Applications can now manually call a screen redraw in a way that I think is thread safe

backends/x/x.go

@@ -1,6 +1,7 @@
 package x
 
 import "os"
+import "sync"
 import "image"
 import "image/draw"
 import "golang.org/x/image/font"
@@ -28,6 +29,8 @@ type Backend struct {
 	canvas      *xgraphics.Image
 	channel     chan(stone.Event)
 
+	drawLock sync.Mutex
+
 	ping struct {
 		before chan(struct { })
 		after  chan(struct { })
@@ -80,6 +83,17 @@ func (backend *Backend) Run (channel chan(stone.Event)) {
 	}
 }
 
+func (backend *Backend) Draw () {
+	backend.drawLock.Lock()
+	defer backend.drawLock.Unlock()
+	
+	backend.drawCells(true)
+	backend.canvas.XDraw()
+	backend.canvas.XPaint(backend.window.Id)
+	// FIXME use this instead once it works
+	// backend.updateWindowAreas(...)
+}
+
 func (backend *Backend) SetTitle (title string) (err error) {
 	err = ewmh.WmNameSet(backend.connection, backend.window.Id, title)
 	return
@@ -191,6 +205,9 @@ func (backend *Backend) calculateWindowSize () (x, y int) {
 }
 
 func (backend *Backend) reallocateCanvas () {
+	backend.drawLock.Lock()
+	defer backend.drawLock.Unlock()
+	
 	if backend.canvas != nil {
 		backend.canvas.Destroy()
 	}