[PATCH 3/4] xwayland: Draw decoration on window manager side

[Uli Schlachter]

Hi,

On 30.07.2013 18:13, Louis-Francis Ratté-Boulianne wrote:
> Draw everything in a cairo image surface before copying it to the XCB
> surface. That removes the flickering visible on rpi whenever the
> decoration were redrawn.
> ---
>  src/xwayland/window-manager.c | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/src/xwayland/window-manager.c b/src/xwayland/window-manager.c
> index b3c9251..57a5d99 100644
> --- a/src/xwayland/window-manager.c
> +++ b/src/xwayland/window-manager.c
> @@ -97,6 +97,7 @@ struct weston_wm_window {
>  	xcb_window_t id;
>  	xcb_window_t frame_id;
>  	cairo_surface_t *cairo_surface;
> +	cairo_surface_t *cairo_xcb_surface;
>  	struct weston_surface *surface;
>  	struct shell_surface *shsurf;
>  	struct wl_listener surface_destroy_listener;
> @@ -900,12 +901,14 @@ weston_wm_handle_map_request(struct weston_wm *wm, xcb_generic_event_t *event)
>  	xcb_map_window(wm->conn, map_request->window);
>  	xcb_map_window(wm->conn, window->frame_id);
>  
> -	window->cairo_surface =
> +	window->cairo_xcb_surface =
>  		cairo_xcb_surface_create_with_xrender_format(wm->conn,
>  							     wm->screen,
>  							     window->frame_id,
>  							     &wm->format_rgba,
>  							     width, height);
> +	window->cairo_surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
> +							    width, height);
[...]

Why do you use an image surface for this? I would suggest to use
cairo_surface_create_similar() instead. This might then give you an XCB surface
drawing to a temporary pixmap (but it could also be an image surface or
something completely different).

If there is some reason for forcing image surfaces and if depending on cairo
1.12 is no problem, I would suggest to use cairo_surface_create_similar_image()
at least. This would make it possible for cairo to use shared memory instead of
sending all the pixels over the X11 socket.

And a third idea would be to use cairo_push_group(); /
cairo_pop_group_to_source(); cairo_paint();. This would need to be done around
the drawing code. I don't know this code and I am too lazy to look it up, but if
this works and could be done easily, this would avoid the memory usage for
keeping the double-buffering surface around always.

Cheers,
Uli
-- 
- He made himself, me nothing, you nothing out of the dust
- Er machte sich mir nichts, dir nichts aus dem Staub