Updating custom scrollbar style

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 305 matching lines @@
     Scrollbar* verticalBar = verticalScrollbar();
     if (verticalBar && verticalBar->isCustomScrollbar())
         setHasVerticalScrollbar(false);
 
     if (m_scrollCorner) {
         m_scrollCorner->destroy();
         m_scrollCorner = nullptr;
     }
 }
 
+void FrameView::recalculateCustomScrollbarStyle()
+{
+    if (hasCustomScrollbars()) {
+        if (m_horizontalScrollbar && m_horizontalScrollbar->isCustomScrollbar()) {
+            IntRect oldRect(m_horizontalScrollbar->frameRect());
+            m_horizontalScrollbar->styleChanged();
+            IntRect hBarRect((shouldPlaceVerticalScrollbarOnLeft() && m_verticalScrollbar) ? m_verticalScrollbar->width() : 0,
+                height() - m_horizontalScrollbar->height(),
+                width() - (m_verticalScrollbar ? m_verticalScrollbar->width() : 0),
+                m_horizontalScrollbar->height());
+            m_horizontalScrollbar->setFrameRect(adjustScrollbarRectForResizer(hBarRect, m_horizontalScrollbar.get()));

[skobes, 2014/11/07 00:13:59]

Calling Scrollbar::styleChanged() makes sense, but we already compute the frame
rects of the scrollbars (and call setFrameRect + invalidate) in
FrameView::updateScrollbarGeometry.  Why do we need to do it here as well?  Can
we just call updateScrollbars(scrollOffsetDouble())?

[MuVen, 2014/11/07 09:46:59]

instead of updateScrollbar, updateScrollbarGeometry should be find, as
updateScrollbar will be called in layout function after this.

+            if (!m_scrollbarsSuppressed && oldRect != m_horizontalScrollbar->frameRect())
+                m_horizontalScrollbar->invalidate();
+        }
+        if (m_verticalScrollbar && m_verticalScrollbar->isCustomScrollbar()) {
+            IntRect oldRect(m_verticalScrollbar->frameRect());
+            m_verticalScrollbar->styleChanged();
+            IntRect vBarRect(shouldPlaceVerticalScrollbarOnLeft() ? 0 : (width() - m_verticalScrollbar->width()),
+                0,
+                m_verticalScrollbar->width(),
+                height() - (m_horizontalScrollbar ? m_horizontalScrollbar->height() : 0));
+            m_verticalScrollbar->setFrameRect(adjustScrollbarRectForResizer(vBarRect, m_verticalScrollbar.get()));
+            if (!m_scrollbarsSuppressed && oldRect != m_verticalScrollbar->frameRect())
+                m_verticalScrollbar->invalidate();
+        }
+    }
+}
+
 void FrameView::recalculateScrollbarOverlayStyle()
 {
     ScrollbarOverlayStyle oldOverlayStyle = scrollbarOverlayStyle();
     ScrollbarOverlayStyle overlayStyle = ScrollbarOverlayStyleDefault;
 
     Color backgroundColor = documentBackgroundColor();
     // Reduce the background color from RGB to a lightness value
     // and determine which scrollbar style to use based on a lightness
     // heuristic.
     double hue, saturation, lightness;
@@ skipping 3598 matching lines @@
         return;
 
     ScrollableArea::setScrollOrigin(origin);
 
     // Update if the scroll origin changes, since our position will be different if the content size did not change.
     if (updatePositionAtAll && updatePositionSynchronously)
         updateScrollbars(scrollOffsetDouble());
 }
 
 } // namespace blink