ContainerBox uses slices.Remove correctly

The convention within Tomo is that On*Change events only fire when
the user interacts with something

go.mod

@@ -1,10 +1,13 @@
 module git.tebibyte.media/tomo/backend
 
-go 1.20
+go 1.21.0
+
+toolchain go1.22.2
 
 require (
-	git.tebibyte.media/tomo/tomo v0.41.1
+	git.tebibyte.media/sashakoshka/goutil v0.3.0
-	git.tebibyte.media/tomo/typeset v0.7.1
+	git.tebibyte.media/tomo/tomo v0.48.0
+	git.tebibyte.media/tomo/typeset v0.8.0
 	git.tebibyte.media/tomo/xgbkb v1.0.1
 	github.com/jezek/xgb v1.1.1
 	github.com/jezek/xgbutil v0.0.0-20231116234834-47f30c120111

go.sum

@@ -1,8 +1,10 @@
+git.tebibyte.media/sashakoshka/goutil v0.3.0 h1:dcZ/9/or7m8eTpf2B1Pu4CscplXh2INTXFartz+ExwE=
+git.tebibyte.media/sashakoshka/goutil v0.3.0/go.mod h1:e1OXLa+wX7x/F8n8gyxz2hnfVCEkWzGrZNX8/k/lR/M=
 git.tebibyte.media/sashakoshka/xgbkb v1.0.0/go.mod h1:pNcE6TRO93vHd6q42SdwLSTTj25L0Yzggz7yLe0JV6Q=
-git.tebibyte.media/tomo/tomo v0.41.1 h1:XdbyF3VjsLj1Zppr70gUaufuh49hU32JQo2ENnw4PcA=
+git.tebibyte.media/tomo/tomo v0.48.0 h1:AE21ElHwUSPsX82ZWCnoNxJFi9Oswyd3dPDPMbxTueQ=
-git.tebibyte.media/tomo/tomo v0.41.1/go.mod h1:C9EzepS9wjkTJjnZaPBh22YvVPyA4hbBAJVU20Rdmps=
+git.tebibyte.media/tomo/tomo v0.48.0/go.mod h1:WrtilgKB1y8O2Yu7X4mYcRiqOlPR8NuUnoA/ynkQWrs=
-git.tebibyte.media/tomo/typeset v0.7.1 h1:aZrsHwCG5ZB4f5CruRFsxLv5ezJUCFUFsQJJso2sXQ8=
+git.tebibyte.media/tomo/typeset v0.8.0 h1:4qA6oW4/3oPHj6/Zrp+JFJ53OmFSDvxs+J6BhO3DW00=
-git.tebibyte.media/tomo/typeset v0.7.1/go.mod h1:PwDpSdBF3l/EzoIsa2ME7QffVVajnTHZN6l3MHEGe1g=
+git.tebibyte.media/tomo/typeset v0.8.0/go.mod h1:PwDpSdBF3l/EzoIsa2ME7QffVVajnTHZN6l3MHEGe1g=
 git.tebibyte.media/tomo/xgbkb v1.0.1 h1:b3HDUopjdQp1MZrb5Vpil4bOtk3NnNXtfQW27Blw2kE=
 git.tebibyte.media/tomo/xgbkb v1.0.1/go.mod h1:P5Du0yo5hUsojchW08t+Mds0XPIJXwMi733ZfklzjRw=
 github.com/BurntSushi/freetype-go v0.0.0-20160129220410-b763ddbfe298 h1:1qlsVAQJXZHsaM8b6OLVo6muQUQd4CwkH/D3fnnbHXA=

internal/system/attribute.go

@@ -1,26 +1,48 @@
 package system
 
 import "git.tebibyte.media/tomo/tomo"
+import "git.tebibyte.media/sashakoshka/goutil/container"
 
 type attrHierarchy [T tomo.Attr] struct {
-	style T
+	fallback T
-	user  T
+	style    ucontainer.Optional[T]
-	userExists bool
+	user     ucontainer.Optional[T]
+}
+
+func (this *attrHierarchy[T]) SetFallback (fallback T) {
+	this.fallback = fallback
 }
 
 func (this *attrHierarchy[T]) SetStyle (style T) (different bool) {
-	styleEquals := this.style.Equals(style)
+	styleEquals := false
-	this.style = style
+	if previous, ok := this.style.Value(); ok {
-	return !styleEquals && !this.userExists
+		styleEquals = previous.Equals(style)
+	}
+	this.style.Set(style)
+	return !styleEquals && !this.user.Exists()
+}
+
+func (this *attrHierarchy[T]) UnsetStyle () (different bool) {
+	different = this.style.Exists()
+	this.style.Unset()
+	return different
 }
 
 func (this *attrHierarchy[T]) SetUser (user T) (different bool) {
-	userEquals := this.user.Equals(user)
+	userEquals := false
-	this.user = user
+	if previous, ok := this.user.Value(); ok {
-	this.userExists = true
+		userEquals = previous.Equals(user)
+	}
+	this.user.Set(user)
 	return !userEquals
 }
 
+func (this *attrHierarchy[T]) UnsetUser () (different bool) {
+	different = this.user.Exists()
+	this.user.Unset()
+	return different
+}
+
 func (this *attrHierarchy[T]) Set (attr T, user bool) (different bool) {
 	if user {
 		return this.SetUser(attr)
@@ -29,10 +51,20 @@ func (this *attrHierarchy[T]) Set (attr T, user bool) (different bool) {
 	}
 }
 
-func (this *attrHierarchy[T]) Value () T {
+func (this *attrHierarchy[T]) Unset (user bool) (different bool) {
-	if this.userExists {
+	if user {
-		return this.user
+		return this.UnsetUser()
 	} else {
-		return this.style
+		return this.UnsetStyle()
+	}
+}
+
+func (this *attrHierarchy[T]) Value () T {
+	if user, ok := this.user.Value(); ok {
+		return user
+	} else if style, ok := this.style.Value(); ok{
+		return style
+	} else {
+		return this.fallback
 	}
 }

internal/system/box.go

@@ -7,20 +7,21 @@ import "git.tebibyte.media/tomo/tomo/data"
 import "git.tebibyte.media/tomo/tomo/input"
 import "git.tebibyte.media/tomo/tomo/event"
 import "git.tebibyte.media/tomo/tomo/canvas"
-import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/sashakoshka/goutil/container"
+import "git.tebibyte.media/sashakoshka/goutil/image/color"
 
 type box struct {
 	system *System
 	parent parent
 	outer  anyBox
 
-	tags            util.Set[string]
+	tags             ucontainer.Set[string]
 	role             tomo.Role
 	lastStyleNonce   int
-	lastIconsNonce  int
+	lastIconSetNonce int
 	styleApplicator  *styleApplicator
 
-	minSize             util.Memo[image.Point]
+	minSize             ucontainer.Memo[image.Point]
 	bounds              image.Rectangle
 	innerClippingBounds image.Rectangle
 	
@@ -41,8 +42,7 @@ type box struct {
 	focused bool
 	pressed bool
 	
-
+	canvas ucontainer.Memo[canvas.Canvas]
-	canvas util.Memo[canvas.Canvas]
 	drawer canvas.Drawer
 
 	on struct {
@@ -69,19 +69,21 @@ func (this *System) newBox (outer anyBox) *box {
 		system:  this,
 		outer:   outer,
 		drawer:  outer,
-		tags:    make(util.Set[string]),
+		tags:    make(ucontainer.Set[string]),
 	}
-	box.canvas = util.NewMemo (func () canvas.Canvas {
+	box.attrColor.SetFallback(tomo.AColor(color.Transparent))
+	box.canvas = ucontainer.NewMemo (func () canvas.Canvas {
 		if box.parent == nil { return nil }
 		parentCanvas := box.parent.getCanvas()
 		if parentCanvas == nil { return nil }
-		return parentCanvas.SubCanvas(box.bounds)
+		drawableArea := box.bounds.Intersect(box.parent.getInnerClippingBounds())
+		return parentCanvas.SubCanvas(drawableArea)
 	})
 	if outer == nil {
 		box.drawer = box
 		box.outer  = box
 	}
-	box.minSize = util.NewMemo(box.calculateMinimumSize)
+	box.minSize = ucontainer.NewMemo(box.calculateMinimumSize)
 	return box
 }
 
@@ -130,17 +132,25 @@ func (this *box) Tag (tag string) bool {
 }
 
 func (this *box) SetTag (tag string, on bool) {
+	wasOn := this.tags.Has(tag)
 	if on {
 		this.tags.Add(tag)
 	} else {
 		delete(this.tags, tag)
 	}
+	if wasOn != on {
+		this.invalidateStyle()
+	}
 }
 
 func (this *box) SetAttr (attr tomo.Attr) {
 	this.outer.setAttr(attr, true)
 }
 
+func (this *box) UnsetAttr (kind tomo.AttrKind) {
+	this.outer.unsetAttr(kind, true)
+}
+
 func (this *box) SetDNDData (dat data.Data) {
 	this.dndData = dat
 }
@@ -201,18 +211,7 @@ func (this *box) setAttr (attr tomo.Attr, user bool) {
 	case tomo.AttrBorder:
 		previousBorderSum := this.borderSum()
 		different         := this.attrBorder.Set(attr, user)
-
+		this.handleBorderChange(previousBorderSum, different)
-		// only invalidate the layout if the border is sized differently
-		if this.borderSum() != previousBorderSum {
-			this.invalidateLayout()
-			this.invalidateMinimum()
-		}
-
-		// if the border takes up the same amount of space, only invalidate the
-		// drawing if it looks different
-		if different {
-			this.invalidateDraw()
-		}
 		
 	case tomo.AttrMinimumSize:
 		if this.attrMinimumSize.Set(attr, user) {
@@ -220,13 +219,66 @@ func (this *box) setAttr (attr tomo.Attr, user bool) {
 		}
 		
 	case tomo.AttrPadding:
-		if this.attrPadding.Set(attr, true) {
+		if this.attrPadding.Set(attr, user) {
 			this.invalidateLayout()
 			this.invalidateMinimum()
 		}
 	}
 }
 
+func (this *box) unsetAttr (kind tomo.AttrKind, user bool) {
+	switch kind {
+	case tomo.AttrKindColor:
+		if this.attrColor.Unset(user) {
+			this.invalidateDraw()
+		}
+		
+	case tomo.AttrKindTexture:
+		if this.attrTexture.Unset(user) {
+			this.invalidateDraw()
+		}
+		
+	case tomo.AttrKindTextureMode:
+		if this.attrTextureMode.Unset(user) {
+			this.invalidateDraw()
+		}
+		
+	case tomo.AttrKindBorder:
+		previousBorderSum := this.borderSum()
+		different         := this.attrBorder.Unset(user)
+		this.handleBorderChange(previousBorderSum, different)
+	
+	case tomo.AttrKindMinimumSize:
+		if this.attrMinimumSize.Unset(user) {
+			this.invalidateMinimum()
+		}
+		
+	case tomo.AttrKindPadding:
+		if this.attrPadding.Unset(user) {
+			this.invalidateLayout()
+			this.invalidateMinimum()
+		}
+	}
+}
+
+func (this *box) unsetAllAttrs (user bool) {
+	// keep this in sync with tomo.AttrKind!
+	this.outer.unsetAttr(tomo.AttrKindColor, user)
+	this.outer.unsetAttr(tomo.AttrKindTexture, user)
+	this.outer.unsetAttr(tomo.AttrKindTextureMode, user)
+	this.outer.unsetAttr(tomo.AttrKindBorder, user)
+	this.outer.unsetAttr(tomo.AttrKindMinimumSize, user)
+	this.outer.unsetAttr(tomo.AttrKindPadding, user)
+	this.outer.unsetAttr(tomo.AttrKindGap, user)
+	this.outer.unsetAttr(tomo.AttrKindTextColor, user)
+	this.outer.unsetAttr(tomo.AttrKindDotColor, user)
+	this.outer.unsetAttr(tomo.AttrKindFace, user)
+	this.outer.unsetAttr(tomo.AttrKindWrap, user)
+	this.outer.unsetAttr(tomo.AttrKindAlign, user)
+	this.outer.unsetAttr(tomo.AttrKindOverflow, user)
+	this.outer.unsetAttr(tomo.AttrKindLayout, user)
+}
+
 func (this *box) setBounds (bounds image.Rectangle) {
 	if this.bounds == bounds { return }
 	this.bounds = bounds
@@ -395,6 +447,13 @@ func (this *box) Draw (can canvas.Canvas) {
 
 	// centered texture
 	if textureMode == tomo.TextureModeCenter && texture != nil {
+		this.centeredTexture(can, texture)
+	}
+}
+
+func (this *box) centeredTexture (can canvas.Canvas, texture canvas.Texture) {
+	pen           := can.Pen()
+	bounds        := this.Bounds()
 	textureBounds := texture.Bounds()
 	textureOrigin :=
 		bounds.Min.
@@ -408,7 +467,6 @@ func (this *box) Draw (can canvas.Canvas) {
 	pen.Fill(color.Transparent)
 	pen.Texture(texture)
 	pen.Rectangle(textureBounds.Sub(textureBounds.Min).Add(textureOrigin))
-	}
 }
 
 func (this *box) drawBorders (can canvas.Canvas) {
@@ -419,7 +477,7 @@ func (this *box) drawBorders (can canvas.Canvas) {
 	rectangle := func (x0, y0, x1, y1 int, c color.Color) {
 		area := image.Rect(x0, y0, x1, y1)
 		if area.Empty() { return }
-		if util.Transparent(c) && this.parent != nil {
+		if ucolor.Transparent(c) && this.parent != nil {
 			this.parent.drawBackgroundPart(can.SubCanvas(area))
 		}
 		pen.Fill(c)
@@ -531,7 +589,21 @@ func (this *box) recursiveRedo () {
 }
 
 func (this *box) recursiveLoseCanvas () {
-	this.canvas.InvalidateTo(nil)
+	this.canvas.Invalidate()
+}
+
+func (this *box) handleBorderChange (previousBorderSum tomo.Inset, different bool) {
+	// only invalidate the layout if the border is sized differently
+	if this.borderSum() != previousBorderSum {
+		this.invalidateLayout()
+		this.invalidateMinimum()
+	}
+
+	// if the border takes up the same amount of space, only invalidate the
+	// drawing if it looks different
+	if different {
+		this.invalidateDraw()
+	}
 }
 
 func (this *box) invalidateStyle () {
@@ -560,7 +632,8 @@ func (this *box) invalidateMinimum () {
 }
 
 func (this *box) recursiveReApply () {
-	if this.getHierarchy() == nil { return }
+	hierarchy := this.getHierarchy()
+	if hierarchy == nil { return }
 	
 	// re-apply styling, icons *if needed*
 
@@ -571,16 +644,17 @@ func (this *box) recursiveReApply () {
 		// applicator for every box, it's so style applicators can cache
 		// information about the boxes they're linked to (like all rules
 		// with a matching role).
+		this.unsetAllAttrs(false)
 		this.lastStyleNonce = hierarchyStyleNonce
-		this.styleApplicator = this.getHierarchy().newStyleApplicator()
+		this.styleApplicator = hierarchy.newStyleApplicator()
 		this.invalidateStyle()
 		this.on.styleChange.Broadcast()
 	}
 
 	// icons
-	hierarchyIconsNonce := this.getIconsNonce()
+	hierarchyIconSetNonce := this.getIconSetNonce()
-	if this.lastIconsNonce != hierarchyIconsNonce {
+	if this.lastIconSetNonce != hierarchyIconSetNonce {
-		this.lastIconsNonce = hierarchyIconsNonce
+		this.lastIconSetNonce = hierarchyIconSetNonce
 		this.on.iconSetChange.Broadcast()
 	}
 }
@@ -609,7 +683,7 @@ func (this *box) transparent () bool {
 	// TODO uncomment once we have
 	// a way to detect texture transparency
 	col := this.attrColor.Value().Color
-	return col == nil || util.Transparent(col) /*&&
+	return col == nil || ucolor.Transparent(col) /*&&
 		(this.texture == nil || !this.texture.Opaque())*/
 }
 
@@ -629,7 +703,7 @@ func (this *box) getStyleNonce () int {
 	return this.getHierarchy().getStyleNonce()
 }
 
-func (this *box) getIconsNonce () int {
+func (this *box) getIconSetNonce () int {
 	// should panic if not in the tree
-	return this.getHierarchy().getIconsNonce()
+	return this.getHierarchy().getIconSetNonce()
 }

internal/system/containerbox.go

@@ -1,11 +1,11 @@
 package system
 
 import "image"
+import "slices"
 import "image/color"
 import "git.tebibyte.media/tomo/tomo"
 import "git.tebibyte.media/tomo/tomo/event"
 import "git.tebibyte.media/tomo/tomo/canvas"
-import "git.tebibyte.media/tomo/backend/internal/util"
 
 type containerBox struct {
 	*box
@@ -50,7 +50,7 @@ func (this *containerBox) OnContentBoundsChange (callback func()) event.Cookie {
 
 func (this *containerBox) Add (child tomo.Object) {
 	box := assertAnyBox(child.GetBox())
-	if util.IndexOf(this.children, box) > -1 { return }
+	if slices.Index(this.children, box) > -1 { return }
 
 	box.setParent(this)
 	box.flushActionQueue()
@@ -61,26 +61,26 @@ func (this *containerBox) Add (child tomo.Object) {
 
 func (this *containerBox) Remove (child tomo.Object) {
 	box := assertAnyBox(child.GetBox())
-	index := util.IndexOf(this.children, box)
+	index := slices.Index(this.children, box)
 	if index < 0 { return }
 
 	box.setParent(nil)
-	this.children = util.Remove(this.children, index)
+	this.children = slices.Delete(this.children, index, index + 1)
 	this.invalidateLayout()
 	this.invalidateMinimum()
 }
 
 func (this *containerBox) Insert (child, before tomo.Object) {
 	box := assertAnyBox(child.GetBox())
-	if util.IndexOf(this.children, box) > -1 { return }
+	if slices.Index(this.children, box) > -1 { return }
 
 	beforeBox := assertAnyBox(before.GetBox())
-	index     := util.IndexOf(this.children, beforeBox)
+	index     := slices.Index(this.children, beforeBox)
 	
 	if index < 0 {
 		this.children = append(this.children, box)
 	} else {
-		this.children = util.Insert(this.children, index, box)
+		this.children = slices.Insert(this.children, index, box)
 	}
 	box.setParent(this)
 
@@ -186,6 +186,53 @@ func (this *containerBox) setAttr (attr tomo.Attr, user bool) {
 	}
 }
 
+func (this *containerBox) unsetAttr (kind tomo.AttrKind, user bool) {
+	switch kind {
+	case tomo.AttrKindColor:
+		if this.attrColor.Unset(user) {
+			this.invalidateTransparentChildren()
+			this.invalidateDraw()
+		}
+		
+	case tomo.AttrKindTexture:
+		if this.attrTexture.Unset(user) {
+			this.invalidateTransparentChildren()
+			this.invalidateDraw()
+		}
+		
+	case tomo.AttrKindTextureMode:
+		if this.attrTextureMode.Unset(user) {
+			this.invalidateTransparentChildren()
+			this.invalidateDraw()
+		}
+
+	case tomo.AttrKindGap:
+		if this.attrGap.Unset(user) {
+			this.invalidateLayout()
+			this.invalidateMinimum()
+		}
+		
+	case tomo.AttrKindAlign:
+		if this.attrAlign.Unset(user) {
+			this.invalidateLayout()
+		}
+		
+	case tomo.AttrKindOverflow:
+		if this.attrOverflow.Unset(user) {
+			this.invalidateLayout()
+			this.invalidateMinimum()
+		}
+		
+	case tomo.AttrKindLayout:
+		if this.attrLayout.Unset(user) {
+			this.invalidateLayout()
+			this.invalidateMinimum()
+		}
+
+	default: this.box.unsetAttr(kind, user)
+	}
+}
+
 func (this *containerBox) recommendedHeight (width int) int {
 	layout := this.attrLayout.Value().Layout
 	if layout == nil || !this.attrOverflow.Value().Y {
@@ -251,6 +298,10 @@ func (this *containerBox) getCanvas () canvas.Canvas {
 	return this.canvas.Value()
 }
 
+func (this *containerBox) getInnerClippingBounds () image.Rectangle {
+	return this.innerClippingBounds
+}
+
 func (this *containerBox) notifyMinimumSizeChange (child anyBox) {
 	this.invalidateMinimum()
 	size   := child.minimumSize()

internal/system/event.go

@@ -2,6 +2,7 @@ package system
 
 import "image"
 import "git.tebibyte.media/tomo/tomo/input"
+import "git.tebibyte.media/tomo/tomo/config"
 
 // TODO: once go v1.23 comes out, replace the explicit iterator calls here with
 // range loops
@@ -39,15 +40,14 @@ func (this *Hierarchy) HandleKeyDown (key input.Key, numberPad bool) {
 	}
 	if caught { return }
 
-	switch key {
+	switch input.KC(key, this.modifiers) {
-	case input.KeyTab:
+	case config.KeyChordFocusNext:                this.focusNext()
-		if this.modifiers.Shift {
+	case config.KeyChordFocusPrevious:            this.focusPrevious()
-			this.focusPrevious()
+	// TODO: up, down, left, and right should find a box to the top, bottom,
-		} else {
+	// left, and right respectively to move the focus to. we might want to
-			this.focusNext()
+	// have four corresponding key chords in tomo/config.
-		}
+	case input.KC(input.KeyDown, input.ModNone):  this.focusNext()
-	case input.KeyUp:   this.focusPrevious()
+	case input.KC(input.KeyUp,   input.ModNone):  this.focusPrevious()
-	case input.KeyDown: this.focusNext()
 	}
 }
 

internal/system/hierarchy.go

@@ -4,7 +4,8 @@ import "image"
 import "git.tebibyte.media/tomo/tomo"
 import "git.tebibyte.media/tomo/tomo/input"
 import "git.tebibyte.media/tomo/tomo/canvas"
-import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/tomo/backend/style"
+import "git.tebibyte.media/sashakoshka/goutil/container"
 
 // Hierarchy is coupled to a tomo.Window implementation, and manages a tree of
 // Boxes.
@@ -24,9 +25,9 @@ type Hierarchy struct {
 	drags         [10][]anyBox
 	minimumSize   image.Point
 
-	needStyle    util.Set[anyBox]
+	needStyle    ucontainer.Set[anyBox]
-	needLayout   util.Set[anyBox]
+	needLayout   ucontainer.Set[anyBox]
-	needDraw     util.Set[anyBox]
+	needDraw     ucontainer.Set[anyBox]
 	needRedo     bool
 	minimumClean bool
 }
@@ -52,9 +53,9 @@ func (this *System) NewHierarchy (link WindowLink) *Hierarchy {
 	hierarchy := &Hierarchy {
 		system:      this,
 		link:        link,
-		needStyle:   make(util.Set[anyBox]),
+		needStyle:   make(ucontainer.Set[anyBox]),
-		needLayout:  make(util.Set[anyBox]),
+		needLayout:  make(ucontainer.Set[anyBox]),
-		needDraw:    make(util.Set[anyBox]),
+		needDraw:    make(ucontainer.Set[anyBox]),
 	}
 	this.hierarchies.Add(hierarchy)
 	return hierarchy
@@ -168,22 +169,34 @@ func (this *Hierarchy) getWindow () tomo.Window {
 	return this.link.GetWindow()
 }
 
-func (this *Hierarchy) getStyle () *tomo.Style {
+func (this *Hierarchy) getStyle () *style.Style {
 	return this.system.style
 }
 
+func (this *Hierarchy) getIconSet () style.IconSet {
+	return this.system.iconSet
+}
+
+func (this *Hierarchy) getFaceSet () style.FaceSet {
+	return this.system.faceSet
+}
+
 func (this *Hierarchy) getStyleNonce () int {
 	return this.system.styleNonce
 }
 
-func (this *Hierarchy) getIconsNonce () int {
+func (this *Hierarchy) getIconSetNonce () int {
-	return this.system.iconsNonce
+	return this.system.iconSetNonce
 }
 
 func (this *Hierarchy) getCanvas () canvas.Canvas {
 	return this.canvas
 }
 
+func (this *Hierarchy) getInnerClippingBounds () image.Rectangle {
+	return this.canvas.Bounds()
+}
+
 func (this *Hierarchy) getModifiers () input.Modifiers {
 	return this.modifiers
 }

internal/system/internal-iface.go

@@ -12,6 +12,9 @@ type parent interface {
 	getHierarchy            () *Hierarchy
 	// canvas returns the canvas held by the parent.
 	getCanvas               () canvas.Canvas
+	// getInnerClippingBounds returns the area of the canvas that children
+	// can draw to.
+	getInnerClippingBounds  () image.Rectangle
 	// notifyMinimumSizeChange informs the parent that the minimum size of
 	// one of its children has changed.
 	notifyMinimumSizeChange (anyBox)
@@ -75,6 +78,9 @@ type anyBox interface {
 	// setAttr sets an attribute at the user or style level depending
 	// on the value of user.
 	setAttr   (attr tomo.Attr, user bool)
+	// unsetAttr unsets an attribute at the user or style level depending
+	// on the value of user.
+	unsetAttr (kind tomo.AttrKind, user bool)
 
 	// propagate recursively calls a function on this anyBox, and all of its
 	// children (if applicable) The normal propagate behavior calls the

internal/system/style.go

@@ -1,11 +1,13 @@
 package system
 
 import "git.tebibyte.media/tomo/tomo"
+import "git.tebibyte.media/tomo/backend/style"
 
 type styleApplicator struct {
-	style *tomo.Style
+	style      *style.Style
 	role       tomo.Role
-	rules []tomo.Rule
+	rules      []style.Rule
+	currentSet style.AttrSet
 }
 
 func (this *styleApplicator) apply (box anyBox) {
@@ -25,7 +27,7 @@ func (this *styleApplicator) apply (box anyBox) {
 	}
 
 	// compile list of attributes by searching through the cached ruleset
-	attrs := make(tomo.AttrSet)
+	attrs := make(style.AttrSet)
 	for _, rule := range this.rules {
 		satisifed := true
 		for _, tag := range rule.Tags {
@@ -40,7 +42,18 @@ func (this *styleApplicator) apply (box anyBox) {
 		}
 	}
 
+	// reset an attribute if it is no longer specified
+	if this.currentSet != nil {
+		for kind := range this.currentSet {
+			_, exists := attrs[kind]
+			if !exists {
+				box.unsetAttr(kind, false)
+			}
+		}
+	}
+
 	// apply that list of attributes
+	this.currentSet = attrs
 	for _, attr := range attrs {
 		box.setAttr(attr, false)
 	}

internal/system/system.go

@@ -2,20 +2,22 @@ package system
 
 import "io"
 import "image"
-import "git.tebibyte.media/tomo/tomo"
 import "git.tebibyte.media/tomo/tomo/canvas"
-import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/tomo/backend/style"
+import "git.tebibyte.media/sashakoshka/goutil/container"
 
 // System is coupled to a tomo.Backend implementation, and manages Hierarchies
 // and Boxes.
 type System struct {
 	link BackendLink
 
-	style      *tomo.Style
+	style        *style.Style
+	iconSet      style.IconSet
+	faceSet      style.FaceSet
 	styleNonce   int
-	iconsNonce int
+	iconSetNonce int
 	
-	hierarchies util.Set[*Hierarchy]
+	hierarchies ucontainer.Set[*Hierarchy]
 }
 
 // BackendLink allows the System to call up into the tomo.Backend implementation
@@ -39,13 +41,13 @@ type SurfaceLink interface {
 func New (link BackendLink) *System {
 	return &System {
 		link:        link,
-		hierarchies: make(util.Set[*Hierarchy]),
+		hierarchies: make(ucontainer.Set[*Hierarchy]),
 	}
 }
 
-// SetStyle sets the tomo.Style that is applied to objects, and notifies them
+// SetStyle sets the style that is applied to objects, and notifies them
 // that the style has changed.
-func (this *System) SetStyle (style *tomo.Style) {
+func (this *System) SetStyle (style *style.Style) {
 	this.style = style
 	this.styleNonce ++
 	for hierarchy := range this.hierarchies {
@@ -53,14 +55,21 @@ func (this *System) SetStyle (style *tomo.Style) {
 	}
 }
 
-// SetIconSet notifies objects that the icons have changed.
+// SetIconSet sets the icon set that provides icon textures, and notifies
-func (this *System) SetIconSet (iconSet tomo.IconSet) {
+// objects that the icons have changed.
-	this.iconsNonce ++
+func (this *System) SetIconSet (iconSet style.IconSet) {
+	this.iconSet = iconSet
+	this.iconSetNonce ++
 	for hierarchy := range this.hierarchies {
 		hierarchy.setIconSet()
 	}
 }
 
+// SetFaceSet sets the face set that provides font faces.
+func (this *System) SetFaceSet (faceSet style.FaceSet) {
+	this.faceSet = faceSet
+}
+
 func (this *System) removeHierarchy (hierarchy *Hierarchy) {
 	delete(this.hierarchies, hierarchy)
 }

internal/system/textbox.go

@@ -1,7 +1,9 @@
 package system
 
 import "image"
+import "unicode"
 import "image/color"
+import "golang.org/x/image/font"
 import "git.tebibyte.media/tomo/tomo"
 import "golang.org/x/image/math/fixed"
 import "git.tebibyte.media/tomo/typeset"
@@ -9,6 +11,8 @@ import "git.tebibyte.media/tomo/tomo/text"
 import "git.tebibyte.media/tomo/tomo/input"
 import "git.tebibyte.media/tomo/tomo/event"
 import "git.tebibyte.media/tomo/tomo/canvas"
+import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/sashakoshka/goutil/container"
 
 type textBox struct {
 	*box
@@ -29,8 +33,11 @@ type textBox struct {
 	selecting   bool
 	selectStart int
 	dot         text.Dot
+	desiredX    fixed.Int26_6
 
 	drawer     typeset.Drawer
+	face       util.Cycler[font.Face]
+	lineHeight ucontainer.Memo[fixed.Int26_6]
 
 	on struct {
 		contentBoundsChange event.FuncBroadcaster
@@ -41,6 +48,14 @@ type textBox struct {
 func (this *System) NewTextBox () tomo.TextBox {
 	box := &textBox { }
 	box.box = this.newBox(box)
+	box.attrTextColor.SetFallback(tomo.ATextColor(color.Black))
+	box.attrDotColor.SetFallback(tomo.ADotColor(color.RGBA { G: 255, B: 255, A: 255}))
+	box.lineHeight = ucontainer.NewMemo(func () fixed.Int26_6 {
+		face := box.face.Value()
+		if face == nil { return 0 }
+		metrics := face.Metrics()
+		return metrics.Height
+	})
 	return box
 }
 
@@ -84,13 +99,41 @@ func (this *textBox) SetSelectable (selectable bool) {
 }
 
 func (this *textBox) Select (dot text.Dot) {
-	if !this.selectable { return }
+	this.selec(dot)
-	if this.dot == dot  { return }
+}
+
+func (this *textBox) selec (dot text.Dot) bool {
+	if this.selectWithoutResettingDesiredX(dot) {
+		this.desiredX = fixed.I(0)
+		return true
+	}
+	return false
+}
+
+func (this *textBox) selectWithoutResettingDesiredX (dot text.Dot) bool {
+	if !this.selectable { return false }
+	if this.dot == dot  { return false }
 	this.SetFocused(true)
 	this.dot = dot
 	this.scrollToDot()
-	this.on.dotChange.Broadcast()
 	this.invalidateDraw()
+	return true
+}
+
+func (this *textBox) userSelect (dot text.Dot) bool {
+	if this.selec(dot) {
+		this.on.dotChange.Broadcast()
+		return true
+	}
+	return false
+}
+
+func (this *textBox) userSelectWithoutResettingDesiredX (dot text.Dot) bool {
+	if this.selectWithoutResettingDesiredX(dot) {
+		this.on.dotChange.Broadcast()
+		return true
+	}
+	return false
 }
 
 func (this *textBox) Dot () text.Dot {
@@ -108,7 +151,6 @@ func (this *textBox) Draw (can canvas.Canvas) {
 
 	texture := this.attrTexture.Value().Texture
 	col     := this.attrColor.Value().Color
-	if col == nil { col = color.Transparent }
 	
 	this.drawBorders(can)
 	
@@ -124,9 +166,8 @@ func (this *textBox) Draw (can canvas.Canvas) {
 		this.drawDot(can)
 	}
 
-	if this.attrFace.Value().Face != nil {
+	if this.face.Value() != nil {
 		textColor := this.attrTextColor.Value().Color
-		if textColor == nil { textColor = color.Black }
 		this.drawer.Draw(can, textColor, this.textOffset())
 	}
 }
@@ -145,23 +186,22 @@ func (this *textBox) setAttr (attr tomo.Attr, user bool) {
 		
 	case tomo.AttrFace:
 		if this.attrFace.Set(attr, user) {
-			this.drawer.SetFace(attr.Face)
+			this.handleFaceChange()
-			this.invalidateMinimum()
-			this.invalidateLayout()
 		}
 		
 	case tomo.AttrWrap:
 		if this.attrWrap.Set(attr, user) {
-			this.drawer.SetWrap(bool(attr))
+			this.drawer.SetWrap(bool(this.attrWrap.Value()))
 			this.invalidateMinimum()
 			this.invalidateLayout()
 		}
 		
 	case tomo.AttrAlign:
 		if this.attrAlign.Set(attr, user) {
+			align := this.attrAlign.Value()
 			this.drawer.SetAlign (
-				typeset.Align(attr.X),
+				typeset.Align(align.X),
-				typeset.Align(attr.Y))
+				typeset.Align(align.Y))
 			this.invalidateDraw()
 		}
 		
@@ -175,6 +215,49 @@ func (this *textBox) setAttr (attr tomo.Attr, user bool) {
 	}
 }
 
+func (this *textBox) unsetAttr (kind tomo.AttrKind, user bool) {
+	switch kind {
+	case tomo.AttrKindTextColor:
+		if this.attrTextColor.Unset(user) && !this.dot.Empty() {
+			this.invalidateDraw()
+		}
+		
+	case tomo.AttrKindDotColor:
+		if this.attrDotColor.Unset(user) && !this.dot.Empty() {
+			this.invalidateDraw()
+		}
+		
+	case tomo.AttrKindFace:
+		if this.attrFace.Unset(user) {
+			this.handleFaceChange()
+		}
+		
+	case tomo.AttrKindWrap:
+		if this.attrWrap.Unset(user) {
+			this.drawer.SetWrap(bool(this.attrWrap.Value()))
+			this.invalidateMinimum()
+			this.invalidateLayout()
+		}
+		
+	case tomo.AttrKindAlign:
+		if this.attrAlign.Unset(user) {
+			align := this.attrAlign.Value()
+			this.drawer.SetAlign (
+				typeset.Align(align.X),
+				typeset.Align(align.Y))
+			this.invalidateDraw()
+		}
+		
+	case tomo.AttrKindOverflow:
+		if this.attrOverflow.Unset(user) {
+			this.invalidateMinimum()
+			this.invalidateLayout()
+		}
+		
+	default: this.box.unsetAttr(kind, user)
+	}
+}
+
 func roundPt (point fixed.Point26_6) image.Point {
 	return image.Pt(point.X.Round(), point.Y.Round())
 }
@@ -184,30 +267,27 @@ func fixPt (point image.Point) fixed.Point26_6 {
 }
 
 func (this *textBox) drawDot (can canvas.Canvas) {
-	if this.attrFace.Value().Face == nil { return }
+	face := this.face.Value()
+	if face == nil { return }
 
-	face      := this.attrFace.Value().Face
 	textColor := this.attrTextColor.Value().Color
 	dotColor  := this.attrDotColor.Value().Color
-	if textColor == nil { textColor = color.Black }
-	if dotColor  == nil { dotColor  = color.RGBA { G: 255, B: 255, A: 255 } }
 	
 	pen := can.Pen()
 
 	bounds   := this.InnerBounds()
 	metrics  := face.Metrics()
-	dot     := this.dot.Canon()
+	dot      := this.dot
-	start   := this.drawer.PositionAt(dot.Start).Add(fixPt(this.textOffset()))
+	canonDot := dot.Canon()
-	end     := this.drawer.PositionAt(dot.End  ).Add(fixPt(this.textOffset()))
+	start    := this.drawer.PositionAt(canonDot.Start).Add(fixPt(this.textOffset()))
+	end      := this.drawer.PositionAt(canonDot.End  ).Add(fixPt(this.textOffset()))
+	canonEnd := this.drawer.PositionAt(dot.End       ).Add(fixPt(this.textOffset()))
 	height   := this.drawer.LineHeight().Round()
 	ascent   := fixed.Point26_6 { Y: metrics.Descent }
 	descent  := fixed.Point26_6 { Y: metrics.Ascent  }
 
 	switch {
-	case dot.Empty():
+	case canonDot.Empty():
-		pen.Stroke(textColor)
-		pen.StrokeWeight(1)
-		pen.Path(roundPt(start.Add(ascent)), roundPt(start.Sub(descent)))
 
 	case start.Y == end.Y:
 		pen.Fill(dotColor)
@@ -241,6 +321,19 @@ func (this *textBox) drawDot (can canvas.Canvas) {
 		rect.Min.X = bounds.Min.X
 		pen.Rectangle(rect)
 	}
+	
+	pen.Stroke(textColor)
+	pen.StrokeWeight(1)
+	beamTop    := roundPt(canonEnd.Add(ascent)).Sub(image.Pt(0, 1))
+	beamBottom := roundPt(canonEnd.Sub(descent))
+	beamSerif  := 3
+	pen.Path(beamTop, beamBottom)
+	pen.Path (
+		beamTop.Sub(image.Pt(beamSerif - 1, 0)),
+		beamTop.Add(image.Pt(beamSerif, 0)))
+	pen.Path (
+		beamBottom.Sub(image.Pt(beamSerif - 1, 0)),
+		beamBottom.Add(image.Pt(beamSerif, 0)))
 }
 
 func (this *textBox) textOffset () image.Point {
@@ -264,7 +357,7 @@ func (this *textBox) handleMouseDown (button input.Button) bool {
 		index           := this.runeUnderMouse()
 		this.selectStart = index
 		this.selecting   = true
-		this.Select(text.Dot { Start: this.selectStart, End: index })
+		this.userSelect(text.Dot { Start: this.selectStart, End: index })
 	}
 	return this.box.handleMouseDown(button)
 }
@@ -273,7 +366,7 @@ func (this *textBox) handleMouseUp (button input.Button) bool {
 	if this.mouseButtonCanDrag(button) && this.selecting {
 		index         := this.runeUnderMouse()
 		this.selecting = false
-		this.Select(text.Dot { Start: this.selectStart, End: index })
+		this.userSelect(text.Dot { Start: this.selectStart, End: index })
 	}
 	return this.box.handleMouseUp(button)
 }
@@ -287,7 +380,7 @@ func (this *textBox) mouseButtonCanDrag (button input.Button) bool {
 func (this *textBox) handleMouseMove () bool {
 	if this.selecting {
 		index := this.runeUnderMouse()
-		this.Select(text.Dot { Start: this.selectStart, End: index })
+		this.userSelect(text.Dot { Start: this.selectStart, End: index })
 	}
 	return this.box.handleMouseMove()
 }
@@ -299,6 +392,8 @@ func (this *textBox) runeUnderMouse () int {
 	return this.drawer.AtPosition(fixPt(position))
 }
 
+// TODO the keynav here should make better use of input key chords.
+
 func (this *textBox) handleKeyDown (key input.Key, numberPad bool) bool {
 	if this.box.handleKeyDown(key, numberPad) { return true  }
 	if !this.selectable                       { return false }
@@ -306,37 +401,87 @@ func (this *textBox) handleKeyDown (key input.Key, numberPad bool) bool {
 	// because fuck you thats why!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 	modifiers := this.Window().Modifiers()
 	dot       := this.Dot()
-	sel       := modifiers.Shift
+	sel       := modifiers.Shift()
-	word      := modifiers.Control
+	word      := modifiers.Control()
+
+	moveVertically := func (delta fixed.Int26_6) {
+		currentDot := 0
+		if sel {
+			currentDot = dot.End
+		} else {
+			currentDot = dot.Canon().Start
+			if delta > fixed.I(0) { currentDot = dot.Canon().End }
+		}
+
+		nextDot := 0
+		if word {
+			if delta > fixed.I(0) {
+				nextDot = nextParagraph(this.runes, currentDot)
+			} else {
+				nextDot = previousParagraph(this.runes, currentDot)
+			}
+		} else {
+			currentPosition := this.drawer.PositionAt(currentDot)
+			if this.desiredX != fixed.I(0) {
+				currentPosition.X = this.desiredX
+			}
+			nextPosition   := currentPosition
+			nextPosition.Y += this.lineHeight.Value().Mul(delta)
+			this.desiredX   = nextPosition.X
+			nextDot         = this.drawer.AtPosition(nextPosition)
+		}
+
+		if sel {
+			dot.End = nextDot
+			this.userSelectWithoutResettingDesiredX(dot)
+		} else {
+			this.userSelectWithoutResettingDesiredX(text.EmptyDot(nextDot))
+		}
+	}
+	
 	switch {
-	case key == input.KeyHome || (modifiers.Alt && key == input.KeyLeft):
+	case key == input.KeyHome || (modifiers.Alt() && key == input.KeyLeft):
+		if word {
 			dot.End = 0
+		} else {
+			dot.End = lineHomeSoft(this.runes, dot.End)
+		}
 		if !sel { dot.Start = dot.End }
-		this.Select(dot)
+		this.userSelect(dot)
 		return true
-	case key == input.KeyEnd || (modifiers.Alt && key == input.KeyRight):
+	case key == input.KeyEnd || (modifiers.Alt() && key == input.KeyRight):
-		dot.End = len(this.text)
+		if word {
+			dot.End = len(this.runes)
+		} else {
+			dot.End = lineEnd(this.runes, dot.End)
+		}
 		if !sel { dot.Start = dot.End }
-		this.Select(dot)
+		this.userSelect(dot)
 		return true
 	case key == input.KeyLeft:
 		if sel {
-			this.Select(text.SelectLeft(this.runes, dot, word))
+			this.userSelect(text.SelectLeft(this.runes, dot, word))
 		} else {
-			this.Select(text.MoveLeft(this.runes, dot, word))
+			this.userSelect(text.MoveLeft(this.runes, dot, word))
 		}
 		return true
 	case key == input.KeyRight:
 		if sel {
-			this.Select(text.SelectRight(this.runes, dot, word))
+			this.userSelect(text.SelectRight(this.runes, dot, word))
 		} else {
-			this.Select(text.MoveRight(this.runes, dot, word))
+			this.userSelect(text.MoveRight(this.runes, dot, word))
 		}
 		return true
-	case key == input.Key('a') && modifiers.Control:
+	case key == input.KeyUp:
+		moveVertically(fixed.I(-1))
+		return true
+	case key == input.KeyDown:
+		moveVertically(fixed.I(1))
+		return true
+	case key == input.Key('a') && modifiers.Control():
 		dot.Start = 0
-		dot.End   = len(this.text)
+		dot.End   = len(this.runes)
-		this.Select(dot)
+		this.userSelect(dot)
 		return true
 	default:
 		return false
@@ -349,15 +494,19 @@ func (this *textBox) handleKeyUp (key input.Key, numberPad bool) bool {
 	
 	modifiers := this.Window().Modifiers()
 	switch {
-	case key == input.KeyHome || (modifiers.Alt && key == input.KeyLeft):
+	case key == input.KeyHome || (modifiers.Alt() && key == input.KeyLeft):
 		return true
-	case key == input.KeyEnd || (modifiers.Alt && key == input.KeyRight):
+	case key == input.KeyEnd || (modifiers.Alt() && key == input.KeyRight):
+		return true
+	case key == input.KeyUp:
+		return true
+	case key == input.KeyDown:
 		return true
 	case key == input.KeyLeft:
 		return true
 	case key == input.KeyRight:
 		return true
-	case key == input.Key('a') && modifiers.Control:
+	case key == input.Key('a') && modifiers.Control():
 		return true
 	default:
 		return false
@@ -447,3 +596,104 @@ func (this *textBox) scrollToDot () {
 	
 	this.ScrollTo(scroll)
 }
+
+func (this *textBox) handleFaceChange () {
+	hierarchy := this.getHierarchy()
+	if hierarchy == nil { return }
+	faceSet := hierarchy.getFaceSet()
+	if faceSet == nil { return }
+	
+	face := faceSet.Face(tomo.Face(this.attrFace.Value()))
+	this.face.Set(face, face)
+	this.drawer.SetFace(face)
+	this.invalidateMinimum()
+	this.invalidateLayout()
+	this.lineHeight.Invalidate()
+}
+
+func (this *textBox) recursiveReApply () {
+	this.box.recursiveReApply()
+	
+	hierarchy := this.getHierarchy()
+	if hierarchy == nil { return }
+	
+	previousFace := this.face.Value()
+	if previousFace == nil {
+		faceSet := hierarchy.getFaceSet()
+		if faceSet == nil { return }
+		face := faceSet.Face(tomo.Face(this.attrFace.Value()))
+		if face != previousFace {
+			this.face.Set(face, face)
+			this.drawer.SetFace(face)
+			this.invalidateMinimum()
+			this.invalidateLayout()
+		}
+	}
+}
+
+// TODO: these two functions really could be better.
+
+func previousParagraph (text []rune, index int) int {
+	consecLF := 0
+	if index >= len(text) { index = len(text) - 1 }
+	for ; index > 0; index -- {
+		char := text[index]
+		if char == '\n' {
+			consecLF ++
+		} else if !unicode.IsSpace(char) {
+			if consecLF >= 2 { return index + 1 }
+			consecLF  = 0
+		}
+	}
+	return index
+}
+
+func nextParagraph (text []rune, index int) int {
+	consecLF := 0
+	for ; index < len(text); index ++ {
+		char := text[index]
+		if char == '\n' {
+			consecLF ++
+		} else if !unicode.IsSpace(char) {
+			if consecLF >= 2 { return index }
+			consecLF = 0
+		}
+	}
+	return index
+}
+
+func lineHome (text []rune, index int) int {
+	liminal := index < len(text) && text[index] == '\n'
+	if index >= len(text) { index = len(text) - 1 }
+	for index := index; index >= 0; index -- {
+		char := text[index]
+		if char == '\n' && !liminal {
+			return index + 1
+		}
+		liminal = false
+	}
+	return 0
+}
+
+func lineHomeSoft (text []rune, index int) int {
+	home  := lineHome(text, index)
+	start := home
+	for start < len(text) && unicode.IsSpace(text[start]) {
+		start ++
+	}
+	if index == start {
+		return home
+	} else {
+		return start
+	}
+}
+
+func lineEnd (text []rune, index int) int {
+	for ; index < len(text); index ++ {
+		char := text[index]
+		if char == '\n' {
+			return index
+		}
+	}
+	return index
+}

internal/util/util.go

@@ -1,106 +1,6 @@
 package util
 
 import "io"
-import "image/color"
-
-// IndexOf returns the index of needle within haystack. If needle does not exist
-// within haystack, it returns -1.
-func IndexOf[T comparable] (haystack []T, needle T) int {
-	for index, test := range haystack {
-		if test == needle {
-			return index
-		}
-	}
-	return -1
-}
-
-// Remove removes an element from slice at index.
-func Remove[T any] (slice []T, index int) []T {
-	return append(slice[:index], slice[index + 1:]...)
-}
-
-// Insert inserts an element into slice at index.
-func Insert[T any] (slice []T, index int, element T) []T {
-	slice = append(slice[:index + 1], slice[index:]...)
-	slice[index] = element
-	return slice
-}
-
-// Transparent returns whether or not a color has transparency.
-func Transparent (c color.Color) bool {
-	_, _, _, a := c.RGBA()
-	return a != 0xFFFF
-}
-
-// Set is a set of unique items, built on top of map.
-type Set[T comparable] map[T] struct { }
-
-// Empty returns true if there are no items in the set.
-func (set Set[T]) Empty () bool {
-	return set == nil || len(set) == 0
-}
-
-// Has returns true if the set contains item.
-func (set Set[T]) Has (item T) bool {
-	if set == nil {
-		return false
-	}
-	_, ok := set[item]
-	return ok
-}
-
-// Add adds an item to the set.
-func (set Set[T]) Add (item T) {
-	set[item] = struct { } { }
-}
-
-// Pop removes the first accessible item from the set and returns it.
-func (set Set[T]) Pop () (item T) {
-	for item := range set {
-		delete(set, item)
-		return item
-	}
-	return
-}
-
-// Memo holds a cached value.
-type Memo[T any] struct {
-	cache  T
-	valid  bool
-	update func () T
-}
-
-// NewMemo creates a new Memo which will take its value from the specified
-// update callback.
-func NewMemo[T any] (update func () T) Memo[T] {
-	return Memo[T] {
-		update: update,
-	}
-}
-
-// Value returns the Memo's value, updating it if the current cached value is
-// invalid.
-func (this *Memo[T]) Value () T {
-	if !this.valid {
-		this.cache = this.update()
-		this.valid = true
-	}
-	return this.cache
-}
-
-// Invalidate marks the Memo's value as invalid, which will cause it to be
-// updated the next time Value is called.
-func (this *Memo[T]) Invalidate () {
-	this.valid = false
-}
-
-// InvalidateTo invalidates the Memo and sets its value. The new value will be
-// entirely inaccessible. This is only intended to be used for setting a
-// reference to nil
-func (this *Memo[T]) InvalidateTo (value T) {
-	this.Invalidate()
-	this.cache = value
-}
 
 // Cycler stores a value and an accompanying io.Closer. When the value is set,
 // the closer associated with the previous value is closed.

style/faceset.go

@@ -0,0 +1,13 @@
+package style
+
+import "golang.org/x/image/font"
+import "git.tebibyte.media/tomo/tomo"
+
+// FaceSet holds a set of font faces.
+type FaceSet interface {
+	// Face returns the font face which most closely matches the given
+	// tomo.Face. The face must be closed when it is done being used. If no
+	// suitable face could be found, This behavior must return a fallback
+	// face (such as basicfont.Face7x13) instead of nil.
+	Face (tomo.Face) font.Face
+}

style/iconset.go

@@ -0,0 +1,28 @@
+package style
+
+import "git.tebibyte.media/tomo/tomo"
+import "git.tebibyte.media/tomo/tomo/data"
+import "git.tebibyte.media/tomo/tomo/canvas"
+
+// 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 (tomo.Icon, tomo.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, tomo.IconSize) canvas.Texture
+}

style/style.go

@@ -0,0 +1,70 @@
+package style
+
+import "image/color"
+import "git.tebibyte.media/tomo/tomo"
+
+// 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[tomo.Color] color.Color
+}
+
+// Rule describes under what circumstances should certain style attributes be
+// active.
+type Rule struct {
+	Role tomo.Role
+	Tags []string
+	Set  AttrSet
+}
+
+// Ru is shorthand for creating a rule structure
+func Ru (set AttrSet, role tomo.Role, tags ...string) Rule {
+	return Rule {
+		Role: role,
+		Tags: tags,
+		Set:  set,
+	}
+}
+
+// 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[tomo.AttrKind] tomo.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 ...tomo.Attr) AttrSet {
+	set := AttrSet { }
+	set.Add(attrs...)
+	return set
+}
+
+// Add adds attributes to the set.
+func (this AttrSet) Add (attrs ...tomo.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)
+	}
+}

x/backend.go

@@ -4,7 +4,9 @@ import "image"
 import "errors"
 import "git.tebibyte.media/tomo/tomo"
 import "git.tebibyte.media/tomo/xgbkb"
+import "git.tebibyte.media/tomo/tomo/data"
 import "git.tebibyte.media/tomo/tomo/canvas"
+import "git.tebibyte.media/tomo/backend/style"
 import "git.tebibyte.media/tomo/backend/x/canvas"
 import "git.tebibyte.media/tomo/backend/internal/system"
 
@@ -18,6 +20,9 @@ type Backend struct {
 	x         *xgbutil.XUtil
 	system    *system.System
 
+	style     *style.Style
+	iconSet   style.IconSet
+	
 	doChannel chan func()
 	windows   map[xproto.Window] *window
 	open      bool
@@ -126,12 +131,33 @@ func (this *Backend) NewCanvas (bounds image.Rectangle) canvas.CanvasCloser {
 	return xcanvas.NewCanvas(this.x, bounds)
 }
 
-func (this *Backend) SetStyle (style *tomo.Style) {
+func (this *Backend) ColorRGBA (id tomo.Color) (r, g, b, a uint32) {
+	if col, ok := this.style.Colors[id]; ok {
+		return col.RGBA()
+	}
+	return 0xFFFF, 0, 0xFFFF, 0xFFFF // punish bad styles
+}
+
+func (this *Backend) IconTexture (id tomo.Icon, size tomo.IconSize) canvas.Texture {
+	return this.iconSet.Icon(id, size)
+}
+
+func (this *Backend) MimeIconTexture (mime data.Mime, size tomo.IconSize) canvas.Texture {
+	return this.iconSet.MimeIcon(mime, size)
+}
+
+func (this *Backend) SetStyle (style *style.Style) {
+	this.style = style
 	this.system.SetStyle(style)
 }
 
-func (this *Backend) SetIconSet (icons tomo.IconSet) {
+func (this *Backend) SetIconSet (iconSet style.IconSet) {
-	this.system.SetIconSet(icons)
+	this.iconSet = iconSet
+	this.system.SetIconSet(iconSet)
+}
+
+func (this *Backend) SetFaceSet (faceSet style.FaceSet) {
+	this.system.SetFaceSet(faceSet)
 }
 
 func (this *Backend) assert () {

x/canvas/canvas.go

@@ -132,3 +132,32 @@ func convertColor (c color.Color) xgraphics.BGRA {
 		A: uint8(a >> 8),
 	}
 }
+
+// For some reason, xgraphics.BGRA does not specify whether or not it uses
+// premultiplied alpha, and information regarding this is contradictory.
+// Basically:
+//   - BGRAModel just takes the result of c.RGBA and bit shifts it, without
+//     un-doing the aplha premultiplication that is required by Color.RGBA,
+//     suggesting that xgraphics.BGRA stores alpha-premultiplied color.
+//   - xgraphics.BlendBGRA lerps between dest and src using only the alpha of
+//     src (temporarily converting the colors to fucking floats for some reason)
+//     which seems to suggest that xgraphics.BGRA *does not* store alpha-
+//     premultiplied color.
+// There is no issues page on xgbutil so we may never get an answer to this
+// question. However, in this package we just use xgraphics.BGRA to store alpha-
+// premultiplied color anyway because its way faster, and I would sooner eat
+// spaghetti with a spoon than convert to and from float64 to blend pixels.
+func blendPremultipliedBGRA (dst, src xgraphics.BGRA) xgraphics.BGRA {
+	// https://en.wikipedia.org/wiki/Alpha_compositing
+	return xgraphics.BGRA {
+		B: blendPremultipliedChannel(dst.B, src.B, src.A),
+		G: blendPremultipliedChannel(dst.G, src.G, src.A),
+		R: blendPremultipliedChannel(dst.R, src.R, src.A),
+		A: blendPremultipliedChannel(dst.A, src.A, src.A),
+	}
+}
+
+func blendPremultipliedChannel (dst, src, a uint8) uint8 {
+	dst16, src16, a16 := uint16(dst), uint16(src), uint16(a)
+	return uint8(src16 + ((dst16 * (255 - a16)) >> 8))
+}

x/canvas/draw.go

@@ -46,7 +46,7 @@ func (this *pen) textureRectangleTransparent (bounds image.Rectangle) {
 		srcPos := pos.Add(offset)
 		dstIndex := this.image.PixOffset(pos.X, pos.Y)
 		srcIndex := this.texture.PixOffset(srcPos.X, srcPos.Y)
-		pixel := xgraphics.BlendBGRA(xgraphics.BGRA {
+		pixel := blendPremultipliedBGRA(xgraphics.BGRA {
 			B: dst[dstIndex + 0],
 			G: dst[dstIndex + 1],
 			R: dst[dstIndex + 2],
@@ -93,7 +93,7 @@ func (this *pen) fillRectangleTransparent (c xgraphics.BGRA, bounds image.Rectan
 	for pos.Y = bounds.Min.Y; pos.Y < bounds.Max.Y; pos.Y ++ {
 	for pos.X = bounds.Min.X; pos.X < bounds.Max.X; pos.X ++ {
 		index := this.image.PixOffset(pos.X, pos.Y)
-		pixel := xgraphics.BlendBGRA(xgraphics.BGRA {
+		pixel := blendPremultipliedBGRA(xgraphics.BGRA {
 			B: this.image.Pix[index + 0],
 			G: this.image.Pix[index + 1],
 			R: this.image.Pix[index + 2],
@@ -256,7 +256,7 @@ func (context *fillingContext) fillPolygonHotTransparent () {
 			// fill pixels in between
 			for x := left; x < right; x ++ {
 				index := context.image.PixOffset(x, context.y)
-				pixel := xgraphics.BlendBGRA(xgraphics.BGRA {
+				pixel := blendPremultipliedBGRA(xgraphics.BGRA {
 					B: context.image.Pix[index + 0],
 					G: context.image.Pix[index + 1],
 					R: context.image.Pix[index + 2],

x/canvas/plot.go

@@ -32,7 +32,7 @@ func (context plottingContext) plot (center image.Point) {
 		for y := square.Min.Y; y < square.Max.Y; y ++ {
 		for x := square.Min.X; x < square.Max.X; x ++ {
 			index := context.image.PixOffset(x, y)
-			pixel := xgraphics.BlendBGRA(xgraphics.BGRA {
+			pixel := blendPremultipliedBGRA(xgraphics.BGRA {
 				B: context.image.Pix[index + 0],
 				G: context.image.Pix[index + 1],
 				R: context.image.Pix[index + 2],

x/event.go

@@ -7,6 +7,7 @@ import "github.com/jezek/xgb/xproto"
 import "git.tebibyte.media/tomo/xgbkb"
 import "github.com/jezek/xgbutil/xevent"
 import "git.tebibyte.media/tomo/tomo/input"
+import "git.tebibyte.media/tomo/tomo/config"
 
 type scrollSum struct {
 	x, y int
@@ -145,12 +146,15 @@ func (window *window) updateBounds () {
 	// need to sum up all their positions.
 	decorGeometry, _ := window.xWindow.DecorGeometry()
 	windowGeometry, _ := window.xWindow.Geometry()
-	origin := image.Pt(
+	origin := image.Pt (
-		windowGeometry.X() + decorGeometry.X(),
+		decorGeometry.X(),
-		windowGeometry.Y() + decorGeometry.Y())
+		decorGeometry.Y())
-	window.metrics.bounds = image.Rectangle {
+	innerOrigin := origin.Add(image.Pt (
-		Min: origin,
+		windowGeometry.X(),
-		Max: origin.Add(image.Pt(windowGeometry.Width(), windowGeometry.Height())),
+		windowGeometry.Y()))
+	window.metrics.innerBounds = image.Rectangle {
+		Min: innerOrigin,
+		Max: innerOrigin.Add(image.Pt(windowGeometry.Width(), windowGeometry.Height())),
 	}
 }
 
@@ -161,9 +165,9 @@ func (window *window) handleConfigureNotify (
 	configureEvent := *event.ConfigureNotifyEvent
 	configureEvent = window.compressConfigureNotify(configureEvent)
 	
-	oldBounds := window.metrics.bounds
+	oldBounds := window.metrics.innerBounds
 	window.updateBounds()
-	newBounds := window.metrics.bounds
+	newBounds := window.metrics.innerBounds
 
 	sizeChanged :=
 		oldBounds.Dx() != newBounds.Dx() ||
@@ -223,7 +227,7 @@ func (window *window) handleKeyPress (
 	key, numberPad := keycodeToKey(keyEvent.Detail, keyEvent.State)
 	window.updateModifiers(keyEvent.State)
 
-	if key == input.KeyEscape && window.shy {
+	if config.KeyChordClose.Pressed(key, window.Modifiers()) && window.shy {
 		window.Close()
 	} else {
 		window.hierarchy.HandleKeyDown(key, numberPad)
@@ -430,14 +434,15 @@ func (window *window) compressMotionNotify (
 
 func (window *window) updateModifiers (state uint16) {
 	xModifiers := xgbkb.StateToModifiers(state)
-	window.hierarchy.HandleModifiers(input.Modifiers {
+	var modifiers input.Modifiers
-		Shift:   xModifiers.Shift || xModifiers.ShiftLock,
+	if xModifiers.Shift     { modifiers |= input.ModShift   }
-		Control: xModifiers.Control,
+	if xModifiers.ShiftLock { modifiers |= input.ModShift   }
-		Alt:     xModifiers.Alt,
+	if xModifiers.Control   { modifiers |= input.ModControl }
-		Meta:    xModifiers.Meta,
+	if xModifiers.Alt       { modifiers |= input.ModAlt     }
-		Super:   xModifiers.Super,
+	if xModifiers.Meta      { modifiers |= input.ModMeta    }
-		Hyper:   xModifiers.Hyper,
+	if xModifiers.Super     { modifiers |= input.ModSuper   }
-	})
+	if xModifiers.Hyper     { modifiers |= input.ModHyper   }
+	window.hierarchy.HandleModifiers(modifiers)
 }
 
 func (window *window) updateMousePosition (x, y int16) {

x/window.go

@@ -1,6 +1,7 @@
 package x
 
 import "image"
+import "strings"
 
 import "git.tebibyte.media/tomo/tomo"
 import "git.tebibyte.media/tomo/tomo/data"
@@ -37,10 +38,14 @@ type window struct {
 	resizeY     bool
 
 	metrics struct {
-		bounds image.Rectangle
+		bounds      image.Rectangle // bounds, including frame
+		innerBounds image.Rectangle // bounds of the drawable area
 	}
 
-	onClose event.FuncBroadcaster
+	on struct {
+		close    event.FuncBroadcaster
+		tryClose event.Broadcaster[func () bool]
+	}
 }
 
 type windowLink struct {
@@ -63,27 +68,12 @@ func (this *windowLink) NotifyMinimumSizeChange () {
 	this.window.doMinimumSize()
 }
 
-func (this *Backend) NewWindow (
+func (this *Backend) NewWindow (kind tomo.WindowKind, bounds image.Rectangle) (tomo.Window, error) {
-	bounds image.Rectangle,
-) (
-	output tomo.Window,
-	err error,
-) {
 	this.assert()
-	return this.newWindow(bounds, false)
+	window, err := this.newWindow(bounds, kind == tomo.WindowKindMenu)
-}
+	if err != nil { return nil, err }
-
+	window.setKind(kind)
-func (this *Backend) NewPlainWindow (
+	return window, nil
-	bounds image.Rectangle,
-) (
-	output tomo.Window,
-	err error,
-) {
-	this.assert()
-	window, err := this.newWindow(bounds, false)
-	window.setType("dock")
-	
-	return window, err
 }
 
 func (this *Backend) newWindow (
@@ -130,7 +120,11 @@ func (this *Backend) newWindow (
 	if err != nil { return }
 
 	window.xWindow.WMGracefulClose (func (xWindow *xwindow.Window) {
-		window.Close()
+		holdOff := false
+		for _, callback := range window.on.tryClose.Listeners() {
+			if !callback() { holdOff = true }
+		}
+		if !holdOff { window.Close() }
 	})
 
 	xevent.ExposeFun(window.handleExpose).
@@ -156,7 +150,7 @@ func (this *Backend) newWindow (
 	// xevent.SelectionRequestFun(window.handleSelectionRequest).
 		// Connect(this.x, window.xWindow.Id)
 	
-	window.metrics.bounds = bounds
+	window.metrics.innerBounds = bounds
 	window.doMinimumSize()
 
 	this.windows[window.xWindow.Id] = window
@@ -165,6 +159,14 @@ func (this *Backend) newWindow (
 	return
 }
 
+func (this *window) Bounds () image.Rectangle {
+	return this.metrics.bounds.Sub(this.metrics.innerBounds.Min)
+}
+
+func (this *window) InnerBounds () image.Rectangle {
+	return this.metrics.innerBounds.Sub(this.metrics.innerBounds.Min)
+}
+
 func (this *window) SetRoot (root tomo.Object) {
 	if root == nil {
 		this.hierarchy.SetRoot(nil)
@@ -238,56 +240,29 @@ func (this *window) SetBounds (bounds image.Rectangle) {
 		bounds.Min.Y + bounds.Dy())
 }
 
-func (this *window) NewChild (bounds image.Rectangle) (tomo.Window, error) {
+func (this *window) NewChild (kind tomo.WindowKind, bounds image.Rectangle) (tomo.Window, error) {
 	leader := this.leader
 	
 	child, err := this.backend.newWindow (
-		bounds.Add(this.metrics.bounds.Min), false)
+		bounds.Add(this.metrics.innerBounds.Min), kind == tomo.WindowKindMenu)
-	child.leader = leader
 	if err != nil { return nil, err }
 	
-	child.setClientLeader(leader)
+	child.leader = leader
-	leader.setClientLeader(leader)
+	err = child.setKind(kind)
+	if err != nil { return nil, err }
+	if kind == tomo.WindowKindModal {
+		this.hasModal     = true
+		child.modalParent = this
+	}
 	
 	icccm.WmTransientForSet (
 		this.backend.x,
 		child.xWindow.Id,
 		leader.xWindow.Id)
-	child.setType("UTILITY")
 	// child.inheritProperties(leader.window)
 	return child, err
 }
 
-func (this *window) NewMenu (bounds image.Rectangle) (tomo.Window, error) {
-	menu, err := this.backend.newWindow (
-		bounds.Add(this.metrics.bounds.Min), true)
-	menu.shy = true
-	icccm.WmTransientForSet (
-		this.backend.x,
-		menu.xWindow.Id,
-		this.xWindow.Id)
-	menu.setType("POPUP_MENU")
-	// menu.inheritProperties(this)
-	return menu, err
-}
-
-func (this *window) NewModal (bounds image.Rectangle) (tomo.Window, error) {
-	modal, err := this.backend.newWindow (
-		bounds.Add(this.metrics.bounds.Min), false)
-	icccm.WmTransientForSet (
-		this.backend.x,
-		modal.xWindow.Id,
-		this.xWindow.Id)
-	ewmh.WmStateSet (
-		this.backend.x,
-		modal.xWindow.Id,
-		[]string { "_NET_WM_STATE_MODAL" })
-	modal.modalParent = this
-	this.hasModal     = true
-	// modal.inheritProperties(window)
-	return modal, err
-}
-
 func (this *window) Modifiers () input.Modifiers {
 	return this.hierarchy.Modifiers()
 }
@@ -321,12 +296,12 @@ func (this *window) Visible () bool {
 	return this.visible
 }
 
-func (this *window) Close () {
+func (this *window) Close () error {
 	xevent   .Detach(this.backend.x, this.xWindow.Id)
 	keybind  .Detach(this.backend.x, this.xWindow.Id)
 	mousebind.Detach(this.backend.x, this.xWindow.Id)
 
-	this.onClose.Broadcast()
+	this.on.close.Broadcast()
 	if this.modalParent != nil {
 		// we are a modal dialog, so unlock the parent
 		this.modalParent.hasModal = false
@@ -336,10 +311,15 @@ func (this *window) Close () {
 	delete(this.backend.windows, this.xWindow.Id)
 	this.xWindow.Destroy()
 	this.hierarchy.Close()
+	return nil // TODO maybe return an error? maybe join them?
 }
 
 func (this *window) OnClose (callback func ()) event.Cookie {
-	return this.onClose.Connect(callback)
+	return this.on.close.Connect(callback)
+}
+
+func (this *window) OnTryClose (callback func () bool) event.Cookie {
+	return this.on.tryClose.Connect(callback)
 }
 
 func (this *window) grabInput () {
@@ -355,6 +335,19 @@ func (this *window) ungrabInput () {
 	mousebind.UngrabPointer(this.backend.x)
 }
 
+func (this *window) setKind (kind tomo.WindowKind) error {
+	err := this.setType(windowKindToType(kind))
+	if err != nil { return err }
+	if kind == tomo.WindowKindModal {
+		err = this.setState("MODAL")
+		if err != nil { return err }
+	}
+	if kind == tomo.WindowKindMenu {
+		this.shy = true
+	}
+	return nil
+}
+
 func (this *window) setType (ty string) error {
 	return ewmh.WmWindowTypeSet (
 		this.backend.x,
@@ -362,6 +355,13 @@ func (this *window) setType (ty string) error {
 		[]string { "_NET_WM_WINDOW_TYPE_" + ty })
 }
 
+func (this *window) setState (state string) error {	
+	return ewmh.WmStateSet (
+		this.backend.x,
+		this.xWindow.Id,
+		[]string { "_NET_WM_STATE_" + state })
+}
+
 func (this *window) setClientLeader (leader *window) error {
 	hints, _ := icccm.WmHintsGet(this.backend.x, this.xWindow.Id)
 	if hints == nil {
@@ -382,8 +382,8 @@ func (this *window) reallocateCanvas () {
 		previousHeight = this.xCanvas.Bounds().Dy()
 	}
 	
-	newWidth  := this.metrics.bounds.Dx()
+	newWidth  := this.metrics.innerBounds.Dx()
-	newHeight := this.metrics.bounds.Dy()
+	newHeight := this.metrics.innerBounds.Dy()
 	larger    := newWidth > previousWidth || newHeight > previousHeight
 	smaller   := newWidth < previousWidth / 2 || newHeight < previousHeight / 2
 
@@ -403,7 +403,7 @@ func (this *window) reallocateCanvas () {
 	}
 
 	this.hierarchy.SetCanvas(this.xCanvas.SubCanvas (
-		this.metrics.bounds.Sub(this.metrics.bounds.Min)))
+		this.metrics.innerBounds.Sub(this.metrics.innerBounds.Min)))
 }
 
 func (this *window) pushAll () {
@@ -458,12 +458,24 @@ func (this *window) doMinimumSize () {
 		this.backend.x,
 		this.xWindow.Id,
 		&hints)
-	newWidth  := this.metrics.bounds.Dx()
+	newWidth  := this.metrics.innerBounds.Dx()
-	newHeight := this.metrics.bounds.Dy()
+	newHeight := this.metrics.innerBounds.Dy()
 	if newWidth  < size.X { newWidth  = size.X }
 	if newHeight < size.Y { newHeight = size.Y }
-	if newWidth != this.metrics.bounds.Dx() ||
+	if newWidth != this.metrics.innerBounds.Dx() ||
-		newHeight != this.metrics.bounds.Dy() {
+		newHeight != this.metrics.innerBounds.Dy() {
 		this.xWindow.Resize(newWidth, newHeight)
 	}
 }
+
+func windowKindToType (kind tomo.WindowKind) string {
+	switch kind {
+	case tomo.WindowKindNormal:  return "NORMAL"
+	case tomo.WindowKindPlain:   return "DOCK"
+	case tomo.WindowKindUtility: return "UTILITY"
+	case tomo.WindowKindToolbar: return "MENU"
+	case tomo.WindowKindMenu:    return "POPUP_MENU"
+	case tomo.WindowKindModal:   return "NORMAL"
+	default:                     return strings.ReplaceAll(strings.ToUpper(string(kind)), " ", "_")
+	}
+}