spicec: add sw canvas diff check

Setting CHECKDIFF=1 environment variable will compare the rendering of
the selected canvas with a software canvas. This is useful for debugging
some rendering issues, however it is far from being perfect, since it's
not able to tell whether one or the other is actually faulty. It's a
strong indication though of which operations are incorrect.

Ideally, all operations should be checked, however, a few of them are
disabled by default because they fail all the time, and it looks like
pixman is not very accurate for blending/compositing (at least visually,
it seems gl has better rendering)

1 files changed, 2 insertions, 0 deletions

diff --git a/client/display_channel.h b/client/display_channel.h
index 197ae73a..8a302896 100644
--- a/client/display_channel.h
+++ b/client/display_channel.h
@@ -187,6 +187,7 @@ private:
 
 private:
     SurfacesCache _surfaces_cache;
+    SurfacesCache _swsurfaces_cache;
     PixmapCache& _pixmap_cache;
     PaletteCache _palette_cache;
     GlzDecoderWindow& _glz_window;
@@ -226,6 +227,7 @@ private:
     InterruptUpdate _interrupt_update;
 
     bool _mig_wait_primary;
+    bool _check_diff;
     friend class SetModeEvent;
     friend class CreatePrimarySurfaceEvent;
     friend class DestroyPrimarySurfaceEvent;