Bug 297508. Allow native theme drawing to overflow the frame bounds in a reliable way by setting the frame's overflow area. Use this to work around drawing errors in some GTK2 themes. r=bryner,sr=blizzard

gfx/public/nsITheme.h

@@ -81,12 +81,20 @@ public:
   // This method can return PR_FALSE to indicate that the CSS padding value
   // should be used.  Otherwise, it will fill in aResult with the desired
   // padding and return PR_TRUE.
-
   virtual PRBool GetWidgetPadding(nsIDeviceContext* aContext,
                                   nsIFrame* aFrame,
                                   PRUint8 aWidgetType,
                                   nsMargin* aResult) = 0;
 
+  // This method can return PR_FALSE to indicate that no special overflow
+  // area is required by the native widget. Otherwise it will fill in
+  // aResult with the desired overflow area and return PR_TRUE.
+  virtual PRBool GetWidgetOverflow(nsIDeviceContext* aContext,
+                                   nsIFrame* aFrame,
+                                   PRUint8 aWidgetType,
+                                   nsRect* aResult)
+  { return PR_FALSE; }
+
   NS_IMETHOD GetMinimumWidgetSize(nsIRenderingContext* aContext, nsIFrame* aFrame,
                                   PRUint8 aWidgetType,
                                   nsSize* aResult,

layout/xul/base/src/nsBox.cpp

@@ -866,7 +866,8 @@ nsBox::SyncLayout(nsBoxLayoutState& aState)
           nsRect bounds;
           if (box->GetStateBits() & NS_FRAME_OUTSIDE_CHILDREN) {
             nsRect* overflowArea = box->GetOverflowAreaProperty();
-            NS_ASSERTION(overflowArea, "Should have created property for overflowing frame");
+            NS_ASSERTION(overflowArea,
+                         "Should have created property for overflowing frame");
             bounds = *overflowArea + box->GetPosition();
           } else {
             bounds = box->GetRect();
@@ -877,6 +878,18 @@ nsBox::SyncLayout(nsBoxLayoutState& aState)
         }
     }
 
+    const nsStyleDisplay* disp = GetStyleDisplay();
+    if (disp->mAppearance && gTheme) {
+      // Add in the theme's desired overflow
+      if (gTheme->ThemeSupportsWidget(presContext, this, disp->mAppearance)) {
+        nsRect r;
+        if (gTheme->GetWidgetOverflow(presContext->DeviceContext(), this,
+                                      disp->mAppearance, &r)) {
+          rect.UnionRect(rect, r);
+        }
+      }
+    }
+
     FinishAndStoreOverflow(&rect, GetSize());
   }
 

layout/xul/base/src/nsSliderFrame.cpp

@@ -659,9 +659,11 @@ nsSliderFrame::CurrentPositionChanged(nsPresContext* aPresContext)
     // set the rect
     thumbFrame->SetRect(newThumbRect);
 
-    // figure out the union of the rect so we know what to redraw
+    // Figure out the union of the rect so we know what to redraw.
+    // Combine the old and new thumb overflow areas.
     nsRect changeRect;
-    changeRect.UnionRect(thumbRect, newThumbRect);
+    changeRect.UnionRect(thumbFrame->GetOverflowRect() + thumbRect.TopLeft(),
+                         thumbFrame->GetOverflowRect() + newThumbRect.TopLeft());
 
     // redraw just the change
     Invalidate(changeRect, mRedrawImmediate);

widget/src/gtk/nsNativeThemeGTK.cpp

@@ -535,6 +535,37 @@ nsNativeThemeGTK::GetWidgetPadding(nsIDeviceContext* aContext,
   return PR_FALSE;
 }
 
+PRBool
+nsNativeThemeGTK::GetWidgetOverflow(nsIDeviceContext* aContext,
+                                    nsIFrame* aFrame, PRUint8 aWidgetType,
+                                    nsRect* aResult)
+{
+  nsIntMargin extraSize(0,0,0,0);
+  // Allow an extra one pixel above and below the thumb for certain
+  // GTK2 themes (Ximian Industrial, Bluecurve, Misty, at least);
+  // see moz_gtk_scrollbar_thumb_paint in gtk2drawing.c
+  switch (aWidgetType) {
+  case NS_THEME_SCROLLBAR_THUMB_VERTICAL:
+    extraSize.top = extraSize.bottom = 1;
+    break;
+  case NS_THEME_SCROLLBAR_THUMB_HORIZONTAL:
+    extraSize.left = extraSize.right = 1;
+    break;
+  default:
+    return PR_FALSE;
+  }
+
+  float p2t = aContext->DevUnitsToAppUnits();
+  nsMargin m(NSIntPixelsToTwips(extraSize.left, p2t),
+             NSIntPixelsToTwips(extraSize.top, p2t),
+             NSIntPixelsToTwips(extraSize.right, p2t),
+             NSIntPixelsToTwips(extraSize.bottom, p2t));
+  nsRect r(nsPoint(0, 0), aFrame->GetSize());
+  r.Inflate(m);
+  *aResult = r;
+  return PR_TRUE;
+}
+
 NS_IMETHODIMP
 nsNativeThemeGTK::GetMinimumWidgetSize(nsIRenderingContext* aContext,
                                        nsIFrame* aFrame, PRUint8 aWidgetType,

widget/src/gtk/nsNativeThemeGTK.h

@@ -67,6 +67,11 @@ public:
                                               PRUint8 aWidgetType,
                                               nsMargin* aResult);
 
+  virtual NS_HIDDEN_(PRBool) GetWidgetOverflow(nsIDeviceContext* aContext,
+                                               nsIFrame* aFrame,
+                                               PRUint8 aWidgetType,
+                                               nsRect* aResult);
+
   NS_IMETHOD GetMinimumWidgetSize(nsIRenderingContext* aContext,
                                   nsIFrame* aFrame, PRUint8 aWidgetType,
                                   nsSize* aResult, PRBool* aIsOverridable);

widget/src/gtk2/gtk2drawing.c

@@ -741,6 +741,11 @@ moz_gtk_scrollbar_thumb_paint(GtkThemeWidgetType widget,
        surrounding the scrollbar if the theme thinks that it's butted
        up against the scrollbar arrows.  Note the increases of the
        clip rect below. */
+    /* Changing the cliprect is pretty bogus. This lets themes draw
+       outside the frame, which means we don't invalidate them
+       correctly. See bug 297508. But some themes do seem to need
+       it. So we modify the frame's overflow area to account for what
+       we're doing here; see nsNativeThemeGTK::GetWidgetOverflow. */
     adj = gtk_range_get_adjustment(GTK_RANGE(scrollbar));
 
     if (widget == MOZ_GTK_SCROLLBAR_THUMB_HORIZONTAL) {

widget/src/gtk2/nsNativeThemeGTK.cpp

@@ -535,6 +535,37 @@ nsNativeThemeGTK::GetWidgetPadding(nsIDeviceContext* aContext,
   return PR_FALSE;
 }
 
+PRBool
+nsNativeThemeGTK::GetWidgetOverflow(nsIDeviceContext* aContext,
+                                    nsIFrame* aFrame, PRUint8 aWidgetType,
+                                    nsRect* aResult)
+{
+  nsIntMargin extraSize(0,0,0,0);
+  // Allow an extra one pixel above and below the thumb for certain
+  // GTK2 themes (Ximian Industrial, Bluecurve, Misty, at least);
+  // see moz_gtk_scrollbar_thumb_paint in gtk2drawing.c
+  switch (aWidgetType) {
+  case NS_THEME_SCROLLBAR_THUMB_VERTICAL:
+    extraSize.top = extraSize.bottom = 1;
+    break;
+  case NS_THEME_SCROLLBAR_THUMB_HORIZONTAL:
+    extraSize.left = extraSize.right = 1;
+    break;
+  default:
+    return PR_FALSE;
+  }
+
+  float p2t = aContext->DevUnitsToAppUnits();
+  nsMargin m(NSIntPixelsToTwips(extraSize.left, p2t),
+             NSIntPixelsToTwips(extraSize.top, p2t),
+             NSIntPixelsToTwips(extraSize.right, p2t),
+             NSIntPixelsToTwips(extraSize.bottom, p2t));
+  nsRect r(nsPoint(0, 0), aFrame->GetSize());
+  r.Inflate(m);
+  *aResult = r;
+  return PR_TRUE;
+}
+
 NS_IMETHODIMP
 nsNativeThemeGTK::GetMinimumWidgetSize(nsIRenderingContext* aContext,
                                        nsIFrame* aFrame, PRUint8 aWidgetType,

widget/src/gtk2/nsNativeThemeGTK.h

@@ -67,6 +67,11 @@ public:
                                               PRUint8 aWidgetType,
                                               nsMargin* aResult);
 
+  virtual NS_HIDDEN_(PRBool) GetWidgetOverflow(nsIDeviceContext* aContext,
+                                               nsIFrame* aFrame,
+                                               PRUint8 aWidgetType,
+                                               nsRect* aResult);
+
   NS_IMETHOD GetMinimumWidgetSize(nsIRenderingContext* aContext,
                                   nsIFrame* aFrame, PRUint8 aWidgetType,
                                   nsSize* aResult, PRBool* aIsOverridable);