TextEditor: Reduce BaseHoverHandler::identifyMatch() calls

...because they are potentially expensive.

Change-Id: Iaa235ea1fa864a0a67f3ed10b7f89d23179c642b
Reviewed-by: David Schulz <david.schulz@qt.io>

5 files changed, 65 insertions, 4 deletions

diff --git a/src/plugins/texteditor/basehoverhandler.cpp b/src/plugins/texteditor/basehoverhandler.cpp
index abbf2154ab..56ad0c0ddb 100644
--- a/src/plugins/texteditor/basehoverhandler.cpp
+++ b/src/plugins/texteditor/basehoverhandler.cpp
@@ -33,9 +33,10 @@ namespace TextEditor {
 BaseHoverHandler::~BaseHoverHandler()
 {}
 
-void BaseHoverHandler::showToolTip(TextEditorWidget *widget, const QPoint &point)
+void BaseHoverHandler::showToolTip(TextEditorWidget *widget, const QPoint &point, bool decorate)
 {
-    decorateToolTip();
+    if (decorate)
+        decorateToolTip();
     operateTooltip(widget, point);
 }
 
diff --git a/src/plugins/texteditor/basehoverhandler.h b/src/plugins/texteditor/basehoverhandler.h
index f5c8d757b7..44dfc61e92 100644
--- a/src/plugins/texteditor/basehoverhandler.h
+++ b/src/plugins/texteditor/basehoverhandler.h
@@ -44,7 +44,7 @@ public:
     QString contextHelpId(TextEditorWidget *widget, int pos);
 
     int checkToolTip(TextEditorWidget *widget, int pos);
-    void showToolTip(TextEditorWidget *widget, const QPoint &point);
+    void showToolTip(TextEditorWidget *widget, const QPoint &point, bool decorate = true);
 
 protected:
     enum {
diff --git a/src/plugins/texteditor/convenience.cpp b/src/plugins/texteditor/convenience.cpp
index 22dcb99e9b..8ee92147dd 100644
--- a/src/plugins/texteditor/convenience.cpp
+++ b/src/plugins/texteditor/convenience.cpp
@@ -86,5 +86,31 @@ QTextCursor flippedCursor(const QTextCursor &cursor)
     return flipped;
 }
 
+static bool isValidIdentifierChar(const QChar &c)
+{
+    return c.isLetter()
+        || c.isNumber()
+        || c == QLatin1Char('_')
+        || c.isHighSurrogate()
+        || c.isLowSurrogate();
+}
+
+QTextCursor wordStartCursor(const QTextCursor &textCursor)
+{
+    const int originalPosition = textCursor.position();
+    QTextCursor cursor(textCursor);
+    cursor.movePosition(QTextCursor::StartOfWord);
+    const int wordStartPosition = cursor.position();
+
+    if (originalPosition == wordStartPosition) {
+        // Cursor is not on an identifier, check whether we are right after one.
+        const QChar c = textCursor.document()->characterAt(originalPosition - 1);
+        if (isValidIdentifierChar(c))
+            cursor.movePosition(QTextCursor::PreviousWord);
+    }
+
+    return cursor;
+}
+
 } // Util
 } // TextEditor
diff --git a/src/plugins/texteditor/convenience.h b/src/plugins/texteditor/convenience.h
index 5cbff33bef..e4f5f0480b 100644
--- a/src/plugins/texteditor/convenience.h
+++ b/src/plugins/texteditor/convenience.h
@@ -47,5 +47,7 @@ TEXTEDITOR_EXPORT QTextCursor selectAt(QTextCursor textCursor, uint line, uint c
 
 TEXTEDITOR_EXPORT QTextCursor flippedCursor(const QTextCursor &cursor);
 
+TEXTEDITOR_EXPORT QTextCursor wordStartCursor(const QTextCursor &cursor);
+
 } // Util
 } // TextEditor
diff --git a/src/plugins/texteditor/texteditor.cpp b/src/plugins/texteditor/texteditor.cpp
index 474e71fb50..aa794ad63c 100644
--- a/src/plugins/texteditor/texteditor.cpp
+++ b/src/plugins/texteditor/texteditor.cpp
@@ -468,6 +468,26 @@ public:
 
     CodeAssistant m_codeAssistant;
     bool m_assistRelevantContentAdded = false;
+
+    struct LastHoverHandlerInfo {
+        LastHoverHandlerInfo() = default;
+        LastHoverHandlerInfo(BaseHoverHandler *handler, int documentRevision, int cursorPosition)
+            : handler(handler)
+            , documentRevision(documentRevision)
+            , cursorPosition(cursorPosition)
+        {}
+
+        bool applies(int documentRevision, int cursorPosition) const
+        {
+            return handler
+                && documentRevision == this->documentRevision
+                && cursorPosition == this->cursorPosition;
+        }
+
+        BaseHoverHandler *handler = nullptr;
+        int documentRevision = -1;
+        int cursorPosition = -1;
+    } m_lastHoverHandlerInfo;
     QList<BaseHoverHandler *> m_hoverHandlers; // Not owned
 
     QPointer<QSequentialAnimationGroup> m_navigationAnimation;
@@ -3161,6 +3181,15 @@ void TextEditorWidgetPrivate::processTooltipRequest(const QTextCursor &c)
         return;
     }
 
+    // Does the last handler still applies?
+    const int documentRevision = m_document->document()->revision();
+    const int cursorPosition = Convenience::wordStartCursor(c).position();
+    if (m_lastHoverHandlerInfo.applies(documentRevision, cursorPosition)) {
+        m_lastHoverHandlerInfo.handler->showToolTip(q, toolTipPoint, /*decorate=*/ false);
+        return;
+    }
+
+    // Determine best handler
     int highestPriority = -1;
     BaseHoverHandler *highest = 0;
     foreach (BaseHoverHandler *handler, m_hoverHandlers) {
@@ -3171,8 +3200,11 @@ void TextEditorWidgetPrivate::processTooltipRequest(const QTextCursor &c)
         }
     }
 
-    if (highest)
+    // Let the best handler show the tooltip
+    if (highest) {
+        m_lastHoverHandlerInfo = LastHoverHandlerInfo{highest, documentRevision, cursorPosition};
         highest->showToolTip(q, toolTipPoint);
+    }
 }
 
 bool TextEditorWidgetPrivate::processAnnotaionTooltipRequest(const QTextBlock &block,