libmetacity: use cairo to render gradient

upstream commits:
https://gitlab.gnome.org/GNOME/metacity/commit/71d5decc
https://gitlab.gnome.org/GNOME/metacity/commit/127638ca
https://gitlab.gnome.org/GNOME/metacity/commit/fc1a21ea
https://gitlab.gnome.org/GNOME/metacity/commit/431e0418

2 files changed, 99 insertions, 58 deletions

diff --git a/src/ui/theme.c b/src/ui/theme.c
index ec922b74..d7932e67 100644
--- a/src/ui/theme.c
+++ b/src/ui/theme.c
@@ -994,6 +994,70 @@ meta_gradient_spec_new (MetaGradientType type)
   return spec;
 }
 
+static cairo_pattern_t *
+create_cairo_pattern_from_gradient_spec (const MetaGradientSpec      *spec,
+                                         const MetaAlphaGradientSpec *alpha_spec,
+                                         GtkStyleContext             *context)
+{
+  gint n_colors;
+  cairo_pattern_t *pattern;
+  GSList *tmp;
+  gint i;
+
+  n_colors = g_slist_length (spec->color_specs);
+  if (n_colors == 0)
+    return NULL;
+
+  if (alpha_spec != NULL && alpha_spec->n_alphas != 1)
+    g_assert (n_colors == alpha_spec->n_alphas);
+
+  if (spec->type == META_GRADIENT_HORIZONTAL)
+    pattern = cairo_pattern_create_linear (0, 0, 1, 0);
+  else if (spec->type == META_GRADIENT_VERTICAL)
+    pattern = cairo_pattern_create_linear (0, 0, 0, 1);
+  else if (spec->type == META_GRADIENT_DIAGONAL)
+    pattern = cairo_pattern_create_linear (0, 0, 1, 1);
+  else
+    g_assert_not_reached ();
+
+  i = 0;
+  tmp = spec->color_specs;
+  while (tmp != NULL)
+    {
+      GdkRGBA color;
+
+      meta_color_spec_render (tmp->data, context, &color);
+
+      if (alpha_spec != NULL)
+        {
+          gdouble alpha;
+
+          if (alpha_spec->n_alphas == 1)
+            alpha = alpha_spec->alphas[0] / 255.0;
+          else
+            alpha = alpha_spec->alphas[i] / 255.0;
+
+          cairo_pattern_add_color_stop_rgba (pattern, i / (gfloat) (n_colors - 1),
+                                             color.red, color.green, color.blue,
+                                             alpha);
+        }
+      else
+        cairo_pattern_add_color_stop_rgb (pattern, i / (gfloat) (n_colors - 1),
+                                          color.red, color.green, color.blue);
+
+      tmp = tmp->next;
+      ++i;
+    }
+
+  if (cairo_pattern_status (pattern) != CAIRO_STATUS_SUCCESS)
+    {
+      cairo_pattern_destroy (pattern);
+      return NULL;
+    }
+
+  return pattern;
+}
+
 static void
 free_color_spec (gpointer spec, gpointer user_data)
 {
@@ -1012,42 +1076,34 @@ meta_gradient_spec_free (MetaGradientSpec *spec)
   g_free (spec);
 }
 
-GdkPixbuf*
-meta_gradient_spec_render (const MetaGradientSpec *spec,
-                           GtkStyleContext        *style,
-                           int                     width,
-                           int                     height)
-{
-  int n_colors;
-  GdkRGBA *colors;
-  GSList *tmp;
-  int i;
-  GdkPixbuf *pixbuf;
-
-  n_colors = g_slist_length (spec->color_specs);
-
-  if (n_colors == 0)
-    return NULL;
-
-  colors = g_new (GdkRGBA, n_colors);
+void
+meta_gradient_spec_render (const MetaGradientSpec      *spec,
+                           const MetaAlphaGradientSpec *alpha_spec,
+                           cairo_t                     *cr,
+                           GtkStyleContext             *context,
+                           gint                         x,
+                           gint                         y,
+                           gint                         width,
+                           gint                         height)
+{
+  cairo_pattern_t *pattern;
+
+  pattern = create_cairo_pattern_from_gradient_spec (spec, alpha_spec, context);
+  if (pattern == NULL)
+    return;
 
-  i = 0;
-  tmp = spec->color_specs;
-  while (tmp != NULL)
-    {
-      meta_color_spec_render (tmp->data, style, &colors[i]);
+  cairo_save (cr);
 
-      tmp = tmp->next;
-      ++i;
-    }
+  cairo_rectangle (cr, x, y, width, height);
 
-  pixbuf = meta_gradient_create_multi (width, height,
-                                       colors, n_colors,
-                                       spec->type);
+  cairo_translate (cr, x, y);
+  cairo_scale (cr, width, height);
 
-  g_free (colors);
+  cairo_set_source (cr, pattern);
+  cairo_fill (cr);
+  cairo_pattern_destroy (pattern);
 
-  return pixbuf;
+  cairo_restore (cr);
 }
 
 gboolean
@@ -3488,18 +3544,6 @@ draw_op_as_pixbuf (const MetaDrawOp    *op,
       }
       break;
 
-    case META_DRAW_GRADIENT:
-      {
-        pixbuf = meta_gradient_spec_render (op->data.gradient.gradient_spec,
-                                            style, width, height);
-
-        pixbuf = apply_alpha (pixbuf,
-                              op->data.gradient.alpha_spec,
-                              FALSE);
-      }
-      break;
-
-
     case META_DRAW_IMAGE:
       {
 	if (op->data.image.colorize_spec)
@@ -3545,6 +3589,7 @@ draw_op_as_pixbuf (const MetaDrawOp    *op,
         break;
       }
 
+    case META_DRAW_GRADIENT:
     case META_DRAW_GTK_ARROW:
     case META_DRAW_GTK_BOX:
     case META_DRAW_GTK_VLINE:
@@ -3838,23 +3883,15 @@ meta_draw_op_draw_with_env (const MetaDrawOp    *op,
     case META_DRAW_GRADIENT:
       {
         int rx, ry, rwidth, rheight;
-        GdkPixbuf *pixbuf;
 
         rx = parse_x_position_unchecked (op->data.gradient.x, env);
         ry = parse_y_position_unchecked (op->data.gradient.y, env);
         rwidth = parse_size_unchecked (op->data.gradient.width, env);
         rheight = parse_size_unchecked (op->data.gradient.height, env);
 
-        pixbuf = draw_op_as_pixbuf (op, style_gtk, info,
-                                    rwidth, rheight);
-
-        if (pixbuf)
-          {
-            gdk_cairo_set_source_pixbuf (cr, pixbuf, rx, ry);
-            cairo_paint (cr);
-
-            g_object_unref (G_OBJECT (pixbuf));
-          }
+        meta_gradient_spec_render (op->data.gradient.gradient_spec,
+                                   op->data.gradient.alpha_spec,
+                                   cr, style_gtk, rx, ry, rwidth, rheight);
       }
       break;
 
diff --git a/src/ui/theme.h b/src/ui/theme.h
index 0713e2ce..ef6af363 100644
--- a/src/ui/theme.h
+++ b/src/ui/theme.h
@@ -956,10 +956,14 @@ gboolean       meta_draw_op_list_contains (MetaDrawOpList    *op_list,
 
 MetaGradientSpec* meta_gradient_spec_new    (MetaGradientType        type);
 void              meta_gradient_spec_free   (MetaGradientSpec       *desc);
-GdkPixbuf*        meta_gradient_spec_render (const MetaGradientSpec *desc,
-                                             GtkStyleContext        *style_gtk,
-                                             int                     width,
-                                             int                     height);
+void              meta_gradient_spec_render (const MetaGradientSpec      *spec,
+                                             const MetaAlphaGradientSpec *alpha_spec,
+                                             cairo_t                     *cr,
+                                             GtkStyleContext             *context,
+                                             gint                         x,
+                                             gint                         y,
+                                             gint                         width,
+                                             gint                         height);
 gboolean          meta_gradient_spec_validate (MetaGradientSpec     *spec,
                                                GError              **error);