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谷歌chrome浏览器的源码分析(五)

發布時間：2025/3/21 HTML 35 豆豆

生活随笔收集整理的這篇文章主要介紹了谷歌chrome浏览器的源码分析(五) 小編覺得挺不錯的,現在分享給大家,幫大家做個參考.

上一次說到類RenderThread和類RenderView把消息處理，那么這兩個類是怎么樣處理消息的呢？又是怎么樣處理瀏覽的消息呢？現在就帶著這兩個問題去分析它的源碼，理解它處理消息的方法。類RenderThread處理消息的代碼如下：

#001??void RenderThread::OnMessageReceived(const IPC::Message& msg) {

#002????// NOTE: We could subclass router_ to intercept OnControlMessageReceived, but

#003????// it seems simpler to just process any control messages that we care about

#004????// up-front and then send the rest of the messages onto router_.

#005?

下面判斷是控制消息，如果是控制消息就在本類里處理，否則就分發到別的地方處理，主要是轉到類RenderView處理。

#006????if (msg.routing_id() == MSG_ROUTING_CONTROL) {

#007??????IPC_BEGIN_MESSAGE_MAP(RenderThread, msg)

#008????????IPC_MESSAGE_HANDLER(ViewMsg_VisitedLink_NewTable, OnUpdateVisitedLinks)

#009????????IPC_MESSAGE_HANDLER(ViewMsg_SetNextPageID, OnSetNextPageID)

#010????????IPC_MESSAGE_HANDLER(ViewMsg_New, OnCreateNewView)

#011????????IPC_MESSAGE_HANDLER(ViewMsg_SetCacheCapacities, OnSetCacheCapacities)

#012????????IPC_MESSAGE_HANDLER(ViewMsg_GetCacheResourceStats,

#013???????????????????????????OnGetCacheResourceStats)

#014????????// send the rest to the router

#015????????IPC_MESSAGE_UNHANDLED(router_.OnMessageReceived(msg))

#016??????IPC_END_MESSAGE_MAP()

#017????} else {

這里是分發消息到別的地方處理。

#018??????router_.OnMessageReceived(msg);

#019????}

#020??}

在瀏覽器里，消息分為兩大類：控制消息和路由消息。像使用IPC_MESSAGE_CONTROL宏定義的消息，就是控制消息；使用IPC_MESSAGE_ROUTED宏定義的消息，就是路由消息。

路由消息分發是由類MessageRouter來負責的，主要處理的代碼如下：

#001?

#002??void MessageRouter::OnMessageReceived(const IPC::Message& msg) {

#003????if (msg.routing_id() == MSG_ROUTING_CONTROL) {

#004??????OnControlMessageReceived(msg);

#005????} else {

#006??????RouteMessage(msg);

#007????}

#008??}

在這里又分為MSG_ROUTING_CONTROL消息和其它路由消息，再一次通過函數RouteMessage分發之后，如下：

#001??bool MessageRouter::RouteMessage(const IPC::Message& msg) {

#002????IPC::Channel::Listener* listener = routes_.Lookup(msg.routing_id());

#003????if (!listener)

#004??????return false;

#005?

#006????listener->OnMessageReceived(msg);

#007????return true;

#008??}

上面這個函數里又把消息通過發送到listener里去，其實listener是根據消息的目標routing_id來選擇的，那么就是說它是選擇發送到不同的窗口里去，因為每個TAB一個窗口。消息經過這樣的處理之后，就到達了終點地---?RenderView::OnMessageReceived函數。下一次再來分析RenderView::OnMessageReceived函數的代碼和后繼處理。

#001??void RenderThread::OnMessageReceived(const IPC::Message& msg) {

#002????// NOTE: We could subclass router_ to intercept OnControlMessageReceived, but

#003????// it seems simpler to just process any control messages that we care about

#004????// up-front and then send the rest of the messages onto router_.

#005?

下面判斷是控制消息，如果是控制消息就在本類里處理，否則就分發到別的地方處理，主要是轉到類RenderView處理。

#006????if (msg.routing_id() == MSG_ROUTING_CONTROL) {

#007??????IPC_BEGIN_MESSAGE_MAP(RenderThread, msg)

#008????????IPC_MESSAGE_HANDLER(ViewMsg_VisitedLink_NewTable, OnUpdateVisitedLinks)

#009????????IPC_MESSAGE_HANDLER(ViewMsg_SetNextPageID, OnSetNextPageID)

#010????????IPC_MESSAGE_HANDLER(ViewMsg_New, OnCreateNewView)

#011????????IPC_MESSAGE_HANDLER(ViewMsg_SetCacheCapacities, OnSetCacheCapacities)

#012????????IPC_MESSAGE_HANDLER(ViewMsg_GetCacheResourceStats,

#013???????????????????????????OnGetCacheResourceStats)

#014????????// send the rest to the router

#015????????IPC_MESSAGE_UNHANDLED(router_.OnMessageReceived(msg))

#016??????IPC_END_MESSAGE_MAP()

#017????} else {

這里是分發消息到別的地方處理。

#018??????router_.OnMessageReceived(msg);

#019????}

#020??}

路由消息分發是由類MessageRouter來負責的，主要處理的代碼如下：

#001?

#002??void MessageRouter::OnMessageReceived(const IPC::Message& msg) {

#003????if (msg.routing_id() == MSG_ROUTING_CONTROL) {

#004??????OnControlMessageReceived(msg);

#005????} else {

#006??????RouteMessage(msg);

#007????}

#008??}

在這里又分為MSG_ROUTING_CONTROL消息和其它路由消息，再一次通過函數RouteMessage分發之后，如下：

#001??bool MessageRouter::RouteMessage(const IPC::Message& msg) {

#002????IPC::Channel::Listener* listener = routes_.Lookup(msg.routing_id());

#003????if (!listener)

#004??????return false;

#005?

#006????listener->OnMessageReceived(msg);

#007????return true;

#008??}

上一次說到消息轉發，并分析了RenderThread類里處理消息的函數，其實大部份的消息都是在RenderView類里的OnMessageReceived函數處理，比如瀏覽的消息也是在這里處理。它的代碼如下：

#001??void RenderView::OnMessageReceived(const IPC::Message& message) {

#002????// Let the resource dispatcher intercept resource messages first.

如果是資源消息，就直接分發去處理，以便提高效率。

#003????if (resource_dispatcher_->OnMessageReceived(message))

#004??????return;

下面開始處理RenderView類里所有的消息。

#005????IPC_BEGIN_MESSAGE_MAP(RenderView, message)

#006??????IPC_MESSAGE_HANDLER(ViewMsg_CreatingNew_ACK, OnCreatingNewAck)

#007??????IPC_MESSAGE_HANDLER(ViewMsg_CaptureThumbnail, SendThumbnail)

#008??????IPC_MESSAGE_HANDLER(ViewMsg_GetPrintedPagesCount, OnGetPrintedPagesCount)

#009??????IPC_MESSAGE_HANDLER(ViewMsg_PrintPages, OnPrintPages)

#010??????IPC_MESSAGE_HANDLER(ViewMsg_Navigate, OnNavigate)

#011??????IPC_MESSAGE_HANDLER(ViewMsg_Stop, OnStop)

#012??????IPC_MESSAGE_HANDLER(ViewMsg_LoadAlternateHTMLText, OnLoadAlternateHTMLText)

#013??????IPC_MESSAGE_HANDLER(ViewMsg_StopFinding, OnStopFinding)

#014??????IPC_MESSAGE_HANDLER(ViewMsg_Undo, OnUndo)

#015??????IPC_MESSAGE_HANDLER(ViewMsg_Redo, OnRedo)

#016??????IPC_MESSAGE_HANDLER(ViewMsg_Cut, OnCut)

#017??????IPC_MESSAGE_HANDLER(ViewMsg_Copy, OnCopy)

#018??????IPC_MESSAGE_HANDLER(ViewMsg_Paste, OnPaste)

#019??????IPC_MESSAGE_HANDLER(ViewMsg_Replace, OnReplace)

#020??????IPC_MESSAGE_HANDLER(ViewMsg_Delete, OnDelete)

#021??????IPC_MESSAGE_HANDLER(ViewMsg_SelectAll, OnSelectAll)

#022??????IPC_MESSAGE_HANDLER(ViewMsg_CopyImageAt, OnCopyImageAt)

#023??????IPC_MESSAGE_HANDLER(ViewMsg_Find, OnFind)

#024??????IPC_MESSAGE_HANDLER(ViewMsg_AlterTextSize, OnAlterTextSize)

#025??????IPC_MESSAGE_HANDLER(ViewMsg_SetPageEncoding, OnSetPageEncoding)

#026??????IPC_MESSAGE_HANDLER(ViewMsg_InspectElement, OnInspectElement)

#027??????IPC_MESSAGE_HANDLER(ViewMsg_ShowJavaScriptConsole, OnShowJavaScriptConsole)

#028??????IPC_MESSAGE_HANDLER(ViewMsg_DownloadImage, OnDownloadImage)

#029??????IPC_MESSAGE_HANDLER(ViewMsg_ScriptEvalRequest, OnScriptEvalRequest)

#030??????IPC_MESSAGE_HANDLER(ViewMsg_AddMessageToConsole, OnAddMessageToConsole)

#031??????IPC_MESSAGE_HANDLER(ViewMsg_DebugAttach, OnDebugAttach)

#032??????IPC_MESSAGE_HANDLER(ViewMsg_DebugDetach, OnDebugDetach)

#033??????IPC_MESSAGE_HANDLER(ViewMsg_ReservePageIDRange, OnReservePageIDRange)

#034??????IPC_MESSAGE_HANDLER(ViewMsg_UploadFile, OnUploadFileRequest)

#035??????IPC_MESSAGE_HANDLER(ViewMsg_FormFill, OnFormFill)

#036??????IPC_MESSAGE_HANDLER(ViewMsg_FillPasswordForm, OnFillPasswordForm)

#037??????IPC_MESSAGE_HANDLER(ViewMsg_DragTargetDragEnter, OnDragTargetDragEnter)

#038??????IPC_MESSAGE_HANDLER(ViewMsg_DragTargetDragOver, OnDragTargetDragOver)

#039??????IPC_MESSAGE_HANDLER(ViewMsg_DragTargetDragLeave, OnDragTargetDragLeave)

#040??????IPC_MESSAGE_HANDLER(ViewMsg_DragTargetDrop, OnDragTargetDrop)

#041??????IPC_MESSAGE_HANDLER(ViewMsg_AllowDomAutomationBindings,

#042?????????????????????????OnAllowDomAutomationBindings)

#043??????IPC_MESSAGE_HANDLER(ViewMsg_AllowBindings, OnAllowBindings)

#044??????IPC_MESSAGE_HANDLER(ViewMsg_SetDOMUIProperty, OnSetDOMUIProperty)

#045??????IPC_MESSAGE_HANDLER(ViewMsg_DragSourceEndedOrMoved, OnDragSourceEndedOrMoved)

#046??????IPC_MESSAGE_HANDLER(ViewMsg_DragSourceSystemDragEnded,

#047?????????????????????????OnDragSourceSystemDragEnded)

#048??????IPC_MESSAGE_HANDLER(ViewMsg_SetInitialFocus, OnSetInitialFocus)

#049??????IPC_MESSAGE_HANDLER(ViewMsg_FindReplyACK, OnFindReplyAck)

#050??????IPC_MESSAGE_HANDLER(ViewMsg_UpdateTargetURL_ACK, OnUpdateTargetURLAck)

#051??????IPC_MESSAGE_HANDLER(ViewMsg_UpdateWebPreferences, OnUpdateWebPreferences)

#052??????IPC_MESSAGE_HANDLER(ViewMsg_SetAltErrorPageURL, OnSetAltErrorPageURL)

#053??????IPC_MESSAGE_HANDLER(ViewMsg_InstallMissingPlugin, OnInstallMissingPlugin)

#054??????IPC_MESSAGE_HANDLER(ViewMsg_RunFileChooserResponse, OnFileChooserResponse)

#055??????IPC_MESSAGE_HANDLER(ViewMsg_EnableViewSourceMode, OnEnableViewSourceMode)

#056??????IPC_MESSAGE_HANDLER(ViewMsg_UpdateBackForwardListCount,

#057?????????????????????????OnUpdateBackForwardListCount)

#058?????IPC_MESSAGE_HANDLER(ViewMsg_GetAllSavableResourceLinksForCurrentPage,

#059?????????????????????????OnGetAllSavableResourceLinksForCurrentPage)

#060?????IPC_MESSAGE_HANDLER(ViewMsg_GetSerializedHtmlDataForCurrentPageWithLocalLinks,

#061?????????????????????????OnGetSerializedHtmlDataForCurrentPageWithLocalLinks)

#062??????IPC_MESSAGE_HANDLER(ViewMsg_GetApplicationInfo, OnGetApplicationInfo)

#063??????IPC_MESSAGE_HANDLER(ViewMsg_ShouldClose, OnMsgShouldClose)

#064??????IPC_MESSAGE_HANDLER(ViewMsg_ClosePage, OnClosePage)

#065??????IPC_MESSAGE_HANDLER(ViewMsg_ThemeChanged, OnThemeChanged)

#066??#ifdef CHROME_PERSONALIZATION

#067??????IPC_MESSAGE_HANDLER(ViewMsg_PersonalizationEvent, OnPersonalizationEvent)

#068??#endif

#069??????IPC_MESSAGE_HANDLER(ViewMsg_HandleMessageFromExternalHost,

#070??????????????????????????OnMessageFromExternalHost)

這里對于沒有處理的消息進行提示。

#071??????// Have the super handle all other messages.

#072??????IPC_MESSAGE_UNHANDLED(RenderWidget::OnMessageReceived(message))

#073????IPC_END_MESSAGE_MAP()

#074??}

從上面這個函數可以看到，它的消息處理是非常多的，下面來分析一個瀏覽網絡連接的消息，它就是ViewMsg_Navigate，可以看到這個消息后面響應函數是OnNavigate，也就是說，當你輸入網絡地址之后按回車，就會通過上說過的IPC機制把消息發送到這里，接著來看這個函數OnNavigate的代碼，如下：

#001??void RenderView::OnNavigate(const ViewMsg_Navigate_Params& params) {

判斷窗口是否關閉，如果關閉就不用去打開連接地址了。

#002????if (!webview())

#003??????return;

#004?

處理一些about的連接處理，比如about:crash。

#005????AboutHandler::MaybeHandle(params.url);

#006?

保存是否重新加載網頁。

#007????bool is_reload = params.reload;

#008?

獲取WEB的顯示框架。

#009????WebFrame* main_frame = webview()->GetMainFrame();

判斷當是重新加載時，而當前又不是歷史網頁的情況。

#010????if (is_reload && !main_frame->HasCurrentState()) {

#011??????// We cannot reload if we do not have any history state.??This happens, for

#012??????// example, when recovering from a crash.??Our workaround here is a bit of

#013??????// a hack since it means that reload after a crashed tab does not cause an

#014??????// end-to-end cache validation.

#015??????is_reload = false;

#016????}

#017?

下面設置緩沖策略。

#018????WebRequestCachePolicy cache_policy;

#019????if (is_reload) {

#020??????cache_policy = WebRequestReloadIgnoringCacheData;

#021????} else if (params.page_id != -1 || main_frame->GetInViewSourceMode()) {

#022??????cache_policy = WebRequestReturnCacheDataElseLoad;

#023????} else {

#024??????cache_policy = WebRequestUseProtocolCachePolicy;

#025????}

#026?

下面創建一個下載請求，并把相關參數設置到請求里面。

#027????scoped_ptr<WebRequest> request(WebRequest::Create(params.url));

#028????request->SetCachePolicy(cache_policy);

#029????request->SetExtraData(new RenderViewExtraRequestData(

#030????????params.page_id, params.transition, params.url));

#031?

設置WEBKIT的請求狀態。

#032????// If we are reloading, then WebKit will use the state of the current page.

#033????// Otherwise, we give it the state to navigate to.

#034????if (!is_reload)

#035??????request->SetHistoryState(params.state);

#036?

讓主WEB顯示框架去下載請求顯示。

#037????main_frame->LoadRequest(request.get());

#038??}

分析這個函數，就可以知道處理瀏覽消息的過程，下一次來分析WebFrame里的接口函數LoadRequest處理過程，到底它是怎么樣處理JavaScript腳本網頁下載的呢？