C++: cache results of linksForIdentifier in HelpItem.

The method linksForIdentifier was called at least thrice when generating
a single valid tooltip in the C++ editor. Now the cached, and the cache
can be "initialised" during construction. This reduces the time spent
for creating a tooltip by 30%.

Task-number: QTCREATORBUG-8970
Change-Id: I5130b769e977c6ffced1a87715831386ef0d5319
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/plugins/cppeditor/cpphoverhandler.cpp

@@ -77,11 +77,19 @@ void CppHoverHandler::identifyMatch(TextEditor::ITextEditor *editor, int pos)
             const QSharedPointer<CppElement> &cppElement = evaluator.cppElement();
             if (!isDiagnosticTooltip())
                 setToolTip(cppElement->tooltip);
-            foreach (const QString &helpId, cppElement->helpIdCandidates) {
+            QStringList candidates = cppElement->helpIdCandidates;
-                if (!Core::HelpManager::instance()->linksForIdentifier(helpId).isEmpty()) {
+            candidates.removeDuplicates();
+            HelpManager *hm = HelpManager::instance();
+            foreach (const QString &helpId, candidates) {
+                if (helpId.isEmpty())
+                    continue;
+
+                const QMap<QString, QUrl> helpLinks = hm->linksForIdentifier(helpId);
+                if (!helpLinks.isEmpty()) {
                     setLastHelpItemIdentified(TextEditor::HelpItem(helpId,
                                                                    cppElement->helpMark,
-                                                                   cppElement->helpCategory));
+                                                                   cppElement->helpCategory,
+                                                                   helpLinks));
                     break;
                 }
             }

src/plugins/texteditor/helpitem.cpp

@@ -32,9 +32,6 @@
 #include <coreplugin/helpmanager.h>
 #include <utils/htmldocextractor.h>
 
-#include <QUrl>
-#include <QMap>
-
 using namespace TextEditor;
 
 HelpItem::HelpItem()
@@ -48,6 +45,11 @@ HelpItem::HelpItem(const QString &helpId, const QString &docMark, Category categ
     m_helpId(helpId), m_docMark(docMark), m_category(category)
 {}
 
+HelpItem::HelpItem(const QString &helpId, const QString &docMark, Category category,
+                   const QMap<QString, QUrl> &helpLinks) :
+    m_helpId(helpId), m_docMark(docMark), m_category(category), m_helpLinks(helpLinks)
+{}
+
 HelpItem::~HelpItem()
 {}
 
@@ -71,7 +73,9 @@ HelpItem::Category HelpItem::category() const
 
 bool HelpItem::isValid() const
 {
-    if (!Core::HelpManager::instance()->linksForIdentifier(m_helpId).isEmpty())
+    if (m_helpId.isEmpty())
+        return false;
+    if (!retrieveHelpLinks().isEmpty())
         return true;
     if (QUrl(m_helpId).isValid())
         return true;
@@ -87,7 +91,7 @@ QString HelpItem::extractContent(bool extended) const
         htmlExtractor.setMode(Utils::HtmlDocExtractor::FirstParagraph);
 
     QString contents;
-    QMap<QString, QUrl> helpLinks = Core::HelpManager::instance()->linksForIdentifier(m_helpId);
+    QMap<QString, QUrl> helpLinks = retrieveHelpLinks();
     if (helpLinks.isEmpty()) {
         // Maybe this is already an URL...
         QUrl url(m_helpId);
@@ -134,3 +138,10 @@ QString HelpItem::extractContent(bool extended) const
     }
     return contents;
 }
+
+QMap<QString, QUrl> HelpItem::retrieveHelpLinks() const
+{
+    if (m_helpLinks.isEmpty())
+        m_helpLinks = Core::HelpManager::instance()->linksForIdentifier(m_helpId);
+    return m_helpLinks;
+}

src/plugins/texteditor/helpitem.h

@@ -32,7 +32,9 @@
 
 #include "texteditor_global.h"
 
+#include <QMap>
 #include <QString>
+#include <QUrl>
 
 namespace TextEditor {
 
@@ -55,6 +57,8 @@ public:
     HelpItem();
     HelpItem(const QString &helpId, Category category);
     HelpItem(const QString &helpId, const QString &docMark, Category category);
+    HelpItem(const QString &helpId, const QString &docMark, Category category,
+             const QMap<QString, QUrl> &helpLinks);
     ~HelpItem();
 
     void setHelpId(const QString &id);
@@ -70,10 +74,14 @@ public:
 
     QString extractContent(bool extended) const;
 
+private:
+    QMap<QString, QUrl> retrieveHelpLinks() const;
+
 private:
     QString m_helpId;
     QString m_docMark;
     Category m_category;
+    mutable QMap<QString, QUrl> m_helpLinks; // cached help links
 };
 
 } // namespace TextEditor