Select all in textBox uses the length of the rune slice

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 v0.46.1
-	git.tebibyte.media/tomo/typeset v0.7.1
+	git.tebibyte.media/sashakoshka/goutil v0.3.0
+	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 v0.46.1 h1:/8fT6I9l4TK529zokrThbNDHGRvUsNgif1Zs++0PBSQ=
-git.tebibyte.media/tomo/tomo v0.46.1/go.mod h1:WrtilgKB1y8O2Yu7X4mYcRiqOlPR8NuUnoA/ynkQWrs=
-git.tebibyte.media/tomo/typeset v0.7.1 h1:aZrsHwCG5ZB4f5CruRFsxLv5ezJUCFUFsQJJso2sXQ8=
-git.tebibyte.media/tomo/typeset v0.7.1/go.mod h1:PwDpSdBF3l/EzoIsa2ME7QffVVajnTHZN6l3MHEGe1g=
+git.tebibyte.media/tomo/tomo v0.48.0 h1:AE21ElHwUSPsX82ZWCnoNxJFi9Oswyd3dPDPMbxTueQ=
+git.tebibyte.media/tomo/tomo v0.48.0/go.mod h1:WrtilgKB1y8O2Yu7X4mYcRiqOlPR8NuUnoA/ynkQWrs=
+git.tebibyte.media/tomo/typeset v0.8.0 h1:4qA6oW4/3oPHj6/Zrp+JFJ53OmFSDvxs+J6BhO3DW00=
+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

@@ -1,12 +1,12 @@
 package system
 
 import "git.tebibyte.media/tomo/tomo"
-import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/sashakoshka/goutil/container"
 
 type attrHierarchy [T tomo.Attr] struct {
 	fallback T
-	style    util.Optional[T]
-	user     util.Optional[T]
+	style    ucontainer.Optional[T]
+	user     ucontainer.Optional[T]
 }
 
 func (this *attrHierarchy[T]) SetFallback (fallback T) {

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
 	lastIconSetNonce int
 	styleApplicator  *styleApplicator
 
-	minSize             util.Memo[image.Point]
+	minSize             ucontainer.Memo[image.Point]
 	bounds              image.Rectangle
 	innerClippingBounds image.Rectangle
 	
@@ -41,7 +42,7 @@ type box struct {
 	focused bool
 	pressed bool
 	
-	canvas util.Memo[canvas.Canvas]
+	canvas ucontainer.Memo[canvas.Canvas]
 	drawer canvas.Drawer
 
 	on struct {
@@ -68,10 +69,10 @@ func (this *System) newBox (outer anyBox) *box {
 		system:  this,
 		outer:   outer,
 		drawer:  outer,
-		tags:    make(util.Set[string]),
+		tags:    make(ucontainer.Set[string]),
 	}
 	box.attrColor.SetFallback(tomo.AColor(color.Transparent))
-	box.canvas = util.NewMemo (func () canvas.Canvas {
+	box.canvas = ucontainer.NewMemo (func () canvas.Canvas {
 		if box.parent == nil { return nil }
 		parentCanvas := box.parent.getCanvas()
 		if parentCanvas == nil { return nil }
@@ -82,7 +83,7 @@ func (this *System) newBox (outer anyBox) *box {
 		box.drawer = box
 		box.outer  = box
 	}
-	box.minSize = util.NewMemo(box.calculateMinimumSize)
+	box.minSize = ucontainer.NewMemo(box.calculateMinimumSize)
 	return box
 }
 
@@ -476,7 +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)
@@ -682,7 +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())*/
 }
 

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)
 	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)
 

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 {
-	case input.KeyTab:
-		if this.modifiers.Shift {
-			this.focusPrevious()
-		} else {
-			this.focusNext()
-		}
-	case input.KeyUp:   this.focusPrevious()
-	case input.KeyDown: this.focusNext()
+	switch input.KC(key, this.modifiers) {
+	case config.KeyChordFocusNext:                this.focusNext()
+	case config.KeyChordFocusPrevious:            this.focusPrevious()
+	// TODO: up, down, left, and right should find a box to the top, bottom,
+	// left, and right respectively to move the focus to. we might want to
+	// have four corresponding key chords in tomo/config.
+	case input.KC(input.KeyDown, input.ModNone):  this.focusNext()
+	case input.KC(input.KeyUp,   input.ModNone):  this.focusPrevious()
 	}
 }
 

internal/system/hierarchy.go

@@ -5,7 +5,7 @@ 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/style"
-import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/sashakoshka/goutil/container"
 
 // Hierarchy is coupled to a tomo.Window implementation, and manages a tree of
 // Boxes.
@@ -25,9 +25,9 @@ type Hierarchy struct {
 	drags         [10][]anyBox
 	minimumSize   image.Point
 
-	needStyle    util.Set[anyBox]
-	needLayout   util.Set[anyBox]
-	needDraw     util.Set[anyBox]
+	needStyle    ucontainer.Set[anyBox]
+	needLayout   ucontainer.Set[anyBox]
+	needDraw     ucontainer.Set[anyBox]
 	needRedo     bool
 	minimumClean bool
 }
@@ -53,9 +53,9 @@ func (this *System) NewHierarchy (link WindowLink) *Hierarchy {
 	hierarchy := &Hierarchy {
 		system:      this,
 		link:        link,
-		needStyle:   make(util.Set[anyBox]),
-		needLayout:  make(util.Set[anyBox]),
-		needDraw:    make(util.Set[anyBox]),
+		needStyle:   make(ucontainer.Set[anyBox]),
+		needLayout:  make(ucontainer.Set[anyBox]),
+		needDraw:    make(ucontainer.Set[anyBox]),
 	}
 	this.hierarchies.Add(hierarchy)
 	return hierarchy

internal/system/system.go

@@ -4,7 +4,7 @@ import "io"
 import "image"
 import "git.tebibyte.media/tomo/tomo/canvas"
 import "git.tebibyte.media/tomo/backend/style"
-import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/sashakoshka/goutil/container"
 
 // System is coupled to a tomo.Backend implementation, and manages Hierarchies
 // and Boxes.
@@ -17,7 +17,7 @@ type System struct {
 	styleNonce   int
 	iconSetNonce int
 	
-	hierarchies util.Set[*Hierarchy]
+	hierarchies ucontainer.Set[*Hierarchy]
 }
 
 // BackendLink allows the System to call up into the tomo.Backend implementation
@@ -41,7 +41,7 @@ type SurfaceLink interface {
 func New (link BackendLink) *System {
 	return &System {
 		link:        link,
-		hierarchies: make(util.Set[*Hierarchy]),
+		hierarchies: make(ucontainer.Set[*Hierarchy]),
 	}
 }
 

internal/system/textbox.go

@@ -1,6 +1,7 @@
 package system
 
 import "image"
+import "unicode"
 import "image/color"
 import "golang.org/x/image/font"
 import "git.tebibyte.media/tomo/tomo"
@@ -11,6 +12,7 @@ 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
@@ -31,9 +33,11 @@ type textBox struct {
 	selecting   bool
 	selectStart int
 	dot         text.Dot
+	desiredX    fixed.Int26_6
 
-	drawer typeset.Drawer
-	face   util.Cycler[font.Face]
+	drawer     typeset.Drawer
+	face       util.Cycler[font.Face]
+	lineHeight ucontainer.Memo[fixed.Int26_6]
 
 	on struct {
 		contentBoundsChange event.FuncBroadcaster
@@ -46,6 +50,12 @@ func (this *System) NewTextBox () tomo.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
 }
 
@@ -89,13 +99,41 @@ func (this *textBox) SetSelectable (selectable bool) {
 }
 
 func (this *textBox) Select (dot text.Dot) {
-	if !this.selectable { return }
-	if this.dot == dot  { return }
+	this.selec(dot)
+}
+
+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 {
@@ -237,20 +275,19 @@ func (this *textBox) drawDot (can canvas.Canvas) {
 	
 	pen := can.Pen()
 
-	bounds  := this.InnerBounds()
-	metrics := face.Metrics()
-	dot     := this.dot.Canon()
-	start   := this.drawer.PositionAt(dot.Start).Add(fixPt(this.textOffset()))
-	end     := 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  }
+	bounds   := this.InnerBounds()
+	metrics  := face.Metrics()
+	dot      := this.dot
+	canonDot := dot.Canon()
+	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():
-		pen.Stroke(textColor)
-		pen.StrokeWeight(1)
-		pen.Path(roundPt(start.Add(ascent)), roundPt(start.Sub(descent)))
+	case canonDot.Empty():
 
 	case start.Y == end.Y:
 		pen.Fill(dotColor)
@@ -284,6 +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 {
@@ -307,7 +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)
 }
@@ -316,7 +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)
 }
@@ -330,7 +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()
 }
@@ -342,6 +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 }
@@ -349,37 +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
-	word      := modifiers.Control
+	sel       := modifiers.Shift()
+	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):
-		dot.End = 0
+	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):
-		dot.End = len(this.text)
+	case key == input.KeyEnd || (modifiers.Alt() && key == input.KeyRight):
+		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)
-		this.Select(dot)
+		dot.End   = len(this.runes)
+		this.userSelect(dot)
 		return true
 	default:
 		return false
@@ -392,15 +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
@@ -502,6 +608,7 @@ func (this *textBox) handleFaceChange () {
 	this.drawer.SetFace(face)
 	this.invalidateMinimum()
 	this.invalidateLayout()
+	this.lineHeight.Invalidate()
 }
 
 func (this *textBox) recursiveReApply () {
@@ -523,3 +630,70 @@ func (this *textBox) recursiveReApply () {
 		}
 	}
 }
+
+// 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

@@ -1,100 +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 () {
-	var zero T
-	this.cache = zero
-	this.valid = false
-}
 
 // Cycler stores a value and an accompanying io.Closer. When the value is set,
 // the closer associated with the previous value is closed.
@@ -124,33 +30,3 @@ func (this *Cycler[T]) Close () error {
 	this.closer = nil
 	return err
 }
-
-// Optional is an optional value.
-type Optional[T any] struct {
-	value T
-	exists bool
-}
-
-// Value returns the value and true if the value exists. If not, it returns the
-// last set value and false.
-func (this *Optional[T]) Value () (T, bool) {
-	return this.value, this.exists
-}
-
-// Set sets the value.
-func (this *Optional[T]) Set (value T) {
-	this.value = value
-	this.exists = true
-}
-
-// Unset unsets the value.
-func (this *Optional[T]) Unset () {
-	var zero T
-	this.value = zero
-	this.exists = false
-}
-
-// Exists returns if the value is currently set.
-func (this *Optional[T]) Exists () bool {
-	return this.exists
-}