一起学libcef--一个应用libcef的简单例子（windows程序）

之前博客《一起学libcef–搭建自己的libcef运行环境（Win32程序，错误C2220解决方案）》讲述了如何在win32程序中搭建libcef的环境，今天就通过一个简单的例子，在windows程序中使用libcef。

现在再重新写一下如何搞？直接在源代码上搞起！

1 打开源码cefclient解决方案

2 确保cefclient例子可以完美运行

3 在cefclient中，除了util.h之外，全部移除

4 manifests 和 resources文件也可以移除（you must remember to remove the additional manifest files from the Visual Studio project file.）

5 libcef_dll_wrapper 是静态链接，所以我们需要更改项目为动态链接。

接下来就要干我们的事儿了：

1 创建一个自己的头文件ExampleCefApp.h， 在这里新建一个类，继承自CefApp:

CefApp 负责所有的工作, 但是这是一个抽象类，需要计数实现

这样, 我们继承自CefApp创建了一个傀儡类，实际上也什么都没做

#include "include/cef_app.h"
class ExampleCefApp : public CefApp
{
public:
ExampleCefApp ()
{
}
virtual ~ExampleCefApp ()
{
}

private:
IMPLEMENT_REFCOUNTING (ExampleCefApp);
};

2创建一个ExampleCefHandler.h文件，这里面实现一个类继承自所有的event handling classes。

#pragma once

#include "include/cef_client.h"
#include "cefclient/util.h"

class ExampleCefHandler : public CefClient,
public CefContextMenuHandler,
public CefDisplayHandler,
public CefDownloadHandler,
public CefDragHandler,
public CefGeolocationHandler,
public CefKeyboardHandler,
public CefLifeSpanHandler,
public CefLoadHandler,
public CefRequestHandler
{
public:
ExampleCefHandler();
virtual ~ExampleCefHandler();
CefRefPtr<CefBrowser> GetBrowser();

#pragma region CefClient
// since we are letting the base implementations handle all of the heavy lifting,
// these functions just return the this pointer
virtual CefRefPtr<CefContextMenuHandler> GetContextMenuHandler () OVERRIDE;
virtual CefRefPtr<CefDisplayHandler> GetDisplayHandler () OVERRIDE;
virtual CefRefPtr<CefDownloadHandler> GetDownloadHandler () OVERRIDE;
virtual CefRefPtr<CefDragHandler> GetDragHandler () OVERRIDE;
virtual CefRefPtr<CefGeolocationHandler> GetGeolocationHandler () OVERRIDE;
virtual CefRefPtr<CefKeyboardHandler> GetKeyboardHandler () OVERRIDE;
virtual CefRefPtr<CefLifeSpanHandler> GetLifeSpanHandler () OVERRIDE;
virtual CefRefPtr<CefLoadHandler> GetLoadHandler () OVERRIDE;
virtual CefRefPtr<CefRequestHandler> GetRequestHandler () OVERRIDE;
#pragma endregion // CefClient

#pragma region CefDownloadHandler
// 这个函数为虚函数，我们必须实现它。但是我们什么也没做，所以下载文件的操作不会工作
virtual void OnBeforeDownload (CefRefPtr<CefBrowser> browser, CefRefPtr<CefDownloadItem> download_item, const CefString& suggested_name, CefRefPtr<CefBeforeDownloadCallback> callback);
#pragma endregion // CefDownloadHandler

#pragma region CefLifeSpanHandler
// 缓存一个指向browser的引用
virtual void OnAfterCreated (CefRefPtr<CefBrowser> browser) OVERRIDE;

// 释放browser引用
virtual void OnBeforeClose (CefRefPtr<CefBrowser> browser) OVERRIDE;
#pragma endregion // CefLifeSpanHandler

protected:
// the browser reference
CefRefPtr<CefBrowser> browser;

// Include the default reference counting implementation.
IMPLEMENT_REFCOUNTING (ExampleCefHandler);
// Include the default locking implementation.
IMPLEMENT_LOCKING (ExampleCefHandler);
};

3.创建一个源文件 ExampleCefHandler.cc:

#include "cefclient/ExampleCefHandler.h"

// defined in main.cppp
extern void AppQuitMessageLoop ();

ExampleCefHandler::ExampleCefHandler ()
{
}

ExampleCefHandler::~ExampleCefHandler ()
{
}

CefRefPtr<CefBrowser> ExampleCefHandler::GetBrowser ()
{
return browser;
}

CefRefPtr<CefContextMenuHandler> ExampleCefHandler::GetContextMenuHandler ()
{
return this;
}

CefRefPtr<CefDisplayHandler> ExampleCefHandler::GetDisplayHandler ()
{
return this;
}

CefRefPtr<CefDownloadHandler> ExampleCefHandler::GetDownloadHandler ()
{
return this;
}

CefRefPtr<CefDragHandler> ExampleCefHandler::GetDragHandler ()
{
return this;
}

CefRefPtr<CefGeolocationHandler> ExampleCefHandler::GetGeolocationHandler ()
{
return this;
}

CefRefPtr<CefKeyboardHandler> ExampleCefHandler::GetKeyboardHandler ()
{
return this;
}

CefRefPtr<CefLifeSpanHandler> ExampleCefHandler::GetLifeSpanHandler ()
{
return this;
}

CefRefPtr<CefLoadHandler> ExampleCefHandler::GetLoadHandler ()
{
return this;
}

CefRefPtr<CefRequestHandler> ExampleCefHandler::GetRequestHandler ()
{
return this;
}

void ExampleCefHandler::OnBeforeDownload (CefRefPtr<CefBrowser> browser,
CefRefPtr<CefDownloadItem> download_item,
const CefString& suggested_name, CefRefPtr<CefBeforeDownloadCallback> callback)
{
UNREFERENCED_PARAMETER (browser);
UNREFERENCED_PARAMETER (download_item);
callback->Continue (suggested_name, true);
}

void ExampleCefHandler::OnAfterCreated(CefRefPtr<CefBrowser> browser) {
REQUIRE_UI_THREAD();
AutoLock lock_scope (this);

this->browser = browser;

CefLifeSpanHandler::OnAfterCreated (browser);
}

void ExampleCefHandler::OnBeforeClose(CefRefPtr<CefBrowser> browser)
{
REQUIRE_UI_THREAD();
AutoLock lock_scope (this);

browser = NULL;
AppQuitMessageLoop();

CefLifeSpanHandler::OnBeforeClose (browser);
}

4. 最后，创建一个主函数:

#include "cefclient/ExampleCefApp.hpp"
#include "cefclient/ExampleCefHandler.hpp"
#include "cefclient/util.h"
#include <windows.h>

#define BROWSER_WINDOW_CLASS TEXT("BrowserWindowClass")
#define INVALID_HWND (HWND)INVALID_HANDLE_VALUE
#define MESSAGE_WINDOW_CLASS TEXT("MessageWindowClass")
#define QUIT_CEF_EXAMPLE 0xABAD1DEA

namespace
{
CefRefPtr<ExampleCefHandler> example_cef_handler;
HWND application_message_window_handle = INVALID_HWND;
}

LRESULT CALLBACK BrowserWindowWndProc (HWND, UINT, WPARAM, LPARAM);
void CreateBrowserWindow (HINSTANCE instance_handle, int show_minimize_or_maximize)
{
WNDCLASSEX wcex = { 0 };
wcex.cbSize        = sizeof (wcex);
wcex.style         = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc   = BrowserWindowWndProc;
wcex.hInstance     = instance_handle;
wcex.hCursor       = LoadCursor (NULL, IDC_ARROW);
wcex.hbrBackground = WHITE_BRUSH;
wcex.lpszClassName = BROWSER_WINDOW_CLASS;
RegisterClassEx (&wcex);
HWND window_handle (CreateWindow (BROWSER_WINDOW_CLASS, BROWSER_WINDOW_CLASS,
WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN, CW_USEDEFAULT, 0,
CW_USEDEFAULT, 0, NULL, NULL, instance_handle, NULL));
ShowWindow (window_handle, show_minimize_or_maximize);
UpdateWindow (window_handle);
}

LRESULT CALLBACK MessageWindowWndProc (HWND, UINT, WPARAM, LPARAM);
HWND CreateMessageWindow (HINSTANCE instance_handle)
{
WNDCLASSEX wcex    = {0};
wcex.cbSize        = sizeof (wcex);
wcex.lpfnWndProc   = MessageWindowWndProc;
wcex.hInstance     = instance_handle;
wcex.lpszClassName = MESSAGE_WINDOW_CLASS;
RegisterClassEx (&wcex);
return CreateWindow (MESSAGE_WINDOW_CLASS, 0, 0, 0, 0, 0, 0, HWND_MESSAGE, 0, instance_handle, 0);
}

// Program entry point function.
int APIENTRY wWinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow)
{
UNREFERENCED_PARAMETER (hPrevInstance);
UNREFERENCED_PARAMETER (lpCmdLine);

int result (0);
CefMainArgs main_args (hInstance);
CefRefPtr<ExampleCefApp> app (new ExampleCefApp);

// CefExecuteProcess returns -1 for the host process
if (CefExecuteProcess(main_args, app.get()) == -1)
{
CefSettings settings;
settings.multi_threaded_message_loop = true;
CefInitialize (main_args, settings, app.get ());
CreateBrowserWindow (hInstance, nCmdShow);
application_message_window_handle = CreateMessageWindow (hInstance);

MSG msg;
while (GetMessage (&msg, NULL, 0, 0))
{
TranslateMessage (&msg);
DispatchMessage (&msg);
}
result = static_cast<int>(msg.wParam);

DestroyWindow (application_message_window_handle);
application_message_window_handle = INVALID_HWND;

// disabled due to https://code.google.com/p/chromiumembedded/issues/detail?id=755 // CefShutdown ();

UnregisterClass (BROWSER_WINDOW_CLASS, hInstance);
UnregisterClass (MESSAGE_WINDOW_CLASS, hInstance);
}
return result;
}

LRESULT CALLBACK BrowserWindowWndProc (HWND window_handle, UINT message, WPARAM w_param, LPARAM l_param)
{
LRESULT result (0);
switch (message)
{
case WM_CREATE:
{
example_cef_handler = new ExampleCefHandler();

RECT rect = { 0 };
GetClientRect (window_handle, &rect);

CefWindowInfo info;
info.SetAsChild(window_handle, rect);

CefBrowserSettings settings;
CefBrowserHost::CreateBrowser(info, example_cef_handler.get(),
CefString ("http://www.google.com"), settings, NULL);
}
break;

case WM_SIZE:
{
// from the cefclient example, do not allow the window to be resized to 0x0 or the layout will break;
// also be aware that if the size gets too small, GPU acceleration disables
if ((w_param != SIZE_MINIMIZED)
&& (example_cef_handler.get ())
&& (example_cef_handler->GetBrowser ()))
{
CefWindowHandle hwnd (example_cef_handler->GetBrowser ()->GetHost ()->GetWindowHandle ());
if (hwnd)
{
RECT rect = { 0 };
GetClientRect (window_handle, &rect);
HDWP hdwp = BeginDeferWindowPos (1);
hdwp = DeferWindowPos (hdwp, hwnd, NULL,rect.left,
rect.top, rect.right - rect.left, rect.bottom - rect.top, SWP_NOZORDER);
EndDeferWindowPos (hdwp);
}
}
}
break;

case WM_ERASEBKGND:
{
if ((example_cef_handler.get ())
&& (example_cef_handler->GetBrowser ()))
{
CefWindowHandle hwnd (example_cef_handler->GetBrowser()->GetHost()->GetWindowHandle());
// from the cefclient example, don't erase the background
// if the browser window has been loaded to avoid flashing
result = hwnd ? 1 : DefWindowProc (window_handle, message, w_param, l_param);
}
}
break;

case WM_ENTERMENULOOP:
{
if (!w_param)
{
CefSetOSModalLoop (true);
}
result = DefWindowProc (window_handle, message, w_param, l_param);
}
break;

case WM_EXITMENULOOP:
{
if (!w_param)
{
CefSetOSModalLoop (false);
}
result = DefWindowProc (window_handle, message, w_param, l_param);
}
break;

case WM_DESTROY:
break;

default:
{
result = DefWindowProc (window_handle, message, w_param, l_param);
}
break;
}
return result;
}

LRESULT CALLBACK MessageWindowWndProc (HWND window_handle, UINT message, WPARAM w_param, LPARAM l_param)
{
LRESULT result (0);
switch (message)
{
case WM_COMMAND:
{
if (w_param == QUIT_CEF_EXAMPLE)
{
PostQuitMessage(0);
}
}
break;

default:
{
result = DefWindowProc (window_handle, message, w_param, l_param);
}
break;
}
return result;
}

void AppQuitMessageLoop ()
{
if (application_message_window_handle != INVALID_HWND)
{
PostMessage(application_message_window_handle, WM_COMMAND, QUIT_CEF_EXAMPLE, 0);
}
}