diff --git a/box.go b/box.go
index ffe5c96..7948f25 100644
--- a/box.go
+++ b/box.go
@@ -10,7 +10,7 @@ import "git.tebibyte.media/tomo/tomo/canvas"
 
 type box struct {
 	backend *Backend
-	window  *window
+	parent   parent
 
 	bounds  image.Rectangle
 	minSize image.Point
@@ -24,9 +24,7 @@ type box struct {
 	focused   bool
 	focusable bool
 
-	drawClean   bool
-	layoutClean bool
-
+	canvas canvas.Canvas
 	drawer canvas.Drawer
 
 	on struct {
@@ -47,11 +45,9 @@ type box struct {
 }
 
 func (backend *Backend) NewBox() tomo.Box {
-	box := &box {
+	return &box {
 		backend: backend,
 	}
-	box.drawer = box
-	return box
 }
 
 func (this *box) Box () tomo.Box {
@@ -59,7 +55,7 @@ func (this *box) Box () tomo.Box {
 }
 
 func (this *box) Window () tomo.Window {
-	return this.window
+	return this.parent.window()
 }
 
 func (this *box) Bounds () image.Rectangle {
@@ -114,9 +110,9 @@ func (this *box) SetDNDAccept (types ...data.Mime) {
 
 func (this *box) SetFocused (focused bool) {
 	if this.Focused () && !focused {
-		this.window.focus(nil)
+		this.parent.window().focus(nil)
 	} else if !this.Focused() && focused {
-		this.window.focus(this)
+		this.parent.window().focus(this)
 	}
 }
 
@@ -129,15 +125,15 @@ func (this *box) SetFocusable (focusable bool) {
 }
 
 func (this *box) Focused () bool {
-	return this == this.window.focused
+	return this == this.parent.window().focused
 }
 
 func (this *box) Modifiers () input.Modifiers {
-	return this.window.modifiers
+	return this.parent.window().modifiers
 }
 
 func (this *box) MousePosition () image.Point {
-	return this.window.mousePosition
+	return this.parent.window().mousePosition
 }
 
 // ----- event handlers ----------------------------------------------------- //
@@ -218,11 +214,32 @@ func (this *box) Draw (can canvas.Canvas) {
 	pen.Rectangle(bounds)
 }
 
+func (this *box) doDraw () {
+	if this.canvas == nil { return }
+	if this.drawer == nil {
+		this.Draw(this.canvas)
+	} else {
+		this.drawer.Draw(this.canvas)
+	}
+}
+
+func (this *box) doLayout () {
+	this.canvas = this.parent.canvas().Clip(this.bounds)
+}
+
+func (this *box) setParent (parent parent) {
+	this.parent = parent
+}
+
+func (this *box) recursiveRedo () {
+	this.doLayout()
+	this.doDraw()
+}
+
 func (this *box) invalidateDraw () {
-	this.drawClean = false
+	this.parent.window().invalidateDraw(this)
 }
 
 func (this *box) invalidateLayout () {
-	this.invalidateDraw()
-	this.layoutClean = false
+	this.parent.window().invalidateLayout(this)
 }
diff --git a/canvas/canvas.go b/canvas/canvas.go
index 048af8a..7bb8d4c 100644
--- a/canvas/canvas.go
+++ b/canvas/canvas.go
@@ -3,6 +3,7 @@ package xcanvas
 import "image"
 import "image/color"
 import "github.com/jezek/xgbutil"
+import "github.com/jezek/xgb/xproto"
 import "git.tebibyte.media/tomo/ggfx"
 import "github.com/jezek/xgbutil/xgraphics"
 import "git.tebibyte.media/tomo/tomo/canvas"
@@ -36,10 +37,16 @@ func (this Canvas) Pen () canvas.Pen {
 }
 
 // Clip returns a sub-canvas of this canvas.
-func (this Canvas) Clip (bounds image.Rectangle) Canvas {
+func (this Canvas) Clip (bounds image.Rectangle) canvas.Canvas {
 	return Canvas { this.Image.SubImage(bounds).(*xgraphics.Image) }
 }
 
+// Push pushes this canvas to the screen.
+func (this Canvas) Push (window xproto.Window) {
+	this.XDraw()
+	this.XExpPaint(window, this.Bounds().Min.X, this.Bounds().Min.Y)
+}
+
 // TODO: we need to implement:
 //  - cap
 //  - joint
diff --git a/event.go b/event.go
new file mode 100644
index 0000000..6faa15f
--- /dev/null
+++ b/event.go
@@ -0,0 +1,135 @@
+package x
+
+import "image"
+
+import "github.com/jezek/xgbutil"
+import "github.com/jezek/xgb/xproto"
+import "github.com/jezek/xgbutil/xevent"
+
+func (window *window) handleExpose (
+	connection *xgbutil.XUtil,
+	event xevent.ExposeEvent,
+) {
+	window.compressExpose(*event.ExposeEvent)
+	window.xCanvas.Push(window.xWindow.Id)
+}
+
+func (window *window) updateBounds () {
+	// FIXME: some window managers parent windows more than once, we might
+	// need to sum up all their positions.
+	decorGeometry, _ := window.xWindow.DecorGeometry()
+	windowGeometry, _ := window.xWindow.Geometry()
+	origin := image.Pt(
+		windowGeometry.X() + decorGeometry.X(),
+		windowGeometry.Y() + decorGeometry.Y())
+	window.metrics.bounds = image.Rectangle {
+		Min: origin,
+		Max: origin.Add(image.Pt(windowGeometry.Width(), windowGeometry.Height())),
+	}
+}
+
+func (window *window) handleConfigureNotify (
+	connection *xgbutil.XUtil,
+	event xevent.ConfigureNotifyEvent,
+) {
+	if window.root == nil { return }
+
+	configureEvent := *event.ConfigureNotifyEvent
+	
+	newWidth  := int(configureEvent.Width)
+	newHeight := int(configureEvent.Height)
+	sizeChanged :=
+		window.metrics.bounds.Dx() != newWidth ||
+		window.metrics.bounds.Dy() != newHeight
+	window.updateBounds()
+
+	if sizeChanged {
+		configureEvent = window.compressConfigureNotify(configureEvent)
+		window.reallocateCanvas()
+		window.root.SetBounds(window.metrics.bounds)
+		// TODO figure out what to do with this
+		// if !window.exposeEventFollows(configureEvent) {
+		// }
+	}
+}
+
+func (window *window) exposeEventFollows (event xproto.ConfigureNotifyEvent) (found bool) {	
+	nextEvents := xevent.Peek(window.backend.x)
+	if len(nextEvents) > 0 {
+		untypedEvent := nextEvents[0]
+		if untypedEvent.Err == nil {
+			typedEvent, ok :=
+				untypedEvent.Event.(xproto.ConfigureNotifyEvent)
+			
+			if ok && typedEvent.Window == event.Window {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+func (window *window) compressExpose (
+	firstEvent xproto.ExposeEvent,
+) (
+	lastEvent xproto.ExposeEvent,
+	region image.Rectangle,
+) {
+	region = image.Rect (
+		int(firstEvent.X), int(firstEvent.Y),
+		int(firstEvent.X + firstEvent.Width),
+		int(firstEvent.Y + firstEvent.Height))
+	
+	window.backend.x.Sync()
+	xevent.Read(window.backend.x, false)
+	lastEvent = firstEvent
+	
+	for index, untypedEvent := range xevent.Peek(window.backend.x) {
+		if untypedEvent.Err != nil { continue }
+		
+		typedEvent, ok := untypedEvent.Event.(xproto.ExposeEvent)
+		if !ok { continue }
+
+		if firstEvent.Window == typedEvent.Window {
+			region = region.Union (image.Rect (
+				int(typedEvent.X), int(typedEvent.Y),
+				int(typedEvent.X + typedEvent.Width),
+				int(typedEvent.Y + typedEvent.Height)))
+		
+			lastEvent = typedEvent
+			defer func (index int) {
+				xevent.DequeueAt(window.backend.x, index)
+			} (index)
+		}
+	}
+
+	return
+}
+
+func (window *window) compressConfigureNotify (
+	firstEvent xproto.ConfigureNotifyEvent,
+) (
+	lastEvent xproto.ConfigureNotifyEvent,
+) {
+	window.backend.x.Sync()
+	xevent.Read(window.backend.x, false)
+	lastEvent = firstEvent
+	
+	for index, untypedEvent := range xevent.Peek(window.backend.x) {
+		if untypedEvent.Err != nil { continue }
+		
+		typedEvent, ok := untypedEvent.Event.(xproto.ConfigureNotifyEvent)
+		if !ok { continue }
+		
+		if firstEvent.Event == typedEvent.Event &&
+			firstEvent.Window == typedEvent.Window {
+
+			lastEvent = typedEvent
+			defer func (index int) {
+				xevent.DequeueAt(window.backend.x, index)
+			} (index)
+		}
+	}
+
+	return
+}
diff --git a/system.go b/system.go
index 82b02c6..1cb96ab 100644
--- a/system.go
+++ b/system.go
@@ -1,20 +1,99 @@
 package x
 
+import "image"
 import "git.tebibyte.media/tomo/tomo"
+import "git.tebibyte.media/tomo/x/canvas"
+import "git.tebibyte.media/tomo/tomo/canvas"
+
+type boxSet map[anyBox] struct { }
+
+func (set boxSet) Empty () bool {
+	return set == nil || len(set) == 0
+}
+
+func (set boxSet) Has (box anyBox) bool {
+	if set == nil { return false }
+	_, ok := set[box]
+	return ok
+}
+
+func (set *boxSet) Add (box anyBox) {
+	if *set == nil {
+		*set = make(boxSet)
+	}
+	(*set)[box] = struct { } { }
+}
+
+func (set *boxSet) Pop () anyBox {
+	for box := range *set {
+		delete(*set, box)
+		return box
+	}
+	return nil
+}
+
+type parent interface {
+	window () *window
+	canvas () canvas.Canvas
+}
 
 type anyBox interface {
 	tomo.Box
-	invalidateDraw ()
-	invalidateLayout ()
+	doDraw        ()
+	doLayout      ()
+	setParent     (parent)
+	recursiveRedo ()
 }
 
 func (window *window) SetRoot (root tomo.Object) {
-	
+	box := root.Box().(anyBox)
+	window.root.setParent(nil)
+	box.setParent(window)
+	window.invalidateLayout(box)
+	window.root = box
 }
 
-func (window *window) focus (bx anyBox) {
-	if window.focused == bx { return }
-	window.focused.invalidateDraw()
-	window.focused = bx
-	bx.invalidateDraw()
+func (window *window) window () *window {
+	return window
+}
+
+func (window *window) canvas () canvas.Canvas {
+	return window.xCanvas
+}
+
+func (window *window) invalidateDraw (box anyBox) {
+	window.needDraw.Add(box)
+}
+
+func (window *window) invalidateLayout (box anyBox) {
+	window.needLayout.Add(box)
+	window.invalidateDraw(box)
+}
+
+func (window *window) focus (box anyBox) {
+	if window.focused == box { return }
+	window.invalidateDraw(window.focused)
+	window.focused = box
+	window.invalidateDraw(box)
+}
+
+func (window *window) afterEvent () {
+	if window.needRedo {
+		if window.root != nil {
+			window.root.recursiveRedo()
+		}
+		window.xCanvas.Push(window.xWindow.Id)
+		return
+	}
+
+	for len(window.needLayout) > 0 {
+		window.needLayout.Pop().doLayout()
+	}
+	var toPush image.Rectangle
+	for len(window.needDraw) > 0 {
+		box := window.needDraw.Pop()
+		box.doDraw()
+		toPush = toPush.Union(box.Bounds())
+	}
+	window.xCanvas.Clip(toPush).(xcanvas.Canvas).Push(window.xWindow.Id)
 }
diff --git a/window.go b/window.go
index 8471498..0f59b2a 100644
--- a/window.go
+++ b/window.go
@@ -4,6 +4,7 @@ import "image"
 // import "errors"
 
 import "git.tebibyte.media/tomo/tomo"
+import "git.tebibyte.media/tomo/x/canvas"
 import "git.tebibyte.media/tomo/tomo/data"
 import "git.tebibyte.media/tomo/tomo/input"
 import "git.tebibyte.media/tomo/tomo/event"
@@ -22,7 +23,8 @@ type mainWindow struct { *window }
 type window struct {
 	backend *Backend
 	xWindow *xwindow.Window
-	xCanvas *xgraphics.Image
+	xImage  *xgraphics.Image
+	xCanvas xcanvas.Canvas
 
 	title string
 
@@ -41,6 +43,10 @@ type window struct {
 
 	root    anyBox
 	focused anyBox
+
+	needDraw   boxSet
+	needLayout boxSet
+	needRedo   bool
 }
 
 func (backend *Backend) NewWindow (
@@ -124,7 +130,7 @@ func (backend *Backend) newWindow (
 	window.metrics.bounds = bounds
 	window.setMinimumSize(8, 8)
 
-	// window.reallocateCanvas()
+	window.reallocateCanvas()
 
 	backend.windows[window.xWindow.Id] = window
 
@@ -237,13 +243,13 @@ func (window *window) Paste (callback func (data.Data, error), accept ...data.Mi
 }
 
 func (window *window) Show () {
-	// if window.child == nil {
-		// window.xCanvas.For (func (x, y int) xgraphics.BGRA {
-			// return xgraphics.BGRA { }
-		// })
-// 
-		// window.pushRegion(window.xCanvas.Bounds())
-	// }
+	// fill the screen with black if there is no active child
+	if window.root == nil {
+		window.xCanvas.For (func (x, y int) xgraphics.BGRA {
+			return xgraphics.BGRA { }
+		})
+		window.xCanvas.Push(window.xWindow.Id)
+	}
 
 	window.xWindow.Map()
 	if window.shy { window.grabInput() }
@@ -265,7 +271,7 @@ func (window *window) Close () {
 		window.modalParent.hasModal = false
 	}
 	window.Hide()
-	// window.Adopt(nil)
+	window.SetRoot(nil)
 	delete(window.backend.windows, window.xWindow.Id)
 	window.xWindow.Destroy()
 }
@@ -307,6 +313,32 @@ func (window *window) setClientLeader (leader *window) error {
 		hints)
 }
 
+func (window *window) reallocateCanvas () {
+	previousWidth  := window.xCanvas.Bounds().Dx()
+	previousHeight := window.xCanvas.Bounds().Dy()
+	
+	newWidth  := window.metrics.bounds.Dx()
+	newHeight := window.metrics.bounds.Dy()
+	larger    := newWidth > previousWidth || newHeight > previousHeight
+	smaller   := newWidth < previousWidth / 2 || newHeight < previousHeight / 2
+
+	allocStep := 128
+	
+	if larger || smaller {
+		if window.xCanvas.Image != nil {
+			window.xCanvas.Destroy()
+		}
+		window.xCanvas = xcanvas.NewFrom(xgraphics.New (
+			window.backend.x,
+			image.Rect (
+				0, 0,
+				(newWidth  / allocStep + 1) * allocStep,
+				(newHeight / allocStep + 1) * allocStep)))
+		window.xCanvas.CreatePixmap()
+	}
+	window.needRedo = true
+}
+
 func (window *window) setMinimumSize (width, height int) {
 	if width  < 8 { width  = 8 }
 	if height < 8 { height = 8 }