ui/gtk-gl-area: Remove extra draw call in refresh

This partially reverts commit 77bf310084dad38b3a2badf01766c659056f1cf2
which causes some guest display corruption when gtk-gl-area
is used for GTK rendering (e.g. Wayland Compositor) possibly due to
simulataneous accesses on the guest frame buffer by host compositor
and the guest.

Fixes: 77bf310084 ("ui/gtk: Draw guest frame at refresh cycle")
Reported-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Reported-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Message-Id: <20250214170813.2234754-1-dongwon.kim@intel.com>
Message-ID: <20250603110204.838117-12-alex.bennee@linaro.org>
Cc: qemu-stable@nongnu.org
Message-ID: <20251016150357.876415-6-alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

diff --git a/ui/gtk-gl-area.c b/ui/gtk-gl-area.c
index 05fc38096eca3221858db8d22eb54bfa25770898..cd86022d264a217b5578f77d41278b39494f6615 100644 (file)
--- a/ui/gtk-gl-area.c
+++ b/ui/gtk-gl-area.c
@@ -165,7 +165,22 @@ void gd_gl_area_refresh(DisplayChangeListener *dcl)
 
     if (vc->gfx.guest_fb.dmabuf &&
         qemu_dmabuf_get_draw_submitted(vc->gfx.guest_fb.dmabuf)) {
-        gd_gl_area_draw(vc);
+        /*
+         * gd_egl_refresh() calls gd_egl_draw() if a DMA-BUF draw has already
+         * been submitted, but this function does not call gd_gl_area_draw() in
+         * such a case due to display corruption.
+         *
+         * Calling gd_gl_area_draw() is necessary to prevent a situation where
+         * there is a scheduled draw event but it won't happen bacause the window
+         * is currently in inactive state (minimized or tabified). If draw is not
+         * done for a long time, gl_block timeout and/or fence timeout (on the
+         * guest) will happen eventually.
+         *
+         * However, it is found that calling gd_gl_area_draw() here causes guest
+         * display corruption on a Wayland Compositor. The display corruption is
+         * more serious than the possible fence timeout so gd_gl_area_draw() is
+         * omitted for now.
+         */
         return;
     }