More doc comment improvements

Or-ing together constants is cleaner than a struct literal with
booleans

attribute.go

@@ -2,143 +2,128 @@ 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 AttrNumber of each attribute and must not be
-// modified directly.
-type AttrSet map[int] Attr
-
-// AS builds an AttrSet out of a vararg list of Attr values.
-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.attr()] = 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.attr()]; !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.
+// Attr modifies one thing about a Box's style.
 type Attr interface {
-	// Equals returns true if both attributes can reasonably be declared
-	// equal.
+	// Equals returns true if both Attrs can reasonably be declared equal.
 	Equals (Attr) bool
-	attr () int
+	Kind   () AttrKind
+	attr   ()
 }
 
-// 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 }
+// AttrKind enumerates all attribute kinds. Each Attr- type has one of these.
+type AttrKind int; const (
+	AttrKindColor AttrKind = iota
+	AttrKindTexture
+	AttrKindTextureMode
+	AttrKindBorder
+	AttrKindMinimumSize
+	AttrKindPadding
+	AttrKindGap
+	AttrKindTextColor
+	AttrKindDotColor
+	AttrKindFace
+	AttrKindWrap
+	AttrKindAlign
+	AttrKindOverflow
+	AttrKindLayout
+	AttrKindCursor
+)
 
-// AColor is a convenience constructor for the color attribute.
+// AttrColor sets the background color of a Box.
+type AttrColor struct { color.Color }
+// AttrTexture sets the texture of a Box.
+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 type face, if the Box is a TextBox.
+type AttrFace Face
+// AttrWrap sets whether or not the text wraps, if the Box is a TextBox.
+type AttrWrap bool
+// AttrAlign sets the layout 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 }
+// AttrCursor sets the mouse cursor shape.
+type AttrCursor Cursor
+
+// AColor is a convenience constructor for AttrColor.
 func AColor (col color.Color) AttrColor {
 	return AttrColor { Color: col }
 }
-// ATexture is a convenience constructor for the texture attribute.
+// ATexture is a convenience constructor for AttrTexture.
 func ATexture (texture canvas.Texture) AttrTexture {
 	return AttrTexture { Texture: texture }
 }
-// ATextureMode is a convenience constructor for the texture mode attribute.
+// ATextureMode is a convenience constructor for AttrTextureMode.
 func ATextureMode (mode TextureMode) AttrTextureMode {
 	return AttrTextureMode(mode)
 }
-// ABorder is a convenience constructor for the border attribute.
+// ABorder is a convenience constructor for AttrBorder.
 func ABorder (borders ...Border) AttrBorder {
 	return AttrBorder(borders)
 }
-// AMinimumSize is a convenience constructor for the minimum size attribute.
+// AMinimumSize is a convenience constructor for AttrMinimumSize.
 func AMinimumSize (x, y int) AttrMinimumSize {
 	return AttrMinimumSize(image.Pt(x, y))
 }
-// APadding is a convenience constructor for the padding attribute.
+// APadding is a convenience constructor for AttrPadding.
 func APadding (sides ...int) AttrPadding {
 	return AttrPadding(I(sides...))
 }
-// AGap is a convenience constructor for the gap attribute.
+// AGap is a convenience constructor for AttrGap.
 func AGap (x, y int) AttrGap {
 	return AttrGap(image.Pt(x, y))
 }
-// ATextColor is a convenience constructor for the text color attribute.
+// ATextColor is a convenience constructor for AttrTextColor.
 func ATextColor (col color.Color) AttrTextColor {
 	return AttrTextColor { Color: col }
 }
-// ADotColor is a convenience constructor for the dot color attribute.
+// ADotColor is a convenience constructor for AttrDotColor.
 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 }
+// AFace is a convenience constructor for AttrFace.
+func AFace (face Face) AttrFace {
+	return AttrFace(face)
 }
-// AWrap is a convenience constructor for the wrap attribute.
+// AWrap is a convenience constructor for AttrWrap.
 func AWrap (wrap bool) AttrWrap {
 	return AttrWrap(wrap)
 }
-// AAlign is a convenience constructor for the align attribute.
+// AAlign is a convenience constructor for AttrAlign.
 func AAlign (x, y Align) AttrAlign {
 	return AttrAlign { X: x, Y: y }
 }
-// AOverflow is a convenience constructor for the overflow attribute.
+// AOverflow is a convenience constructor for AttrOverflow.
 func AOverflow (x, y bool) AttrOverflow {
 	return AttrOverflow { X: x, Y: y }
 }
-// ALayout is a convenience constructor for the overflow attribute.
+// ALayout is a convenience constructor for AttrLayout.
 func ALayout (layout Layout) AttrLayout {
 	return AttrLayout { Layout: layout }
 }
+// ACursor is a convenience constructor for AttrCursor.
+func ACursor (cursor Cursor) AttrCursor {
+	return AttrCursor(cursor)
+}
 
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrColor) Equals (other Attr) bool {
 	if other, ok := other.(AttrColor); ok {
 		return this == other
@@ -146,7 +131,7 @@ func (this AttrColor) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrTexture) Equals (other Attr) bool {
 	if other, ok := other.(AttrTexture); ok {
 		return this == other
@@ -154,7 +139,7 @@ func (this AttrTexture) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrTextureMode) Equals (other Attr) bool {
 	if other, ok := other.(AttrTextureMode); ok {
 		return this == other
@@ -162,7 +147,7 @@ func (this AttrTextureMode) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs 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 }
@@ -176,7 +161,7 @@ func (this AttrBorder) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrMinimumSize) Equals (other Attr) bool {
 	if other, ok := other.(AttrMinimumSize); ok {
 		return this == other
@@ -184,7 +169,7 @@ func (this AttrMinimumSize) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrPadding) Equals (other Attr) bool {
 	if other, ok := other.(AttrPadding); ok {
 		return this == other
@@ -192,7 +177,7 @@ func (this AttrPadding) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrGap) Equals (other Attr) bool {
 	if other, ok := other.(AttrGap); ok {
 		return this == other
@@ -200,7 +185,7 @@ func (this AttrGap) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrTextColor) Equals (other Attr) bool {
 	if other, ok := other.(AttrTextColor); ok {
 		return this == other
@@ -208,7 +193,7 @@ func (this AttrTextColor) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrDotColor) Equals (other Attr) bool {
 	if other, ok := other.(AttrDotColor); ok {
 		return this == other
@@ -216,7 +201,7 @@ func (this AttrDotColor) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrFace) Equals (other Attr) bool {
 	if other, ok := other.(AttrFace); ok {
 		return this == other
@@ -224,7 +209,7 @@ func (this AttrFace) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrWrap) Equals (other Attr) bool {
 	if other, ok := other.(AttrWrap); ok {
 		return this == other
@@ -232,7 +217,7 @@ func (this AttrWrap) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrAlign) Equals (other Attr) bool {
 	if other, ok := other.(AttrAlign); ok {
 		return this == other
@@ -240,7 +225,7 @@ func (this AttrAlign) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrOverflow) Equals (other Attr) bool {
 	if other, ok := other.(AttrOverflow); ok {
 		return this == other
@@ -248,33 +233,50 @@ func (this AttrOverflow) Equals (other Attr) bool {
 		return false
 	}
 }
-// Equals returns true if both attributes can reasonably be declared equal.
+// Equals returns true if both Attrs can reasonably be declared equal.
 func (this AttrLayout) Equals (other Attr) bool {
-	if other, ok := other.(AttrLayout); ok {
+	// 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
+}
+// Equals returns true if both Attrs can reasonably be declared equal.
+func (this AttrCursor) Equals (other Attr) bool {
+	if other, ok := other.(AttrCursor); ok {
 		return this == other
 	} else {
 		return false
 	}
 }
 
-// AttrNumber returns the number of an attribute. Each attribute type has a
-// unique number. The exact values of these numbers are not part of the API and
-// may change.
-func AttrNumber (attr Attr) int {
-	return attr.attr()
-}
+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 (AttrCursor)      Kind () AttrKind { return AttrKindCursor }
 
-func (AttrColor)       attr () int { return  0 }
-func (AttrTexture)     attr () int { return  1 }
-func (AttrTextureMode) attr () int { return  2 }
-func (AttrBorder)      attr () int { return  3 }
-func (AttrMinimumSize) attr () int { return  4 }
-func (AttrPadding)     attr () int { return  5 }
-func (AttrGap)         attr () int { return  6 }
-func (AttrTextColor)   attr () int { return  7 }
-func (AttrDotColor)    attr () int { return  8 }
-func (AttrFace)        attr () int { return  9 }
-func (AttrWrap)        attr () int { return 10 }
-func (AttrAlign)       attr () int { return 11 }
-func (AttrOverflow)    attr () int { return 12 }
-func (AttrLayout)      attr () int { return 13 }
+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 () { }
+func (AttrCursor)      attr () { }

backend.go

@@ -1,15 +1,15 @@
 package tomo
 
-import "sort"
+import "sync"
 import "image"
-import "errors"
+import "git.tebibyte.media/tomo/tomo/data"
 import "git.tebibyte.media/tomo/tomo/canvas"
 
 // Backend is any Tomo implementation. Backends handle window creation, layout,
 // rendering, and events so that there can be as many platform-specific
 // optimizations as possible.
 type Backend interface {
-	// These methods create new objects. The backend must reject any object
+	// These methods create new Objects. The backend must reject any Object
 	// that was not made by it.
 	NewBox          () Box
 	NewTextBox      () TextBox
@@ -18,37 +18,40 @@ type Backend interface {
 	NewContainerBox () ContainerBox
 
 	// NewWindow creates a normal Window and returns it.
-	NewWindow (image.Rectangle) (Window, error)
+	NewWindow (WindowKind, 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 creates a new canvs.Texture from an image. The backend
+	// must reject any texture that was not made by it.
 	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 creates a new canvas.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)
+	// ColorRGBA returns the RGBA of a color according to the current style,
+	// as specified in color.Color.RGBA. It may be rendered invalid if the
+	// visual style changes, but the Backend must send a StyleChange event
+	// to all managed boxes when this happens.
+	ColorRGBA (id Color) (r, g, b, a uint32)
 
-	// 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)
+	// IconTexture returns the canvas.Texture of an Icon. It may be closed
+	// and therefore rendered invalid if the icon set changes, but the
+	// Backend must send an IconSetChange event to all managed boxes when
+	// this happens.
+	IconTexture (Icon, IconSize) canvas.Texture
 
-	// Run runs the event loop until Stop() is called, or the backend
+	// MimeIconTexture returns the canvas.Texture of an icon corresponding
+	// to the specified MIME type. It may be closed and therefore rendered
+	// invalid if the icon set changes, but the Backend must send an
+	// IconSetChange event to all managed boxes when this happens.
+	MimeIconTexture (data.Mime, IconSize) canvas.Texture
+
+	// Run runs the event loop until Stop is called, or the Backend
 	// experiences a fatal error.
 	Run () error
 	
-	// Stop must unblock run.
+	// Stop must unblock Run. This behavior may only be called from within
+	// tomo.Stop.
 	Stop ()
 
 	// Do performs a callback function in the event loop thread as soon as
@@ -56,54 +59,21 @@ type Backend interface {
 	Do (func ())
 }
 
-// Factory is a function that attempts to instatiate a backend. If the
-// instantiation process fails at any point, it must clean up all resources and
-// return nil and an error explaining what happened.
-type Factory func () (Backend, error)
+var backendLock sync.Mutex
+var backend Backend
 
-var registered []factoryEntry
-type factoryEntry struct {
-	Factory
-	priority int
+func assertBackend () {
+	if backend == nil { panic("nil backend") }
 }
 
-// Register registers a backend factory with the given priority number.
-func Register (priority int, factory Factory) {
-	registered = append(registered, factoryEntry {
-		priority: priority,
-		Factory:  factory,
-	})
-}
+// SetBackend sets the Backend that functions in this package will call upon.
+// This function will panic if there is already a Backend running.
+func SetBackend (back Backend) {
+	backendLock.Lock()
+	defer backendLock.Unlock()
 
-// 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) {
-	backend, err := instantiate()
-	if err != nil { return nil, err }
-	return backend, err
-}
-
-func instantiate () (Backend, error) {
-	if len(registered) < 0 {
-		return nil, errors.New("no available backends")
+	if backend != nil {
+		panic("SetBackend called while another backend was running")
 	}
-
-	// sort backends by priority
-	sort.Slice(registered, func (left, right int) bool {
-		return registered[left].priority < registered[right].priority
-	})
-
-	// attempt to instantiate
-	errorLog := ""
-	for _, factory := range registered {
-		backend, err := factory.Factory()
-		if err == nil {
-			return backend, nil
-		} else {
-			errorLog += "  " + err.Error() + "\n"
-		}
-	}
-	return nil, errors.New("all backends failed:\n" + errorLog)
+	backend = back
 }

canvas/canvas.go

@@ -33,7 +33,7 @@ type StrokeAlign int; const (
 // have multiple pens associated with it, each maintaining their own drawing
 // state.
 type Pen interface {
-	// Rectangle draws a rectangle.
+	// Rectangle draws an image.Rectangle.
 	Rectangle (image.Rectangle)
 
 	// Path draws a path, which is a series of connected points.
@@ -69,7 +69,7 @@ type Pen interface {
 type Canvas interface {
 	draw.Image
 
-	// Pen returns a new pen for this canvas.
+	// Pen returns a new pen for this Canvas.
 	Pen () Pen
 
 	// SubCanvas returns a returns a Canvas representing the portion of this
@@ -87,11 +87,11 @@ type CanvasCloser interface {
 
 // Drawer can draw to a canvas.
 type Drawer interface {
-	// Draw draws to the given canvas.
+	// Draw draws to the given Canvas.
 	Draw (Canvas)
 }
 
-// PushCanvas is a canvas that can push a region of itself to the screen (or
+// PushCanvas is a Canvas that can push a region of itself to the screen (or
 // some other destination).
 type PushCanvas interface {
 	Canvas

canvas/shatter.go

@@ -2,7 +2,10 @@ package canvas
 
 import "image"
 
-// Shatter takes in a bounding rectangle, and several rectangles to be
+// TODO look into other options besides returning a slice, as that causes memory
+// allocations.
+
+// Shatter takes in a bounding rectangle, and several image.Rectangles to be
 // subtracted from it. It returns a slice of rectangles that tile together to
 // make up the difference between them. This is intended to be used for figuring
 // out which areas of a container box's background are covered by other boxes so

canvas/texture.go

@@ -3,7 +3,7 @@ package canvas
 import "io"
 import "image"
 
-// Texture is a handle that points to a 2D raster image managed by the backend.
+// Texture is a handle that points to a 2D raster image.
 type Texture interface {
 	image.Image
 
@@ -13,7 +13,7 @@ type Texture interface {
 	SubTexture (image.Rectangle) Texture
 }
 
-// TextureCloser is a texture that can be closed. Anything that receives a
+// TextureCloser is a Texture that can be closed. Anything that receives a
 // TextureCloser must close it after use.
 type TextureCloser interface {
 	Texture

config/config.go

@@ -0,0 +1,44 @@
+// Package config stores common configuration parameters. They are unmanaged,
+// and do not broadcast events when changed. Thus, they must be queried each
+// time they are used, whether that be by backends, applications, or objects.
+// They are intended to be set by things like application frameworks. Values set
+// by other things are subject to being overridden.
+package config
+
+import "time"
+import "git.tebibyte.media/tomo/tomo/input"
+
+// DoubleClickDelay is the maximum amount of time that can pass between two
+// consecutive clicks for them to be considered a double-click.
+var DoubleClickDelay time.Duration = time.Second
+
+// ScrollSpeed is how many units (pixels at a scale of 1.0) the content of a
+// ContentBox should be moved in response to a scroll delta of 1.0.
+var ScrollSpeed int = 16
+
+// KeyChordConfirm is used to activate focused objects, and commonly to signal
+// to the application that the user wishes to submit a value they have entered
+// using the keyboard into an input field.
+var KeyChordConfirm = input.KC(input.KeyEnter, input.ModNone)
+
+// KeyChordClose is used to break out of some mode or state, such as a modal
+// dialog.
+var KeyChordClose = input.KC(input.KeyEscape, input.ModNone)
+
+// KeyChordFocusNext is used to advance the input focus to the next focusable
+// object.
+var KeyChordFocusNext = input.KC(input.KeyTab, input.ModNone)
+
+// KeyChordFocusPrevious is used to advance the input focus to the previous
+// focusable object.
+var KeyChordFocusPrevious = input.KC(input.KeyTab, input.ModShift)
+
+// ButtonChordInteract is used to select, activate, and drag objects.
+var ButtonChordInteract = input.BC(input.ButtonLeft, input.ModNone)
+
+// ButtonChordContextMenu is used to open a context menu on an object.
+var ButtonChordContextMenu = input.BC(input.ButtonRight, input.ModNone)
+
+// ButtonChordPan is used to move the content of a content object relative to
+// its inner bounds.
+var ButtonChordPan = input.BC(input.ButtonMiddle, input.ModNone)

cursor.go

@@ -0,0 +1,35 @@
+package tomo
+
+// Cursor represents a mouse cursor shape.
+type Cursor string
+
+// A list of standard cursor shapes. This is based off of the XDG Cursor
+// Conventions Specification
+// (https://www.freedesktop.org/wiki/Specifications/cursor-spec/).
+const (
+	CursorUnknown      Cursor = ""
+	CursorDefault      Cursor = "Default"
+	CursorText         Cursor = "Text"
+	CursorPointer      Cursor = "Pointer"
+	CursorHelp         Cursor = "Help"
+	CursorProgress     Cursor = "Progress"
+	CursorWait         Cursor = "Wait"
+	CursorCopy         Cursor = "Copy"
+	CursorAlias        Cursor = "Alias"
+	CursorNoDrop       Cursor = "NoDrop"
+	CursorNotAllowed   Cursor = "NotAllowed"
+	CursorAllScroll    Cursor = "AllScroll"
+	CursorRowResize    Cursor = "RowResize"
+	CursorColResize    Cursor = "ColResize"
+	CursorEResize      Cursor = "EResize"
+	CursorNEResize     Cursor = "NEResize"
+	CursorNWResize     Cursor = "NWResize"
+	CursorNResize      Cursor = "NResize"
+	CursorSEResize     Cursor = "SEResize"
+	CursorSWResize     Cursor = "SWResize"
+	CursorSResize      Cursor = "SResize"
+	CursorWResize      Cursor = "WResize"
+	CursorVerticalText Cursor = "VerticalText"
+	CursorCrosshair    Cursor = "Crosshair"
+	CursorCell         Cursor = "Cell"
+)

event/event.go

@@ -2,11 +2,36 @@
 // handlers.
 package event
 
-// A cookie is returned when you add an event handler so you can remove it
-// later if you so choose.
-type Cookie interface {
-	// Close removes the event handler this cookie is for.
-	Close ()
+import "io"
+import "errors"
+
+// Cookie is returned when you add an event handler so you can remove it later
+// if you so choose. When the Close behavior is called, the handler must be
+// removed, even if an error is returned.
+type Cookie io.Closer
+
+// FuncCookie is a cookie that calls a function (itself) when closed.
+type FuncCookie func () error
+func (cookie FuncCookie) Close () error { return cookie () }
+
+// NoCookie is a cookie that does nothing when closed.
+type NoCookie struct { }
+func (NoCookie) Close () error { return nil }
+
+type multiCookie []Cookie
+
+// MultiCookie creates a single cookie that, when closed, closes a list of other
+// cookies.
+func MultiCookie (cookies ...Cookie) Cookie {
+	return multiCookie(cookies)
+}
+
+func (cookies multiCookie) Close () error {
+	errs := make([]error, len(cookies))
+	for index, cookie := range cookies {
+		errs[index] = cookie.Close()
+	}
+	return errors.Join(errs...)
 }
 
 // Broadcaster manages event listeners.
@@ -16,7 +41,7 @@ type Broadcaster[L any] struct {
 }
 
 // Connect adds a new listener to the broadcaster and returns a corresponding
-// cookie.
+// Cookie.
 func (broadcaster *Broadcaster[L]) Connect (listener L) Cookie {
 	broadcaster.ensure()
 	
@@ -31,9 +56,9 @@ func (broadcaster *Broadcaster[L]) Listeners () map[int] L {
 	return broadcaster.listeners
 }
 
-func (broadcaster *Broadcaster[L]) newCookie () cookie[L] {
+func (broadcaster *Broadcaster[L]) newCookie () broadcasterCookie[L] {
 	broadcaster.lastID ++
-	return cookie[L] {
+	return broadcasterCookie[L] {
 		id:          broadcaster.lastID,
 		broadcaster: broadcaster,
 	}
@@ -45,20 +70,17 @@ func (broadcaster *Broadcaster[L]) ensure () {
 	}
 }
 
-// NoCookie is a cookie that does nothing when closed.
-type NoCookie struct { }
-func (NoCookie) Close () { }
-
-type cookie[L any] struct {
+type broadcasterCookie[L any] struct {
 	id int
 	broadcaster *Broadcaster[L]
 }
 
-func (cookie cookie[L]) Close () {
+func (cookie broadcasterCookie[L]) Close () error {
 	delete(cookie.broadcaster.listeners, cookie.id)
+	return nil
 }
 
-// FuncBroadcaster is a broadcaster that manages functions with no arguments.
+// FuncBroadcaster is a Broadcaster that manages functions with no arguments.
 type FuncBroadcaster struct {
 	Broadcaster[func ()]
 }
@@ -69,17 +91,3 @@ func (broadcaster *FuncBroadcaster) Broadcast () {
 		listener()
 	}
 }
-
-type multiCookie []Cookie
-
-// MultiCookie creates a single cookie that, when closed, closes a list of other
-// cookies.
-func MultiCookie (cookies ...Cookie) Cookie {
-	return multiCookie(cookies)
-}
-
-func (cookies multiCookie) Close () {
-	for _, cookie := range cookies {
-		cookie.Close()
-	}
-}

go.mod

@@ -1,5 +1,3 @@
 module git.tebibyte.media/tomo/tomo
 
 go 1.20
-
-require golang.org/x/image v0.11.0

go.sum

@@ -1,33 +0,0 @@
-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 v0.11.0 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=
-golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
-golang.org/x/net v0.6.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
-golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
-golang.org/x/term v0.5.0/go.mod h1:jMB1sMXY+tzblOD4FWmEbocvup2/aLOaQEp7JmGp78k=
-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 v0.12.0/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=
-golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
-golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

icon.go

@@ -1,21 +1,32 @@
 package tomo
 
+import "fmt"
 import "git.tebibyte.media/tomo/tomo/data"
 import "git.tebibyte.media/tomo/tomo/canvas"
 
-// IconSize represents the size of an icon.
+// IconSize represents the size of an Icon.
 type IconSize int; const (
 	IconSizeSmall IconSize = iota;
 	IconSizeMedium
 	IconSizeLarge
 )
 
+func (size IconSize) String () string {
+	switch size {
+	case IconSizeSmall:  return "IconSizeSmall"
+	case IconSizeMedium: return "IconSizeMedium"
+	case IconSizeLarge:  return "IconSizeLarge"
+	default:             return fmt.Sprintf("IconSize(%d)", size)
+	}
+}
+
 // 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 should be a blank space the size of a regular Icon.
 	IconUnknown                      Icon = ""
 
 	// actions
@@ -90,6 +101,9 @@ const (
 	// actions: list
 	IconListAdd                      Icon = "ListAdd"
 	IconListRemove                   Icon = "ListRemove"
+	IconListChoose                   Icon = "ListChoose"
+	IconListExpand                   Icon = "ListExpand"
+	IconListContract                 Icon = "ListContract"
 	// actions: mail
 	IconMailForward                  Icon = "MailForward"
 	IconMailMarkImportant            Icon = "MailMarkImportant"
@@ -275,9 +289,6 @@ const (
 	IconPlaceHistory                 Icon = "PlaceHistory"
 	IconPlacePreferences             Icon = "PlacePreferences"
 
-	// status: checkbox
-	IconCheckboxChecked              Icon = "CheckboxChecked"
-	IconCheckboxUnchecked            Icon = "CheckboxUnchecked"
 	// status: appointments
 	IconAppointmentMissed            Icon = "AppointmentMissed"
 	IconAppointmentSoon              Icon = "AppointmentSoon"
@@ -370,46 +381,20 @@ const (
 	IconWeatherStorm                 Icon = "WeatherStorm"
 )
 
-// Texture returns a texture of the corresponding icon ID.
+// Texture returns a canvas.Texture of the corresponding icon ID. It may be
+// closed and therefore rendered invalid if the icon set changes, so it is
+// necessary to subscribe to the IconSetChange event in order to get a new icon
+// texture when this happens.
 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)
+	return backend.IconTexture(id, size)
+}
+
+// MimeIconTexture returns a canvas.Texture of the icon corresponding to a MIME
+// type. It may be closed and therefore rendered invalid if the icon set
+// changes, so it is necessary to subscribe to the IconSetChange event in order
+// to get a new icon texture when this happens.
+func MimeIconTexture (mime data.Mime, size IconSize) canvas.Texture {
+	assertBackend()
+	return backend.MimeIconTexture(mime, size)
 }

input/input.go

@@ -107,11 +107,80 @@ func (key Key) Printable () (printable bool) {
 // Modifiers lists what modifier keys are being pressed. These should be used
 // instead of attempting to track the state of the modifier keys, because there
 // is no guarantee that one press event will be coupled with one release event.
-type Modifiers struct {
-	Shift   bool
-	Control bool
-	Alt     bool
-	Meta    bool
-	Super   bool
-	Hyper   bool
+type Modifiers uint; const (
+	ModNone    Modifiers = 0
+	ModShift   Modifiers = 1 << iota
+	ModControl
+	ModAlt
+	ModMeta
+	ModSuper
+	ModHyper
+)
+
+// Shift returns whether the list of modifiers includes the shift key.
+func (modifiers Modifiers) Shift () bool {
+	return modifiers & ModShift != ModNone
+}
+
+// Control returns whether the list of modifiers includes the control key.
+func (modifiers Modifiers) Control () bool {
+	return modifiers & ModControl != ModNone
+}
+
+// Alt returns whether the list of modifiers includes the alt key.
+func (modifiers Modifiers) Alt () bool {
+	return modifiers & ModAlt != ModNone
+}
+
+// Meta returns whether the list of modifiers includes the meta key.
+func (modifiers Modifiers) Meta () bool {
+	return modifiers & ModAlt != ModNone
+}
+
+// Super returns whether the list of modifiers includes the super key.
+func (modifiers Modifiers) Super () bool {
+	return modifiers & ModSuper != ModNone
+}
+
+// Hyper returns whether the list of modifiers includes the hyper key.
+func (modifiers Modifiers) Hyper () bool {
+	return modifiers & ModHyper != ModNone
+}
+
+// KeyChord combines a keyboard key with Modifiers.
+type KeyChord struct {
+	Key       Key
+	Modifiers Modifiers
+}
+
+// KC is a convenience constructor for a KeyChord.
+func KC (key Key, modifiers Modifiers) KeyChord {
+	return KeyChord {
+		Key:       key,
+		Modifiers: modifiers,
+	}
+}
+
+// Pressed returns true if the given Key Modifiers match the KeyChord.
+func (chord KeyChord) Pressed (key Key, modifiers Modifiers) bool {
+	return chord == KC(key, modifiers)
+}
+
+// ButtonChord combines a mouse button with a number of modifiers.
+type ButtonChord struct {
+	Button    Button
+	Modifiers Modifiers
+}
+
+// BC is a convenience constructor for a ButtonChord.
+func BC (button Button, modifiers Modifiers) ButtonChord {
+	return ButtonChord {
+		Button:    button,
+		Modifiers: modifiers,
+	}
+}
+
+// Pressed returns true if the given Button and Modifiers match the ButtonChord.
+func (chord ButtonChord) Pressed (button Button, modifiers Modifiers) bool {
+	return chord == BC(button, modifiers)
 }

object.go

@@ -14,7 +14,7 @@ type Object interface {
 	GetBox () Box
 }
 
-// ContentObject is an object that has some kind of content.
+// ContentObject is an Object that contains some kind of content.
 type ContentObject interface {
 	Object
 
@@ -29,44 +29,49 @@ type ContentObject interface {
 	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.
+// Box is a basic box with no content. 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
-	// Bounds returns the outer bounding rectangle of the Box relative to
-	// the Window.
+	// Bounds returns the outer bounding image.Rectangle of the Box relative
+	// to the Window.
 	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 returns the inner bounding image.Rectangle of the box. It
+	// is the value of Bounds inset by the Box's border and padding.
 	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 sets what role this Box takes on. It is used by the Backend
+	// for applying styling.
 	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 returns whether or not a named tag exists. These are used by the
+	// Backend 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 config.ButtonChordInteract
 	Tag (string) bool
 	// SetTag adds or removes a named tag.
 	SetTag (string, bool)
 
-	// SetAttr overrides a style attribute.
-	SetAttr(Attr)
+	// 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)
-	// 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.
+	// SetDNDAccept sets the types of data which can be dropped onto this
+	// Box. If none are specified (which is the default), this Box will
+	// reject all drops.
 	SetDNDAccept (...data.Mime)
 	// SetFocused sets whether or not this Box has keyboard focus. If set to
 	// true, this method will steal focus away from whichever Object
@@ -79,7 +84,7 @@ type Box interface {
 	// 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.
+	// returned event.Cookie.
 	OnFocusEnter    (func ()         ) event.Cookie
 	OnFocusLeave    (func ()         ) event.Cookie
 	OnStyleChange   (func ()         ) event.Cookie
@@ -94,8 +99,13 @@ type Box interface {
 	// 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.
+	// the event.
+	// 
+	// Generally, if the event was successfully handled, the callbacks ought
+	// to return true. Additionally, when subscribing to an event that is
+	// often paired with a second one (for example, KeyDown and KeyUp), it
+	// is good practice to subscribe to both and return true/false under the
+	// same circumstances.
 	OnMouseMove     (func ()                              bool) event.Cookie
 	OnButtonDown    (func (button input.Button)           bool) event.Cookie
 	OnButtonUp      (func (button input.Button)           bool) event.Cookie
@@ -104,46 +114,50 @@ type Box interface {
 	OnKeyUp         (func (key input.Key, numberPad bool) bool) event.Cookie
 }
 
-// CanvasBox is a box that can be drawn to.
+// CanvasBox is a Box that can be drawn to.
 type CanvasBox interface {
 	Box
 
-	// SetDrawer sets the Drawer that will be called upon to draw the Box's
-	// 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 sets the canvas.Drawer that will be called upon to draw the
+	// Box's 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.
+	//   - Its Bounds will describe the portion of the CanvasBox visible on
+	//     screen. Therefore, it should not be used to determine the
+	//     position of anything drawn within it. The Bounds of the CanvasBox
+	//     should be used for this purpose.
 	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 causes the CanvasBox's area to be redrawn at the end of
+	// the event cycle, even if it wouldn't otherwise be. This will call the
+	// canvas.Drawer specified by SetDrawer.
 	Invalidate ()
 }
 
-// SurfaceBox is a box that can be drawn to via a hardware accelerated (or
+// SurfaceBox is a Box that can be drawn to via a hardware accelerated (or
 // platform-specific) graphics context.
 type SurfaceBox interface {
 	Box
 
 	// 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,
+	// 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.
+	// and Backend agree on it. Applications should fail gracefully if the
+	// expected type was not found. If the surface has been destroyed by the
+	// Backend, it will return nil.
 	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.
+	// screen at the end of the event cycle, even if it wouldn't otherwise
+	// be.
 	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.
+	// Box is changed, the surface is re-allocated, or the surface is
+	// destroyed. The application must call Surface() each time this event
+	// fires in order to not draw onto a closed surface.
 	OnSizeChange (func ())
 }
 
@@ -155,7 +169,7 @@ type ContentBox interface {
 	// 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.
+	// Box's InnerBounds, offset by the given image.Point.
 	ScrollTo (image.Point)
 	
 	// OnContentBoundsChange specifies a function to be called when the
@@ -187,8 +201,8 @@ type TextBox interface {
 type ContainerBox interface {
 	ContentBox
 
-	// Add appends a child Object. If the object is already a child of
-	// another object, it will be removed from that object first.
+	// 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)
@@ -215,7 +229,7 @@ type ContainerBox interface {
 	// types.
 }
 
-// LayoutHints are passed to a layout to tell it how to arrange child boxes.
+// LayoutHints are passed to a layout to tell it how to arrange child Boxes.
 type LayoutHints struct {
 	// Bounds is the bounding rectangle that children should be placed
 	// within. Any padding values are already applied.
@@ -238,7 +252,7 @@ type Layout interface {
 	// MinimumSize returns the minimum width and height of
 	// LayoutHints.Bounds needed to properly lay out all child Boxes.
 	MinimumSize (LayoutHints, BoxQuerier) image.Point
-	// Arrange arranges child boxes according to the given LayoutHints.
+	// Arrange arranges child Boxes according to the given LayoutHints.
 	Arrange (LayoutHints, BoxArranger)
 	// RecommendedHeight returns the recommended height for a given width,
 	// if supported. Otherwise, it should just return the minimum height.
@@ -254,18 +268,18 @@ type Layout interface {
 
 // BoxQuerier allows the attributes of a ContainerBox's children to be queried.
 type BoxQuerier interface {
-	// Len returns the amount of boxes.
+	// Len returns the amount of Boxes.
 	Len () int
-	// MinimumSize returns the minimum size of a box.
+	// 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
+	// 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
+	// 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.
 	RecommendedHeight (index int, width int) int
 }
@@ -275,39 +289,65 @@ type BoxQuerier interface {
 type BoxArranger interface {
 	BoxQuerier
 	
-	// SetBounds sets the bounds of a box.
+	// 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.
+// WindowKind specifies a Window's kind, which determines how it is displayed
+// and managed by the operating system.
+type WindowKind string; const (
+	// Normal is a normal Window.
+	WindowKindNormal WindowKind = "Normal"
+	// Plain is an undecorated Window that does not appear in window lists.
+	// It is intended for things like docks, panels, etc.
+	WindowKindPlain WindowKind = "Plain"
+	// Utility is a small Window for toolboxes, command palletes, etc. It is
+	// usually given special styling and management by the OS.
+	WindowKindUtility WindowKind = "Utility"
+	// Toolbar is a small Window for menus and panes which have been "torn
+	// off" from their main Window or position. It is usually given special
+	// styling and management by the OS.
+	WindowKindToolbar WindowKind = "Toolbar"
+	// Menu is an undecorated Window for drop down menus, context menus,
+	// etc. It closes once the user interacts outside of it.
+	WindowKindMenu WindowKind = "Menu"
+	// Modal, while open, blocks all user input from reaching its parent
+	// window, forcing the user's attention. It is usually given special
+	// styling and management by the OS. Note that in some environments it
+	// will not be given window controls, so it should contain some "Close"
+	// or "Cancel" button.
+	WindowKindModal WindowKind = "Modal"
+)
+
+// Window is an operating system Window. It can directly contain one object,
+// which is usually a container. 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
+	// Bounds returns the bounds of the Window including its frame, if
+	// possible. This means that the top-left point of the bounds will be
+	// either zero or negative.
+	Bounds () image.Rectangle
+	// InnerBounds returns the inner bounds of the Window, not including its
+	// frame. This means that the top-left point of the bounds will be zero.
+	InnerBounds () image.Rectangle
+	// 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)
-	// SetTitle sets the title of the window.
+	// SetTitle sets the title of the Window.
 	SetTitle (string)
-	// SetIcon sets the icon of the window.
+	// SetIcon sets the icon of the Window.
 	SetIcon (Icon)
-	// SetResizable sets whether the window can be resized by the user in
+	// 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.
+	// 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 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)
+	// 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.
+	NewChild (WindowKind, image.Rectangle) (Window, error)
 	// Modifiers returns which modifier keys on the keyboard are currently
 	// being held down.
 	Modifiers () input.Modifiers
@@ -324,8 +364,13 @@ type Window interface {
 	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.
+	// Close closes the window. This does not trigger the TryClose event.
+	Close () error
+	// OnTryClose specifies a function to be called when the user attempts
+	// to close the Window. If any registered handlers returns false, the
+	// Window will not be closed. This can be used to display some sort of
+	// "Unsaved changes" warning to the user.
+	OnTryClose (func () bool) event.Cookie
+	// OnClose specifies a function to be called when the Window is closed.
 	OnClose (func ()) event.Cookie
 }

style.go

@@ -1,80 +0,0 @@
-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,
-	}
-}

tomo.go

@@ -2,67 +2,49 @@ package tomo
 
 import "sync"
 import "image"
-import "errors"
 import "git.tebibyte.media/tomo/tomo/canvas"
 
-var backendLock sync.Mutex
-var backend Backend
+// TODO this really sucks. It might be a good idea to have Do be the entry point
+// for every off-thread call, and Stop should just call backend.Stop within
+// backend.Do. This is because Do is a queue and is not vulnerable to recursive
+// locking.
 
-// Run initializes a backend, runs the specified callback function, and runs the
-// event loop in that order. This function blocks until Stop is called, or the
-// backend experiences a fatal error.
-func Run (callback func ()) error {
-	if backend != nil {
-		return errors.New("there is already a backend running")
-	}
-
-	back, err := initialize()
-	if err != nil { return err }
-	
-	backendLock.Lock()
-	backend = back
-	backendLock.Unlock()
-
-	callback()
-	// callback may have called tomo.Stop
-	if backend == nil { return nil }
-	return backend.Run()
+var stopping bool
+var stoppingLock sync.Mutex
+func isStopping () bool {
+	stoppingLock.Lock()
+	defer stoppingLock.Unlock()
+	return stopping
+}
+func setStopping (is bool) {
+	stoppingLock.Lock()
+	defer stoppingLock.Unlock()
+	stopping = is
 }
 
-func assertBackend () {
-	if backend == nil { panic("nil backend") }
-}
-
-// Stop stops the backend, unblocking run. Run may be called again after calling
-// Stop.
+// Stop stops the currently running Backend.
 func Stop () {
-	assertBackend()
-	backend.Stop()
-	
+	if isStopping() { return }
+	setStopping(true)
 	backendLock.Lock()
+	defer backendLock.Unlock()
+	if backend == nil { return }
+	backend.Stop()
 	backend = nil
-	backendLock.Unlock()
+	setStopping(false)
 }
 
 // Do performs a callback function in the event loop thread as soon as possible.
 func Do (callback func ()) {
 	backendLock.Lock()
+	defer backendLock.Unlock()
 	if backend != nil { backend.Do(callback) }
-	backendLock.Unlock()
 }
 
-// NewWindow creates and returns a window within the specified bounds on screen.
-func NewWindow (bounds image.Rectangle) (Window, error) {
+// NewWindow creates and returns a Window within the specified bounds on screen.
+func NewWindow (kind WindowKind, 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)
+	return backend.NewWindow(kind, bounds)
 }
 
 // NewBox creates and returns a basic Box.
@@ -89,8 +71,8 @@ func NewContainerBox () ContainerBox {
 	return backend.NewContainerBox()
 }
 
-// NewTexture creates a new texture from an image. When no longer in use, it
-// must be freed using Close().
+// NewTexture creates a new canvas.Texture from an image. When no longer in use,
+// it must be freed using Close().
 func NewTexture (source image.Image) canvas.TextureCloser {
 	assertBackend()
 	return backend.NewTexture(source)

unit.go

@@ -1,5 +1,6 @@
 package tomo
 
+import "fmt"
 import "image"
 import "image/color"
 
@@ -11,6 +12,16 @@ type Side int; const (
 	SideLeft
 )
 
+func (side Side) String () string {
+	switch side {
+	case SideTop:    return "SideTop"
+	case SideRight:  return "SideRight"
+	case SideBottom: return "SideBottom"
+	case SideLeft:   return "SideLeft"
+	default:         return fmt.Sprintf("Side(%d)", side)
+	}
+}
+
 // Inset represents a rectangle inset that can have a different value for each
 // side.
 type Inset [4]int
@@ -37,9 +48,13 @@ func I (sides ...int) Inset {
 	}
 }
 
-// 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
+func (inset Inset) String () string {
+	return fmt.Sprintf("%d %d %d %d", inset[0], inset[1], inset[2], inset[3])
+}
+
+// Apply returns the given image.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
@@ -61,7 +76,7 @@ func (inset Inset) Apply (bigger image.Rectangle) (smaller image.Rectangle) {
 	return
 }
 
-// Inverse returns a negated version of the inset.
+// Inverse returns a negated version of the Inset.
 func (inset Inset) Inverse () (prime Inset) {
 	return Inset {
 		inset[0] * -1,
@@ -81,12 +96,18 @@ func (inset Inset) Vertical () int {
 	return inset[SideTop] + inset[SideBottom]
 }
 
-// Border represents a single border of a box.
+// Border represents a single border of a Box.
 type Border struct {
 	Width Inset
 	Color [4]color.Color
 }
 
+func (border Border) String () string {
+	return fmt.Sprintf("%v %v %v %v / %v",
+		border.Color[0], border.Color[1], border.Color[2], border.Color[3],
+		border.Width)
+}
+
 // Align lists basic alignment types.
 type Align int; const (
 	AlignStart Align = iota // similar to left-aligned text
@@ -95,6 +116,16 @@ type Align int; const (
 	AlignEven               // similar to justified text
 )
 
+func (align Align) String () string {
+	switch align {
+	case AlignStart:  return "AlignStart"
+	case AlignMiddle: return "AlignMiddle"
+	case AlignEnd:    return "AlignEnd"
+	case AlignEven:   return "AlignEven"
+	default:          return fmt.Sprintf("Align(%d)", align)
+	}
+}
+
 // TextureMode lists texture rendering modes.
 type TextureMode int; const (
 	TextureModeTile TextureMode = iota
@@ -103,3 +134,92 @@ type TextureMode int; const (
 	// TODO more modes: fit, fill, and stretch
 	// Of course canvas will need to have a concept of this.
 )
+
+func (mode TextureMode) String () string {
+	switch mode {
+	case TextureModeTile:   return "TextureModeTile"
+	case TextureModeCenter: return "TextureModeCenter"
+	default:                return fmt.Sprintf("TextureMode(%d)", mode)
+	}
+}
+
+// Face represents a typeface. 
+type Face struct {
+	// Font specifies the font name. This should be searched for in a list
+	// of installed fonts.
+        Font string
+        // Size is the point size of the face.
+        Size float64
+	// Weight is the weight of the face. If zero, it should be interpreted
+	// as normal (equivalent to 400).
+        Weight int
+        // Italic is how italicized the face is. It ranges from 0 to 1. It is
+        // different from Slant in that it may alter the design of the glyphs
+        // instead of simply skewing them.
+        Italic float64
+        // Slant is how slanted the face is. It ranges from 0 to 1. It is
+        // different from Italic in that it simply skews the glyphs without
+        // altering their design.
+        Slant float64
+}
+
+func (face Face) String () string {
+	return fmt.Sprintf (
+		"%s %fpt W%d I%f S%f",
+		face.Font, face.Size, face.Weight, face.Italic, face.Slant)
+}
+
+// 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 a convenience constructor for Role.
+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
+)
+
+func (id Color) String () string {
+	switch id {
+	case ColorBackground: return "ColorBackground"
+	case ColorForeground: return "ColorForeground"
+	case ColorRaised:     return "ColorRaised"
+	case ColorSunken:     return "ColorSunken"
+	case ColorAccent:     return "ColorAccent"
+	default:              return fmt.Sprintf("Color(%d)", id)
+	}
+}
+
+// RGBA satisfies the color.Color interface. The result of this method may be
+// rendered invalid if the visual style changes, so it is often necessary to
+// subscribe to the StyleChange event in order to get new RGBA values when this
+// happens.
+func (id Color) RGBA () (r, g, b, a uint32) {
+	assertBackend()
+	return backend.ColorRGBA(id)
+}