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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UI_BASE_WIN_HWND_SUBCLASS_H_
#define UI_BASE_WIN_HWND_SUBCLASS_H_
#include <windows.h>
#include <memory>
#include <vector>
#include "base/component_export.h"
#include "base/memory/raw_ptr.h"
#include "ui/base/view_prop.h"
namespace ui {
// Classes implementing this interface get the opportunity to handle and consume
// messages before they are sent to their target HWND.
class COMPONENT_EXPORT(UI_BASE) HWNDMessageFilter {
public:
virtual ~HWNDMessageFilter();
// A derived class overrides this method to perform filtering of the messages.
// Return true to prevent other HWNDMessageFilter's of the target HWND and the
// system message handler |original_wnd_proc_| from receiving the message.
// Return false to propagate the message further to other HWNDMessageFilters
// and eventually to |original_wnd_proc|.
// The order in which HWNDMessageFilters are added in HWNDSubclass::AddFilter
// determines which filter gets to see the message first (a filter added first
// will see the message first).
virtual bool FilterMessage(HWND hwnd,
UINT message,
WPARAM w_param,
LPARAM l_param,
LRESULT* l_result) = 0;
};
// An object that instance-subclasses a window. If the window has already been
// instance-subclassed, that subclassing is lost.
class COMPONENT_EXPORT(UI_BASE) HWNDSubclass {
public:
HWNDSubclass(const HWNDSubclass&) = delete;
HWNDSubclass& operator=(const HWNDSubclass&) = delete;
~HWNDSubclass();
// Adds |filter| to the HWNDSubclass of |target|. Caller retains ownership of
// |filter|. See the comment about the order in which filters are added in
// HWNDMessageFilter::FilterMessage.
static void AddFilterToTarget(HWND target, HWNDMessageFilter* filter);
// Removes |filter| from any HWNDSubclass that has it.
static void RemoveFilterFromAllTargets(HWNDMessageFilter* filter);
// Returns a non-null HWNDSubclass corresponding to the HWND |target|. Creates
// one if none exists. Retains ownership of the returned pointer.
static HWNDSubclass* GetHwndSubclassForTarget(HWND target);
// Adds |filter| if not already added to this HWNDSubclass. Caller retains
// ownership of |filter|. See the comment about the order in which filters are
// added in HWNDMessageFilter::FilterMessage.
void AddFilter(HWNDMessageFilter* filter);
// Removes |filter| from this HWNDSubclass instance if present.
void RemoveFilter(HWNDMessageFilter* filter);
LRESULT OnWndProc(HWND hwnd, UINT message, WPARAM w_param, LPARAM l_param);
private:
class HWNDSubclassFactory;
friend class HWNDSubclassFactory;
explicit HWNDSubclass(HWND target);
HWND target_;
std::vector<raw_ptr<HWNDMessageFilter, VectorExperimental>> filters_;
WNDPROC original_wnd_proc_;
ui::ViewProp prop_;
};
} // namespace ui
#endif // UI_BASE_WIN_HWND_SUBCLASS_H_
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