Merge 69257 - 2010-10-06 Peter Kasting <pkasting@google.com>...

WebCore/platform/ScrollView.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 653 matching lines @@
 {
     // We don't allow mouse wheeling to happen in a ScrollView that has had its scrollbars explicitly disabled.
 #if PLATFORM(WX)
     if (!canHaveScrollbars()) {
 #else
     if (!canHaveScrollbars() || platformWidget()) {
 #endif
         return;
     }
 
-    // Determine how much we want to scroll.  If we can move at all, we will accept the event.
+    // Accept the event if we have a scrollbar in that direction and can still
+    // scroll any further.
+    float deltaX = m_horizontalScrollbar ? e.deltaX() : 0;
+    float deltaY = m_verticalScrollbar ? e.deltaY() : 0;
     IntSize maxScrollDelta = maximumScrollPosition() - scrollPosition();
-    if ((e.deltaX() < 0 && maxScrollDelta.width() > 0) ||
-        (e.deltaX() > 0 && scrollOffset().width() > 0) ||
-        (e.deltaY() < 0 && maxScrollDelta.height() > 0) ||
-        (e.deltaY() > 0 && scrollOffset().height() > 0)) {
+    if ((deltaX < 0 && maxScrollDelta.width() > 0)
+        || (deltaX > 0 && scrollOffset().width() > 0)
+        || (deltaY < 0 && maxScrollDelta.height() > 0)
+        || (deltaY > 0 && scrollOffset().height() > 0)) {
         e.accept();
-        float deltaX = e.deltaX();
-        float deltaY = e.deltaY();
         if (e.granularity() == ScrollByPageWheelEvent) {
-            ASSERT(deltaX == 0);
+            ASSERT(!e.deltaX());
             bool negative = deltaY < 0;
             deltaY = max(max(static_cast<float>(visibleHeight()) * Scrollbar::minFractionToStepWhenPaging(), static_cast<float>(visibleHeight() - Scrollbar::maxOverlapBetweenPages())), 1.0f);
             if (negative)
                 deltaY = -deltaY;
         }
 
-        // Should we fall back on scrollBy() if there is no scrollbar for a non-zero delta?
-        if (deltaY && m_verticalScrollbar)
+        if (deltaY)
             m_verticalScrollbar->scroll(ScrollUp, ScrollByPixel, deltaY);
-        if (deltaX && m_horizontalScrollbar)
+        if (deltaX)
             m_horizontalScrollbar->scroll(ScrollLeft, ScrollByPixel, deltaX);
     }
 }
 
 void ScrollView::setFrameRect(const IntRect& newRect)
 {
     IntRect oldRect = frameRect();
     
     if (newRect == oldRect)
         return;
@@ skipping 357 matching lines @@
 
 bool ScrollView::platformIsOffscreen() const
 {
     return false;
 }
 
 #endif
 
 }