content/renderer/webscrollbarbehavior_impl_gtkoraura.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/renderer/webscrollbarbehavior_impl_gtkoraura.h"
   6
   7 #include "third_party/WebKit/public/platform/WebPoint.h"
   8 #include "third_party/WebKit/public/platform/WebRect.h"
   9
  10 namespace content {
  11
  12 bool WebScrollbarBehaviorImpl::shouldCenterOnThumb(
  13       blink::WebScrollbarBehavior::Button mouseButton,
  14       bool shiftKeyPressed,
  15       bool altKeyPressed) {
  16 #if (defined(OS_LINUX) && !defined(OS_CHROMEOS))
  17   if (mouseButton == blink::WebScrollbarBehavior::ButtonMiddle)
  18     return true;
  19 #endif
  20   return (mouseButton == blink::WebScrollbarBehavior::ButtonLeft) &&
  21       shiftKeyPressed;
  22 }
  23
  24 bool WebScrollbarBehaviorImpl::shouldSnapBackToDragOrigin(
  25     const blink::WebPoint& eventPoint,
  26     const blink::WebRect& scrollbarRect,
  27     bool isHorizontal) {
  28   // Constants used to figure the drag rect outside which we should snap the
  29   // scrollbar thumb back to its origin. These calculations are based on
  30   // observing the behavior of the MSVC8 main window scrollbar + some
  31   // guessing/extrapolation.
  32   static const int kOffEndMultiplier = 3;
  33   static const int kOffSideMultiplier = 8;
  34   static const int kDefaultWinScrollbarThickness = 17;
  35
  36   // Find the rect within which we shouldn't snap, by expanding the track rect
  37   // in both dimensions.
  38   gfx::Rect noSnapRect(scrollbarRect);
  39   int thickness = isHorizontal ? noSnapRect.height() : noSnapRect.width();
  40   // Even if the platform's scrollbar is narrower than the default Windows one,
  41   // we still want to provide at least as much slop area, since a slightly
  42   // narrower scrollbar doesn't necessarily imply that users will drag
  43   // straighter.
  44   thickness = std::max(thickness, kDefaultWinScrollbarThickness);
  45   noSnapRect.Inset(
  46       (isHorizontal ? kOffEndMultiplier : kOffSideMultiplier) * -thickness,
  47       (isHorizontal ? kOffSideMultiplier : kOffEndMultiplier) * -thickness);
  48
  49   // On most platforms, we should snap iff the event is outside our calculated
  50   // rect.  On Linux, however, we should not snap for events off the ends, but
  51   // not the sides, of the rect.
  52 #if (defined(OS_LINUX) && !defined(OS_CHROMEOS))
  53   return isHorizontal ?
  54       (eventPoint.y < noSnapRect.y() || eventPoint.y >= noSnapRect.bottom()) :
  55       (eventPoint.x < noSnapRect.x() || eventPoint.x >= noSnapRect.right());
  56 #else
  57   return !noSnapRect.Contains(eventPoint);
  58 #endif
  59 }
  60
  61 }  // namespace content