Merge 67001 - 2010-09-08 Peter Kasting <pkasting@google.com>...

WebKit/chromium/src/win/WebInputEventFactory.cpp

 /*
  * Copyright (C) 2006-2009 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 385 matching lines @@
 
     // Convert wheel delta amount to a number of pixels to scroll.
     //
     // How many pixels should we scroll per line?  Gecko uses the height of the
     // current line, which means scroll distance changes as you go through the
     // page or go to different pages.  IE 8 is ~60 px/line, although the value
     // seems to vary slightly by page and zoom level.  Also, IE defaults to
     // smooth scrolling while Firefox doesn't, so it can get away with somewhat
     // larger scroll values without feeling as jerky.  Here we use 100 px per
     // three lines (the default scroll amount is three lines per wheel tick).
+    // Even though we have smooth scrolling, we don't make this as large as IE
+    // because subjectively IE feels like it scrolls farther than you want while
+    // reading articles.
     static const float scrollbarPixelsPerLine = 100.0f / 3.0f;
     wheelDelta /= WHEEL_DELTA;
     float scrollDelta = wheelDelta;
     if (horizontalScroll) {
         unsigned long scrollChars = defaultScrollCharsPerWheelDelta;
         SystemParametersInfo(SPI_GETWHEELSCROLLCHARS, 0, &scrollChars, 0);
         // TODO(pkasting): Should probably have a different multiplier
         // scrollbarPixelsPerChar here.
         scrollDelta *= static_cast<float>(scrollChars) * scrollbarPixelsPerLine;
     } else {
@@ skipping 12 matching lines @@
         result.wheelTicksX = wheelDelta;
     } else {
         result.deltaY = scrollDelta;
         result.wheelTicksY = wheelDelta;
     }
 
     return result;
 }
 
 } // namespace WebKit