ui/gfx/win/direct_manipulation.h

   1 // Copyright 2015 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 #ifndef UI_GFX_WIN_DIRECT_MANIPULATION_H_
   6 #define UI_GFX_WIN_DIRECT_MANIPULATION_H_
   7
   8 #include <directmanipulation.h>
   9
  10 #include "base/memory/scoped_ptr.h"
  11 #include "base/win/scoped_comptr.h"
  12 #include "ui/gfx/geometry/rect.h"
  13 #include "ui/gfx/gfx_export.h"
  14
  15 namespace gfx {
  16 namespace win {
  17
  18 // Windows 10 provides a new API called Direct Manipulation which generates
  19 // smooth scroll events via WM_MOUSEWHEEL messages with predictable deltas
  20 // on high precision touch pads. This basically requires the application window
  21 // to register as a Direct Manipulation consumer. The way mouse wheel messages
  22 // are dispatched is
  23 // 1. The foreground window is checked to see if it is a Direct Manipulation
  24 //    consumer.
  25 // 2. If it is then Direct Manipulation takes over and sends the following
  26 //    messages. WM_POINTERACTIVATE, WM_POINTERDOWN and DM_POINTERHITTEST.
  27 // 3. It then posts WM_MOUSEWHEEL messages with precision deltas which vary
  28 //    based on the amount of the scroll.
  29 // 4. If the foreground window is not a Direct Manipulation consumer, it
  30 //    then takes a fallback route where it posts WM_MOUSEWHEEL messages
  31 //    with precision but varying deltas to the window. There is a also
  32 //    a slight delay in receiving the first set of mouse wheel messages.
  33 //    This causes scrolling to appear janky and jumpy.
  34 // Our approach for addressing this is to do the absolute minimum to
  35 // register our window as a Direct Manipulation consumer. This class
  36 // provides the necessary functionality to register the passed in HWND as a
  37 // Direct Manipulation consumer. We don't rely on Direct manipulation
  38 // to do the smooth scrolling in the background thread as documented on
  39 // msdn.
  40 class GFX_EXPORT DirectManipulationHelper {
  41  public:
  42   // Creates an instance of this class if Direct Manipulation is enabled on
  43   // the platform. If not returns NULL.
  44   static scoped_ptr<DirectManipulationHelper> CreateInstance();
  45
  46   // This function instantiates Direct Manipulation and creates a viewport for
  47   // the passed in |window|.
  48   // consumer. Most of the code is boiler plate and is based on the sample.
  49   void Initialize(HWND window);
  50
  51   // Sets the bounds of the fake Direct manipulation viewport to match those
  52   // of the legacy window.
  53   void SetBounds(const gfx::Rect& bounds);
  54
  55   // Registers and activates the passed in |window| as a Direct Manipulation
  56   // consumer.
  57   void Activate(HWND window);
  58
  59   // Deactivates Direct Manipulation processing on the passed in |window|.
  60   void Deactivate(HWND window);
  61
  62   // Passes the WM_MOUSEWHEEL messages to Direct Manipulation. This is for
  63   // logistics purposes.
  64   void HandleMouseWheel(HWND window, UINT message, WPARAM w_param,
  65       LPARAM l_param);
  66
  67   ~DirectManipulationHelper();
  68
  69  private:
  70   DirectManipulationHelper();
  71
  72   base::win::ScopedComPtr<IDirectManipulationManager2> manager_;
  73   base::win::ScopedComPtr<IDirectManipulationCompositor> compositor_;
  74   base::win::ScopedComPtr<IDirectManipulationUpdateManager> update_manager_;
  75   base::win::ScopedComPtr<IDirectManipulationFrameInfoProvider> frame_info_;
  76   base::win::ScopedComPtr<IDirectManipulationViewport2> view_port_outer_;
  77
  78   DISALLOW_COPY_AND_ASSIGN(DirectManipulationHelper);
  79 };
  80
  81 }  // namespace win
  82 }  // namespace gfx
  83
  84 #endif  // UI_GFX_WIN_DIRECT_MANIPULATION_H_