[Mesa-dev] [PATCH] egl/wayland: Ignore rects from SwapBuffersWithDamage

[Daniel Stone]

eglSwapBuffersWithDamage accepts damage-region rectangles to hint the
compositor that it only needs to redraw certain areas, which was passed
through the wl_surface_damage request, as designed.

Wayland also offers a buffer transformation interface, e.g. to allow
users to render pre-rotated buffers. Unfortunately, there is no way to
query buffer transforms, and the damage region was provided in surface,
rather than buffer, co-ordinate space.

Users could perhaps account for this themselves, but EGL also requires
co-ordinates to be passed in GL/mathematical co-ordinate space, with an
inversion to Wayland's natural/scanout co-orodinate space, so the
transformation is so convoluted that it's unreasonable to expect anyone
to do it.

Pending creation and acceptance of a wl_surface.buffer_damage request,
which will accept co-ordinates in buffer co-ordinate space, pessimise to
always sending full-surface damage.

bce64c6c provides the explanation for why we send maximum-range damage,
rather than the full size of the surface: in the presence of buffer
transformations, full-surface damage may not actually cover the entire
surface.

Signed-off-by: Daniel Stone <daniels at collabora.com>
Cc: Jasper St. Pierre <jasper at mecheye.net>
---
 src/egl/drivers/dri2/platform_wayland.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/src/egl/drivers/dri2/platform_wayland.c b/src/egl/drivers/dri2/platform_wayland.c
index 0d161f6..9e8e6ce 100644
--- a/src/egl/drivers/dri2/platform_wayland.c
+++ b/src/egl/drivers/dri2/platform_wayland.c
@@ -703,18 +703,8 @@ dri2_wl_swap_buffers_with_damage(_EGLDriver *drv,
    dri2_surf->dx = 0;
    dri2_surf->dy = 0;
 
-   if (n_rects == 0) {
-      wl_surface_damage(dri2_surf->wl_win->surface,
-                        0, 0, INT32_MAX, INT32_MAX);
-   } else {
-      for (i = 0; i < n_rects; i++) {
-         const int *rect = &rects[i * 4];
-         wl_surface_damage(dri2_surf->wl_win->surface,
-                           rect[0],
-                           dri2_surf->base.Height - rect[1] - rect[3],
-                           rect[2], rect[3]);
-      }
-   }
+    wl_surface_damage(dri2_surf->wl_win->surface,
+                      0, 0, INT32_MAX, INT32_MAX);
 
    if (dri2_dpy->is_different_gpu) {
       _EGLContext *ctx = _eglGetCurrentContext();
-- 
2.5.0