Made text inside <input> elements scrollable using touch gestures

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 1304 matching lines @@
 IntRect RenderLayer::scrollableAreaBoundingBox() const
 {
     return renderer()->absoluteBoundingBoxRect();
 }
 
 bool RenderLayer::userInputScrollable(ScrollbarOrientation orientation) const
 {
     RenderBox* box = renderBox();
     ASSERT(box);
 
+    if (box->isTextField())

[tdanderson, 2013/08/08 20:01:16]

I would re-write as:

if (box->isTextField())
    return orientation == HorizontalScrollbar;

since vertical scrolling of text fields is not possible.

Also (as you mentioned to me in person) a follow-up patch to rename
ScrollbarOrientation to ScrollOrientation may be in order, since elements such
as text fields or divs may in fact be scrollable in a certain direction but not
have any scrollbars.

[bokan, 2013/08/12 16:19:29]

Done.

+        return true;
+
     EOverflow overflowStyle = (orientation == HorizontalScrollbar) ?
         renderer()->style()->overflowX() : renderer()->style()->overflowY();
     return (overflowStyle == OSCROLL || overflowStyle == OAUTO || overflowStyle == OOVERLAY);
 }
 
 int RenderLayer::pageStep(ScrollbarOrientation orientation) const
 {
     RenderBox* box = renderBox();
     ASSERT(box);
 
@@ skipping 608 matching lines @@
 
 void RenderLayer::convertToLayerCoords(const RenderLayer* ancestorLayer, LayoutRect& rect) const
 {
     LayoutPoint delta;
     convertToLayerCoords(ancestorLayer, delta);
     rect.move(-delta.x(), -delta.y());
 }
 
 bool RenderLayer::usesCompositedScrolling() const
 {
+    // Scroll textfields on the main thread so we get appropriate touch gesture propagation

[tdanderson, 2013/08/08 20:01:16]

Add a period at the end of the comment.

[bokan, 2013/08/12 16:19:29]

Done.

+    if (renderBox() && renderBox()->isTextField())

[tdanderson, 2013/08/08 20:01:16]

Are you sure that usesCompositedScrolling() is called every time there is a
user-generated scroll event (fling or otherwise) originating in a text field?

[bokan, 2013/08/12 16:19:29]

It's called when a frame has its layout updated to compute which portions of the
page should be scrolled on the main thread/impl thread.

+        return false;
+
     return isComposited() && backing()->scrollingLayer();
 }
 
 bool RenderLayer::needsCompositedScrolling() const
 {
     switch (m_forceNeedsCompositedScrolling) {
     case DoNotForceCompositedScrolling:
         return m_needsCompositedScrolling;
     case CompositedScrollingAlwaysOn:
         return true;
@@ skipping 4361 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif