Libcef 基本对象

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##CefApp

Libcef需要一个CefApp实例，通常为了监听某些事件，还需要继承其他的一些process Handler

CefBrowserProcessHandler
CefRenderProcessHandler

class SimpleApp: public CefApp, public CefBrowserProcessHandler, public CefRenderProcessHandler{

// Entry point function for all processes. int main(int argc, char* argv[]) { // SimpleApp implements application-level callbacks. It will create the first // browser instance in OnContextInitialized() after CEF has initialized. CefRefPtr app(new SimpleApp);
```
 // CEF applications have multiple sub-processes (render, plugin, GPU, etc)
 // that share the same executable. This function checks the command-line and,
 // if this is a sub-process, executes the appropriate logic.
 int exit_code = CefExecuteProcess(main_args, app.get(), NULL);

 // Initialize CEF for the browser process.
 CefInitialize(main_args, settings, app.get(), NULL);
```

在CefApp中，声明了一些获取对象的接口。他们都返回空。这里需要注意，继承的那些Handler的消息，是以来于CefApp中获取特殊对象的接口实现，而不是简单地返回一个NULL

///
// Return the handler for resource bundle events. If
// CefSettings.pack_loading_disabled is true a handler must be returned. If no
// handler is returned resources will be loaded from pack files. This method
// is called by the browser and render processes on multiple threads.
///
/*--cef()--*/
virtual CefRefPtr<CefResourceBundleHandler> GetResourceBundleHandler()
{
	return NULL;
}

///
// Return the handler for functionality specific to the browser process. This
// method is called on multiple threads in the browser process.
///
/*--cef()--*/
virtual CefRefPtr<CefBrowserProcessHandler> GetBrowserProcessHandler()
{
	return NULL;
}

///
// Return the handler for functionality specific to the render process. This
// method is called on the render process main thread.
///
/*--cef()--*/
virtual CefRefPtr<CefRenderProcessHandler> GetRenderProcessHandler()
{
	return NULL;
}

##CefClient

创建浏览器对象时需传入一个CefClient，通常需要继承一些其他对象来监听消息

void SimpleApp::OnContextInitialized()
{
	// SimpleHandler implements browser-level callbacks.
	CefRefPtr<SimpleHandler> handler(new SimpleHandler());

	// Create the first browser window.
	CefBrowserHost::CreateBrowser(window_info, handler.get(), url,
			browser_settings, NULL);
}	

class SimpleHandler : public CefClient,
	public CefDisplayHandler,
	public CefLifeSpanHandler,
	public CefLoadHandler {	

###更新标题栏

通常都实现了改函数，因为桌面系统的任务栏文字和标题栏的文字是一致的（通常使用cef时都不会保留标题栏）

///
// Implement this interface to handle events related to browser display state.
// The methods of this class will be called on the UI thread.
///
/*--cef(source=client)--*/
class CefDisplayHandler: public virtual CefBase
{
public:

	///
	// Called when the page title changes.
	///
	/*--cef(optional_param=title)--*/
	virtual void OnTitleChange(CefRefPtr<CefBrowser> browser,
			const CefString& title)
	{
	}

CefContextMenuHandler，回调类，主要用于处理 Context Menu 事件。
CefDialogHandler，回调类，主要用来处理对话框事件。
CefDisplayHandler，回调类，处理与页面状态相关的事件，如页面加载情况的变化，地址栏变化，标题变化等事件。
CefDownloadHandler，回调类，主要用来处理文件下载。
CefFocusHandler，回调类，主要用来处理焦点事件。
CefGeolocationHandler，回调类，用于申请 geolocation 权限。
CefJSDialogHandler，回调类，主要用来处理 JS 对话框事件。
CefKeyboardHandler，回调类，主要用来处理键盘输入事件。
CefLifeSpanHandler，回调类，主要用来处理与浏览器生命周期相关的事件，与浏览器对象的创建、销毁以及弹出框的管理。
CefLoadHandler，回调类，主要用来处理浏览器页面加载状态的变化，如页面加载开始，完成，出错等。
CefRenderHandler，回调类，主要用来处在在窗口渲染功能被关闭的情况下的事件。
CefRequestHandler，回调类，主要用来处理与浏览器请求相关的的事件，如资源的的加载，重定向等。

##CefBrowser && CefFrame

通常我们在CefLifeSpanHandler的OnAfterCreated和OnBeforeClose消息中保留CefBrowser的指针。

每个浏览器都有一个CefFrame对象，以及若干子Frame

The CefBrowser and CefFrame objects are used for sending commands to the browser and for retrieving state information in callback methods. Each CefBrowser object will have a single main CefFrame object representing the top-level frame and zero or more CefFrame objects representing sub-frames. For example, a browser that loads two iframes will have three CefFrame objects (the top-level frame and the two iframes).

void ClientHandler::OnAfterCreated(CefRefPtr<CefBrowser> browser)
{
	// 保存 browser 指针
}

void ClientHandler::OnBeforeClose(CefRefPtr<CefBrowser> browser)
{
	// 释放 browser 指针
}

///
// Class used to represent a browser window. When used in the browser process
// the methods of this class may be called on any thread unless otherwise
// indicated in the comments. When used in the render process the methods of
// this class may only be called on the main thread.
///
/*--cef(source=library)--*/
class CefBrowser: public virtual CefBase
{
	///
	// Returns the main (top-level) frame for the browser window.
	///
	/*--cef()--*/
	virtual CefRefPtr<CefFrame> GetMainFrame() =0;
	
	///
	// Returns the browser host object. This method can only be called in the
	// browser process.
	///
	/*--cef()--*/
	virtual CefRefPtr<CefBrowserHost> GetHost() =0;
};

####操作浏览器行为

///
// Class used to represent a browser window. When used in the browser process
// the methods of this class may be called on any thread unless otherwise
// indicated in the comments. When used in the render process the methods of
// this class may only be called on the main thread.
///
/*--cef(source=library)--*/
class CefBrowser: public virtual CefBase
{
	///
	// Returns true if the browser can navigate backwards.
	///
	/*--cef()--*/
	virtual bool CanGoBack() =0;

	///
	// Navigate backwards.
	///
	/*--cef()--*/
	virtual void GoBack() =0;

	///
	// Returns true if the browser can navigate forwards.
	///
	/*--cef()--*/
	virtual bool CanGoForward() =0;

	///
	// Navigate forwards.
	///
	/*--cef()--*/
	virtual void GoForward() =0;

	///
	// Returns true if the browser is currently loading.
	///
	/*--cef()--*/
	virtual bool IsLoading() =0;

	///
	// Reload the current page.
	///
	/*--cef()--*/
	virtual void Reload() =0;

	///
	// Reload the current page ignoring any cached data.
	///
	/*--cef()--*/
	virtual void ReloadIgnoreCache() =0;

	///
	// Stop loading the page.
	///
	/*--cef()--*/
	virtual void StopLoad() =0;

	///
	// Returns the globally unique identifier for this browser.
	///
	/*--cef()--*/
	virtual int GetIdentifier() =0;

	// ... ...
};

####获得窗口原生句柄

CefBrowserHost::GetWindowHandle

///
// Class used to represent a browser window. When used in the browser process
// the methods of this class may be called on any thread unless otherwise
// indicated in the comments. When used in the render process the methods of
// this class may only be called on the main thread.
///
/*--cef(source=library)--*/
class CefBrowser: public virtual CefBase
{	
	///
	// Returns the browser host object. This method can only be called in the
	// browser process.
	///
	/*--cef()--*/
	virtual CefRefPtr<CefBrowserHost> GetHost() =0;
};

///
// Class used to represent the browser process aspects of a browser window. The
// methods of this class can only be called in the browser process. They may be
// called on any thread in that process unless otherwise indicated in the
// comments.
///
/*--cef(source=library)--*/
class CefBrowserHost : public virtual CefBase 
{
	///
	// Retrieve the window handle for this browser.
	///
	/*--cef()--*/
	virtual CefWindowHandle GetWindowHandle() =0;
}

##参考

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