Application must now manually call application.Draw in all cases

This behavior is way more consistent, and it makes the drawing code
a bit simpler.

backends/x/x.go

@@ -53,6 +53,11 @@ type Backend struct {
 		paddingY     int
 		descent      int
 	}
+
+	memory struct {
+		windowWidth  int
+		windowHeight int
+	}
 }
 
 func (backend *Backend) Run (channel chan(stone.Event)) {
@@ -87,6 +92,16 @@ func (backend *Backend) Draw () {
 	backend.drawLock.Lock()
 	defer backend.drawLock.Unlock()
 
+	boundsChanged :=
+		backend.memory.windowWidth  != backend.metrics.windowWidth ||
+		backend.memory.windowHeight != backend.metrics.windowHeight
+	backend.memory.windowWidth  = backend.metrics.windowWidth
+	backend.memory.windowHeight = backend.metrics.windowHeight
+
+	if boundsChanged {
+		backend.reallocateCanvas()
+	}
+	
 	backend.drawCells(true)
 	backend.canvas.XDraw()
 	backend.canvas.XPaint(backend.window.Id)
@@ -152,10 +167,6 @@ func (backend *Backend) handleXEvent (event xgb.Event) {
 		if sizeChanged {
 			configureEvent =
 				backend.compressConfigureNotify(configureEvent)
-			// TODO: remove draw functions from reallocate canvas,
-			// and only reallocate when drawing and the window
-			// dimensions have changed
-			backend.reallocateCanvas()
 			backend.application.SetSize(backend.calculateBufferSize())
 			backend.channel <- stone.EventResize { }
 		}
@@ -214,9 +225,6 @@ func (backend *Backend) calculateBufferSize () (width, height int) {
 }
 
 func (backend *Backend) reallocateCanvas () {
-	backend.drawLock.Lock()
-	defer backend.drawLock.Unlock()
-	
 	if backend.canvas != nil {
 		backend.canvas.Destroy()
 	}
@@ -230,28 +238,7 @@ func (backend *Backend) reallocateCanvas () {
 		return backend.colors[stone.ColorApplication]
 	})
 	
-	// backend.drawRune(0, 0, 'T')
-	// backend.drawRune(1, 0, 'h')
-	// backend.drawRune(2, 0, 'e')
-	// backend.drawRune(4, 0, 'q')
-	// backend.drawRune(5, 0, 'u')
-	// backend.drawRune(6, 0, 'i')
-	// backend.drawRune(7, 0, 'c')
-	// backend.drawRune(8, 0, 'k')
-	// backend.drawRune(0, 1, 'b')
-	// backend.drawRune(1, 1, 'r')
-	// backend.drawRune(2, 1, 'o')
-	// backend.drawRune(3, 1, 'w')
-	// backend.drawRune(4, 1, 'n')
-	// backend.drawRune(6, 1, 'f')
-	// backend.drawRune(7, 1, 'o')
-	// backend.drawRune(8, 1, 'x')
-
-	backend.drawCells(true)
-	
 	backend.canvas.XSurfaceSet(backend.window.Id)
-	backend.canvas.XDraw()
-	backend.canvas.XPaint(backend.window.Id)
 }
 
 func (backend *Backend) drawCells (forceRedraw bool) (areas []image.Rectangle) {

examples/hello/main.go

@@ -33,14 +33,12 @@ func main () {
 	if err != nil { panic(err) }
 	
 	redraw()
-	application.Draw()
 	go tick()
 
 	for {
 		select {
 		case <- tickPing:
 			redraw()
-			application.Draw()
 		
 		case event := <- channel:
 			switch event.(type) {
@@ -72,6 +70,8 @@ func redraw () {
 	application.SetRune(5, 1, ':')
 	application.SetRune(6, 1, rune(second / 10 + 48))
 	application.SetRune(7, 1, rune(second % 10 + 48))
+	
+	application.Draw()
 }
 
 func tick () {