rpi: Support opaque regions
This is needed for XWayland surfaces with alpha channel, as X will be
sending crap in there that should be discarded.
This is currently done with a copy in the compositor, while we wait for
support in the VideoCore side.
diff --git a/src/compositor.c b/src/compositor.c
index b8b7c0f..96f83f1 100644
--- a/src/compositor.c
+++ b/src/compositor.c
@@ -3719,6 +3719,8 @@
" --single-buffer\tUse single-buffered Dispmanx elements.\n"
" --transform=TR\tThe output transformation, TR is one of:\n"
"\tnormal 90 180 270 flipped flipped-90 flipped-180 flipped-270\n"
+ " --opaque-regions\tEnable support for opaque regions, can be "
+ "very slow without support in the GPU firmware.\n"
"\n");
#endif