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xwayland: reduce over-damage

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If an X11 app draws a little here, some there, and a tiny bit in the
opposite corner, using RegionExtents for the damage to be sent to the
Wayland compositor will cause massive over-damaging.

However, we cannot blindly send an arbitrary number of damage
rectangles, because there is a risk of overflowing the Wayland
connection. If that happens, it triggers an abort in libwayland-client.

Try to be more accurate with the damage by sending up to 256 rectangles
per window, and fall back to extents otherwise. The number is completely
arbitrary.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Daniel Stone <daniels@collabora.com>
This commit is contained in:
Pekka Paalanen 2017-12-20 13:18:45 +02:00 committed by Adam Jackson
parent a5e9bcad7a
commit f72587ecc7
1 changed files with 15 additions and 3 deletions
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18
hw/xwayland/xwayland.c
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@ -629,6 +629,7 @@ xwl_window_post_damage(struct xwl_window *xwl_window)
BoxPtr box;
struct wl_buffer *buffer;
PixmapPtr pixmap;
int i;
assert(!xwl_window->frame_callback);
@ -644,9 +645,20 @@ xwl_window_post_damage(struct xwl_window *xwl_window)
wl_surface_attach(xwl_window->surface, buffer, 0, 0);
box = RegionExtents(region);
wl_surface_damage(xwl_window->surface, box->x1, box->y1,
box->x2 - box->x1, box->y2 - box->y1);
/* Arbitrary limit to try to avoid flooding the Wayland
* connection. If we flood it too much anyway, this could
* abort in libwayland-client.
*/
if (RegionNumRects(region) > 256) {
box = RegionExtents(region);
wl_surface_damage(xwl_window->surface, box->x1, box->y1,
box->x2 - box->x1, box->y2 - box->y1);
} else {
box = RegionRects(region);
for (i = 0; i < RegionNumRects(region); i++, box++)
wl_surface_damage(xwl_window->surface, box->x1, box->y1,
box->x2 - box->x1, box->y2 - box->y1);
}
xwl_window->frame_callback = wl_surface_frame(xwl_window->surface);
wl_callback_add_listener(xwl_window->frame_callback, &frame_listener, xwl_window);