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QT分析之WebKit
分三个阶段对QWebView进行分析：初始化（获取数据）、HTML解析、页面显示。从QT自带的文档中可以知道：
QWebView -& QWebPage =& QWebFrame（一个QWebPage含多个QWebFrame）
在界面中选择了Open URL，输入URL之后，调用的是：void MainWindow::openUrl()
void MainWindow::openUrl(){QString url = QInputDialog::getText(this, tr(“Enter a URL”),tr(“URL:”), QLineEdit::Normal, “http://”, &ok);
if (ok && !url.isEmpty()) {centralWidget-&webView-&setUrl(url);}}
调用的是QWebView::setUrl()
void QWebView::setUrl(const QUrl &url){page()-&mainFrame()-&setUrl(url);}
其中page()是获取QWebPage指针，QWebPage::mainFrame()获取的是QWebFrame指针。
所以调用的是：QWebFrame::setUrl()
void QWebFrame::setUrl(const QUrl &url){d-&frame-&loader()-&begin(ensureAbsoluteUrl(url));d-&frame-&loader()-&end();load(ensureAbsoluteUrl(url));}
ensureAbsoluteUrl()函数作用是，确保URL是绝对URL（完整URL）。所谓相对URL是指没有输入http://或者https://等前缀的web地址。先看第一句的调用。其中隐含了从QUrl到KURL的变换。
void FrameLoader::begin(const KURL& url, bool dispatch, SecurityOrigin* origin){// We need to take a reference to the security origin because |clear|// might destroy the document that owns it.RefPtr&SecurityOrigin& forcedSecurityOrigin =
bool resetScripting = !(m_isDisplayingInitialEmptyDocument && m_frame-&document() && m_frame-&document()-&securityOrigin()-&isSecureTransitionTo(url));clear(resetScripting, resetScripting);
// 清除上一次的数据，为本次装载准备if (resetScripting)m_frame-&script()-&updatePlatformScriptObjects();
// 在Windows平台下，这是空函数if (dispatch)dispatchWindowObjectAvailable();
m_needsClear =m_isComplete =m_didCallImplicitClose =m_isLoadingMainResource =m_isDisplayingInitialEmptyDocument = m_creatingInitialEmptyD
KURL ref(url);ref.setUser(String());ref.setPass(String());ref.setRef(String());m_outgoingReferrer = ref.string();m_URL =
RefPtr&Document&
if (!m_isDisplayingInitialEmptyDocument && m_client-&shouldUsePluginDocument(m_responseMIMEType))document = PluginDocument::create(m_frame);elsedocument = DOMImplementation::createDocument(m_responseMIMEType, m_frame, m_frame-&inViewSourceMode());
// 创建DOM文件，m_responseMIMEType不同实体不同。
// 如果是”text/html”创建HTMLDocument实体；”application/xhtml+xml”创建Document实体
// 如果是”application/x-ftp-directory”则是FTPDirectoryDocument实体
// text/vnd.wap.wml 对应 WMLDocument 实体（无线）
// “application/pdf” /”text/plain” 对应 PluginDocument实体
// 如果是MediaPlayer::supportsType(type)，创建的是MediaDocument实体
// “image/svg+xml” 对应 SVGDocument实体m_frame-&setDocument(document);
document-&setURL(m_URL);if (m_decoder)document-&setDecoder(m_decoder.get());if (forcedSecurityOrigin)document-&setSecurityOrigin(forcedSecurityOrigin.get());
m_frame-&domWindow()-&setURL(document-&url());m_frame-&domWindow()-&setSecurityOrigin(document-&securityOrigin());
updatePolicyBaseURL(); // 更新排布策略的基础URL
Settings* settings = document-&settings();document-&docLoader()-&setAutoLoadImages(settings && settings-&loadsImagesAutomatically());
if (m_documentLoader) {String dnsPrefetchControl = m_documentLoader-&response().httpHeaderField(“X-DNS-Prefetch-Control”);if (!dnsPrefetchControl.isEmpty())document-&parseDNSPrefetchControlHeader(dnsPrefetchControl);}
#if FRAME_LOADS_USER_STYLESHEETKURL userStyleSheet = settings ? settings-&userStyleSheetLocation() : KURL();if (!userStyleSheet.isEmpty())m_frame-&setUserStyleSheetLocation(userStyleSheet);#endif
restoreDocumentState();
document-&implicitOpen();
if (m_frame-&view())m_frame-&view()-&setContentsSize(IntSize());
#if USE(LOW_BANDWIDTH_DISPLAY)// Low bandwidth display is a first pass display without external resources// used to give an instant visual feedback. We currently only enable it for// HTML documents in the top frame.if (document-&isHTMLDocument() && !m_frame-&tree()-&parent() && m_useLowBandwidthDisplay) {m_pendingSourceInLowBandwidthDisplay = String();m_finishedParsingDuringLowBandwidthDisplay =m_needToSwitchOutLowBandwidthDisplay =document-&setLowBandwidthDisplay(true);}#endif}
看其中document-&implicitOpen()的代码：
void Document::implicitOpen(){cancelParsing();
clear();m_tokenizer = createTokenizer();setParsing(true);}
Tokenizer *HTMLDocument::createTokenizer(){bool reportErrors =if (frame())if (Page* page = frame()-&page())reportErrors = page-&inspectorController()-&windowVisible();
return new HTMLTokenizer(this, reportErrors);}
新创建的HTMLTokenizer对象，就是HTML的解析器。
回到QWebFrame::setUrl()的第二句：d-&frame-&loader()-&end();
只是把上次未完的解析停止：
void FrameLoader::endIfNotLoadingMainResource(){if (m_isLoadingMainResource || !m_frame-&page())
// // The frame’s last ref may be removed and it can be deleted by checkCompleted(),// so we’ll add a protective refcountRefPtr&Frame& protector(m_frame);
// make sure nothing’s left in thereif (m_frame-&document()) {write(0, 0, true);m_frame-&document()-&finishParsing();} else// WebKit partially uses WebCore when loading non-HTML docs.
In these cases doc==nil, but// WebCore is enough involved that we need to checkCompleted() in order for m_bComplete to// become true.
An example is when a subframe is a pure text doc, and that subframe is the// last one to complete.checkCompleted();}
再来看QWebFrame::setUrl()的第三句：load(ensureAbsoluteUrl(url));
void QWebFrame::load(const QUrl &url){load(QNetworkRequest(ensureAbsoluteUrl(url)));}
新建一个QNetworkRequest对象，然后调用
void load(const QNetworkRequest &request,QNetworkAccessManager::Operation operation = QNetworkAccessManager::GetOperation,const QByteArray &body = QByteArray());看其代码：
void QWebFrame::load(const QNetworkRequest &req,QNetworkAccessManager::Operation operation,const QByteArray &body){if (d-&parentFrame())d-&page-&d-&insideOpenCall =
QUrl url = ensureAbsoluteUrl(req.url());
WebCore::ResourceRequest request(url);
switch (operation) {case QNetworkAccessManager::HeadOperation:request.setHTTPMethod(“HEAD”);case QNetworkAccessManager::GetOperation:request.setHTTPMethod(“GET”);case QNetworkAccessManager::PutOperation:request.setHTTPMethod(“PUT”);case QNetworkAccessManager::PostOperation:request.setHTTPMethod(“POST”);case QNetworkAccessManager::UnknownOperation:// eh?}
QList&QByteArray& httpHeaders = req.rawHeaderList();for (int i = 0; i & httpHeaders.size(); ++i) {const QByteArray &headerName = httpHeaders.at(i);request.addHTTPHeaderField(QString::fromLatin1(headerName), QString::fromLatin1(req.rawHeader(headerName)));}
if (!body.isEmpty())request.setHTTPBody(WebCore::FormData::create(body.constData(), body.size()));
d-&frame-&loader()-&load(request);
if (d-&parentFrame())d-&page-&d-&insideOpenCall =}
看关键的FrameLoader::load()
void FrameLoader::load(const ResourceRequest& request){load(request, SubstituteData());}
void FrameLoader::load(const ResourceRequest& request, const SubstituteData& substituteData){if (m_inStopAllLoaders)
// FIXME: is this the right place to reset loadType? Perhaps this should be done after loading is finished or aborted.m_loadType = FrameLoadTypeSload(m_client-&createDocumentLoader(request, substituteData).get());}
上面m_client对应的是FrameLoaderClientQt实体，m_client-&createDocumentLoader()创建的是DocumentLoader对象。进一步看FrameLoader::load(DocumentLoader *)的代码：
void FrameLoader::load(DocumentLoader* newDocumentLoader){ResourceRequest& r = newDocumentLoader-&request();addExtraFieldsToMainResourceRequest(r);FrameLoadT
if (shouldTreatURLAsSameAsCurrent(newDocumentLoader-&originalRequest().url())) {r.setCachePolicy(ReloadIgnoringCacheData);type = FrameLoadTypeS} elsetype = FrameLoadTypeS
if (m_documentLoader)newDocumentLoader-&setOverrideEncoding(m_documentLoader-&overrideEncoding());
// When we loading alternate content for an unreachable URL that we’re// visiting in the history list, we treat it as a reload so the history list// is appropriately maintained.//// FIXME: This seems like a dangerous overloading of the meaning of “FrameLoadTypeReload” …// shouldn’t a more explicit type of reload be defined, that means roughly// “load without affecting history” ?if (shouldReloadToHandleUnreachableURL(newDocumentLoader)) {ASSERT(type == FrameLoadTypeStandard);type = FrameLoadTypeR}
loadWithDocumentLoader(newDocumentLoader, type, 0);}
接昨天的分析，看FrameLoader::loadWithDocumentLoader()的代码：void FrameLoader::loadWithDocumentLoader(DocumentLoader* loader, FrameLoadType type, PassRefPtr&FormState& prpFormState){ASSERT(m_client-&hasWebView());
// Unfortunately the view must be non-nil, this is ultimately due// to parser requiring a FrameView.
We should fix this dependency.
ASSERT(m_frame-&view());
m_policyLoadType =RefPtr&FormState& formState = prpFormSbool isFormSubmission = formS
const KURL& newURL = loader-&request().url();
if (shouldScrollToAnchor(isFormSubmission, m_policyLoadType, newURL)) {RefPtr&DocumentLoader& oldDocumentLoader = m_documentLNavigationAction action(newURL, m_policyLoadType, isFormSubmission);
oldDocumentLoader-&setTriggeringAction(action);stopPolicyCheck();checkNavigationPolicy(loader-&request(), oldDocumentLoader.get(), formState,callContinueFragmentScrollAfterNavigationPolicy, this);} else {if (Frame* parent = m_frame-&tree()-&parent())loader-&setOverrideEncoding(parent-&loader()-&documentLoader()-&overrideEncoding());
stopPolicyCheck();setPolicyDocumentLoader(loader);
checkNavigationPolicy(loader-&request(), loader, formState,callContinueLoadAfterNavigationPolicy, this);}}上面调用checkNavigationPolicy()是关键，看其实现：void FrameLoader::checkNavigationPolicy(const ResourceRequest& request, DocumentLoader* loader,PassRefPtr&FormState& formState, NavigationPolicyDecisionFunction function, void* argument){NavigationAction action = loader-&triggeringAction();if (action.isEmpty()) {action = NavigationAction(request.url(), NavigationTypeOther);loader-&setTriggeringAction(action);}
// Don’t ask more than once for the same request or if we are loading an empty URL.// This avoids confusion on the part of the client.if (equalIgnoringHeaderFields(request, loader-&lastCheckedRequest()) || (!request.isNull() && request.url().isEmpty())) {function(argument, request, 0, true);loader-&setLastCheckedRequest(request);}
// We are always willing to show alternate content for unreachable URLs;// treat it like a reload so it maintains the right state for b/f list.if (loader-&substituteData().isValid() && !loader-&substituteData().failingURL().isEmpty()) {if (isBackForwardLoadType(m_policyLoadType))m_policyLoadType = FrameLoadTypeRfunction(argument, request, 0, true);}
loader-&setLastCheckedRequest(request);
m_policyCheck.set(request, formState.get(), function, argument);
m_delegateIsDecidingNavigationPolicy =m_client-&dispatchDecidePolicyForNavigationAction(&FrameLoader::continueAfterNavigationPolicy,action, request, formState);m_delegateIsDecidingNavigationPolicy =}其中m_client是FrameLoaderClientQt实体指针，void FrameLoaderClientQt::dispatchDecidePolicyForNavigationAction(FramePolicyFunction function, const WebCore::NavigationAction& action, const WebCore::ResourceRequest& request, PassRefPtr&WebCore::FormState&){Q_ASSERT(!m_policyFunction);Q_ASSERT(m_webFrame);m_policyFunction =#if QT_VERSION & 0×040400QWebNetworkRequest r(request);#elseQNetworkRequest r(request.toNetworkRequest());#endifQWebPage*page = m_webFrame-&page();
if (!page-&d-&acceptNavigationRequest(m_webFrame, r, QWebPage::NavigationType(action.type()))) {if (action.type() == NavigationTypeFormSubmitted || action.type() == NavigationTypeFormResubmitted)m_frame-&loader()-&resetMultipleFormSubmissionProtection();
if (action.type() == NavigationTypeLinkClicked && r.url().hasFragment()) {ResourceRequest emptyRm_frame-&loader()-&activeDocumentLoader()-&setLastCheckedRequest(emptyRequest);}
slotCallPolicyFunction(PolicyIgnore);}slotCallPolicyFunction(PolicyUse);}void FrameLoaderClientQt::slotCallPolicyFunction(int action){if (!m_frame || !m_policyFunction)FramePolicyFunction function = m_policyFm_policyFunction = 0;(m_frame-&loader()-&*function)(WebCore::PolicyAction(action));}用函数指针回调，FrameLoader::continueAfterNavigationPolicy(PolicyAction policy)，参数为PolicyUsevoid FrameLoader::continueAfterNavigationPolicy(PolicyAction policy){PolicyCheck check = m_policyCm_policyCheck.clear();
bool shouldContinue = policy == PolicyU
switch (policy) {case PolicyIgnore:check.clearRequest();case PolicyDownload:m_client-&startDownload(check.request());check.clearRequest();case PolicyUse: {ResourceRequest request(check.request());
if (!m_client-&canHandleRequest(request)) {handleUnimplementablePolicy(m_client-&cannotShowURLError(check.request()));check.clearRequest();shouldContinue =}}}
check.call(shouldContinue);}上面调用的是PolicyCheck::call()，参数为truevoid PolicyCheck::call(bool shouldContinue){if (m_navigationFunction)m_navigationFunction(m_argument, m_request, m_formState.get(), shouldContinue);if (m_newWindowFunction)m_newWindowFunction(m_argument, m_request, m_formState.get(), m_frameName, shouldContinue);ASSERT(!m_contentFunction);}m_navigationFunction又是一个函数指针，指向的是FrameLoader::callContinueLoadAfterNavigationPolicy()void FrameLoader::callContinueLoadAfterNavigationPolicy(void* argument,const ResourceRequest& request, PassRefPtr&FormState& formState, bool shouldContinue){FrameLoader* loader = static_cast&FrameLoader*&(argument);loader-&continueLoadAfterNavigationPolicy(request, formState, shouldContinue);}
void FrameLoader::continueLoadAfterNavigationPolicy(const ResourceRequest&, PassRefPtr&FormState& formState, bool shouldContinue){// If we loaded an alternate page to replace an unreachableURL, we’ll get in here with a// nil policyDataSource because loading the alternate page will have passed// through this method already, otherwise, policyDataSource should still be set.ASSERT(m_policyDocumentLoader || !m_provisionalDocumentLoader-&unreachableURL().isEmpty());
bool isTargetItem = m_provisionalHistoryItem ? m_provisionalHistoryItem-&isTargetItem() :
// Two reasons we can’t continue://
1) Navigation policy delegate said we can’t so request is nil. A primary case of this//
is the user responding Cancel to the form repost nag sheet.//
2) User responded Cancel to an alert popped up by the before unload event handler.// The “before unload” event handler runs only for the main frame.bool canContinue = shouldContinue && (!isLoadingMainFrame() || m_frame-&shouldClose());
if (!canContinue) {// If we were waiting for a quick redirect, but the policy delegate decided to ignore it, then we// need to report that the client redirect was cancelled.if (m_quickRedirectComing)clientRedirectCancelledOrFinished(false);
setPolicyDocumentLoader(0);
// If the navigation request came from the back/forward menu, and we punt on it, we have the// problem that we have optimistically moved the b/f cursor already, so move it back.
For sanity,// we only do this when punting a navigation for the target frame or top-level frame.if ((isTargetItem || isLoadingMainFrame()) && isBackForwardLoadType(m_policyLoadType))if (Page* page = m_frame-&page()) {Frame* mainFrame = page-&mainFrame();if (HistoryItem* resetItem = mainFrame-&loader()-&m_currentHistoryItem.get()) {page-&backForwardList()-&goToItem(resetItem);Settings* settings = m_frame-&settings();page-&setGlobalHistoryItem((!settings || settings-&privateBrowsingEnabled()) ? 0 : resetItem);}}}
FrameLoadType type = m_policyLoadTstopAllLoaders();
// &rdar://problem/6250856& - In certain circumstances on pages with multiple frames, stopAllLoaders()// might detach the current FrameLoader, in which case we should bail on this newly defunct load.if (!m_frame-&page())
setProvisionalDocumentLoader(m_policyDocumentLoader.get());m_loadType =setState(FrameStateProvisional);
setPolicyDocumentLoader(0);
if (isBackForwardLoadType(type) && loadProvisionalItemFromCachedPage())
if (formState)m_client-&dispatchWillSubmitForm(&FrameLoader::continueLoadAfterWillSubmitForm, formState);elsecontinueLoadAfterWillSubmitForm();}
void FrameLoader::continueLoadAfterWillSubmitForm(PolicyAction){if (!m_provisionalDocumentLoader)
// DocumentLoader calls back to our prepareForLoadStartm_provisionalDocumentLoader-&prepareForLoadStart();
// The load might be cancelled inside of prepareForLoadStart(), nulling out the m_provisionalDocumentLoader,// so we need to null check it again.if (!m_provisionalDocumentLoader)// 先看活动的DocumentLoader能否装载DocumentLoader* activeDocLoader = activeDocumentLoader();if (activeDocLoader && activeDocLoader-&isLoadingMainResource())// 看Cache中能否装载m_provisionalDocumentLoader-&setLoadingFromCachedPage(false);
unsigned long identifier = 0;
if (Page* page = m_frame-&page()) {identifier = page-&progress()-&createUniqueIdentifier();dispatchAssignIdentifierToInitialRequest(identifier, m_provisionalDocumentLoader.get(), m_provisionalDocumentLoader-&originalRequest());}
if (!m_provisionalDocumentLoader-&startLoadingMainResource(identifier))m_provisionalDocumentLoader-&updateLoading();}上面的装载过程，如果是第一次并且只有m_provisionalDocumentLoader的话，只会执行最后一中装载。bool DocumentLoader::startLoadingMainResource(unsigned long identifier){ASSERT(!m_mainResourceLoader);m_mainResourceLoader = MainResourceLoader::create(m_frame);m_mainResourceLoader-&setIdentifier(identifier);
// FIXME: Is there any way the extra fields could have not been added by now?// If not, it would be great to remove this line of code.frameLoader()-&addExtraFieldsToMainResourceRequest(m_request);
if (!m_mainResourceLoader-&load(m_request, m_substituteData)) {// FIXME: If this should really be caught, we should just ASSERT this doesn’// should it be caught by other parts of WebKit or other parts of the app?LOG_ERROR(“could not create WebResourceHandle for URL %s -- should be caught by policy handler level”, m_request.url().string().ascii().data());m_mainResourceLoader = 0;}
}创建MainResourceLoader对象，并调用load()bool MainResourceLoader::load(const ResourceRequest& r, const SubstituteData& substituteData){ASSERT(!m_handle);
m_substituteData = substituteD
#if ENABLE(OFFLINE_WEB_APPLICATIONS)// Check if this request should be loaded from the application cacheif (!m_substituteData.isValid() && frameLoader()-&frame()-&settings() && frameLoader()-&frame()-&settings()-&offlineWebApplicationCacheEnabled()) {ASSERT(!m_applicationCache);
m_applicationCache = ApplicationCacheGroup::cacheForMainRequest(r, m_documentLoader.get());
if (m_applicationCache) {// Get the resource from the application cache. By definition, cacheForMainRequest() returns a cache that contains the resource.ApplicationCacheResource* resource = m_applicationCache-&resourceForRequest(r);m_substituteData = SubstituteData(resource-&data(),resource-&response().mimeType(),resource-&response().textEncodingName(), KURL());}}#endif
ResourceRequest request(r);bool defer = defersLoading();if (defer) {bool shouldLoadEmpty = shouldLoadAsEmptyDocument(r.url());if (shouldLoadEmpty)defer =}if (!defer) {if (loadNow(request)) {// Started as an empty document, but was redirected to something non-empty.ASSERT(defersLoading());defer =}}if (defer)m_initialRequest =
}继续深入看MainResourceLoader::loadNow()bool MainResourceLoader::loadNow(ResourceRequest& r){bool shouldLoadEmptyBeforeRedirect = shouldLoadAsEmptyDocument(r.url());
ASSERT(!m_handle);ASSERT(shouldLoadEmptyBeforeRedirect || !defersLoading());
// Send this synthetic delegate callback since clients expect it, and// we no longer send the callback from within NSURLConnection for// initial requests.willSendRequest(r, ResourceResponse());
// &rdar://problem/4801066&// willSendRequest() is liable to make the call to frameLoader() return NULL, so we need to check that hereif (!frameLoader())
const KURL& url = r.url();bool shouldLoadEmpty = shouldLoadAsEmptyDocument(url) && !m_substituteData.isValid();
if (shouldLoadEmptyBeforeRedirect && !shouldLoadEmpty && defersLoading())
if (m_substituteData.isValid())handleDataLoadSoon(r);else if (shouldLoadEmpty || frameLoader()-&representationExistsForURLScheme(url.protocol()))handleEmptyLoad(url, !shouldLoadEmpty);elsem_handle = ResourceHandle::create(r, this, m_frame.get(), false, true, true);
}主要两个调用：willSendRequest()和ResourceHandle::create()，前面一个估计是发送请求前的相关设定；后一个就是请求发送了。先看前一个：void MainResourceLoader::willSendRequest(ResourceRequest& newRequest, const ResourceResponse& redirectResponse){// Note that there are no asserts here as there are for the other callbacks. This is due to the// fact that this “callback” is sent when starting every load, and the state of callback// deferrals plays less of a part in this function in preventing the bad behavior deferring// callbacks is meant to prevent.ASSERT(!newRequest.isNull());
// The additional processing can do anything including possibly removing the last// refe one example of this is 3266216.RefPtr&MainResourceLoader& protect(this);
// Update cookie policy base URL as URL changes, except for subframes, which use the// URL of the main frame which doesn’t change when we redirect.if (frameLoader()-&isLoadingMainFrame())newRequest.setMainDocumentURL(newRequest.url());
// If we’re fielding a redirect in response to a POST, force a load from origin, since// this is a common site technique to return to a page viewing some data that the POST// just modified.// Also, POST requests always load from origin, but this does not affect subresources.if (newRequest.cachePolicy() == UseProtocolCachePolicy && isPostOrRedirectAfterPost(newRequest, redirectResponse))newRequest.setCachePolicy(ReloadIgnoringCacheData);
ResourceLoader::willSendRequest(newRequest, redirectResponse);
// Don’t set this on the first request. It is set when the main load was started.m_documentLoader-&setRequest(newRequest);
// FIXME: Ideally we’d stop the I/O until we hear back from the navigation policy delegate// listener. But there’s no way to do that in practice. So instead we cancel later if the// listener tells us to. In practice that means the navigation policy needs to be decided// synchronously for these redirect cases.
ref(); // balanced by deref in continueAfterNavigationPolicyframeLoader()-&checkNavigationPolicy(newRequest, callContinueAfterNavigationPolicy, this);}主要是调用ResourceLoader::willSendRequest()函数：void ResourceLoader::willSendRequest(ResourceRequest& request, const ResourceResponse& redirectResponse){// Protect this in this delegate method since the additional processing can do// anything including po one example of this is Radar 3266216.RefPtr&ResourceLoader& protector(this);
ASSERT(!m_reachedTerminalState);
if (m_sendResourceLoadCallbacks) {if (!m_identifier) {m_identifier = m_frame-&page()-&progress()-&createUniqueIdentifier();frameLoader()-&assignIdentifierToInitialRequest(m_identifier, request);}
frameLoader()-&willSendRequest(this, request, redirectResponse);}
m_request =}进一步调用FrameLoader::willSendRequest()void FrameLoader::willSendRequest(ResourceLoader* loader, ResourceRequest& clientRequest, const ResourceResponse& redirectResponse){applyUserAgent(clientRequest);dispatchWillSendRequest(loader-&documentLoader(), loader-&identifier(), clientRequest, redirectResponse);}更多的调用：void FrameLoader::dispatchWillSendRequest(DocumentLoader* loader, unsigned long identifier, ResourceRequest& request, const ResourceResponse& redirectResponse){StringImpl* oldRequestURL = request.url().string().impl();m_documentLoader-&didTellClientAboutLoad(request.url());
m_client-&dispatchWillSendRequest(loader, identifier, request, redirectResponse);
// If the URL changed, then we want to put that new URL in the “did tell client” set too.if (oldRequestURL != request.url().string().impl())m_documentLoader-&didTellClientAboutLoad(request.url());
if (Page* page = m_frame-&page())page-&inspectorController()-&willSendRequest(loader, identifier, request, redirectResponse);}?~~还有下一步吗？？m_client-&dispatchWillSendRequest()实际调用的是FrameLoaderClientQt::dispatchWillSendRequest()，目前是一个空函数（仅在dump的时候打印信息）。void InspectorController::willSendRequest(DocumentLoader*, unsigned long identifier, ResourceRequest& request, const ResourceResponse& redirectResponse){if (!enabled())
InspectorResource* resource = m_resources.get(identifier).get();if (!resource)
resource-&startTime = currentTime();
if (!redirectResponse.isNull()) {updateResourceRequest(resource, request);updateResourceResponse(resource, redirectResponse);}
if (resource != m_mainResource && windowVisible()) {if (!resource-&scriptObject)addScriptResource(resource);elseupdateScriptResourceRequest(resource);
updateScriptResource(resource, resource-&startTime, resource-&responseReceivedTime, resource-&endTime);
if (!redirectResponse.isNull())updateScriptResourceResponse(resource);}}在这里设定了开始时间，猜测是供请求超时判断用的，请求超时的定时器在何处设定有待进一步分析。看都是一些Resource的更新，感觉意义不大，不再进一步追踪。回到MainResourceLoader::loadNow()，看下一步ResourceHandle::create()PassRefPtr&ResourceHandle& ResourceHandle::create(const ResourceRequest& request, ResourceHandleClient* client,Frame* frame, bool defersLoading, bool shouldContentSniff, bool mightDownloadFromHandle){RefPtr&ResourceHandle& newHandle(adoptRef(new ResourceHandle(request, client, defersLoading, shouldContentSniff, mightDownloadFromHandle)));
if (!request.url().isValid()) {newHandle-&scheduleFailure(InvalidURLFailure);return newHandle.release();}// 检查端口号(port)是否合法if (!portAllowed(request)) {newHandle-&scheduleFailure(BlockedFailure);return newHandle.release();}
if (newHandle-&start(frame))return newHandle.release();
return 0;}看关键的ResourceHandle::start调用：bool ResourceHandle::start(Frame* frame){if (!frame)
Page *page = frame-&page();// If we are no longer attached to a Page, this must be an attempted load from an// onUnload handler, so let’s just block it.if (!page)
getInternal()-&m_frame = static_cast&FrameLoaderClientQt*&(frame-&loader()-&client())-&webFrame();#if QT_VERSION & 0×040400return QWebNetworkManager::self()-&add(this, getInternal()-&m_frame-&page()-&d-&networkInterface);#elseResourceHandleInternal *d = getInternal();d-&m_job = new QNetworkReplyHandler(this, QNetworkReplyHandler::LoadMode(d-&m_defersLoading));#endif}新创建了一个QNetworkReplyHandler对象，QNetworkReplyHandler在构造的时候会调用QNetworkReplyHandler::start()void QNetworkReplyHandler::start(){m_shouldStart =
ResourceHandleInternal* d = m_resourceHandle-&getInternal();
QNetworkAccessManager* manager = d-&m_frame-&page()-&networkAccessManager();
const QUrl url = m_request.url();const QString scheme = url.scheme();// Post requests on files and data don’t really make sense, but for// fast/forms/form-post-urlencoded.html and for fast/forms/button-state-restore.html// we still need to retrieve the file/data, which means we map it to a Get instead.if (m_method == QNetworkAccessManager::PostOperation&& (!url.toLocalFile().isEmpty() || url.scheme() == QLatin1String(“data”)))m_method = QNetworkAccessManager::GetO
m_startTime = QDateTime::currentDateTime().toTime_t();
switch (m_method) {case QNetworkAccessManager::GetOperation:m_reply = manager-&get(m_request);case QNetworkAccessManager::PostOperation: {FormDataIODevice* postDevice = new FormDataIODevice(d-&m_request.httpBody());m_reply = manager-&post(m_request, postDevice);postDevice-&setParent(m_reply);}case QNetworkAccessManager::HeadOperation:m_reply = manager-&head(m_request);case QNetworkAccessManager::PutOperation: {FormDataIODevice* putDevice = new FormDataIODevice(d-&m_request.httpBody());m_reply = manager-&put(m_request, putDevice);putDevice-&setParent(m_reply);}case QNetworkAccessManager::UnknownOperation: {m_reply = 0;ResourceHandleClient* client = m_resourceHandle-&client();if (client) {ResourceError error(url.host(), 400 /*bad request*/,url.toString(),QCoreApplication::translate(“QWebPage”, “Bad HTTP request”));client-&didFail(m_resourceHandle, error);}}}
m_reply-&setParent(this);
connect(m_reply, SIGNAL(finished()),this, SLOT(finish()), Qt::QueuedConnection);
// For http(s) we know that the headers are complete upon metaDataChanged() emission, so we// can send the response as early as possibleif (scheme == QLatin1String(“http”) || scheme == QLatin1String(“https”))connect(m_reply, SIGNAL(metaDataChanged()),this, SLOT(sendResponseIfNeeded()), Qt::QueuedConnection);
connect(m_reply, SIGNAL(readyRead()),this, SLOT(forwardData()), Qt::QueuedConnection);}看到了熟悉的QNetworkAccessManager、QNetworkReply。跟踪至此，初始化和URL请求发送基本完成。
前面分析WebView初始化的时候，在QNetworkReplyHandler::start()里有设定读取数据的处理函数：connect(m_reply, SIGNAL(finished()),this, SLOT(finish()), Qt::QueuedConnection);
// For http(s) we know that the headers are complete upon metaDataChanged() emission, so we// can send the response as early as possibleif (scheme == QLatin1String(“http”) || scheme == QLatin1String(“https”))connect(m_reply, SIGNAL(metaDataChanged()),this, SLOT(sendResponseIfNeeded()), Qt::QueuedConnection);
connect(m_reply, SIGNAL(readyRead()),this, SLOT(forwardData()), Qt::QueuedConnection);
先看QNetworkReplyHandler::forwardData()void QNetworkReplyHandler::forwardData(){m_shouldForwardData = (m_loadMode == LoadDeferred);if (m_loadMode == LoadDeferred)
sendResponseIfNeeded();
// don’t emit the “Document has moved here” type of HTMLif (m_redirected)
if (!m_resourceHandle)
QByteArray data = m_reply-&read(m_reply-&bytesAvailable());
ResourceHandleClient* client = m_resourceHandle-&client();if (!client)
if (!data.isEmpty())client-&didReceiveData(m_resourceHandle, data.constData(), data.length(), data.length() /*FixMe*/);}实际就是两个调用：read()和didReceiveData()。其中QNetworkReply::read()前面分析过不再重复；ResourceHandleClient* client-&didReceiveData()实际调用的是MainResourceLoader::didReceiveData()void MainResourceLoader::didReceiveData(const char* data, int length, long long lengthReceived, bool allAtOnce){ASSERT(data);ASSERT(length != 0);
// There is a bug in CFNetwork where callbacks can be dispatched even when loads are deferred.// See &rdar://problem/6304600& for more details.#if !PLATFORM(CF)ASSERT(!defersLoading());#endif
// The additional processing can do anything including possibly removing the last// refe one example of this is 3266216.RefPtr&MainResourceLoader& protect(this);
ResourceLoader::didReceiveData(data, length, lengthReceived, allAtOnce);}进一步看其调用：void ResourceLoader::didReceiveData(const char* data, int length, long long lengthReceived, bool allAtOnce){// Protect this in this delegate method since the additional processing can do// anything including po one example of this is Radar 3266216.RefPtr&ResourceLoader& protector(this);
addData(data, length, allAtOnce);// FIXME: If we get a resource with more than 2B bytes, this code won’t do the right thing.// However, with today’s computers and networking speeds, this won’t happen in practice.// Could be an issue with a giant local file.if (m_sendResourceLoadCallbacks && m_frame)frameLoader()-&didReceiveData(this, data, length, static_cast&int&(lengthReceived));}在ResourceLoader类中addData()是虚函数，client-&didReceiveData()中client指针实际的实体为MainResourceLoader对象，所以addData()先调用MainResourceLoader::addData()void MainResourceLoader::addData(const char* data, int length, bool allAtOnce){ResourceLoader::addData(data, length, allAtOnce);frameLoader()-&receivedData(data, length);}这里只有两个调用，前一个是将接收到的数据保存到一个buffer中，供后续语法扫描使用（猜测的），暂不深入分析。看frameLoader-&receivedData()void FrameLoader::receivedData(const char* data, int length){activeDocumentLoader()-&receivedData(data, length);}
void DocumentLoader::receivedData(const char* data, int length){m_gotFirstByte =if (doesProgressiveLoad(m_response.mimeType()))commitLoad(data, length);}其中doesProgressiveLoad()会测试MIME的类型，重点是commitLoad()
void DocumentLoader::commitLoad(const char* data, int length){// Both unloading the old page and parsing the new page may execute JavaScript which destroys the datasource// by starting a new load, so retain temporarily.RefPtr&DocumentLoader& protect(this);
commitIfReady();if (FrameLoader* frameLoader = DocumentLoader::frameLoader())frameLoader-&committedLoad(this, data, length);}前面一个调用：commitIfReady()是清理前一次页面扫描的中间数据；committedLoad()才是正题。
void FrameLoader::committedLoad(DocumentLoader* loader, const char* data, int length){if (ArchiveFactory::isArchiveMimeType(loader-&response().mimeType()))m_client-&committedLoad(loader, data, length);}其中m_client指向的是FrameLoaderClientQT对象实体。
void FrameLoaderClientQt::committedLoad(WebCore::DocumentLoader* loader, const char* data, int length){if (!m_pluginView) {if (!m_frame)FrameLoader *fl = loader-&frameLoader();if (m_firstData) {fl-&setEncoding(m_response.textEncodingName(), false);m_firstData =}fl-&addData(data, length);}
// We re-check here as the plugin can have been createdif (m_pluginView) {if (!m_hasSentResponseToPlugin) {m_pluginView-&didReceiveResponse(loader-&response());// didReceiveResponse sets up a new stream to the plug-in. on a full-page plug-in, a failure in// setting up this stream can cause the main document load to be cancelled, setting m_pluginView// to nullif (!m_pluginView)m_hasSentResponseToPlugin =}m_pluginView-&didReceiveData(data, length);}}
其中fl-&setEncoding()是根据服务器返回的HTML数据流设定编码格式（例如：中文gb2312），另外处理了其他一些事情，例如Redirect等。fl-&addData()是关键：
void FrameLoader::addData(const char* bytes, int length){ASSERT(m_workingURL.isEmpty());ASSERT(m_frame-&document());ASSERT(m_frame-&document()-&parsing());write(bytes, length);}上面的FrameLoader::write()调用，启动了HTML/JS分析扫描。后一篇深入HTML扫描分析。
在继续分析FrameLoader::write()之前，先回到《QT分析之WebKit（二）》。那里曾经保存了一个完整的调用堆栈，……QtWebKitd4.dll!WebCore::HTMLTokenizer::write(const WebCore::SegmentedString & str={…}, bool appendData=true)
行1730 + 0×23 字节
C++QtWebKitd4.dll!WebCore::FrameLoader::write(const char *可知调用的次序为：FrameLoader::write()调用了HTMLTokenizer::write()。下面是FrameLoader::write()的定义：void write(const char* str, int len = -1, bool flush = false);这里包含了两个缺省值调用定义，在前一篇，调用的形式是：write(bytes, length);实际传递的的是：write(bytes, length, false);接着看write()的实现：void FrameLoader::write(const char* str, int len, bool flush){if (len == 0 && !flush)
if (len == -1)len = strlen(str);
Tokenizer* tokenizer = m_frame-&document()-&tokenizer();if (tokenizer && tokenizer-&wantsRawData()) {if (len & 0)tokenizer-&writeRawData(str, len);}
if (!m_decoder) {Settings* settings = m_frame-&settings();m_decoder = TextResourceDecoder::create(m_responseMIMEType, settings ? settings-&defaultTextEncodingName() : String());if (m_encoding.isEmpty()) {Frame* parentFrame = m_frame-&tree()-&parent();if (parentFrame && parentFrame-&document()-&securityOrigin()-&canAccess(m_frame-&document()-&securityOrigin()))m_decoder-&setEncoding(parentFrame-&document()-&inputEncoding(), TextResourceDecoder::DefaultEncoding);} else {m_decoder-&setEncoding(m_encoding,m_encodingWasChosenByUser ? TextResourceDecoder::UserChosenEncoding : TextResourceDecoder::EncodingFromHTTPHeader);}m_frame-&document()-&setDecoder(m_decoder.get());}
String decoded = m_decoder-&decode(str, len);if (flush)decoded += m_decoder-&flush();if (decoded.isEmpty())
#if USE(LOW_BANDWIDTH_DISPLAY)if (m_frame-&document()-&inLowBandwidthDisplay())m_pendingSourceInLowBandwidthDisplay.append(decoded);#endif
if (!m_receivedData) {m_receivedData =if (m_decoder-&encoding().usesVisualOrdering())m_frame-&document()-&setVisuallyOrdered();m_frame-&document()-&recalcStyle(Node::Force);}
if (tokenizer) {ASSERT(!tokenizer-&wantsRawData());tokenizer-&write(decoded, true);}}怎么和HTMLTokenizer关联的呢？就是在《QT分析之WebKit（三）》初始化Document对象的时候关联上的。DOMImplementation::createDocument()上面做了一些边缘的工作，例如设定编码（因为可以在HTTP协议、HTML的TITLE部分或者浏览器特别指定编码），主要是新建一个decoder另外一个是调用tokenizer-&write()
接着前面的分析，先看m_decoder-&decode(str, len);String TextResourceDecoder::decode(const char* data, size_t len){if (!m_checkedForBOM)checkForBOM(data, len);
// 检查是否为Unicode编码
bool movedDataToBuffer =
if (m_contentType == CSS && !m_checkedForCSSCharset)if (!checkForCSSCharset(data, len, movedDataToBuffer))
// 如果是CSS，则检查CSS的字符集return “”;
if ((m_contentType == HTML || m_contentType == XML) && !m_checkedForHeadCharset) // HTML and XMLif (!checkForHeadCharset(data, len, movedDataToBuffer))
// 检查HTML/XML的字符集return “”;
// Do the auto-detect if our default encoding is one of the Japanese ones.// FIXME: It seems wrong to change our encoding downstream after we have already done some decoding.if (m_source != UserChosenEncoding && m_source != AutoDetectedEncoding && encoding().isJapanese())detectJapaneseEncoding(data, len);
// 检查日文编码（为什么没有检查中文编码的啊？）
ASSERT(encoding().isValid());
if (m_buffer.isEmpty())return m_decoder.decode(data, len, false, m_contentType == XML, m_sawError);
if (!movedDataToBuffer) {size_t oldSize = m_buffer.size();m_buffer.grow(oldSize + len);memcpy(m_buffer.data() + oldSize, data, len);}
String result = m_decoder.decode(m_buffer.data(), m_buffer.size(), false, m_contentType == XML, m_sawError);m_buffer.clear();}再回到tokenizer-&write(decoded, true);看其具体实现：bool HTMLTokenizer::write(const SegmentedString& str, bool appendData){if (!m_buffer)
if (m_parserStopped)
SegmentedString source(str);if (m_executingScript)source.setExcludeLineNumbers();
if ((m_executingScript && appendData) || !m_pendingScripts.isEmpty()) {// don’ we will do this laterif (m_currentPrependingSrc)m_currentPrependingSrc-&append(source);else {m_pendingSrc.append(source);#if PRELOAD_SCANNER_ENABLEDif (m_preloadScanner && m_preloadScanner-&inProgress() && appendData)m_preloadScanner-&write(source);#endif}}
#if PRELOAD_SCANNER_ENABLEDif (m_preloadScanner && m_preloadScanner-&inProgress() && appendData)m_preloadScanner-&end();#endif
if (!m_src.isEmpty())m_src.append(source);elsesetSrc(source);
// Once a timer is set, it has control of when the tokenizer continues.if (m_timer.isActive())
bool wasInWrite = m_inWm_inWrite =
#ifdef INSTRUMENT_LAYOUT_SCHEDULINGif (!m_doc-&ownerElement())printf(“Beginning write at time %d “, m_doc-&elapsedTime());#endif
int processedCount = 0;double startTime = currentTime();
Frame* frame = m_doc-&frame();
State state = m_
while (!m_src.isEmpty() && (!frame || !frame-&loader()-&isScheduledLocationChangePending())) {if (!continueProcessing(processedCount, startTime, state))
// do we need to enlarge the buffer?checkBuffer();
UChar cc = *m_
bool wasSkipLF = state.skipLF();if (wasSkipLF)state.setSkipLF(false);
if (wasSkipLF && (cc == ‘ ‘))m_src.advance();else if (state.needsSpecialWriteHandling()) {// it’s important to keep needsSpecialWriteHandling with the flags this block testsif (state.hasEntityState())state = parseEntity(m_src, m_dest, state, m_cBufferPos, false, state.hasTagState());else if (state.inPlainText())state = parseText(m_src, state);else if (state.inAnySpecial())state = parseSpecial(m_src, state);else if (state.inComment())state = parseComment(m_src, state);else if (state.inDoctype())state = parseDoctype(m_src, state);else if (state.inServer())state = parseServer(m_src, state);else if (state.inProcessingInstruction())state = parseProcessingInstruction(m_src, state);else if (state.hasTagState())state = parseTag(m_src, state);else if (state.startTag()) {state.setStartTag(false);
switch(cc) {case ‘/’:case ‘!’: {// orsearchCount = 1; // Look for ‘
m_doctypeSearchCount = 1;}case ‘?’: {// xml processing instructionstate.setInProcessingInstruction(true);tquote = NoQstate = parseProcessingInstruction(m_src, state);
}case ‘%’:if (!m_brokenServer) {// &% server stuff, handle as comment %&state.setInServer(true);tquote = NoQstate = parseServer(m_src, state);}// else fall throughdefault: {if( ((cc &= ‘a’) && (cc &= ‘z’)) || ((cc &= ‘A’) && (cc &= ‘Z’))) {// Start of a Start-Tag} else {// Invalid tag// Add as is*m_dest = ‘&’;m_dest++;}}}; // end case
processToken();
m_cBufferPos = 0;state.setTagState(TagName);state = parseTag(m_src, state);}} else if (cc == ‘&’ && !m_src.escaped()) {m_src.advancePastNonNewline();state = parseEntity(m_src, m_dest, state, m_cBufferPos, true, state.hasTagState());} else if (cc == ‘&’ && !m_src.escaped()) {m_currentTagStartLineNumber = m_lineNm_src.advancePastNonNewline();state.setStartTag(true);state.setDiscardLF(false);} else if (cc == ‘ ‘ || cc == ‘ ‘) {if (state.discardLF())// Ignore this LFstate.setDiscardLF(false); // We have discarded 1 LFelse {// Process this LF*m_dest++ = ‘ ‘;if (cc == ‘ ‘ && !m_src.excludeLineNumbers())m_lineNumber++;}
/* Check for MS-DOS CRLF sequence */if (cc == ‘ ‘)state.setSkipLF(true);m_src.advance(m_lineNumber);} else {state.setDiscardLF(false);*m_dest++ =m_src.advancePastNonNewline();}}
#ifdef INSTRUMENT_LAYOUT_SCHEDULINGif (!m_doc-&ownerElement())printf(“Ending write at time %d “, m_doc-&elapsedTime());#endif
m_inWrite = wasInW
if (m_noMoreData && !m_inWrite && !state.loadingExtScript() && !m_executingScript && !m_timer.isActive()) {end(); // this actually causes us to be deleted}}在调用的时候，因为调用参数decoded是String类型的，所以先隐含转化成SegmentedString。SegmentedString可以附带行号，也可以不带行号（可以设定）。上面程序中的while循环主体，就是一个分析程序主体。
“document.getElementById(x).style.background=”yellow”;”
HTML文本文件，通常是以&HTML&开头，以&/HTML&结尾。但是&HTML& tag并不对应DOM Tree的根节点，而是根以下的第一个子节点，即HTMLHtmlElement节点。
初看Figure 2 觉得有点意外，当用户在浏览器里打开一个空白页面的时候，立刻生成了DOM Tree的根节点HTMLDocument，与Rendering Tree的根节点RenderView。而这个时候，用户并没有给定URL，也就是说，对于浏览器来讲，这时候具体的HTML文本文件并不存在。根节点与 具体HTML内容相脱节，或许暗示了Webkit的两个设计思路，
a. DOM Tree的根节点HTMLDocument，与Rendering Tree的根节点RenderView，可以重复利用。
当用户在同一个浏览器页面中，先后打开两个不同的URLs，也就是两个不同的HTML文本文时，HTMLDocument和RenderView两个根节点并没有发生改变，改变的是HTMLHtmlElement以下的子树，以及对应的Rendering Tree的子树。
为什么这样设计？原因是HTMLDocument和RenderView服从于浏览器页面的设置，譬如页面的大小和在整个屏幕中的位置等等。这些设置与页面中要显示什 么的内容无关。同时HTMLDocument绑定HTMLTokenizer和HTMLParser，这两个构件也与某一个具体的HTML内容无关。
b. 同一个DOM Tree的根节点可以悬挂多个HTML子树，同一个Rendering Tree的根节点可以悬挂多个RenderBlock子树。
在 我们目前所见到的浏览器中，每一个页面通常只显示一个HTML文件。虽然一个HTML文件可以分割成多个frames，每个frame承载一个独立的 HTML文件，但是从DOM Tree结构来讲，HTMLDocument根节点以下，只有一个子节点，这个子节点是HTMLHtmlElement，它领衔某个HTML文本文件对应 的子树。Rendering Tree也一样，目前我们见到的网页中，一个RenderView根节点以下，也只有一个RenderBlock子节点。
但是Webkit的设计，却允许同一个根以下，悬挂多个HTML子树。虽然我们目前没有看到一个页面中，并存多个HTML文件，并存多个布局和渲染风格的 情景，但是Webkit为将来的拓展留下了空间。前文中所设想的个性化
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