Simplify shm buffer handling

There was a lot of code here to do a lot of work we didn't need to do.
If we damage a surface with a shm buffer attached, all we need to do
is to re-upload the damaged region to the texture.  As for drm buffers,
we don't assume anything changes on attach and only update the
regions the client tells us to update in the damage request.

clients/simple-shm.c

@@ -142,7 +142,6 @@ redraw(void *data, struct wl_callback *callback, uint32_t time)
 	offset = time >> 4;
 	for (i = 0; i < end; i++)
 		p[i] = (i + offset) * 0x0080401;
-	wl_buffer_damage(window->buffer, 0, 0, window->width, window->height);
 
 	wl_surface_attach(window->surface, window->buffer, 0, 0);
 	wl_surface_damage(window->surface,

clients/simple-touch.c

@@ -184,9 +184,7 @@ touch_paint(struct touch *touch, int32_t x, int32_t y, int32_t id)
 	p += touch->width;
 	p[1] = c;
 
-	wl_buffer_damage(touch->buffer, 0, 0, touch->width, touch->height);
-	wl_surface_damage(touch->surface,
-			  0, 0, touch->width, touch->height);
+	wl_surface_damage(touch->surface, 0, 0, touch->width, touch->height);
 }
 
 static void
@@ -312,7 +310,6 @@ touch_create(int width, int height)
 	wl_surface_set_user_data(touch->surface, touch);
 
 	memset(touch->data, 64, width * height * 4);
-	wl_buffer_damage(touch->buffer, 0, 0, width, height);
 	wl_surface_attach(touch->surface, touch->buffer, 0, 0);
 	wl_surface_damage(touch->surface, 0, 0, width, height);
 

clients/smoke.c

@@ -220,8 +220,6 @@ redraw_handler(struct widget *widget, void *data)
 
 	render(smoke, surface);
 
-	display_surface_damage(smoke->display, surface,
-			       0, 0, smoke->width, smoke->height);
 	window_damage(smoke->window, 0, 0, smoke->width, smoke->height);
 
 	cairo_surface_destroy(surface);

clients/window.c

@@ -782,21 +782,8 @@ window_attach_surface(struct window *window)
 void
 window_flush(struct window *window)
 {
-	if (window->cairo_surface) {
-		switch (window->buffer_type) {
-		case WINDOW_BUFFER_TYPE_EGL_IMAGE:
-		case WINDOW_BUFFER_TYPE_SHM:
-			display_surface_damage(window->display,
-					       window->cairo_surface,
-					       0, 0,
-					       window->allocation.width,
-					       window->allocation.height);
-			break;
-		default:
-			break;
-		}
+	if (window->cairo_surface)
 		window_attach_surface(window);
-	}
 }
 
 void
@@ -2279,17 +2266,6 @@ window_get_title(struct window *window)
 	return window->title;
 }
 
-void
-display_surface_damage(struct display *display, cairo_surface_t *cairo_surface,
-		       int32_t x, int32_t y, int32_t width, int32_t height)
-{
-	struct wl_buffer *buffer;
-
-	buffer = display_get_buffer_for_surface(display, cairo_surface);
-
-	wl_buffer_damage(buffer, x, y, width, height);
-}
-
 void
 window_damage(struct window *window, int32_t x, int32_t y,
 	      int32_t width, int32_t height)