theme: Render window control buttons and icons as surfaces

When loading window control buttons and icon as pixbufs, we just set
them as the source for the cairo context used to paint them. Instead, we
now convert them to cairo surfaces and scale them to the correct display
density before painting them.

This allows us to load higher resolution assets (i.e. at twice the size)
and by explicitly setting the intended size in the theme draw_ops, we
can then scale them down to fit lower resolution displays, or render
them at full density for HiDPI displays.

2 files changed, 291 insertions, 24 deletions

diff --git a/src/ui/theme.c b/src/ui/theme.c
index 3b11c131..d277b687 100644
--- a/src/ui/theme.c
+++ b/src/ui/theme.c
@@ -96,6 +96,114 @@ static void hls_to_rgb			(gdouble	 *h,
  */
 static MetaTheme *meta_current_theme = NULL;
 
+static cairo_surface_t *
+scale_surface (cairo_surface_t *surface,
+               gdouble          old_width,
+               gdouble          old_height,
+               gdouble          new_width,
+               gdouble          new_height,
+               gboolean         vertical_stripes,
+               gboolean         horizontal_stripes)
+{
+  gdouble scale_x;
+  gdouble scale_y;
+  cairo_content_t content;
+  gint width;
+  gint height;
+  cairo_surface_t *scaled;
+  cairo_t *cr;
+
+  scale_x = new_width / old_width;
+  scale_y = new_height / old_height;
+
+  if (horizontal_stripes && !vertical_stripes)
+    {
+      new_width = old_width;
+      scale_x = 1.0;
+    }
+  else if (vertical_stripes && !horizontal_stripes)
+    {
+      new_height = old_height;
+      scale_y = 1.0;
+    }
+
+  content = CAIRO_CONTENT_COLOR_ALPHA;
+  width = ceil (new_width);
+  height = ceil (new_height);
+
+  scaled = cairo_surface_create_similar (surface, content, width, height);
+  cr = cairo_create (scaled);
+
+  cairo_scale (cr, scale_x, scale_y);
+  cairo_set_source_surface (cr, surface, 0, 0);
+
+  cairo_pattern_set_extend (cairo_get_source (cr), CAIRO_EXTEND_PAD);
+
+  cairo_paint (cr);
+  cairo_destroy (cr);
+
+  return scaled;
+}
+
+static cairo_surface_t *
+get_surface_from_pixbuf (GdkPixbuf         *pixbuf,
+                         MetaImageFillType  fill_type,
+                         gdouble            width,
+                         gdouble            height,
+                         gboolean           vertical_stripes,
+                         gboolean           horizontal_stripes)
+{
+  gdouble pixbuf_width;
+  gdouble pixbuf_height;
+  cairo_surface_t *surface;
+  cairo_content_t content;
+  cairo_surface_t *copy;
+  cairo_t *cr;
+
+  pixbuf_width = gdk_pixbuf_get_width (pixbuf);
+  pixbuf_height = gdk_pixbuf_get_height (pixbuf);
+  surface = gdk_cairo_surface_create_from_pixbuf (pixbuf, 1, NULL);
+
+  if (pixbuf_width == width && pixbuf_height == height)
+    {
+      return surface;
+    }
+
+  if (fill_type != META_IMAGE_FILL_TILE)
+    {
+      cairo_surface_t *scaled;
+
+      scaled = scale_surface (surface, pixbuf_width, pixbuf_height,
+                              width, height, vertical_stripes,
+                              horizontal_stripes);
+
+      cairo_surface_destroy (surface);
+      surface = scaled;
+    }
+
+  content = CAIRO_CONTENT_COLOR_ALPHA;
+  width = ceil (width);
+  height = ceil (height);
+
+  copy = cairo_surface_create_similar (surface, content, width, height);
+  cr = cairo_create (copy);
+
+  cairo_set_source_surface (cr, surface, 0, 0);
+
+  if (fill_type == META_IMAGE_FILL_TILE ||
+      vertical_stripes || horizontal_stripes)
+    {
+      cairo_pattern_set_extend (cairo_get_source (cr), CAIRO_EXTEND_REPEAT);
+    }
+
+  cairo_paint (cr);
+  cairo_destroy (cr);
+
+  cairo_surface_destroy (surface);
+
+  return copy;
+}
+
 static GdkPixbuf *
 colorize_pixbuf (GdkPixbuf *orig,
                  GdkRGBA   *new_color)
@@ -1151,6 +1259,38 @@ meta_alpha_gradient_spec_free (MetaAlphaGradientSpec *spec)
   g_free (spec);
 }
 
+cairo_pattern_t *
+meta_alpha_gradient_spec_get_mask (const MetaAlphaGradientSpec *spec)
+{
+  gint n_alphas;
+  cairo_pattern_t *pattern;
+  gint i;
+
+  /* Hardcoded in theme-parser.c */
+  g_assert (spec->type == META_GRADIENT_HORIZONTAL);
+
+  n_alphas = spec->n_alphas;
+  if (n_alphas == 0)
+    return NULL;
+
+  if (n_alphas == 1)
+    return cairo_pattern_create_rgba (0, 0, 0, spec->alphas[0] / 255.0);
+
+  pattern = cairo_pattern_create_linear (0, 0, 1, 0);
+
+  for (i = 0; i < n_alphas; i++)
+    cairo_pattern_add_color_stop_rgba (pattern, i / (gfloat) (n_alphas - 1),
+                                       0, 0, 0, spec->alphas[i] / 255.0);
+
+  if (cairo_pattern_status (pattern) != CAIRO_STATUS_SUCCESS)
+    {
+      cairo_pattern_destroy (pattern);
+      return NULL;
+    }
+
+  return pattern;
+}
+
 MetaColorSpec*
 meta_color_spec_new (MetaColorSpecType type)
 {
@@ -3627,6 +3767,94 @@ draw_op_as_pixbuf (const MetaDrawOp    *op,
   return pixbuf;
 }
 
+static cairo_surface_t *
+draw_op_as_surface (const MetaDrawOp   *op,
+                    GtkStyleContext    *style,
+                    const MetaDrawInfo *info,
+                    gdouble             width,
+                    gdouble             height)
+{
+  cairo_surface_t *surface;
+
+  surface = NULL;
+
+  switch (op->type)
+    {
+    case META_DRAW_IMAGE:
+      {
+        if (op->data.image.colorize_spec)
+          {
+            GdkRGBA color;
+
+            meta_color_spec_render (op->data.image.colorize_spec,
+                                    style, &color);
+
+            if (op->data.image.colorize_cache_pixbuf == NULL ||
+                op->data.image.colorize_cache_pixel != GDK_COLOR_RGB (color))
+              {
+                if (op->data.image.colorize_cache_pixbuf)
+                  g_object_unref (G_OBJECT (op->data.image.colorize_cache_pixbuf));
+
+                /* const cast here */
+                ((MetaDrawOp*)op)->data.image.colorize_cache_pixbuf =
+                  colorize_pixbuf (op->data.image.pixbuf,
+                                   &color);
+                ((MetaDrawOp*)op)->data.image.colorize_cache_pixel =
+                  GDK_COLOR_RGB (color);
+              }
+
+            if (op->data.image.colorize_cache_pixbuf)
+              {
+                surface = get_surface_from_pixbuf (op->data.image.colorize_cache_pixbuf,
+                                                   op->data.image.fill_type,
+                                                   width, height,
+                                                   op->data.image.vertical_stripes,
+                                                   op->data.image.horizontal_stripes);
+              }
+          }
+        else
+          {
+            surface = get_surface_from_pixbuf (op->data.image.pixbuf,
+                                               op->data.image.fill_type,
+                                               width, height,
+                                               op->data.image.vertical_stripes,
+                                               op->data.image.horizontal_stripes);
+          }
+        break;
+      }
+
+    case META_DRAW_ICON:
+      if (info->mini_icon &&
+          width <= gdk_pixbuf_get_width (info->mini_icon) &&
+          height <= gdk_pixbuf_get_height (info->mini_icon))
+        surface = get_surface_from_pixbuf (info->mini_icon, op->data.icon.fill_type,
+                                           width, height, FALSE, FALSE);
+      else if (info->icon)
+        surface = get_surface_from_pixbuf (info->icon, op->data.icon.fill_type,
+                                           width, height, FALSE, FALSE);
+      break;
+
+    case META_DRAW_TINT:
+    case META_DRAW_LINE:
+    case META_DRAW_RECTANGLE:
+    case META_DRAW_ARC:
+    case META_DRAW_CLIP:
+    case META_DRAW_GRADIENT:
+    case META_DRAW_GTK_ARROW:
+    case META_DRAW_GTK_BOX:
+    case META_DRAW_GTK_VLINE:
+    case META_DRAW_TITLE:
+    case META_DRAW_OP_LIST:
+    case META_DRAW_TILE:
+      break;
+
+    default:
+      break;
+    }
+
+  return surface;
+}
+
 static void
 fill_env (MetaPositionExprEnv *env,
           const MetaDrawInfo  *info,
@@ -3899,8 +4127,12 @@ meta_draw_op_draw_with_env (const MetaDrawOp    *op,
 
     case META_DRAW_IMAGE:
       {
-        int rx, ry, rwidth, rheight;
-        GdkPixbuf *pixbuf;
+        gint scale;
+        gdouble rx, ry, rwidth, rheight;
+        cairo_surface_t *surface;
+
+        scale = gdk_window_get_scale_factor (gdk_get_default_root_window ());
+        cairo_scale (cr, 1.0 / scale, 1.0 / scale);
 
         if (op->data.image.pixbuf)
           {
@@ -3908,21 +4140,36 @@ meta_draw_op_draw_with_env (const MetaDrawOp    *op,
             env->object_height = gdk_pixbuf_get_height (op->data.image.pixbuf);
           }
 
-        rwidth = parse_size_unchecked (op->data.image.width, env);
-        rheight = parse_size_unchecked (op->data.image.height, env);
+        rwidth = parse_size_unchecked (op->data.image.width, env) * scale;
+        rheight = parse_size_unchecked (op->data.image.height, env) * scale;
 
-        pixbuf = draw_op_as_pixbuf (op, style_gtk, info,
-                                    rwidth, rheight);
+        surface = draw_op_as_surface (op, style_gtk, info, rwidth, rheight);
 
-        if (pixbuf)
+        if (surface)
           {
-            rx = parse_x_position_unchecked (op->data.image.x, env);
-            ry = parse_y_position_unchecked (op->data.image.y, env);
+            rx = parse_x_position_unchecked (op->data.image.x, env) * scale;
+            ry = parse_y_position_unchecked (op->data.image.y, env) * scale;
 
-            gdk_cairo_set_source_pixbuf (cr, pixbuf, rx, ry);
-            cairo_paint (cr);
+            cairo_set_source_surface (cr, surface, rx, ry);
 
-            g_object_unref (G_OBJECT (pixbuf));
+            if (op->data.image.alpha_spec)
+              {
+                cairo_pattern_t *pattern;
+
+                cairo_translate (cr, rx, ry);
+                cairo_scale (cr, rwidth, rheight);
+
+                pattern = meta_alpha_gradient_spec_get_mask (op->data.image.alpha_spec);
+                cairo_mask (cr, pattern);
+
+                cairo_pattern_destroy (pattern);
+              }
+            else
+              {
+                cairo_paint (cr);
+              }
+
+            cairo_surface_destroy (surface);
           }
       }
       break;
@@ -3991,24 +4238,43 @@ meta_draw_op_draw_with_env (const MetaDrawOp    *op,
 
     case META_DRAW_ICON:
       {
-        int rx, ry, rwidth, rheight;
-        GdkPixbuf *pixbuf;
+        gint scale;
+        gdouble rx, ry, rwidth, rheight;
+        cairo_surface_t *surface;
+
+        scale = gdk_window_get_scale_factor (gdk_get_default_root_window ());
+        cairo_scale (cr, 1.0 / scale, 1.0 / scale);
 
-        rwidth = parse_size_unchecked (op->data.icon.width, env);
-        rheight = parse_size_unchecked (op->data.icon.height, env);
+        rwidth = parse_size_unchecked (op->data.icon.width, env) * scale;
+        rheight = parse_size_unchecked (op->data.icon.height, env) * scale;
 
-        pixbuf = draw_op_as_pixbuf (op, style_gtk, info,
-                                    rwidth, rheight);
+        surface = draw_op_as_surface (op, style_gtk, info, rwidth, rheight);
 
-        if (pixbuf)
+        if (surface)
           {
-            rx = parse_x_position_unchecked (op->data.icon.x, env);
-            ry = parse_y_position_unchecked (op->data.icon.y, env);
+            rx = parse_x_position_unchecked (op->data.icon.x, env) * scale;
+            ry = parse_y_position_unchecked (op->data.icon.y, env) * scale;
 
-            gdk_cairo_set_source_pixbuf (cr, pixbuf, rx, ry);
-            cairo_paint (cr);
+            cairo_set_source_surface (cr, surface, rx, ry);
 
-            g_object_unref (G_OBJECT (pixbuf));
+            if (op->data.icon.alpha_spec)
+              {
+                cairo_pattern_t *pattern;
+
+                cairo_translate (cr, rx, ry);
+                cairo_scale (cr, rwidth, rheight);
+
+                pattern = meta_alpha_gradient_spec_get_mask (op->data.icon.alpha_spec);
+                cairo_mask (cr, pattern);
+
+                cairo_pattern_destroy (pattern);
+              }
+            else
+              {
+                cairo_paint (cr);
+              }
+
+            cairo_surface_destroy (surface);
           }
       }
       break;
diff --git a/src/ui/theme.h b/src/ui/theme.h
index 34b98935..9dfb8d89 100644
--- a/src/ui/theme.h
+++ b/src/ui/theme.h
@@ -964,6 +964,7 @@ gboolean          meta_gradient_spec_validate (MetaGradientSpec     *spec,
 MetaAlphaGradientSpec* meta_alpha_gradient_spec_new  (MetaGradientType       type,
                                                       int                    n_alphas);
 void                   meta_alpha_gradient_spec_free (MetaAlphaGradientSpec *spec);
+cairo_pattern_t *      meta_alpha_gradient_spec_get_mask (const MetaAlphaGradientSpec *spec);
 
 
 MetaFrameStyle* meta_frame_style_new   (MetaFrameStyle *parent);