Add config package

Closes #6

attribute.go

@@ -2,49 +2,8 @@ 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
@@ -54,6 +13,8 @@ type Attr interface {
 	attr   ()
 }
 
+// AttrKind enumerates all attribute kinds. There is one of these for each
+// attribute type.
 type AttrKind int; const (
 	AttrKindColor AttrKind = iota
 	AttrKindTexture
@@ -69,11 +30,12 @@ type AttrKind int; const (
 	AttrKindAlign
 	AttrKindOverflow
 	AttrKindLayout
+	AttrKindCursor
 )
 
 // AttrColor sets the background color of a box.
 type AttrColor struct { color.Color }
-// AttrTexture sets the texture of a box to a named texture.
+// AttrTexture sets the texture of a box to a texture.
 type AttrTexture struct { canvas.Texture }
 // AttrTextureMode sets the rendering mode of a box's texture.
 type AttrTextureMode TextureMode
@@ -89,8 +51,8 @@ type AttrGap image.Point
 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 }
+// AttrFace sets the type face, if the box is a TextBox.
+type AttrFace 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.
@@ -99,6 +61,8 @@ type AttrAlign struct { X, Y Align }
 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 the color attribute.
 func AColor (col color.Color) AttrColor {
@@ -137,8 +101,8 @@ 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 }
+func AFace (face Face) AttrFace {
+	return AttrFace(face)
 }
 // AWrap is a convenience constructor for the wrap attribute.
 func AWrap (wrap bool) AttrWrap {
@@ -156,6 +120,10 @@ func AOverflow (x, y bool) AttrOverflow {
 func ALayout (layout Layout) AttrLayout {
 	return AttrLayout { Layout: layout }
 }
+// ACursor is a convenience constructor for the cursor attribute.
+func ACursor (cursor Cursor) AttrCursor {
+	return AttrCursor(cursor)
+}
 
 // Equals returns true if both attributes can reasonably be declared equal.
 func (this AttrColor) Equals (other Attr) bool {
@@ -274,6 +242,14 @@ func (this AttrLayout) Equals (other Attr) bool {
 	// two layouts cannot "reasonably" be declared equal
 	return false
 }
+// Equals returns true if both attributes can reasonably be declared equal.
+func (this AttrCursor) Equals (other Attr) bool {
+	if other, ok := other.(AttrCursor); ok {
+		return this == other
+	} else {
+		return false
+	}
+}
 
 func (AttrColor)       Kind () AttrKind { return AttrKindColor }
 func (AttrTexture)     Kind () AttrKind { return AttrKindTexture }
@@ -289,6 +265,7 @@ 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 () { }
 func (AttrTexture)     attr () { }
@@ -304,3 +281,4 @@ func (AttrWrap)        attr () { }
 func (AttrAlign)       attr () { }
 func (AttrOverflow)    attr () { }
 func (AttrLayout)      attr () { }
+func (AttrCursor)      attr () { }

backend.go

@@ -1,8 +1,8 @@
 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,
@@ -18,12 +18,7 @@ type Backend interface {
 	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)
+	NewWindow (WindowKind, image.Rectangle) (Window, error)
 
 	// NewTexture creates a new texture from an image. The backend must
 	// reject any texture that was not made by it.
@@ -33,22 +28,30 @@ type Backend interface {
 	// 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 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 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
 }

config/config.go

@@ -0,0 +1,15 @@
+// Package config stores common configuration parameters. These are unmanaged,
+// and must be queried each time they are used. These are intended to be set by
+// things like application frameworks. Values set by objects or applications are
+// subject to being overridden.
+package config
+
+import "time"
+
+// 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

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
 
+import "io"
+import "errors"
+
 // 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 ()
+// 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.
@@ -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,
 	}
@@ -45,17 +70,14 @@ 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.
@@ -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

@@ -16,6 +16,7 @@ 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 +91,9 @@ 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 +279,6 @@ 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 +371,20 @@ const (
 	IconWeatherStorm                 Icon = "WeatherStorm"
 )
 
-// Texture returns a texture of the corresponding icon ID.
+// Texture returns a 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 an 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)
 }

object.go

@@ -283,10 +283,43 @@ type BoxArranger interface {
 	SetBounds (index int, bounds image.Rectangle)
 }
 
+// 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 window 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 contain one object. Windows
 // themselves are completely transparent, and become opaque once an opaque
 // object is added as their root.
 type Window interface {
+	// 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)
@@ -303,15 +336,8 @@ type Window interface {
 	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)
+	// 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
@@ -328,8 +354,13 @@ type Window interface {
 	SetVisible (bool)
 	// Visible returns whether or not this window is visible.
 	Visible () bool
-	// Close closes the window.
-	Close ()
+	// 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) {
+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.

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
@@ -37,6 +48,10 @@ func I (sides ...int) Inset {
 	}
 }
 
+func (inset Inset) String () string {
+	return fmt.Sprintf("%d %d %d %d", inset[0], inset[1], inset[2], inset[3])
+}
+
 // 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
@@ -87,6 +102,12 @@ type Border struct {
 	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 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
+)
+
+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)
+}