window_proc_delegate_manager.h

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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#ifndef FLUTTER_SHELL_PLATFORM_WINDOWS_WINDOW_PROC_DELEGATE_MANAGER_H_
#define FLUTTER_SHELL_PLATFORM_WINDOWS_WINDOW_PROC_DELEGATE_MANAGER_H_
 
#include <Windows.h>
 
#include <optional>
#include <vector>
 
#include "flutter/fml/macros.h"
#include "flutter/shell/platform/windows/public/flutter_windows.h"
 
namespace flutter {
 
// Handles registration, unregistration, and dispatching for WindowProc
// delegation.
class WindowProcDelegateManager {
 public:
  explicit WindowProcDelegateManager();
  ~WindowProcDelegateManager();
 
  // Adds |callback| as a delegate to be called for |OnTopLevelWindowProc|.
  //
  // Multiple calls with the same |callback| will replace the previous
  // registration, even if |user_data| is different.
  void RegisterTopLevelWindowProcDelegate(
      FlutterDesktopWindowProcCallback callback,
      void* user_data);
 
  // Unregisters |callback| as a delegate for |OnTopLevelWindowProc|.
  void UnregisterTopLevelWindowProcDelegate(
      FlutterDesktopWindowProcCallback callback);
 
  // Calls any registered WindowProc delegates in the order they were
  // registered.
  //
  // If a result is returned, then the message was handled in such a way that
  // further handling should not be done.
  std::optional<LRESULT> OnTopLevelWindowProc(HWND hwnd,
                                              UINT message,
                                              WPARAM wparam,
                                              LPARAM lparam) const;
 
 private:
  struct WindowProcDelegate {
    FlutterDesktopWindowProcCallback callback = nullptr;
    void* user_data = nullptr;
  };
 
  std::vector<WindowProcDelegate> delegates_;
 
  FML_DISALLOW_COPY_AND_ASSIGN(WindowProcDelegateManager);
};
 
}  // namespace flutter
 
#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_WINDOW_PROC_DELEGATE_MANAGER_H_