Bug 1367576 - Cache results of getting GTK widget borders. r=karlt

See comments in the header file.

This also clears out mSafeWidgetStates in ThemeChanged since that seems
like a good thing to do, and marks nsNativeThemeGTK as final.

MozReview-Commit-ID: 5Zne4eGbGlh

widget/gtk/gtk3drawing.cpp

@@ -2074,7 +2074,10 @@ GetMarginBorderPadding(GtkStyleContext* aStyle)
 
 gint
 moz_gtk_get_widget_border(WidgetNodeType widget, gint* left, gint* top,
-                          gint* right, gint* bottom, GtkTextDirection direction)
+                          gint* right, gint* bottom,
+                          // NOTE: callers depend on direction being used
+                          // only for MOZ_GTK_DROPDOWN widgets.
+                          GtkTextDirection direction)
 {
     GtkWidget* w;
     GtkStyleContext* style;

widget/gtk/gtkdrawing.h

@@ -356,7 +356,9 @@ moz_gtk_widget_paint(WidgetNodeType widget, cairo_t *cr,
  * Get the border size of a widget
  * left/right:  [OUT] the widget's left/right border
  * top/bottom:  [OUT] the widget's top/bottom border
- * direction:   the text direction for the widget
+ * direction:   the text direction for the widget.  Callers depend on this
+ *              being used only for MOZ_GTK_DROPDOWN widgets, and cache
+ *              results for other widget types across direction values.
  *
  * returns:    MOZ_GTK_SUCCESS if there was no error, an error code otherwise
  */

widget/gtk/nsNativeThemeGTK.cpp

@@ -70,8 +70,7 @@ nsNativeThemeGTK::nsNativeThemeGTK()
     mozilla::services::GetObserverService();
   obsServ->AddObserver(this, "xpcom-shutdown", false);
 
-  memset(mDisabledWidgetTypes, 0, sizeof(mDisabledWidgetTypes));
-  memset(mSafeWidgetStates, 0, sizeof(mSafeWidgetStates));
+  ThemeChanged();
 }
 
 nsNativeThemeGTK::~nsNativeThemeGTK() {
@@ -1269,8 +1268,20 @@ nsNativeThemeGTK::GetCachedWidgetBorder(nsIFrame* aFrame, uint8_t aWidgetType,
   gint unusedFlags;
   if (GetGtkWidgetAndState(aWidgetType, aFrame, gtkWidgetType, nullptr,
                            &unusedFlags)) {
-    moz_gtk_get_widget_border(gtkWidgetType, &aResult->left, &aResult->top,
-                              &aResult->right, &aResult->bottom, aDirection);
+    MOZ_ASSERT(0 <= gtkWidgetType && gtkWidgetType < MOZ_GTK_WIDGET_NODE_COUNT);
+    uint8_t cacheIndex = gtkWidgetType / 8;
+    uint8_t cacheBit = 1u << (gtkWidgetType % 8);
+
+    if (mBorderCacheValid[cacheIndex] & cacheBit) {
+      *aResult = mBorderCache[gtkWidgetType];
+    } else {
+      moz_gtk_get_widget_border(gtkWidgetType, &aResult->left, &aResult->top,
+                                &aResult->right, &aResult->bottom, aDirection);
+      if (aWidgetType != MOZ_GTK_DROPDOWN) { // depends on aDirection
+        mBorderCacheValid[cacheIndex] |= cacheBit;
+        mBorderCache[gtkWidgetType] = *aResult;
+      }
+    }
   }
 }
 
@@ -1780,6 +1791,8 @@ NS_IMETHODIMP
 nsNativeThemeGTK::ThemeChanged()
 {
   memset(mDisabledWidgetTypes, 0, sizeof(mDisabledWidgetTypes));
+  memset(mSafeWidgetStates, 0, sizeof(mSafeWidgetStates));
+  memset(mBorderCacheValid, 0, sizeof(mBorderCacheValid));
   return NS_OK;
 }
 

widget/gtk/nsNativeThemeGTK.h

@@ -15,9 +15,9 @@
 #include <gtk/gtk.h>
 #include "gtkdrawing.h"
 
-class nsNativeThemeGTK: private nsNativeTheme,
-                        public nsITheme,
-                        public nsIObserver {
+class nsNativeThemeGTK final : private nsNativeTheme,
+                               public nsITheme,
+                               public nsIObserver {
 public:
   NS_DECL_ISUPPORTS_INHERITED
 
@@ -89,8 +89,13 @@ private:
   uint8_t mSafeWidgetStates[1024];    // 256 widgets * 32 bits per widget
   static const char* sDisabledEngines[];
 
+  // Because moz_gtk_get_widget_border can be slow, we cache its results
+  // by widget type.  Each bit in mBorderCacheValid says whether the
+  // corresponding entry in mBorderCache is valid.
   void GetCachedWidgetBorder(nsIFrame* aFrame, uint8_t aWidgetType,
                              GtkTextDirection aDirection, nsIntMargin* aResult);
+  uint8_t mBorderCacheValid[(MOZ_GTK_WIDGET_NODE_COUNT + 7) / 8];
+  nsIntMargin mBorderCache[MOZ_GTK_WIDGET_NODE_COUNT];
 };
 
 #endif