X backend uses Close method instead of Destroy to free canvas

internal/system/system.go

@@ -15,8 +15,6 @@ type System struct {
 type BackendLink interface {
 	// NewTexture creates a new texture from an image.
 	NewTexture (image.Image) canvas.TextureCloser
-	// NewCanvas creates a new blank canvas with the specified bounds.
-	NewCanvas  (image.Rectangle) canvas.Canvas
 	// NewSurface creates a new surface with the specified bounds.
 	NewSurface (image.Rectangle) (SurfaceLink, error)
 }

x/backend.go

@@ -31,10 +31,6 @@ func (this *backendLink) NewTexture (source image.Image) canvas.TextureCloser {
 	return this.backend.NewTexture(source)
 }
 
-func (this *backendLink) NewCanvas (bounds image.Rectangle) canvas.Canvas {
-	return this.backend.NewCanvas(bounds)
-}
-
 func (this *backendLink) NewSurface (bounds image.Rectangle) (system.SurfaceLink, error) {
 	// TODO
 	return nil, errors.New("x: not implemented")

x/window.go

@@ -361,7 +361,7 @@ func (this *window) reallocateCanvas () {
 	
 	if larger || smaller {
 		if this.xCanvas != nil {
-			this.xCanvas.Destroy()
+			this.xCanvas.Close()
 		}
 		this.xCanvas = xcanvas.NewCanvasFrom(xgraphics.New (
 			this.backend.x,