// Copyright (c) 2010 The Chromium 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 CHROME_BROWSER_HANG_MONITOR_HUNG_WINDOW_DETECTOR_H__
#define CHROME_BROWSER_HANG_MONITOR_HUNG_WINDOW_DETECTOR_H__
#include "base/synchronization/lock.h"
#include "chrome/common/worker_thread_ticker.h"
// This class provides the following functionality:
// Given a top-level window handle, it enumerates all descendant windows
// of that window and, on finding a window that belongs to a different
// thread from that of the top-level window, it tests to see if that window
// is responding to messages. It does this test by first calling the
// IsHungAppWindow API and, additionally (since the IsHungAppWindow API
// does not deal correctly with suspended threads), send a dummy message
// (WM_NULL) to the window and verifies that the call does not timeout.
// This class is typically used in conjunction with the WorkerThreadTicker
// class so that the checking can happen on a periodic basis.
// If a hung window is detected it calls back the specified implementation of
// the HungWindowNotification interface. Currently this class only supports
// a single callback but it can be extended later to support multiple
// callbacks.
class HungWindowDetector : public WorkerThreadTicker::Callback {
public:
// This property specifies the message timeout for a child window.
static const wchar_t kHungChildWindowTimeout[];
// This is the notification callback interface that is used to notify
// callers about a non-responsive window
class HungWindowNotification {
public:
enum ActionOnHungWindow {
HUNG_WINDOW_IGNORE,
HUNG_WINDOW_TERMINATE_PROCESS,
};
// This callback method is invoked when a hung window is detected.
// A return value of false indicates that we should stop enumerating the
// child windows of the browser window to check if they are hung.
virtual bool OnHungWindowDetected(HWND hung_window, HWND top_level_window,
ActionOnHungWindow* action) = 0;
};
// The notification object is not owned by this class. It is assumed that
// this pointer will be valid throughout the lifetime of this class.
// Ownership of this pointer is not transferred to this class.
// Note that the Initialize method needs to be called to initiate monitoring
// of hung windows.
explicit HungWindowDetector(HungWindowNotification* notification);
~HungWindowDetector();
// This method initialized the monitoring of hung windows. All descendant
// windows of the passed-in top-level window which belong to a thread
// different from that of the top-level window are monitored. The
// message_response_timeout parameter indicates how long this class must
// wait for a window to respond to a sent message before it is considered
// to be non-responsive.
// Initialize can be called multiple times to change the actual window to
// be monitored as well as the message response timeout
bool Initialize(HWND top_level_window,
int message_response_timeout);
// Implementation of the WorkerThreadTicker::Callback interface
virtual void OnTick();
private:
// Helper function that checks whether the specified child window is hung.
// If so, it invokes the HungWindowNotification interface implementation
bool CheckChildWindow(HWND child_window);
static BOOL CALLBACK ChildWndEnumProc(HWND child_window, LPARAM param);
// Pointer to the HungWindowNotification callback interface. This class does
// not RefCount this pointer and it is assumed that the pointer will be valid
// throughout the lifetime of this class.
HungWindowNotification* notification_;
HWND top_level_window_;
// How long do we wait before we consider a window hung (in ms)
int message_response_timeout_;
base::Lock hang_detection_lock_;
// Indicates if this object is currently enumerating hung windows
bool enumerating_;
DISALLOW_COPY_AND_ASSIGN(HungWindowDetector);
};
#endif // CHROME_BROWSER_HANG_MONITOR_HUNG_WINDOW_DETECTOR_H__