData) Supported () (supported []Mime) {
+	for _, individual := range merged {
+		supported = append(individual.Supported(), supported...)
+	}
+	return supported
+}
+
+// Merge combines several Datas together. If multiple Datas provide a reader for
+// the same mime type, the ones first in the list will take precedence.
+func Merge (individual ...Data) (combined Data) {
+	return mergedData(individual)
 }

go.sum

@@ -1,8 +1,6 @@
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
-golang.org/x/image v0.8.0 h1:agUcRXV/+w6L9ryntYYsF2x9fQTMd4T8fiiYXAVW6Jg=
-golang.org/x/image v0.8.0/go.mod h1:PwLxp3opCYg4WR2WO9P0L6ESnsD6bLTWcw8zanLMVFM=
 golang.org/x/image v0.11.0 h1:ds2RoQvBvYTiJkwpSFDwCcDFNX7DqjL2WsUgTNk0Ooo=
 golang.org/x/image v0.11.0/go.mod h1:bglhjqbqVuEb9e9+eNR45Jfu7D+T4Qan+NhQk8Ck2P8=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
@@ -27,7 +25,6 @@ golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
 golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
-golang.org/x/text v0.10.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
 golang.org/x/text v0.12.0/go.mod h1:TvPlkZtksWOMsz7fbANvkp4WM8x/WCo/om8BMLbz+aE=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=

icon.go

@@ -0,0 +1,415 @@
+package tomo
+
+import "git.tebibyte.media/tomo/tomo/data"
+import "git.tebibyte.media/tomo/tomo/canvas"
+
+// IconSize represents the size of an icon.
+type IconSize int; const (
+	IconSizeSmall IconSize = iota;
+	IconSizeMedium
+	IconSizeLarge
+)
+
+// Icon represents an icon ID.
+type Icon string
+
+// A list of standard icon IDs. This is roughly based off of the XDG Icon Naming
+// Specification (https://specifications.freedesktop.org/icon-naming-spec/icon-naming-spec-latest.html).
+const (
+	IconUnknown                      Icon = ""
+
+	// actions
+	IconAddressBookNew               Icon = "AddressBookNew"
+	IconApplicationExit              Icon = "ApplicationExit"
+	IconAppointmentNew               Icon = "AppointmentNew"
+	IconCallStart                    Icon = "CallStart"
+	IconCallStop                     Icon = "CallStop"
+	IconContactNew                   Icon = "ContactNew"
+	// actions: dialog
+	IconDialogOkay                   Icon = "DialogOkay"
+	IconDialogCancel                 Icon = "DialogCancel"
+	// actions: edit
+	IconEditClear                    Icon = "EditClear"
+	IconEditCopy                     Icon = "EditCopy"
+	IconEditCut                      Icon = "EditCut"
+	IconEditDelete                   Icon = "EditDelete"
+	IconEditFind                     Icon = "EditFind"
+	IconEditFindReplace              Icon = "EditFindReplace"
+	IconEditPaste                    Icon = "EditPaste"
+	IconEditRedo                     Icon = "EditRedo"
+	IconEditSelectAll                Icon = "EditSelectAll"
+	IconEditUndo                     Icon = "EditUndo"
+	// actions: file
+	IconFileNew                      Icon = "FileNew"
+	IconDirectoryNew                 Icon = "DirectoryNew"
+	IconFileOpen                     Icon = "FileOpen"
+	IconFileOpenRecent               Icon = "FileOpenRecent"
+	IconFilePageSetup                Icon = "FilePageSetup"
+	IconFilePrint                    Icon = "FilePrint"
+	IconFilePrintPreview             Icon = "FilePrintPreview"
+	IconFilePermissions              Icon = "FilePermissions"
+	IconFileProperties               Icon = "FileProperties"
+	IconFileRename                   Icon = "FileRename"
+	IconFileRevert                   Icon = "FileRevert"
+	IconFileSave                     Icon = "FileSave"
+	IconFileSaveAs                   Icon = "FileSaveAs"
+	IconFileSend                     Icon = "FileSend"
+	// actions: format
+	IconFormatIndentLess             Icon = "FormatIndentLess"
+	IconFormatIndentMore             Icon = "FormatIndentMore"
+	IconFormatAlignCenter            Icon = "FormatAlignCenter"
+	IconFormatAlignEven              Icon = "FormatAlignEven"
+	IconFormatAlignLeft              Icon = "FormatAlignLeft"
+	IconFormatAlignRight             Icon = "FormatAlignRight"
+	IconFormatTextDirectionLtr       Icon = "FormatTextDirectionLtr"
+	IconFormatTextDirectionRtl       Icon = "FormatTextDirectionRtl"
+	IconFormatTextBold               Icon = "FormatTextBold"
+	IconFormatTextItalic             Icon = "FormatTextItalic"
+	IconFormatTextUnderline          Icon = "FormatTextUnderline"
+	IconFormatTextStrikethrough      Icon = "FormatTextStrikethrough"
+	// actions: go
+	IconGoBottom                     Icon = "GoBottom"
+	IconGoDown                       Icon = "GoDown"
+	IconGoFirst                      Icon = "GoFirst"
+	IconGoHome                       Icon = "GoHome"
+	IconGoJump                       Icon = "GoJump"
+	IconGoLast                       Icon = "GoLast"
+	IconGoNext                       Icon = "GoNext"
+	IconGoPrevious                   Icon = "GoPrevious"
+	IconGoTop                        Icon = "GoTop"
+	IconGoUp                         Icon = "GoUp"
+	// actions: help
+	IconHelpAbout                    Icon = "HelpAbout"
+	IconHelpContents                 Icon = "HelpContents"
+	IconHelpFaq                      Icon = "HelpFaq"
+	// actions: insert
+	IconInsertImage                  Icon = "InsertImage"
+	IconInsertLink                   Icon = "InsertLink"
+	IconInsertObject                 Icon = "InsertObject"
+	IconInsertText                   Icon = "InsertText"
+	// actions: list
+	IconListAdd                      Icon = "ListAdd"
+	IconListRemove                   Icon = "ListRemove"
+	// actions: mail
+	IconMailForward                  Icon = "MailForward"
+	IconMailMarkImportant            Icon = "MailMarkImportant"
+	IconMailMarkJunk                 Icon = "MailMarkJunk"
+	IconMailMarkNotJunk              Icon = "MailMarkNotJunk"
+	IconMailMarkRead                 Icon = "MailMarkRead"
+	IconMailMarkUnread               Icon = "MailMarkUnread"
+	IconMailMessageNew               Icon = "MailMessageNew"
+	IconMailReplyAll                 Icon = "MailReplyAll"
+	IconMailReplySender              Icon = "MailReplySender"
+	IconMailSend                     Icon = "MailSend"
+	IconMailReceive                  Icon = "MailReceive"
+	// actions: media
+	IconMediaEject                   Icon = "MediaEject"
+	IconMediaPlaybackPause           Icon = "MediaPlaybackPause"
+	IconMediaPlaybackStart           Icon = "MediaPlaybackStart"
+	IconMediaPlaybackStop            Icon = "MediaPlaybackStop"
+	IconMediaRecord                  Icon = "MediaRecord"
+	IconMediaSeekBackward            Icon = "MediaSeekBackward"
+	IconMediaSeekForward             Icon = "MediaSeekForward"
+	IconMediaSkipBackward            Icon = "MediaSkipBackward"
+	IconMediaSkipForward             Icon = "MediaSkipForward"
+	// actions: object
+	IconObjectFlipHorizontal         Icon = "ObjectFlipHorizontal"
+	IconObjectFlipVertical           Icon = "ObjectFlipVertical"
+	IconObjectRotateLeft             Icon = "ObjectRotateLeft"
+	IconObjectRotateRight            Icon = "ObjectRotateRight"
+	// actions: process
+	IconProcessStop                  Icon = "ProcessStop"
+	// actions: system
+	IconSystemLockScreen             Icon = "SystemLockScreen"
+	IconSystemLogOut                 Icon = "SystemLogOut"
+	IconSystemRun                    Icon = "SystemRun"
+	IconSystemSearch                 Icon = "SystemSearch"
+	IconSystemReboot                 Icon = "SystemReboot"
+	IconSystemShutdown               Icon = "SystemShutdown"
+	// actions: tools
+	IconToolsCheckSpelling           Icon = "ToolsCheckSpelling"
+	// actions: value
+	IconValueIncrement               Icon = "ValueIncrement"
+	IconValueDecrement               Icon = "ValueDecrement"
+	IconValueReset                   Icon = "ValueReset"
+	// actions: view
+	IconViewFullscreen               Icon = "ViewFullscreen"
+	IconViewRefresh                  Icon = "ViewRefresh"
+	IconViewRestore                  Icon = "ViewRestore"
+	IconViewSortAscending            Icon = "ViewSortAscending"
+	IconViewSortDescending           Icon = "ViewSortDescending"
+	// actions: window
+	IconWindowClose                  Icon = "WindowClose"
+	IconWindowNew                    Icon = "WindowNew"
+	// actions: zoom
+	IconZoomFitBest                  Icon = "ZoomFitBest"
+	IconZoomIn                       Icon = "ZoomIn"
+	IconZoomOriginal                 Icon = "ZoomOriginal"
+	IconZoomOut                      Icon = "ZoomOut"
+	
+	// applications
+	// Keep these in sync with nasin.ApplicationRole!
+	IconApplication                  Icon = "Application" // generic
+	IconApplicationWebBrowser        Icon = "ApplicationWebBrowser"
+	IconApplicationMesssanger        Icon = "ApplicationMesssanger"
+	IconApplicationPhone             Icon = "ApplicationPhone"
+	IconApplicationMail              Icon = "ApplicationMail"
+	IconApplicationTerminalEmulator  Icon = "ApplicationTerminalEmulator"
+	IconApplicationFileBrowser       Icon = "ApplicationFileBrowser"
+	IconApplicationTextEditor        Icon = "ApplicationTextEditor"
+	IconApplicationDocumentViewer    Icon = "ApplicationDocumentViewer"
+	IconApplicationWordProcessor     Icon = "ApplicationWordProcessor"
+	IconApplicationSpreadsheet       Icon = "ApplicationSpreadsheet"
+	IconApplicationSlideshow         Icon = "ApplicationSlideshow"
+	IconApplicationCalculator        Icon = "ApplicationCalculator"
+	IconApplicationPreferences       Icon = "ApplicationPreferences"
+	IconApplicationProcessManager    Icon = "ApplicationProcessManager"
+	IconApplicationSystemInformation Icon = "ApplicationSystemInformation"
+	IconApplicationManual            Icon = "ApplicationManual"
+	IconApplicationCamera            Icon = "ApplicationCamera"
+	IconApplicationImageViewer       Icon = "ApplicationImageViewer"
+	IconApplicationMediaPlayer       Icon = "ApplicationMediaPlayer"
+	IconApplicationImageEditor       Icon = "ApplicationImageEditor"
+	IconApplicationAudioEditor       Icon = "ApplicationAudioEditor"
+	IconApplicationVideoEditor       Icon = "ApplicationVideoEditor"
+	IconApplicationClock             Icon = "ApplicationClock"
+	IconApplicationCalendar          Icon = "ApplicationCalendar"
+	IconApplicationChecklist         Icon = "ApplicationChecklist"
+
+	// categories: applications
+	IconApplications                 Icon = "Applications"
+	IconApplicationsAccessories      Icon = "ApplicationsAccessories"
+	IconApplicationsDevelopment      Icon = "ApplicationsDevelopment"
+	IconApplicationsEngineering      Icon = "ApplicationsEngineering"
+	IconApplicationsGames            Icon = "ApplicationsGames"
+	IconApplicationsGraphics         Icon = "ApplicationsGraphics"
+	IconApplicationsInternet         Icon = "ApplicationsInternet"
+	IconApplicationsMultimedia       Icon = "ApplicationsMultimedia"
+	IconApplicationsOffice           Icon = "ApplicationsOffice"
+	IconApplicationsScience          Icon = "ApplicationsScience"
+	IconApplicationsSystem           Icon = "ApplicationsSystem"
+	IconApplicationsUtilities        Icon = "ApplicationsUtilities"
+	// categories: preferences
+	IconPreferences                  Icon = "Preferences"
+	IconPreferencesDesktop           Icon = "PreferencesDesktop"
+	IconPreferencesPeripherals       Icon = "PreferencesPeripherals"
+	IconPreferencesPersonal          Icon = "PreferencesPersonal"
+	IconPreferencesSystem            Icon = "PreferencesSystem"
+	IconPreferencesNetwork           Icon = "PreferencesNetwork"
+
+	// devices
+	IconDevice                       Icon = "Device"
+	IconDeviceCamera                 Icon = "DeviceCamera"
+	IconDeviceWebCamera              Icon = "DeviceWebCamera"
+	IconDeviceComputer               Icon = "DeviceComputer"
+	IconDevicePda                    Icon = "DevicePda"
+	IconDevicePhone                  Icon = "DevicePhone"
+	IconDevicePrinter                Icon = "DevicePrinter"
+	IconDeviceScanner                Icon = "DeviceScanner"
+	IconDeviceMultimediaPlayer       Icon = "DeviceMultimediaPlayer"
+	IconDeviceVideoDisplay           Icon = "DeviceVideoDisplay"
+	IconDeviceAudioInput             Icon = "DeviceAudioInput"
+	IconDeviceAudioOutput            Icon = "DeviceAudioOutput"
+	// devices: hardware
+	IconHardware                     Icon = "Hardware"
+	IconHardwareCPU                  Icon = "HardwareCPU"
+	IconHardwareGPU                  Icon = "HardwareGPU"
+	IconHardwareRAM                  Icon = "HardwareRAM"
+	IconHardwareSoundCard            Icon = "HardwareSoundCard"
+	IconHardwareNetworkAdapter       Icon = "HardwareNetworkAdapter"
+	// devices: power
+	IconPowerBattery                 Icon = "PowerBattery"
+	// devices: storage
+	IconStorageHardDisk              Icon = "StorageHardDisk"
+	IconStorageFloppyDisk            Icon = "StorageFloppyDisk"
+	IconStorageSolidState            Icon = "StorageSolidState"
+	IconStorageOptical               Icon = "StorageOptical"
+	IconStorageFlashStick            Icon = "StorageFlashStick"
+	IconStorageFlashCard             Icon = "StorageFlashCard"
+	IconStorageMagneticTape          Icon = "StorageMagneticTape"
+	// devices: input
+	IconInputGaming                  Icon = "InputGaming"
+	IconInputKeyboard                Icon = "InputKeyboard"
+	IconInputMouse                   Icon = "InputMouse"
+	IconInputTablet                  Icon = "InputTablet"
+	// devices: network
+	IconNetworkWired                 Icon = "NetworkWired"
+	IconNetworkWireless              Icon = "NetworkWireless"
+	IconNetworkCellular              Icon = "NetworkCellular"
+	IconNetworkLocal                 Icon = "NetworkLocal"
+	IconNetworkInternet              Icon = "NetworkInternet"
+	IconNetworkVPN                   Icon = "NetworkVPN"
+	IconNetworkServer                Icon = "NetworkServer"
+	IconNetworkWorkgroup             Icon = "NetworkWorkgroup"
+
+	// emblems
+	IconEmblemDefault                Icon = "EmblemDefault"
+	IconEmblemEncrypted              Icon = "EmblemEncrypted"
+	IconEmblemFavorite               Icon = "EmblemFavorite"
+	IconEmblemImportant              Icon = "EmblemImportant"
+	IconEmblemReadOnly               Icon = "EmblemReadOnly"
+	IconEmblemShared                 Icon = "EmblemShared"
+	IconEmblemSymbolicLink           Icon = "EmblemSymbolicLink"
+	IconEmblemSynchronized           Icon = "EmblemSynchronized"
+	IconEmblemSystem                 Icon = "EmblemSystem"
+	IconEmblemUnreadable             Icon = "EmblemUnreadable"
+
+	// places
+	IconPlaceDirectory               Icon = "PlaceDirectory"
+	IconPlaceRemote                  Icon = "PlaceRemote"
+	IconPlaceHome                    Icon = "PlaceHome"
+	IconPlaceDownloads               Icon = "PlaceDownloads"
+	IconPlaceDesktop                 Icon = "PlaceDesktop"
+	IconPlacePhotos                  Icon = "PlacePhotos"
+	IconPlaceBooks                   Icon = "PlaceBooks"
+	IconPlaceBookmarks               Icon = "PlaceBookmarks"
+	IconPlaceTrash                   Icon = "PlaceTrash"
+	IconPlaceDocuments               Icon = "PlaceDocuments"
+	IconPlaceRepositories            Icon = "PlaceRepositories"
+	IconPlaceMusic                   Icon = "PlaceMusic"
+	IconPlaceArchives                Icon = "PlaceArchives"
+	IconPlaceFonts                   Icon = "PlaceFonts"
+	IconPlaceBinaries                Icon = "PlaceBinaries"
+	IconPlaceVideos                  Icon = "PlaceVideos"
+	IconPlace3DObjects               Icon = "Place3DObjects"
+	IconPlaceHistory                 Icon = "PlaceHistory"
+	IconPlacePreferences             Icon = "PlacePreferences"
+
+	// status: checkbox
+	IconCheckboxChecked              Icon = "CheckboxChecked"
+	IconCheckboxUnchecked            Icon = "CheckboxUnchecked"
+	// status: appointments
+	IconAppointmentMissed            Icon = "AppointmentMissed"
+	IconAppointmentSoon              Icon = "AppointmentSoon"
+	// status: dialogs
+	IconDialogError                  Icon = "DialogError"
+	IconDialogInformation            Icon = "DialogInformation"
+	IconDialogPassword               Icon = "DialogPassword"
+	IconDialogQuestion               Icon = "DialogQuestion"
+	IconDialogWarning                Icon = "DialogWarning"
+	// status: directories
+	IconDirectoryDragAccept          Icon = "DirectoryDragAccept"
+	IconDirectoryFull                Icon = "DirectoryFull"
+	IconDirectoryOpen                Icon = "DirectoryOpen"
+	IconDirectoryVisiting            Icon = "DirectoryVisiting"
+	// status: trash
+	IconTrashFull                    Icon = "TrashFull"
+	// status: resource
+	IconResourceLoading              Icon = "ResourceLoading"
+	IconResourceMissing              Icon = "ResourceMissing"
+	// status: mail
+	IconMailAttachment               Icon = "MailAttachment"
+	IconMailUnread                   Icon = "MailUnread"
+	IconMailReplied                  Icon = "MailReplied"
+	IconMailSigned                   Icon = "MailSigned"
+	IconMailSignedVerified           Icon = "MailSignedVerified"
+	// status: network
+	IconCellularSignal0              Icon = "CellularSignal0"
+	IconCellularSignal1              Icon = "CellularSignal1"
+	IconCellularSignal2              Icon = "CellularSignal2"
+	IconCellularSignal3              Icon = "CellularSignal3"
+	IconWirelessSignal0              Icon = "WirelessSignal0"
+	IconWirelessSignal1              Icon = "WirelessSignal1"
+	IconWirelessSignal2              Icon = "WirelessSignal2"
+	IconWirelessSignal3              Icon = "WirelessSignal3"
+	IconNetworkError                 Icon = "NetworkError"
+	IconNetworkIdle                  Icon = "NetworkIdle"
+	IconNetworkOffline               Icon = "NetworkOffline"
+	IconNetworkReceive               Icon = "NetworkReceive"
+	IconNetworkTransmit              Icon = "NetworkTransmit"
+	IconNetworkTransmitReceive       Icon = "NetworkTransmitReceive"
+	// status: print
+	IconPrintError                   Icon = "PrintError"
+	IconPrintPrinting                Icon = "PrintPrinting"
+	// status: security
+	IconSecurityHigh                 Icon = "SecurityHigh"
+	IconSecurityMedium               Icon = "SecurityMedium"
+	IconSecurityLow                  Icon = "SecurityLow"
+	// status: software
+	IconSoftwareUpdateAvailable      Icon = "SoftwareUpdateAvailable"
+	IconSoftwareUpdateUrgent         Icon = "SoftwareUpdateUrgent"
+	IconSoftwareInstalling           Icon = "SoftwareInstalling"
+	// status: sync
+	IconSyncError                    Icon = "SyncError"
+	IconSyncSynchronizing            Icon = "SyncSynchronizing"
+	// status: tasks
+	IconTaskDue                      Icon = "TaskDue"
+	IconTaskPastDue                  Icon = "TaskPastDue"
+	// status: users
+	IconUserAvailable                Icon = "UserAvailable"
+	IconUserAway                     Icon = "UserAway"
+	IconUserIdle                     Icon = "UserIdle"
+	IconUserOffline                  Icon = "UserOffline"
+	// status: power
+	IconBattery0                     Icon = "Battery0"
+	IconBattery1                     Icon = "Battery1"
+	IconBattery2                     Icon = "Battery2"
+	IconBattery3                     Icon = "Battery3"
+	IconBrightness0                  Icon = "Brightness0"
+	IconBrightness1                  Icon = "Brightness1"
+	IconBrightness2                  Icon = "Brightness2"
+	IconBrightness3                  Icon = "Brightness3"
+	// status: media
+	IconVolume0                      Icon = "Volume0"
+	IconVolume1                      Icon = "Volume1"
+	IconVolume2                      Icon = "Volume2"
+	IconVolume3                      Icon = "Volume3"
+	IconPlaylistRepeat               Icon = "PlaylistRepeat"
+	IconPlaylistShuffle              Icon = "PlaylistShuffle"
+	// status: weather
+	IconWeatherClear                 Icon = "WeatherClear"
+	IconWeatherClearNight            Icon = "WeatherClearNight"
+	IconWeatherFewClouds             Icon = "WeatherFewClouds"
+	IconWeatherFewCloudsNight        Icon = "WeatherFewCloudsNight"
+	IconWeatherFog                   Icon = "WeatherFog"
+	IconWeatherOvercast              Icon = "WeatherOvercast"
+	IconWeatherSevereAlert           Icon = "WeatherSevereAlert"
+	IconWeatherShowers               Icon = "WeatherShowers"
+	IconWeatherShowersScattered      Icon = "WeatherShowersScattered"
+	IconWeatherSnow                  Icon = "WeatherSnow"
+	IconWeatherStorm                 Icon = "WeatherStorm"
+)
+
+// Texture returns a texture of the corresponding icon ID.
+func (id Icon) Texture (size IconSize) canvas.Texture {
+	if iconSet == nil { return nil }
+	return iconSet.Icon(id, size)
+}
+
+// MimeIcon returns an icon corresponding to a MIME type.
+func MimeIcon (mime data.Mime, size IconSize) canvas.Texture {
+	if iconSet == nil { return nil }
+	return iconSet.MimeIcon(mime, size)
+}
+
+// IconSet holds a set of icon textures.
+type IconSet interface {
+	// A word on textures:
+	//
+	// Because textures can be linked to some resource that is outside of
+	// the control of Go's garbage collector, methods of IconSet must not
+	// allocate new copies of a texture each time they are called. It is
+	// fine to lazily load textures and save them for later use, but the
+	// same texture must never be allocated multiple times as this could
+	// cause a memory leak.
+	//
+	// As such, textures returned by these methods must be protected.
+	
+	// Icon returns a texture of the corresponding icon ID. If there is no
+	// suitable option, it should return nil.
+	Icon (Icon, IconSize) canvas.Texture
+
+	// MimeIcon returns a texture of an icon corresponding to a MIME type.
+	// If there is no suitable specific option, it should return a more
+	// generic icon or a plain file icon.
+	MimeIcon (data.Mime, IconSize) canvas.Texture
+}
+
+var iconSet IconSet
+
+// SetIconSet sets the icon set.
+func SetIconSet (set IconSet) {
+	assertBackend()
+	iconSet = set
+	backend.SetIconSet(set)
+}

object.go

@@ -1,155 +1,73 @@
 package tomo
 
 import "image"
-import "image/color"
-import "golang.org/x/image/font"
 import "git.tebibyte.media/tomo/tomo/text"
 import "git.tebibyte.media/tomo/tomo/data"
 import "git.tebibyte.media/tomo/tomo/event"
 import "git.tebibyte.media/tomo/tomo/input"
 import "git.tebibyte.media/tomo/tomo/canvas"
 
-// Side represents one side of a rectangle.
-type Side int; const (
-	SideTop Side = iota
-	SideRight
-	SideBottom
-	SideLeft
-)
-
-// Inset represents a rectangle inset that can have a different value for each
-// side.
-type Inset [4]int
-
-// I allows you to create an inset in a CSS-ish way:
-//
-//   - One argument: all sides are set to this value
-//   - Two arguments: the top and bottom sides are set to the first value, and
-//     the left and right sides are set to the second value.
-//   - Three arguments: the top side is set by the first value, the left and
-//     right sides are set by the second vaue, and the bottom side is set by the
-//     third value.
-//   - Four arguments: each value corresponds to a side.
-//
-// This function will panic if an argument count that isn't one of these is
-// given.
-func I (sides ...int) Inset {
-	switch len(sides) {
-	case 1: return Inset { sides[0], sides[0], sides[0], sides[0] }
-	case 2: return Inset { sides[0], sides[1], sides[0], sides[1] }
-	case 3: return Inset { sides[0], sides[1], sides[2], sides[1] }
-	case 4: return Inset { sides[0], sides[1], sides[2], sides[3] }
-	default: panic("I: illegal argument count.")
-	}
-}
-
-// Apply returns the given rectangle, shrunk on all four sides by the given
-// inset. If a measurment of the inset is negative, that side will instead be
-// expanded outward. If the rectangle's dimensions cannot be reduced any
-// further, an empty rectangle near its center will be returned.
-func (inset Inset) Apply (bigger image.Rectangle) (smaller image.Rectangle) {
-	smaller = bigger
-	if smaller.Dx() < inset[3] + inset[1] {
-		smaller.Min.X = (smaller.Min.X + smaller.Max.X) / 2
-		smaller.Max.X = smaller.Min.X
-	} else {
-		smaller.Min.X += inset[3]
-		smaller.Max.X -= inset[1]
-	}
-
-	if smaller.Dy() < inset[0] + inset[2] {
-		smaller.Min.Y = (smaller.Min.Y + smaller.Max.Y) / 2
-		smaller.Max.Y = smaller.Min.Y
-	} else {
-		smaller.Min.Y += inset[0]
-		smaller.Max.Y -= inset[2]
-	}
-	return
-}
-
-// Inverse returns a negated version of the inset.
-func (inset Inset) Inverse () (prime Inset) {
-	return Inset {
-		inset[0] * -1,
-		inset[1] * -1,
-		inset[2] * -1,
-		inset[3] * -1,
-	}
-}
-
-// Horizontal returns the sum of SideRight and SideLeft.
-func (inset Inset) Horizontal () int {
-	return inset[SideRight] + inset[SideLeft]
-}
-
-// Vertical returns the sum of SideTop and SideBottom.
-func (inset Inset) Vertical () int {
-	return inset[SideTop] + inset[SideBottom]
-}
-
-// Border represents a single border of a box.
-type Border struct {
-	Width Inset
-	Color [4]color.Color
-}
-
-// Align lists basic alignment types.
-type Align int; const (
-	AlignStart Align = iota // similar to left-aligned text
-	AlignMiddle             // similar to center-aligned text
-	AlignEnd                // similar to right-aligned text
-	AlignEven               // similar to justified text
-)
-
-// Object is any obscreen object. Each object must be linked to a box, even if
-// it is that box.
+// Object is any onscreen object that is linked to a box (or is that box).
+// Unlike the Box interface and associated interfaces, Object implementations
+// may originate from anywhere.
 type Object interface {
 	GetBox () Box
 }
 
-// Box is a basic styled box.
+// ContentObject is an object that has some kind of content.
+type ContentObject interface {
+	Object
+
+	// ContentBounds returns the bounds of the inner content of the Box
+	// relative to the Box's InnerBounds.
+	ContentBounds () image.Rectangle
+	// ScrollTo shifts the origin of the Box's content to the origin of the
+	// Box's InnerBounds, offset by the given point.
+	ScrollTo (image.Point)
+	// OnContentBoundsChange specifies a function to be called when the
+	// Box's ContentBounds or InnerBounds changes.
+	OnContentBoundsChange (func ()) event.Cookie
+}
+
+// Box is a basic styled box. Implementations of Box, as well as any interface
+// that embed Box, may only originate from a Backend.
 type Box interface {
 	Object
 
 	// Window returns the Window this Box is a part of.
-	Window         () Window
+	Window () Window
 	// Bounds returns the outer bounding rectangle of the Box relative to
 	// the Window.
-	Bounds         () image.Rectangle
+	Bounds () image.Rectangle
 	// InnerBounds returns the inner bounding rectangle of the box. It is
 	// the value of Bounds inset by the Box's border and padding.
-	InnerBounds    () image.Rectangle
-	// MinimumSize returns the minimum width and height this Box's bounds
-	// can be set to. This will return the value of whichever of these is
-	// greater:
-	//   - The size as set by SetMinimumSize
-	//   - The size taken up by the Box's border and padding. If there is
-	//     internal content that does not overflow, the size of that is also
-	//     taken into account here.
-	MinimumSize    () image.Point
-	// SetBounds sets the bounding rectangle of this Box relative to the
-	// Window.
-	SetBounds      (image.Rectangle)
-	// SetColor sets the background color of this Box.
-	SetColor       (color.Color)
-	// SetTexture sets a repeating background texture. If the texture is
-	// transparent, it will be overlayed atop the color specified by
-	// SetColor().
-	SetTexture     (canvas.Texture)
-	// SetBorder sets the Border(s) of the box. The first Border will be the
-	// most outset, and the last Border will be the most inset.
-	SetBorder      (...Border)
-	// SetMinimumSize sets the minimum width and height of the box, as
-	// described in MinimumSize.
-	SetMinimumSize (image.Point)
-	// SetPadding sets the padding between the Box's innermost Border and
-	// its content.
-	SetPadding     (Inset)
+	InnerBounds () image.Rectangle
+	// Role returns this Box's role as set by SetRole.
+	Role () Role
+	// SetRole sets what role this Box takes on. It is used to apply styling
+	// from a theme.
+	SetRole (Role)
+	// Tag returns whether or not a named tag exists. These are used for
+	// applying styling, among other things. There are some special tags
+	// that are only and always extant during certain user input states:
+	//   - hovered: The mouse pointer is within the box
+	//   - focused: The box has keyboard focus
+	//   - pressed: The box is being pressed by the left mouse button
+	Tag (string) bool
+	// SetTag adds or removes a named tag.
+	SetTag (string, bool)
+
+	// SetAttr sets a style attribute, overriding the currently applied
+	// style.
+	SetAttr (Attr)
+	// UnsetAttr reverts a style attribute to whatever is specified by the
+	// currently applied style.
+	UnsetAttr (AttrKind)
 
 	// SetDNDData sets the data that will be picked up if this Box is
 	// dragged. If this is nil (which is the default), this Box will not be
 	// picked up.
-	SetDNDData   (data.Data)
+	SetDNDData (data.Data)
 	// SetDNDAccept sets the type of data that can be dropped onto this Box.
 	// If this is nil (which is the default), this Box will reject all
 	// drops.
@@ -157,37 +75,37 @@ type Box interface {
 	// SetFocused sets whether or not this Box has keyboard focus. If set to
 	// true, this method will steal focus away from whichever Object
 	// currently has focus.
-	SetFocused   (bool)
+	SetFocused (bool)
 	// SetFocusable sets whether or not this Box can receive keyboard focus.
 	// If set to false and the Box is already focused. the focus is removed.
 	SetFocusable (bool)
 
-	// Focused returns whether or not this Box has keyboard focus.
-	Focused       () bool
-	// Modifiers returns which modifier keys on the keyboard are currently
-	// being held down.
-	Modifiers     () input.Modifiers
-	// MousePosition returns the position of the mouse pointer relative to
-	// the Window.
-	MousePosition () image.Point
-
-	// These are event subscription functions that allow callbacks to be
+	// These are event subscription behaviors that allow callbacks to be
 	// connected to particular events. Multiple callbacks may be connected
 	// to the same event at once. Callbacks can be removed by closing the
 	// returned cookie.
-	OnFocusEnter  (func ()) event.Cookie
-	OnFocusLeave  (func ()) event.Cookie
-	OnDNDEnter    (func ()) event.Cookie
-	OnDNDLeave    (func ()) event.Cookie
-	OnDNDDrop     (func (data.Data)) event.Cookie
-	OnMouseEnter  (func ()) event.Cookie
-	OnMouseLeave  (func ()) event.Cookie
-	OnMouseMove   (func ()) event.Cookie
-	OnMouseDown   (func (input.Button)) event.Cookie
-	OnMouseUp     (func (input.Button)) event.Cookie
-	OnScroll      (func (deltaX, deltaY float64)) event.Cookie
-	OnKeyDown     (func (key input.Key, numberPad bool)) event.Cookie
-	OnKeyUp       (func (key input.Key, numberPad bool)) event.Cookie
+	OnFocusEnter    (func ()         ) event.Cookie
+	OnFocusLeave    (func ()         ) event.Cookie
+	OnStyleChange   (func ()         ) event.Cookie
+	OnIconSetChange (func ()         ) event.Cookie
+	OnDNDEnter      (func ()         ) event.Cookie
+	OnDNDLeave      (func ()         ) event.Cookie
+	OnDNDDrop       (func (data.Data)) event.Cookie
+	OnMouseEnter    (func ()         ) event.Cookie
+	OnMouseLeave    (func ()         ) event.Cookie
+	// These event subscription behaviors require their callbacks to return
+	// a bool value. Under normal circumstances, these events are propagated
+	// to the Box which is most directly affected by them, and then to all
+	// of its parents from the bottom-up. Returning true from the callback
+	// will cause the propagation to stop immediately, thereby "catching"
+	// the event. Generally, if the event was successfully handled, the
+	// callbacks ought to return true.
+	OnMouseMove     (func ()                              bool) event.Cookie
+	OnButtonDown    (func (button input.Button)           bool) event.Cookie
+	OnButtonUp      (func (button input.Button)           bool) event.Cookie
+	OnScroll        (func (deltaX, deltaY float64)        bool) event.Cookie
+	OnKeyDown       (func (key input.Key, numberPad bool) bool) event.Cookie
+	OnKeyUp         (func (key input.Key, numberPad bool) bool) event.Cookie
 }
 
 // CanvasBox is a box that can be drawn to.
@@ -195,32 +113,55 @@ type CanvasBox interface {
 	Box
 
 	// SetDrawer sets the Drawer that will be called upon to draw the Box's
-	// content when it is invalidated.
-	SetDrawer  (canvas.Drawer)
+	// content when it is invalidated. The Canvas passed to the drawer will
+	// have these properties:
+	//   - It will have the same origin (0, 0) as the window which contains
+	//     the CanvasBox
+	//   - The Canvas bounds will describe the portion of the CanvasBox
+	//     visible on screen
+	SetDrawer (canvas.Drawer)
 
 	// Invalidate causes the Box's area to be redrawn at the end of the
 	// event cycle, even if it wouldn't be otherwise.
 	Invalidate ()
 }
 
-// ContentBox is an abstract box that has some kind of content. Its only purpose
-// is to be embedded into TextBox and ContainerBox.
-type ContentBox interface {
+// SurfaceBox is a box that can be drawn to via a hardware accelerated (or
+// platform-specific) graphics context.
+type SurfaceBox interface {
 	Box
 
-	// SetOverflow sets whether or not the Box's content overflows
-	// horizontally and vertically. Overflowing content is clipped to the
-	// bounds of the Box inset by all Borders (but not padding).
-	SetOverflow           (horizontal, vertical bool)
-	// SetAlign sets how the Box's content is distributed horizontally and
-	// vertically.
-	SetAlign              (x, y Align)
+	// Surface returns the underlying graphics context. The result must be
+	// asserted to the expected type or passed through a type switch before
+	// use. The exact type returned here depends on the backend being used,
+	// and it is up to the application author to ensure that the application
+	// and backend agree on it. Applications should fail gracefully if the
+	// expected type was not found.
+	Surface () any
+	
+	// Invalidate causes the data within the surface to be pushed to the
+	// screen at the end of the event cycle, even if it wouldn't be
+	// otherwise.
+	Invalidate ()
+
+	// OnSizeChange specifies a function to be called when the size of the
+	// Box is changed, or the surface is re-allocated. The application must
+	// call Surface() each time this event fires in order to not draw to a
+	// closed surface.
+	OnSizeChange (func ())
+}
+
+// ContentBox is a box that has some kind of content.
+type ContentBox interface {
+	Box
+	
 	// ContentBounds returns the bounds of the inner content of the Box
-	// relative to the window.
-	ContentBounds         () image.Rectangle
+	// relative to the Box's InnerBounds.
+	ContentBounds () image.Rectangle
 	// ScrollTo shifts the origin of the Box's content to the origin of the
 	// Box's InnerBounds, offset by the given point.
-	ScrollTo              (image.Point)
+	ScrollTo (image.Point)
+	
 	// OnContentBoundsChange specifies a function to be called when the
 	// Box's ContentBounds or InnerBounds changes.
 	OnContentBoundsChange (func ()) event.Cookie
@@ -231,26 +172,18 @@ type TextBox interface {
 	ContentBox
 
 	// SetText sets the text content of the Box.
-	SetText       (string)
-	// SetTextColor sets the text color.
-	SetTextColor  (color.Color)
-	// SetFace sets the font face text is rendered in.
-	SetFace       (font.Face)
-	// SetWrap sets whether or not the text wraps.
-	SetWrap       (bool)
-
+	SetText (string)
+	
 	// SetSelectable sets whether or not the text content can be
 	// highlighted/selected.
 	SetSelectable (bool)
-	// SetDotColor sets the highlight color of selected text.
-	SetDotColor   (color.Color)
 	// Select sets the text cursor or selection.
-	Select        (text.Dot)
+	Select (text.Dot)
 	// Dot returns the text cursor or selection.
-	Dot           () text.Dot
+	Dot () text.Dot
 	// OnDotChange specifies a function to be called when the text cursor or
 	// selection changes.
-	OnDotChange   (func ()) event.Cookie
+	OnDotChange (func ()) event.Cookie
 }
 
 // ContentBox is a box that can contain child Objects. It arranges them
@@ -258,30 +191,32 @@ type TextBox interface {
 type ContainerBox interface {
 	ContentBox
 
-	// SetPropagateEvents specifies whether or not child Objects will
-	// receive user input events. It is true by default. If it is false, all
-	// user input that would otherwise be directed to a child Box is
-	// directed to this Box.
-	SetPropagateEvents (bool)
-	// SetGap sets the gap between child Objects.
-	SetGap             (image.Point)
-	// Add appends a child Object.
-	Add                (Object)
-	// Delete removes a child Object, if it is a child of this Box.
-	Delete             (Object)
+	// Add appends a child Object. If the object is already a child of
+	// another object, it will be removed from that object first.
+	Add (Object)
+	// Remove removes a child Object, if it is a child of this Box.
+	Remove (Object)
 	// Insert inserts a child Object before a specified Object. If the
 	// before Object is nil or is not contained within this Box, the
 	// inserted Object is appended.
-	Insert             (child Object, before Object)
+	Insert (child Object, before Object)
 	// Clear removes all child Objects.
-	Clear              ()
-	// Length returns the amount of child objects.
-	Length             () int
+	Clear ()
+	// Len returns the amount of child Objects.
+	Len () int
 	// At returns the child Object at the specified index.
-	At                 (int) Object
-	// SetLayout sets the layout of this Box. Child Objects will be
-	// positioned according to it.
-	SetLayout          (Layout)
+	At (int) Object
+	// SetInputMask sets whether or not user input events will be sent to
+	// this Box's children. If false, which is the default, input events
+	// will be sent to this Box as well as all of its children. If true,
+	// any input events that would otherwise go to this Box's children are
+	// sent to it instead. This prevents children from performing event
+	// catching as described in the documentation for Box.
+	SetInputMask (bool)
+
+	// TODO: if it turns out selecting specific kinds of events to mask off
+	// is a good idea, have SetInputMask take in a vararg list of event
+	// types.
 }
 
 // LayoutHints are passed to a layout to tell it how to arrange child boxes.
@@ -289,14 +224,14 @@ type LayoutHints struct {
 	// Bounds is the bounding rectangle that children should be placed
 	// within. Any padding values are already applied.
 	Bounds image.Rectangle
-	// OverflowX and OverflowY control wether child Boxes may be positioned
+	// OverflowX and OverflowY control whether child Boxes may be positioned
 	// outside of Bounds.
 	OverflowX bool
 	OverflowY bool
 	// AlignX and AlignY control how child Boxes are aligned horizontally
 	// and vertically. The effect of this may vary depending on the Layout.
-	AlignX    Align
-	AlignY    Align
+	AlignX Align
+	AlignY Align
 	// Gap controls the amount of horizontal and vertical spacing in-between
 	// child Boxes.
 	Gap image.Point
@@ -306,54 +241,95 @@ type LayoutHints struct {
 type Layout interface {
 	// MinimumSize returns the minimum width and height of
 	// LayoutHints.Bounds needed to properly lay out all child Boxes.
-	MinimumSize (LayoutHints, []Box) image.Point
+	MinimumSize (LayoutHints, BoxQuerier) image.Point
 	// Arrange arranges child boxes according to the given LayoutHints.
-	Arrange     (LayoutHints, []Box)
+	Arrange (LayoutHints, BoxArranger)
+	// RecommendedHeight returns the recommended height for a given width,
+	// if supported. Otherwise, it should just return the minimum height.
+	// The result of this behavior may or may not be respected, depending on
+	// the situation.
+	RecommendedHeight (LayoutHints, BoxQuerier, int) int
+	// RecommendedWidth returns the recommended width for a given height, if
+	// supported. Otherwise, it should just return the minimum width. The
+	// result of this behavior may or may not be respected, depending on the
+	// situation.
+	RecommendedWidth (LayoutHints, BoxQuerier, int) int
 }
 
-// Window is an operating system window. It can contain one object.
+// BoxQuerier allows the attributes of a ContainerBox's children to be queried.
+type BoxQuerier interface {
+	// Len returns the amount of boxes.
+	Len () int
+	// MinimumSize returns the minimum size of a box.
+	MinimumSize (index int) image.Point
+	// RecommendedWidth returns the recommended width for a given height for
+	// a box, if supported. Otherwise, it should just return the minimum
+	// width of that box. The result of this behavior may or may not be
+	// respected, depending on the situation.
+	RecommendedWidth (index int, height int) int
+	// RecommendedHeight returns the recommended height for a given width
+	// for a box, if supported. Otherwise, it should just return the minimum
+	// width of that box. The result of this behavireor may or may not be
+	// respected, depending on the situation.
+	RecommendedHeight (index int, width int) int
+}
+
+// BoxArranger is a BoxQuerier that allows arranging child boxes according to a
+// layout.
+type BoxArranger interface {
+	BoxQuerier
+	
+	// SetBounds sets the bounds of a box.
+	SetBounds (index int, bounds image.Rectangle)
+}
+
+// Window is an operating system window. It can contain one object. Windows
+// themselves are completely transparent, and become opaque once an opaque
+// object is added as their root.
 type Window interface {
 	// SetRoot sets the root child of the window. There can only be one at
 	// a time, and setting it will remove the current child if there is one.
-	SetRoot  (Object)
+	SetRoot (Object)
 	// SetTitle sets the title of the window.
 	SetTitle (string)
-	// SetIcon sets the icon of the window. When multiple icon sizes are
-	// provided, the best fitting one is chosen for display.
-	SetIcon  (... image.Image)
-	// Widget returns a window representing a smaller iconified form of this
-	// window. How exactly this window is used depends on the platform.
-	// Subsequent calls to this method on the same window will return the
-	// same window object.
-	Widget   () (Window, error)
-	// NewMenu creates a new menu window. This window is undecorated and
-	// will close once the user clicks outside of it.
-	NewMenu  (image.Rectangle) (Window, error)
-	// NewModal creates a new modal window that blocks all input to this
-	// window until it is closed.
-	NewModal (image.Rectangle) (Window, error)
-	// Copy copies data to the clipboard.
-	Copy     (data.Data)
-	// Paste reads data from the clipboard. When the data is available or an
-	// error has occurred, the provided function will be called.
-	Paste    (callback func (data.Data, error), accept ...data.Mime)
-	// Show shows the window.
-	Show     ()
-	// Hide hides the window.
-	Hide     ()
-	// Close closes the window.
-	Close    ()
-	// OnClose specifies a function to be called when the window is closed.
-	OnClose  (func ()) event.Cookie
-}
-
-// MainWindow is a top-level operating system window.
-type MainWindow interface {
-	Window
-
+	// SetIcon sets the icon of the window.
+	SetIcon (Icon)
+	// SetResizable sets whether the window can be resized by the user in
+	// the X and Y directions. If one or both axes are false, the ones that
+	// are will be shrunk to the window's minimum size.
+	SetResizable (x, y bool)
+	// SetBounds sets this window's bounds. This may or may not have any
+	// effect on the window's position on screen depending on the platform.
+	SetBounds (image.Rectangle)
 	// NewChild creates a new window that is semantically a child of this
 	// window. It does not actually reside within this window, but it may be
 	// linked to it via some other means. This is intended for things like
 	// toolboxes and tear-off menus.
 	NewChild (image.Rectangle) (Window, error)
+	// NewMenu creates a new menu window. This window is undecorated and
+	// will close once the user clicks outside of it.
+	NewMenu (image.Rectangle) (Window, error)
+	// NewModal creates a new modal window that blocks all input to this
+	// window until it is closed.
+	NewModal (image.Rectangle) (Window, error)
+	// Modifiers returns which modifier keys on the keyboard are currently
+	// being held down.
+	Modifiers () input.Modifiers
+	// MousePosition returns the position of the mouse pointer relative to
+	// the Window.
+	MousePosition () image.Point
+	// Copy copies data to the clipboard.
+	Copy (data.Data)
+	// Paste reads data from the clipboard. When the data is available or an
+	// error has occurred, the provided function will be called.
+	Paste (callback func (data.Data, error), accept ...data.Mime)
+	// SetVisible sets whether or not this window is visible. Windows are
+	// invisible by default.
+	SetVisible (bool)
+	// Visible returns whether or not this window is visible.
+	Visible () bool
+	// Close closes the window.
+	Close ()
+	// OnClose specifies a function to be called when the window is closed.
+	OnClose (func ()) event.Cookie
 }

plugin.go

@@ -1,55 +0,0 @@
-package tomo
-
-import "os"
-import "plugin"
-import "path/filepath"
-
-var pluginPaths []string
-
-func loadPlugins () {
-	for _, dir := range pluginPaths {
-		if dir != "" {
-			loadPluginsFrom(dir)
-		}
-	}
-}
-
-func loadPluginsFrom (dir string) {
-	entries, err := os.ReadDir(dir)
-	// its no big deal if one of the dirs doesn't exist
-	if err != nil { return }
-
-	for _, entry := range entries {
-		if entry.IsDir() { continue }
-		if filepath.Ext(entry.Name()) != ".so" { continue }
-		pluginPath := filepath.Join(dir, entry.Name())
-		loadPlugin(pluginPath)
-	}
-}
-
-func loadPlugin (path string) {
-	die := func (reason string) {
-		println("tomo: could not load plugin at", path + ":", reason)
-	}
-
-	plugin, err := plugin.Open(path)
-	if err != nil {
-		die(err.Error())
-		return
-	}
-
-	// check for and obtain basic plugin functions
-	name, ok := extract[func () string](plugin, "Name")
-	if !ok { die("does not implement Name() string"); return }
-	_, ok = extract[func () string](plugin, "Description")
-	if !ok { die("does not implement Description() string"); return }
-
-	println("tomo: loaded plugin", name())
-}
-
-func extract[T any] (plugin *plugin.Plugin, name string) (value T, ok bool) {
-	symbol, err := plugin.Lookup(name)
-	if err != nil { return }
-	value, ok = symbol.(T)
-	return
-}

style.go

@@ -0,0 +1,80 @@
+package tomo
+
+import "fmt"
+import "image/color"
+
+// Role describes the role of an object.
+type Role struct {
+	// Package is an optional namespace field. If specified, it should be
+	// the package name or module name the object is from.
+	Package string
+
+	// Object specifies what type of object it is. For example:
+	//   - TextInput
+	//   - Table
+	//   - Label
+	//   - Dial
+	// This should correspond directly to the type name of the object.
+	Object string
+}
+
+// String satisfies the fmt.Stringer interface. It follows the format of:
+//   Package.Object
+func (r Role) String () string {
+	return fmt.Sprintf("%s.%s", r.Package, r.Object)
+}
+
+// R is shorthand for creating a role structure.
+func R (pack, object string) Role {
+	return Role { Package: pack, Object: object }
+}
+
+// Color represents a color ID.
+type Color int; const (
+	ColorBackground Color = iota
+	ColorForeground
+	ColorRaised
+	ColorSunken
+	ColorAccent
+)
+
+// RGBA satisfies the color.Color interface.
+func (id Color) RGBA () (r, g, b, a uint32) {
+	if style == nil { return }
+	return style.Colors[id].RGBA()
+}
+
+var style *Style
+
+// SetStyle sets the style.
+func SetStyle (sty *Style) {
+	assertBackend()
+	style = sty
+	backend.SetStyle(sty)
+}
+
+// Style can apply a visual style to different objects.
+type Style struct {
+	// Rules determines which styles get applied to which Objects.
+	Rules []Rule
+
+	// Colors maps tomo.Color values to color.RGBA values.
+	Colors map[Color] color.Color
+}
+
+// Rule describes under what circumstances should certain style attributes be
+// active.
+type Rule struct {
+	Role Role
+	Tags []string
+	Set  AttrSet
+}
+
+// Ru is shorthand for creating a rule structure
+func Ru (set AttrSet, role Role, tags ...string) Rule {
+	return Rule {
+		Role: role,
+		Tags: tags,
+		Set:  set,
+	}
+}

theme/icon.go

@@ -1,293 +0,0 @@
-package theme
-
-import "git.tebibyte.media/tomo/tomo/data"
-import "git.tebibyte.media/tomo/tomo/canvas"
-
-// IconSize represents the size of an icon.
-type IconSize int; const (
-	IconSizeSmall IconSize = iota;
-	IconSizeMedium
-	IconSizeLarge
-)
-
-// Icon represents an icon ID.
-type Icon int; const (
-	// --- Objects --- //
-
-	// files
-	IconFile Icon = iota
-	IconDirectory
-	IconDirectoryFull
-
-	// places
-	IconDownloads
-	IconPhotos
-	IconBooks
-	IconDocuments
-	IconRepositories
-	IconMusic
-	IconArchives
-	IconFonts
-	IconBinaries
-	IconVideos
-	Icon3DObjects
-	IconHistory
-	IconPreferences
-
-	// storage
-	IconStorage // generic
-	IconMagneticTape
-	IconFloppyDisk
-	IconHardDisk
-	IconSolidStateDrive
-	IconFlashDrive
-	IconMemoryCard
-	IconROMDisk
-	IconRAMDisk
-	IconCD
-	IconDVD
-
-	// network
-	IconNetwork // generic
-	IconLocalNetwork
-	IconInternet
-	IconEthernet
-	IconWireless
-	IconCell
-	IconBluetooth
-	IconRadio
-
-	// devices
-	IconDevice // generic
-	IconRouter
-	IconServer
-	IconDesktop
-	IconLaptop
-	IconTablet
-	IconPhone
-	IconWatch
-	IconCamera
-
-	// peripherals
-	IconPeripheral // generic
-	IconKeyboard
-	IconMouse
-	IconMonitor
-	IconWebcam
-	IconMicrophone
-	IconSpeaker
-	IconPenTablet
-	IconTrackpad
-	IconController
-
-	// i/o
-	IconPort // generic
-	IconEthernetPort
-	IconUSBPort
-	IconParallelPort
-	IconSerialPort
-	IconPS2Port
-	IconDisplayConnector
-	IconCGAPort
-	IconVGAPort
-	IconHDMIPort
-	IconDisplayPort
-	IconInfrared
-
-	// --- Actions --- //
-
-	// files
-	IconOpen
-	IconOpenIn
-	IconSave
-	IconSaveAs
-	IconPrints
-	IconNew
-	IconNewDirectory
-	IconDelete
-	IconRename
-	IconGetInformation
-	IconChangePermissions
-	IconRevert
-
-	// list management
-	IconAdd
-	IconRemove
-	IconAddBookmark
-	IconRemoveBookmark
-	IconAddFavorite
-	IconRemoveFavorite
-
-	// media
-	IconPlay
-	IconPause
-	IconStop
-	IconFastForward
-	IconRewind
-	IconToBeginning
-	IconToEnd
-	IconRecord
-	IconVolumeUp
-	IconVolumeDown
-	IconMute
-
-	// editing
-	IconUndo
-	IconRedo
-	IconCut
-	IconCopy
-	IconPaste
-	IconFind
-	IconReplace
-	IconSelectAll
-	IconSelectNone
-	IconIncrement
-	IconDecrement
-
-	// window management
-	IconClose
-	IconQuit
-	IconIconify
-	IconShade
-	IconMaximize
-	IconFullScreen
-	IconRestore
-
-	// view controls
-	IconExpand
-	IconContract
-	IconBack
-	IconForward
-	IconUp
-	IconDown
-	IconReload
-	IconZoomIn
-	IconZoomOut
-	IconZoomReset
-	IconMove
-	IconResize
-	IconGoTo
-
-	// tools
-	IconTransform
-	IconTranslate
-	IconRotate
-	IconScale
-	IconWarp
-	IconCornerPin
-	IconSelectRectangle
-	IconSelectEllipse
-	IconSelectLasso
-	IconSelectGeometric
-	IconSelectAuto
-	IconCrop
-	IconFill
-	IconGradient
-	IconPencil
-	IconBrush
-	IconEraser
-	IconText
-	IconEyedropper
-
-	// --- Status --- //
-
-	// dialogs
-	IconInformation
-	IconQuestion
-	IconWarning
-	IconError
-	IconCancel
-	IconOkay
-
-	// network
-	IconCellSignal0
-	IconCellSignal1
-	IconCellSignal2
-	IconCellSignal3
-	IconWirelessSignal0
-	IconWirelessSignal1
-	IconWirelessSignal2
-	IconWirelessSignal3
-
-	// power
-	IconBattery0
-	IconBattery1
-	IconBattery2
-	IconBattery3
-	IconBrightness0
-	IconBrightness1
-	IconBrightness2
-	IconBrightness3
-
-	// media
-	IconVolume0
-	IconVolume1
-	IconVolume2
-	IconVolume3
-)
-
-// Texture returns a texture of the corresponding icon ID.
-func (id Icon) Texture (size IconSize) canvas.Texture {
-	if current == nil { return nil }
-	return current.Icon(id, size)
-}
-
-// MimeIcon returns an icon corresponding to a MIME type.
-func MimeIcon (mime data.Mime, size IconSize) canvas.Texture {
-	if current == nil { return nil }
-	return current.MimeIcon(mime, size)
-}
-
-// ApplicationIcon describes the icon of the application.
-type ApplicationIcon struct {
-	// The name or ID of the application. If applicable, this should
-	// correspond to the file name (without the path or extension) of the
-	// icon on the system. This field is optional.
-	Name string
-
-	// Role describes what the application does. If a specific icon file
-	// cannot be found, a generic one is picked using this field.
-	Role ApplicationRole
-}
-
-// Texture returns a texture of the corresponding icon ID.
-func (icon ApplicationIcon) Texture (size IconSize) canvas.Texture {
-	if current == nil { return nil }
-	return current.ApplicationIcon(icon, size)
-}
-
-// ApplicationRole describes what an application does.
-type ApplicationRole int; const (
-	RoleUnknown ApplicationRole = iota
-
-	RoleWebBrowser
-	RoleMesssanger
-	RolePhone
-	RoleMail
-
-	RoleTerminalEmulator
-	RoleFileBrowser
-	RoleTextEditor
-
-	RoleDocumentViewer
-	RoleWordProcessor
-	RoleSpreadsheet
-	RoleSlideshow
-	RoleCalculator
-
-	RolePreferences
-	RoleProcessManager
-	RoleSystemInformation
-	RoleManual
-
-	RoleCamera
-	RoleImageViewer
-	RoleMediaPlayer
-	RoleImageEditor
-	RoleAudioEditor
-	RoleVideoEditor
-
-	RoleClock
-	RoleCalendar
-	RoleChecklist
-)

theme/theme.go

@@ -1,88 +0,0 @@
-package theme
-
-import "git.tebibyte.media/tomo/tomo"
-import "git.tebibyte.media/tomo/tomo/data"
-import "git.tebibyte.media/tomo/tomo/event"
-import "git.tebibyte.media/tomo/tomo/canvas"
-
-// Role describes the role of an object.
-type Role struct {
-	// Package is an optional namespace field. If specified, it should be
-	// the package name or module name the object is from.
-	Package string
-
-	// Object specifies what type of object it is. For example:
-	//   - TextInput
-	//   - Table
-	//   - Label
-	//   - Dial
-	// This should correspond directly to the type name of the object.
-	Object string
-
-	// Variant is an optional field to be used when an object has one or
-	// more soft variants under one type. For example, an object "Slider"
-	// may have variations "horizontal" and "vertical".
-	Variant string
-}
-
-// R is shorthand for creating a Role structure.
-func R (pack, object, variant string) Role {
-	return Role { Package: pack, Object: object, Variant: variant }
-}
-
-// Color represents a color ID.
-type Color int; const (
-	ColorBackground Color = iota
-	ColorForeground
-	ColorRaised
-	ColorSunken
-	ColorAccent
-)
-
-// RGBA satisfies the color.Color interface.
-func (id Color) RGBA () (r, g, b, a uint32) {
-	if current == nil { return }
-	return current.RGBA(id)
-}
-
-// Theme is an object that can apply a visual style to different objects.
-type Theme interface {
-	// Apply applies the theme to the given object, according to the given
-	// role. This may register event listeners with the given object;
-	// closing the returned cookie will remove them.
-	Apply (tomo.Object, Role) event.Cookie
-
-	// RGBA returns the RGBA values of the corresponding color ID.
-	RGBA (Color) (r, g, b, a uint32)
-
-	// Icon returns a texture of the corresponding icon ID. This texture
-	// should be protected, unless a new copy of it is returned with each
-	// subsequent call.
-	Icon (Icon, IconSize) canvas.Texture
-
-	// MimeIcon returns an icon corresponding to a MIME type. This texture
-	// should be protected, unless a new copy of it is returned with each
-	// subsequent call.
-	MimeIcon (data.Mime, IconSize) canvas.Texture
-
-	// ApplicationIcon returns an icon corresponding to an application. This
-	// texture should be protected, unless a new copy of it is returned with
-	// each subsequent call.
-	ApplicationIcon (ApplicationIcon, IconSize) canvas.Texture
-}
-
-var current Theme
-
-// SetTheme sets the theme.
-func SetTheme (theme Theme) {
-	current = theme
-}
-
-// Apply applies the current theme to the given object, according to the given
-// role. This may register event listeners with the given object; closing the
-// returned cookie will remove them.
-func Apply (object tomo.Object, role Role) event.Cookie {
-	if current == nil { return event.NoCookie { } }
-	return current.Apply(object, role)
-}
-

tomo.go

@@ -12,13 +12,11 @@ var backend Backend
 // event loop in that order. This function blocks until Stop is called, or the
 // backend experiences a fatal error.
 func Run (callback func ()) error {
-	loadPlugins()
-
 	if backend != nil {
 		return errors.New("there is already a backend running")
 	}
 
-	back, err := Initialize()
+	back, err := initialize()
 	if err != nil { return err }
 	
 	backendLock.Lock()
@@ -26,6 +24,8 @@ func Run (callback func ()) error {
 	backendLock.Unlock()
 
 	callback()
+	// callback may have called tomo.Stop
+	if backend == nil { return nil }
 	return backend.Run()
 }
 
@@ -52,11 +52,19 @@ func Do (callback func ()) {
 }
 
 // NewWindow creates and returns a window within the specified bounds on screen.
-func NewWindow (bounds image.Rectangle) (MainWindow, error) {
+func NewWindow (bounds image.Rectangle) (Window, error) {
 	assertBackend()
 	return backend.NewWindow(bounds)
 }
 
+// NewPlainWindow is like NewWindow, but it creates an undecorated window that
+// does not appear in window lists. It is intended for creating things like
+// docks, panels, etc.
+func NewPlainWindow (bounds image.Rectangle) (Window, error) {
+	assertBackend()
+	return backend.NewPlainWindow(bounds)
+}
+
 // NewBox creates and returns a basic Box.
 func NewBox () Box {
 	assertBackend()
@@ -83,7 +91,14 @@ func NewContainerBox () ContainerBox {
 
 // NewTexture creates a new texture from an image. When no longer in use, it
 // must be freed using Close().
-func NewTexture (source image.Image) canvas.Texture {
+func NewTexture (source image.Image) canvas.TextureCloser {
 	assertBackend()
 	return backend.NewTexture(source)
 }
+
+// NewCanvas creates a new canvas with the specified bounds. When no longer in
+// use, it must be freed using Close().
+func NewCanvas (bounds image.Rectangle) canvas.CanvasCloser {
+	assertBackend()
+	return backend.NewCanvas(bounds)
+}

unit.go

@@ -0,0 +1,105 @@
+package tomo
+
+import "image"
+import "image/color"
+
+// Side represents one side of a rectangle.
+type Side int; const (
+	SideTop Side = iota
+	SideRight
+	SideBottom
+	SideLeft
+)
+
+// Inset represents a rectangle inset that can have a different value for each
+// side.
+type Inset [4]int
+
+// I allows you to create an inset in a CSS-ish way:
+//
+//   - One argument: all sides are set to this value
+//   - Two arguments: the top and bottom sides are set to the first value, and
+//     the left and right sides are set to the second value.
+//   - Three arguments: the top side is set by the first value, the left and
+//     right sides are set by the second vaue, and the bottom side is set by the
+//     third value.
+//   - Four arguments: each value corresponds to a side.
+//
+// This function will panic if an argument count that isn't one of these is
+// given.
+func I (sides ...int) Inset {
+	switch len(sides) {
+	case 1: return Inset { sides[0], sides[0], sides[0], sides[0] }
+	case 2: return Inset { sides[0], sides[1], sides[0], sides[1] }
+	case 3: return Inset { sides[0], sides[1], sides[2], sides[1] }
+	case 4: return Inset { sides[0], sides[1], sides[2], sides[3] }
+	default: panic("I: illegal argument count.")
+	}
+}
+
+// Apply returns the given rectangle, shrunk on all four sides by the given
+// inset. If a measurment of the inset is negative, that side will instead be
+// expanded outward. If the rectangle's dimensions cannot be reduced any
+// further, an empty rectangle near its center will be returned.
+func (inset Inset) Apply (bigger image.Rectangle) (smaller image.Rectangle) {
+	smaller = bigger
+	if smaller.Dx() < inset[3] + inset[1] {
+		smaller.Min.X = (smaller.Min.X + smaller.Max.X) / 2
+		smaller.Max.X = smaller.Min.X
+	} else {
+		smaller.Min.X += inset[3]
+		smaller.Max.X -= inset[1]
+	}
+
+	if smaller.Dy() < inset[0] + inset[2] {
+		smaller.Min.Y = (smaller.Min.Y + smaller.Max.Y) / 2
+		smaller.Max.Y = smaller.Min.Y
+	} else {
+		smaller.Min.Y += inset[0]
+		smaller.Max.Y -= inset[2]
+	}
+	return
+}
+
+// Inverse returns a negated version of the inset.
+func (inset Inset) Inverse () (prime Inset) {
+	return Inset {
+		inset[0] * -1,
+		inset[1] * -1,
+		inset[2] * -1,
+		inset[3] * -1,
+	}
+}
+
+// Horizontal returns the sum of SideRight and SideLeft.
+func (inset Inset) Horizontal () int {
+	return inset[SideRight] + inset[SideLeft]
+}
+
+// Vertical returns the sum of SideTop and SideBottom.
+func (inset Inset) Vertical () int {
+	return inset[SideTop] + inset[SideBottom]
+}
+
+// Border represents a single border of a box.
+type Border struct {
+	Width Inset
+	Color [4]color.Color
+}
+
+// Align lists basic alignment types.
+type Align int; const (
+	AlignStart Align = iota // similar to left-aligned text
+	AlignMiddle             // similar to center-aligned text
+	AlignEnd                // similar to right-aligned text
+	AlignEven               // similar to justified text
+)
+
+// TextureMode lists texture rendering modes.
+type TextureMode int; const (
+	TextureModeTile TextureMode = iota
+	TextureModeCenter
+
+	// TODO more modes: fit, fill, and stretch
+	// Of course canvas will need to have a concept of this.
+)

unix.go

@@ -1,22 +0,0 @@
-//go:build linux || darwin || freebsd
-
-package tomo
-
-import "os"
-import "strings"
-import "path/filepath"
-
-func init () {
-	pathVariable := os.Getenv("TOMO_PLUGIN_PATH")
-	pluginPaths = strings.Split(pathVariable, ":")
-	pluginPaths = append (
-		pluginPaths,
-		"/usr/lib/tomo/plugins",
-		"/usr/local/lib/tomo/plugins")
-	homeDir, err := os.UserHomeDir()
-	if err == nil {
-		pluginPaths = append (
-			pluginPaths,
-			filepath.Join(homeDir, ".local/lib/tomo/plugins"))
-	}
-}