[gtk+] renderbackground: Minimize style lookups

[Timm Bäder <baedert src gnome org>]

commit 99026d2df8ceb0989cfb0cafcfe91d73a5ef7f4e
Author: Timm Bäder <mail baedert org>
Date:   Thu Oct 19 15:22:00 2017 +0200

    renderbackground: Minimize style lookups
    
    Move the early returns up so we don't look up all those css values for
    no reason.

 gtk/gtkrenderbackground.c |   32 +++++++++++++++++++-------------
 1 files changed, 19 insertions(+), 13 deletions(-)
---
diff --git a/gtk/gtkrenderbackground.c b/gtk/gtkrenderbackground.c
index 8e87e9e..0d3f31a 100644
--- a/gtk/gtkrenderbackground.c
+++ b/gtk/gtkrenderbackground.c
@@ -334,9 +334,9 @@ gtk_theming_background_paint_layer (GtkThemingBackground *bg,
 }
 
 static void
-gtk_theming_background_snapshot_layer (GtkThemingBackground *bg,
-                                       guint                 idx,
-                                       GtkSnapshot          *snapshot)
+gtk_theming_background_snapshot_layer (const GtkThemingBackground *bg,
+                                       guint                       idx,
+                                       GtkSnapshot                *snapshot)
 {
   GtkCssRepeatStyle hrepeat, vrepeat;
   const GtkCssValue *pos, *repeat;
@@ -345,32 +345,38 @@ gtk_theming_background_snapshot_layer (GtkThemingBackground *bg,
   double image_width, image_height;
   double width, height;
 
-  pos = _gtk_css_array_value_get_nth (gtk_css_style_get_value (bg->style, 
GTK_CSS_PROPERTY_BACKGROUND_POSITION), idx);
-  repeat = _gtk_css_array_value_get_nth (gtk_css_style_get_value (bg->style, 
GTK_CSS_PROPERTY_BACKGROUND_REPEAT), idx);
-  hrepeat = _gtk_css_background_repeat_value_get_x (repeat);
-  vrepeat = _gtk_css_background_repeat_value_get_y (repeat);
   image = _gtk_css_image_value_get_image (
               _gtk_css_array_value_get_nth (
                   gtk_css_style_get_value (bg->style, GTK_CSS_PROPERTY_BACKGROUND_IMAGE),
                   idx));
 
+  if (image == NULL)
+    return;
+
+  pos = _gtk_css_array_value_get_nth (gtk_css_style_get_value (bg->style, 
GTK_CSS_PROPERTY_BACKGROUND_POSITION), idx);
+  repeat = _gtk_css_array_value_get_nth (gtk_css_style_get_value (bg->style, 
GTK_CSS_PROPERTY_BACKGROUND_REPEAT), idx);
+  hrepeat = _gtk_css_background_repeat_value_get_x (repeat);
+  vrepeat = _gtk_css_background_repeat_value_get_y (repeat);
+
+
   origin = &bg->boxes[
                _gtk_css_area_value_get (
                    _gtk_css_array_value_get_nth (
                        gtk_css_style_get_value (bg->style, GTK_CSS_PROPERTY_BACKGROUND_ORIGIN),
                        idx))];
-  clip = &bg->boxes[
-              _gtk_css_area_value_get (
-                                _gtk_css_array_value_get_nth (
-                                                    gtk_css_style_get_value (bg->style, 
GTK_CSS_PROPERTY_BACKGROUND_CLIP),
-                                                                      idx))];
 
   width = origin->bounds.size.width;
   height = origin->bounds.size.height;
 
-  if (image == NULL || width <= 0 || height <= 0)
+  if (width <= 0 || height <= 0)
     return;
 
+  clip = &bg->boxes[
+              _gtk_css_area_value_get (
+                                _gtk_css_array_value_get_nth (
+                                                    gtk_css_style_get_value (bg->style, 
GTK_CSS_PROPERTY_BACKGROUND_CLIP),
+                                                                      idx))];
+
   _gtk_css_bg_size_value_compute_size (_gtk_css_array_value_get_nth (gtk_css_style_get_value (bg->style, 
GTK_CSS_PROPERTY_BACKGROUND_SIZE), idx),
                                        image,
                                        width,