attributes: Make alpha work without color

Improve the behavior of the cairo renderer to take
alpha into account even if no color specified.

https://bugzilla.gnome.org/show_bug.cgi?id=773767

1 files changed, 29 insertions, 8 deletions

diff --git a/pango/pangocairo-render.c b/pango/pangocairo-render.c
index b1efb37f..73b1ae36 100644
--- a/pango/pangocairo-render.c
+++ b/pango/pangocairo-render.c
@@ -191,17 +191,38 @@ set_color (PangoCairoRenderer *crenderer,
 	   PangoRenderPart     part)
 {
   PangoColor *color = pango_renderer_get_color ((PangoRenderer *) (crenderer), part);
-  guint16 alpha = pango_renderer_get_alpha ((PangoRenderer *) (crenderer), part);
+  guint16 a = pango_renderer_get_alpha ((PangoRenderer *) (crenderer), part);
+  gdouble red, green, blue, alpha;
 
-  if (!alpha)
-    alpha = 0xffff;
+  if (!a && !color)
+    return;
 
   if (color)
-    cairo_set_source_rgba (crenderer->cr,
-			   color->red / 65535.,
-			   color->green / 65535.,
-			   color->blue / 65535.,
-                           alpha / 65535.);
+    {
+      red = color->red / 65535.;
+      green = color->green / 65535.;
+      blue = color->blue / 65535.;
+      alpha = 1.;
+    }
+  else
+    {
+      cairo_pattern_t *pattern = cairo_get_source (crenderer->cr);
+
+      if (pattern && cairo_pattern_get_type (pattern) == CAIRO_PATTERN_TYPE_SOLID)
+        cairo_pattern_get_rgba (pattern, &red, &green, &blue, &alpha);
+      else
+        {
+          red = 0.;
+          green = 0.;
+          blue = 0.;
+          alpha = 1.;
+        }
+    }
+
+  if (a)
+    alpha = a / 65535.;
+
+  cairo_set_source_rgba (crenderer->cr, red, green, blue, alpha);
 }
 
 /* note: modifies crenderer->cr without doing cairo_save/restore() */