[gtk/wip/baedert/css-values] cssimagefallback: Don't snapshot invisible colors

[Timm Bäder <baedert src gnome org>]

commit f6d032bdbc582aa9c46318197e90841e0f1f60a1
Author: Timm Bäder <mail baedert org>
Date:   Thu Jan 16 13:41:55 2020 +0100

    cssimagefallback: Don't snapshot invisible colors
    
    This avoids a few render nodes later.

 gtk/gtkcssimagefallback.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)
---
diff --git a/gtk/gtkcssimagefallback.c b/gtk/gtkcssimagefallback.c
index d922da942b..c6549c6bd4 100644
--- a/gtk/gtkcssimagefallback.c
+++ b/gtk/gtkcssimagefallback.c
@@ -70,15 +70,18 @@ gtk_css_image_fallback_snapshot (GtkCssImage *image,
 
   if (fallback->used < 0)
     {
-      GdkRGBA red = { 1, 0, 0, 1 };
-      const GdkRGBA *color;
-
       if (fallback->color)
-        color = gtk_css_color_value_get_rgba (fallback->color);
+        {
+          const GdkRGBA *color = gtk_css_color_value_get_rgba (fallback->color);
+          if (!gdk_rgba_is_clear (color))
+            gtk_snapshot_append_color (snapshot, color,
+                                       &GRAPHENE_RECT_INIT (0, 0, width, height));
+        }
       else
-        color = &red;
-
-      gtk_snapshot_append_color (snapshot, color, &GRAPHENE_RECT_INIT (0, 0, width, height));
+        {
+          gtk_snapshot_append_color (snapshot, &(GdkRGBA) {1, 0, 0, 1},
+                                     &GRAPHENE_RECT_INIT (0, 0, width, height));
+        }
     }
   else
     gtk_css_image_snapshot (fallback->images[fallback->used], snapshot, width, height);