Box doesn't crash when cetering a nil texture

Remedy #8

README.md

@@ -3,12 +3,3 @@
 [![Go Reference](https://pkg.go.dev/badge/git.tebibyte.media/tomo/x.svg)](https://pkg.go.dev/git.tebibyte.media/tomo/x)
 
 An X11 backend for Tomo.
-
-## Installation
-
-```
-cd x/x
-go build -buildmode=plugin .
-mkdir -p ~/.local/lib/tomo/plugins
-mv x.so ~/.local/lib/tomo/plugins
-```

box.go

@@ -9,23 +9,29 @@ import "git.tebibyte.media/tomo/tomo/input"
 import "git.tebibyte.media/tomo/tomo/event"
 import "git.tebibyte.media/tomo/tomo/canvas"
 
+type textureMode int; const (
+	textureModeTile textureMode = iota
+	textureModeCenter
+)
+
 type box struct {
 	backend *Backend
 	parent   parent
 	outer    anyBox
 
-	bounds      image.Rectangle
-	minSize     image.Point
-	userMinSize image.Point
+	bounds              image.Rectangle
+	minSize             image.Point
+	userMinSize         image.Point
 	innerClippingBounds image.Rectangle
 	
 	minSizeQueued bool
 	focusQueued   *bool
 
-	padding tomo.Inset
-	border  []tomo.Border
-	color   color.Color
-	texture *xcanvas.Texture
+	padding     tomo.Inset
+	border      []tomo.Border
+	color       color.Color
+	texture     *xcanvas.Texture
+	textureMode textureMode
 
 	dndData   data.Data
 	dndAccept []data.Mime
@@ -116,15 +122,43 @@ func (this *box) SetColor (c color.Color) {
 	this.invalidateDraw()
 }
 
-func (this *box) SetTexture (texture canvas.Texture) {
+func (this *box) SetTextureTile (texture canvas.Texture) {
+	if this.texture == texture && this.textureMode == textureModeTile { return }
+	this.textureMode = textureModeTile
 	this.texture = xcanvas.AssertTexture(texture)
 	this.invalidateDraw()
 }
 
-func (this *box) SetBorder (border ...tomo.Border) {
-	this.border = border
-	this.invalidateLayout()
-	this.invalidateMinimum()
+func (this *box) SetTextureCenter (texture canvas.Texture) {
+	if this.texture == texture && this.textureMode == textureModeCenter { return }
+	this.texture = xcanvas.AssertTexture(texture)
+	this.textureMode = textureModeCenter
+	this.invalidateDraw()
+}
+
+func (this *box) SetBorder (borders ...tomo.Border) {
+	previousBorderSum := this.borderSum()
+	previousBorders   := this.border
+	this.border = borders
+
+	// only invalidate the layout if the border is sized differently
+	if this.borderSum() != previousBorderSum {
+		this.invalidateLayout()
+		this.invalidateMinimum()
+		return
+	}
+
+	// if the border takes up the same amount of space, only invalidate the
+	// drawing if it looks different
+	for index, newBorder := range this.border {
+		different :=
+			index >= len(previousBorders) ||
+			newBorder != previousBorders[index]
+		if different {
+			this.invalidateDraw()
+			return
+		}
+	}
 }
 
 func (this *box) SetMinimumSize (size image.Point) {
@@ -279,13 +313,34 @@ func (this *box) handleKeyUp (key input.Key, numberPad bool) {
 func (this *box) Draw (can canvas.Canvas) {
 	if can == nil { return }
 	pen := can.Pen()
+	bounds := this.Bounds()
+
+	// background
 	pen.Fill(this.color)
-	pen.Texture(this.texture)
-	
+	if this.textureMode == textureModeTile {
+		pen.Texture(this.texture)
+	}
 	if this.transparent() && this.parent != nil {
 		this.parent.drawBackgroundPart(can)
 	}
-	pen.Rectangle(can.Bounds())
+	pen.Rectangle(bounds)
+
+	// centered texture
+	if this.textureMode == textureModeCenter && this.texture != nil {
+		textureBounds := this.texture.Bounds()
+		textureOrigin :=
+			bounds.Min.
+			Add(image.Pt (
+				bounds.Dx() / 2,
+				bounds.Dy() / 2)).
+			Sub(image.Pt (
+				textureBounds.Dx() / 2,
+				textureBounds.Dy() / 2))
+	
+		pen.Fill(color.Transparent)
+		pen.Texture(this.texture)
+		pen.Rectangle(textureBounds.Sub(textureBounds.Min).Add(textureOrigin))
+	}
 }
 
 func (this *box) drawBorders (can canvas.Canvas) {
@@ -296,7 +351,7 @@ 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 transparent(c) && this.parent != nil {
-			this.parent.drawBackgroundPart(can.Clip(area))
+			this.parent.drawBackgroundPart(can.SubCanvas(area))
 		}
 		pen.Fill(c)
 		pen.Rectangle(area)
@@ -356,20 +411,28 @@ func (this *box) doMinimumSize () {
 	}
 }
 
+// var drawcnt int
 func (this *box) doDraw () {
+	// println("DRAW", drawcnt)
+	// drawcnt ++
+	
 	if this.canvas == nil { return }
 	if this.drawer != nil {
 		this.drawBorders(this.canvas)
-		this.drawer.Draw(this.canvas.Clip(this.innerClippingBounds))
+		this.drawer.Draw(this.canvas.SubCanvas(this.innerClippingBounds))
 	}
 }
 
+// var laycnt int
 func (this *box) doLayout () {
+	// println("LAYOUT", laycnt)
+	// laycnt ++
+	
 	this.innerClippingBounds = this.borderSum().Apply(this.bounds)
 	if this.parent == nil { this.canvas = nil; return  }
 	parentCanvas := this.parent.canvas()
 	if parentCanvas == nil { this.canvas = nil; return }
-	this.canvas = parentCanvas.Clip(this.bounds)
+	this.canvas = parentCanvas.SubCanvas(this.bounds)
 }
 
 func (this *box) setParent (parent parent) {
@@ -401,12 +464,12 @@ func (this *box) recursiveRedo () {
 
 func (this *box) invalidateLayout () {
 	if this.parent == nil || this.parent.window() == nil { return }
-	this.parent.window().invalidateLayout(this.outer)
+	this.window().invalidateLayout(this.outer)
 }
 
 func (this *box) invalidateDraw () {
 	if this.parent == nil || this.parent.window() == nil { return }
-	this.parent.window().invalidateDraw(this.outer)
+	this.window().invalidateDraw(this.outer)
 }
 
 func (this *box) invalidateMinimum () {
@@ -414,7 +477,7 @@ func (this *box) invalidateMinimum () {
 		this.minSizeQueued = true
 		return
 	}
-	this.parent.window().invalidateMinimum(this.outer)
+	this.window().invalidateMinimum(this.outer)
 }
 
 func (this *box) canBeFocused () bool {
@@ -441,3 +504,8 @@ func (this *box) transparent () bool {
 	return transparent(this.color) &&
 		(this.texture == nil || !this.texture.Opaque())
 }
+
+func (this *box) window () *window {
+	if this.parent == nil { return nil }
+	return this.parent.window()
+}

canvas/canvas.go

@@ -32,8 +32,8 @@ func (this *Canvas) Pen () canvas.Pen {
 	}
 }
 
-// Clip returns a sub-canvas of this canvas.
-func (this *Canvas) Clip (bounds image.Rectangle) canvas.Canvas {
+// SubCanvas returns a subset of this canvas that points to the same data.
+func (this *Canvas) SubCanvas (bounds image.Rectangle) canvas.Canvas {
 	this.assert()
 	subImage := this.Image.SubImage(bounds)
 	if subImage == nil { return nil }

canvas/texture.go

@@ -86,8 +86,8 @@ func (this *Texture) Close () error {
 	return nil
 }
 
-// Clip returns a subset of this texture that points to the same data.
-func (this *Texture) Clip (bounds image.Rectangle) canvas.Texture {
+// SubTexture returns a subset of this texture that points to the same data.
+func (this *Texture) SubTexture (bounds image.Rectangle) canvas.Texture {
 	clipped := *this
 	clipped.rect = bounds
 	return &clipped

canvasbox.go

@@ -31,5 +31,5 @@ func (this *canvasBox) Invalidate () {
 func (this *canvasBox) Draw (can canvas.Canvas) {
 	this.box.Draw(can)
 	this.userDrawer.Draw (
-		can.Clip(this.padding.Apply(this.innerClippingBounds)))
+		can.SubCanvas(this.padding.Apply(this.innerClippingBounds)))
 }

containerbox.go

@@ -31,12 +31,20 @@ func (backend *Backend) NewContainerBox() tomo.ContainerBox {
 }
 
 func (this *containerBox) SetColor (c color.Color) {
+	if this.color == c { return }
 	this.box.SetColor(c)
 	this.invalidateTransparentChildren()
 }
 
-func (this *containerBox) SetTexture (texture canvas.Texture) {
-	this.box.SetTexture(texture)
+func (this *containerBox) SetTextureTile (texture canvas.Texture) {
+	if this.texture == texture { return }
+	this.box.SetTextureTile(texture)
+	this.invalidateTransparentChildren()
+}
+
+func (this *containerBox) SetTextureCenter (texture canvas.Texture) {
+	if this.texture == texture { return }
+	this.box.SetTextureTile(texture)
 	this.invalidateTransparentChildren()
 }
 
@@ -59,7 +67,7 @@ func (this *containerBox) ContentBounds () image.Rectangle {
 }
 
 func (this *containerBox) ScrollTo (point image.Point) {
-	// TODO: constrain scroll
+	if this.scroll == point { return }
 	this.scroll = point
 	this.invalidateLayout()
 }
@@ -68,19 +76,19 @@ func (this *containerBox) OnContentBoundsChange (callback func()) event.Cookie {
 	return this.on.contentBoundsChange.Connect(callback)
 }
 
-func (this *containerBox)  CaptureDND (capture bool) {
+func (this *containerBox) CaptureDND (capture bool) {
 	this.capture[eventCategoryDND] = capture
 }
 
-func (this *containerBox)  CaptureMouse (capture bool) {
+func (this *containerBox) CaptureMouse (capture bool) {
 	this.capture[eventCategoryMouse] = capture
 }
 
-func (this *containerBox)  CaptureScroll (capture bool) {
+func (this *containerBox) CaptureScroll (capture bool) {
 	this.capture[eventCategoryScroll] = capture
 }
 
-func (this *containerBox)  CaptureKeyboard (capture bool) {
+func (this *containerBox) CaptureKeyboard (capture bool) {
 	this.capture[eventCategoryKeyboard] = capture
 }
 
@@ -102,7 +110,7 @@ func (this *containerBox) Add (child tomo.Object) {
 	this.invalidateMinimum()
 }
 
-func (this *containerBox) Delete (child tomo.Object) {
+func (this *containerBox) Remove (child tomo.Object) {
 	box := assertAnyBox(child.GetBox())
 	index := indexOf(this.children, tomo.Box(box))
 	if index < 0 { return }
@@ -165,7 +173,7 @@ func (this *containerBox) Draw (can canvas.Canvas) {
 		rocks[index] = box.Bounds()
 	}
 	for _, tile := range canvas.Shatter(this.bounds, rocks...) {
-		clipped := can.Clip(tile)
+		clipped := can.SubCanvas(tile)
 		if this.transparent() && this.parent != nil {
 			this.parent.drawBackgroundPart(clipped)
 		}
@@ -226,9 +234,7 @@ func (this *containerBox) notifyMinimumSizeChange (child anyBox) {
 }
 
 func (this *containerBox) layoutHints () tomo.LayoutHints {
-	innerBounds := this.InnerBounds().Sub(this.scroll)
 	return tomo.LayoutHints {
-		Bounds:    innerBounds,
 		OverflowX: this.hOverflow,
 		OverflowY: this.vOverflow,
 		AlignX:    this.hAlign,
@@ -240,10 +246,12 @@ func (this *containerBox) layoutHints () tomo.LayoutHints {
 func (this *containerBox) contentMinimum () image.Point {
 	minimum := this.box.contentMinimum()
 	if this.layout != nil {
-		minimum = minimum.Add (
-			this.layout.MinimumSize (
-				this.layoutHints(),
-				this.children))
+		layoutMinimum := this.layout.MinimumSize (
+			this.layoutHints(),
+			this.children)
+		if this.hOverflow { layoutMinimum.X = 0 }
+		if this.vOverflow { layoutMinimum.Y = 0 }
+		minimum = minimum.Add(layoutMinimum)
 	}
 	return minimum
 }
@@ -251,14 +259,73 @@ func (this *containerBox) contentMinimum () image.Point {
 func (this *containerBox) doLayout () {
 	this.box.doLayout()
 	previousContentBounds := this.contentBounds
+
+	// by default, use innerBounds (translated to 0, 0) for contentBounds.
+	// if a direction overflows, use the layout's minimum size for it.
+	var minimum image.Point
 	if this.layout != nil {
-		this.layout.Arrange(this.layoutHints(), this.children)
+		minimum = this.layout.MinimumSize (
+			this.layoutHints(),
+			this.children)
 	}
+	innerBounds := this.InnerBounds()
+	this.contentBounds = innerBounds.Sub(innerBounds.Min)
+	if this.hOverflow { this.contentBounds.Max.X = this.contentBounds.Min.X + minimum.X }
+	if this.vOverflow { this.contentBounds.Max.Y = this.contentBounds.Min.Y + minimum.Y }
+	
+	// arrange children
+	if this.layout != nil {
+		layoutHints := this.layoutHints()
+		layoutHints.Bounds = this.contentBounds
+		this.layout.Arrange(layoutHints, this.children)
+	}
+
+	// build an accurate contentBounds by unioning the bounds of all child
+	// boxes
+	this.contentBounds = image.Rectangle { }
+	for _, box := range this.children {
+		bounds := box.Bounds()
+		this.contentBounds = this.contentBounds.Union(bounds)
+	}
+
+	// constrain the scroll
+	this.constrainScroll()
+
+	// offset children and contentBounds by scroll
+	for _, box := range this.children {
+		box.SetBounds(box.Bounds().Add(this.scroll).Add(innerBounds.Min))
+	}
+	this.contentBounds = this.contentBounds.Add(this.scroll)
+	
 	if previousContentBounds != this.contentBounds {
 		this.on.contentBoundsChange.Broadcast()
 	}
 }
 
+func (this *containerBox) constrainScroll () {
+	innerBounds := this.InnerBounds()
+	width  := this.contentBounds.Dx()
+	height := this.contentBounds.Dy()
+
+	// X
+	if width <= innerBounds.Dx() {
+		this.scroll.X = 0
+	} else if this.scroll.X > 0 {
+		this.scroll.X = 0
+	} else if this.scroll.X < innerBounds.Dx() - width  {
+		this.scroll.X =  innerBounds.Dx() - width
+	}
+
+	// Y
+	if height <= innerBounds.Dy() {
+		this.scroll.Y = 0
+	} else if this.scroll.Y > 0 {
+		this.scroll.Y = 0
+	} else if this.scroll.Y < innerBounds.Dy() - height {
+		this.scroll.Y = innerBounds.Dy() - height
+	}
+}
+
 func (this *containerBox) recursiveRedo () {
 	this.doLayout()
 	this.doDraw()
@@ -268,6 +335,8 @@ func (this *containerBox) recursiveRedo () {
 }
 
 func (this *containerBox) boxUnder (point image.Point, category eventCategory) anyBox {
+	if !point.In(this.bounds) { return nil }
+
 	if !this.capture[category] {
 		for _, box := range this.children {
 			candidate := box.(anyBox).boxUnder(point, category)
@@ -275,7 +344,7 @@ func (this *containerBox) boxUnder (point image.Point, category eventCategory) a
 		}
 	}
 
-	return this.box.boxUnder(point, category)
+	return this
 }
 
 func (this *containerBox) propagate (callback func (anyBox) bool) bool {

event.go

@@ -161,16 +161,17 @@ func (window *window) handleConfigureNotify (
 	if window.root == nil { return }
 	
 	configureEvent := *event.ConfigureNotifyEvent
+	configureEvent = window.compressConfigureNotify(configureEvent)
 	
-	newWidth  := int(configureEvent.Width)
-	newHeight := int(configureEvent.Height)
-	sizeChanged :=
-		window.metrics.bounds.Dx() != newWidth ||
-		window.metrics.bounds.Dy() != newHeight
+	oldBounds := window.metrics.bounds
 	window.updateBounds()
+	newBounds := window.metrics.bounds
+
+	sizeChanged :=
+		oldBounds.Dx() != newBounds.Dx() ||
+		oldBounds.Dy() != newBounds.Dy()
 
 	if sizeChanged {
-		configureEvent = window.compressConfigureNotify(configureEvent)
 		window.reallocateCanvas()
 
 		// TODO figure out what to do with this

examples/blank/main.go

@@ -0,0 +1,18 @@
+package main
+
+import "image"
+import "git.tebibyte.media/tomo/x"
+import "git.tebibyte.media/tomo/tomo"
+
+func main () {
+	tomo.Register(0, x.NewBackend)
+	err := tomo.Run(run)
+	if err != nil { panic(err) }
+}
+
+func run () {
+	window, err := tomo.NewWindow(image.Rect(0, 0, 200, 300))
+	if err != nil { panic(err) }
+	window.OnClose(tomo.Stop)
+	window.SetVisible(true)
+}

examples/text/main.go

@@ -0,0 +1,29 @@
+package main
+
+import "image"
+import "image/color"
+import "git.tebibyte.media/tomo/x"
+import "git.tebibyte.media/tomo/tomo"
+import "golang.org/x/image/font/basicfont"
+
+func main () {
+	tomo.Register(0, x.NewBackend)
+	err := tomo.Run(run)
+	if err != nil { panic(err) }
+}
+
+func run () {
+	window, err := tomo.NewWindow(image.Rectangle { })
+	if err != nil { panic(err) }
+
+	text := tomo.NewTextBox()
+	text.SetText("hello, world!")
+	text.SetTextColor(color.White)
+	text.SetColor(color.Black)
+	text.SetFace(basicfont.Face7x13)
+	text.SetPadding(tomo.I(8))
+	window.SetRoot(text)
+	
+	window.OnClose(tomo.Stop)
+	window.SetVisible(true)
+}

examples/texture/main.go

@@ -0,0 +1,83 @@
+package main
+
+import "math"
+import "image"
+import "math/rand"
+import "image/color"
+import "git.tebibyte.media/tomo/x"
+import "git.tebibyte.media/tomo/tomo"
+
+func main () {
+	tomo.Register(0, x.NewBackend)
+	err := tomo.Run(run)
+	if err != nil { panic(err) }
+}
+
+func run () {
+	window, err := tomo.NewWindow(image.Rect(0, 0, 256, 256))
+	if err != nil { panic(err) }
+	
+	texture := tomo.NewTexture(coolTexture())
+	
+	box := tomo.NewBox()
+	box.SetColor(color.Black)
+	box.SetTextureCenter(texture)
+	box.SetBorder (
+		tomo.Border {
+			Color: [4] color.Color {
+				color.Black, color.Black,
+				color.Black, color.Black },
+			Width: tomo.I(2),
+		},
+		tomo.Border {
+			Color: [4] color.Color {
+			color.White, color.White,
+			color.White, color.White },
+			Width: tomo.I(2),
+		})
+	
+	window.SetRoot(box)
+	window.OnClose(tomo.Stop)
+	window.SetVisible(true)
+}
+
+func coolTexture () image.Image {
+	// this picture IS COOL because i spent AN HOUR on it when i could have
+	// been FIXING BUGS!
+	speedX := 0.015
+	speedY := 0.035
+	bitmap := image.NewRGBA (image.Rect(0, 0, 200, 200))
+	for y := bitmap.Bounds().Min.Y; y < bitmap.Bounds().Max.Y; y++ {
+	for x := bitmap.Bounds().Min.X; x < bitmap.Bounds().Max.X; x++ {
+		value := ((
+			math.Sin(float64(y) * speedY) +
+			math.Cos(float64(x) * speedX)) + 2) / 4
+		value *= 0.7
+
+		r := value * 0.7 + 0.3
+		g := math.Sin(value * 7) * 0.7
+		b := (1 - value) * 0.7
+
+		noise := math.Mod(rand.Float64(), 1)
+		noise = math.Pow(noise, 2) + noise * 0.5
+		noise *= 0.05
+		
+		channel := func (f float64) uint8 {
+			contrast := 1.4
+			f = f * (contrast) - ((contrast - 1) / 2)
+			
+			if f < 0 { f = 0 }
+			if f > 1 { f = 1 }
+			
+			return uint8(f * 255)
+		}
+		
+		bitmap.Set(x, y, color.RGBA {
+			R: channel(r + noise),
+			G: channel(g + noise),
+			B: channel(b + noise),
+			A: 255,
+		})
+	}}
+	return bitmap
+}

go.mod

@@ -3,7 +3,7 @@ module git.tebibyte.media/tomo/x
 go 1.20
 
 require (
-	git.tebibyte.media/tomo/tomo v0.31.0
+	git.tebibyte.media/tomo/tomo v0.34.0
 	git.tebibyte.media/tomo/typeset v0.7.1
 	git.tebibyte.media/tomo/xgbkb v1.0.1
 	github.com/jezek/xgb v1.1.0

go.sum

@@ -1,6 +1,6 @@
 git.tebibyte.media/sashakoshka/xgbkb v1.0.0/go.mod h1:pNcE6TRO93vHd6q42SdwLSTTj25L0Yzggz7yLe0JV6Q=
-git.tebibyte.media/tomo/tomo v0.31.0 h1:LHPpj3AWycochnC8F441aaRNS6Tq6w6WnBrp/LGjyhM=
-git.tebibyte.media/tomo/tomo v0.31.0/go.mod h1:C9EzepS9wjkTJjnZaPBh22YvVPyA4hbBAJVU20Rdmps=
+git.tebibyte.media/tomo/tomo v0.34.0 h1:r5yJPks9rtzdDI2RyAUdqa1qb6BebG0QFe2cTmcFi+0=
+git.tebibyte.media/tomo/tomo v0.34.0/go.mod h1:C9EzepS9wjkTJjnZaPBh22YvVPyA4hbBAJVU20Rdmps=
 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/xgbkb v1.0.1 h1:b3HDUopjdQp1MZrb5Vpil4bOtk3NnNXtfQW27Blw2kE=

surfacebox.go

@@ -0,0 +1,8 @@
+package x
+
+import "errors"
+import "git.tebibyte.media/tomo/tomo"
+
+func (backend *Backend) NewSurfaceBox() (tomo.SurfaceBox, error) {
+	return nil, errors.New("SurfaceBox not implemented yet")
+}

system.go

@@ -241,7 +241,9 @@ func (window *window) afterEvent () {
 		// set child bounds
 		childBounds := window.metrics.bounds
 		childBounds = childBounds.Sub(childBounds.Min)
-		window.root.SetBounds(childBounds)
+		if window.root != nil {
+			window.root.SetBounds(childBounds)	
+		}
 
 		// full relayout/redraw
 		if window.root != nil {

textbox.go

@@ -222,12 +222,11 @@ func (this *textBox) drawDot (can canvas.Canvas) {
 
 func (this *textBox) textOffset () image.Point {
 	return this.InnerBounds().Min.
-		Sub(this.scroll).
+		Add(this.scroll).
 		Sub(this.drawer.LayoutBoundsSpace().Min)
 }
 
 func (this *textBox) handleFocusLeave () {
-	this.dot = text.EmptyDot(0)
 	this.on.dotChange.Broadcast()
 	this.invalidateDraw()
 	this.box.handleFocusLeave()
@@ -294,6 +293,7 @@ func (this *textBox) doLayout () {
 	this.contentBounds = this.normalizedLayoutBoundsSpace()
 	this.constrainScroll()
 	this.contentBounds = this.contentBounds.Add(this.scroll)
+	// println(this.InnerBounds().String(), this.contentBounds.String())
 
 	if previousContentBounds != this.contentBounds {
 		this.on.contentBoundsChange.Broadcast()
@@ -308,19 +308,19 @@ func (this *textBox) constrainScroll () {
 	// X
 	if width <= innerBounds.Dx() {
 		this.scroll.X = 0
-	} else if this.scroll.X < 0 {
+	} else if this.scroll.X > 0 {
 		this.scroll.X = 0
-	} else if this.scroll.X > width - innerBounds.Dx() {
-		this.scroll.X = width - innerBounds.Dx()
+	} else if this.scroll.X < innerBounds.Dx() - width  {
+		this.scroll.X =  innerBounds.Dx() - width
 	}
 
 	// Y
 	if height <= innerBounds.Dy() {
 		this.scroll.Y = 0
-	} else if this.scroll.Y < 0 {
+	} else if this.scroll.Y > 0 {
 		this.scroll.Y = 0
-	} else if this.scroll.Y > height - innerBounds.Dy() {
-		this.scroll.Y = height - innerBounds.Dy()
+	} else if this.scroll.Y < innerBounds.Dy() - height {
+		this.scroll.Y = innerBounds.Dy() - height
 	}
 }
 
@@ -333,16 +333,16 @@ func (this *textBox) scrollToDot () {
 
 	// X
 	if dot.X < innerBounds.Min.X + em {
-		scroll.X -= innerBounds.Min.X - dot.X + em
+		scroll.X += innerBounds.Min.X - dot.X + em
 	} else if dot.X > innerBounds.Max.X - em {
-		scroll.X += dot.X - innerBounds.Max.X + em
+		scroll.X -= dot.X - innerBounds.Max.X + em
 	}
 
 	// Y
 	if dot.Y < innerBounds.Min.Y + lineHeight {
-		scroll.Y -= innerBounds.Min.Y - dot.Y + lineHeight
+		scroll.Y += innerBounds.Min.Y - dot.Y + lineHeight
 	} else if dot.Y > innerBounds.Max.Y - lineHeight {
-		scroll.Y += dot.Y - innerBounds.Max.Y + lineHeight
+		scroll.Y -= dot.Y - innerBounds.Max.Y + lineHeight
 	}
 	
 	this.ScrollTo(scroll)

window.go

@@ -32,6 +32,7 @@ type window struct {
 	modalParent *window
 	hasModal    bool
 	shy         bool
+	visible     bool
 
 	metrics struct {
 		bounds image.Rectangle
@@ -265,14 +266,21 @@ func (window *window) Paste (callback func (data.Data, error), accept ...data.Mi
 	// TODO
 }
 
-func (window *window) Show () {
-	window.xWindow.Map()
-	if window.shy { window.grabInput() }
+func (window *window) SetVisible (visible bool) {
+	if window.visible == visible { return }
+	window.visible = visible
+	
+	if window.visible {
+		window.xWindow.Map()
+		if window.shy { window.grabInput() }
+	} else {
+		window.xWindow.Unmap()
+		if window.shy { window.ungrabInput() }
+	}
 }
 
-func (window *window) Hide () {
-	window.xWindow.Unmap()
-	if window.shy { window.ungrabInput() }
+func (window *window) Visible () bool {
+	return window.visible
 }
 
 func (window *window) Close () {
@@ -285,7 +293,7 @@ func (window *window) Close () {
 		// we are a modal dialog, so unlock the parent
 		window.modalParent.hasModal = false
 	}
-	window.Hide()
+	window.SetVisible(false)
 	window.SetRoot(nil)
 	delete(window.backend.windows, window.xWindow.Id)
 	window.xWindow.Destroy()
@@ -369,7 +377,7 @@ func (window *window) pushRegion (region image.Rectangle) {
 		return
 	}
 	
-	subCanvas := window.xCanvas.Clip(region)
+	subCanvas := window.xCanvas.SubCanvas(region)
 	if subCanvas == nil {
 		return
 	}