ui/base/win/hwnd_subclass.h

   1 // Copyright (c) 2012 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_BASE_WIN_HWND_SUBCLASS_H_
   6 #define UI_BASE_WIN_HWND_SUBCLASS_H_
   7
   8 #include <windows.h>
   9 #include <vector>
  10
  11 #include "base/gtest_prod_util.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "ui/base/ui_base_export.h"
  14 #include "ui/base/view_prop.h"
  15
  16 namespace ui {
  17
  18 // Classes implementing this interface get the opportunity to handle and consume
  19 // messages before they are sent to their target HWND.
  20 class UI_BASE_EXPORT HWNDMessageFilter {
  21  public:
  22   virtual ~HWNDMessageFilter();
  23
  24   // A derived class overrides this method to perform filtering of the messages.
  25   // Return true to prevent other HWNDMessageFilter's of the target HWND and the
  26   // system message handler |original_wnd_proc_| from receiving the message.
  27   // Return false to propagate the message further to other HWNDMessageFilters
  28   // and eventually to |original_wnd_proc|.
  29   // The order in which HWNDMessageFilters are added in HWNDSubclass::AddFilter
  30   // determines which filter gets to see the message first (a filter added first
  31   // will see the message first).
  32   virtual bool FilterMessage(HWND hwnd,
  33                              UINT message,
  34                              WPARAM w_param,
  35                              LPARAM l_param,
  36                              LRESULT* l_result) = 0;
  37 };
  38
  39 // An object that instance-subclasses a window. If the window has already been
  40 // instance-subclassed, that subclassing is lost.
  41 class UI_BASE_EXPORT HWNDSubclass {
  42  public:
  43   ~HWNDSubclass();
  44
  45   // Adds |filter| to the HWNDSubclass of |target|. Caller retains ownership of
  46   // |filter|. See the comment about the order in which filters are added in
  47   // HWNDMessageFilter::FilterMessage.
  48   static void AddFilterToTarget(HWND target, HWNDMessageFilter* filter);
  49
  50   // Removes |filter| from any HWNDSubclass that has it.
  51   static void RemoveFilterFromAllTargets(HWNDMessageFilter* filter);
  52
  53   // Returns a non-null HWNDSubclass corresponding to the HWND |target|. Creates
  54   // one if none exists. Retains ownership of the returned pointer.
  55   static HWNDSubclass* GetHwndSubclassForTarget(HWND target);
  56
  57   // Adds |filter| if not already added to this HWNDSubclass. Caller retains
  58   // ownership of |filter|. See the comment about the order in which filters are
  59   // added in HWNDMessageFilter::FilterMessage.
  60   void AddFilter(HWNDMessageFilter* filter);
  61
  62   // Removes |filter|  from this HWNDSubclass instance if present.
  63   void RemoveFilter(HWNDMessageFilter* filter);
  64
  65   LRESULT OnWndProc(HWND hwnd, UINT message, WPARAM w_param, LPARAM l_param);
  66
  67  private:
  68   class HWNDSubclassFactory;
  69   friend class HWNDSubclassFactory;
  70
  71   explicit HWNDSubclass(HWND target);
  72
  73   HWND target_;
  74   std::vector<HWNDMessageFilter*> filters_;
  75   WNDPROC original_wnd_proc_;
  76   ui::ViewProp prop_;
  77
  78   DISALLOW_COPY_AND_ASSIGN(HWNDSubclass);
  79 };
  80
  81 }  // namespace ui
  82
  83 #endif  // UI_BASE_WIN_HWND_SUBCLASS_H_