compositor: triangle fan debug

Draw the borders of all the triangles.

v1: original
v2: add keybinding to enable/disable fan debug (super-alt-space),
    cycle colors to make it easier to see individual draws, and
    redraw undamaged region to clean up previous frames debug
    lines

Signed-off-by: Rob Clark <rob@ti.com>
diff --git a/src/compositor-wayland.c b/src/compositor-wayland.c
index 2f4d4a2..1f45def 100644
--- a/src/compositor-wayland.c
+++ b/src/compositor-wayland.c
@@ -330,7 +330,7 @@
 
 static void
 wayland_output_repaint(struct weston_output *output_base,
-		       pixman_region32_t *damage)
+		       pixman_region32_t *damage, int flip)
 {
 	struct wayland_output *output = (struct wayland_output *) output_base;
 	struct wayland_compositor *compositor =
@@ -348,6 +348,9 @@
 	wl_list_for_each_reverse(surface, &compositor->base.surface_list, link)
 		weston_surface_draw(surface, &output->base, damage);
 
+	if (!flip)
+		return;
+
 	draw_border(output);
 
 	wl_signal_emit(&output->base.frame_signal, output);