Automatically trigger completion for C++ editor after three characters

Similar behaviour as for the QML editor. However, for now without
removing the completion box when you have typed the whole word, since it
could still be useful for automatically inserting other characters.

Task-number: QTCREATORBUG-67

src/plugins/cpptools/cppcodecompletion.cpp

@@ -438,6 +438,7 @@ CppCodeCompletion::CppCodeCompletion(CppModelManager *manager)
       m_manager(manager),
       m_editor(0),
       m_startPosition(-1),
+      m_shouldRestartCompletion(false),
       m_forcedCompletion(false),
       m_completionOperator(T_EOF_SYMBOL),
       m_objcEnabled(true)
@@ -632,8 +633,13 @@ TextEditor::ITextEditable *CppCodeCompletion::editor() const
 int CppCodeCompletion::startPosition() const
 { return m_startPosition; }
 
+bool CppCodeCompletion::shouldRestartCompletion()
+{ return m_shouldRestartCompletion; }
+
 bool CppCodeCompletion::triggersCompletion(TextEditor::ITextEditable *editor)
 {
+    m_editor = editor;
+
     const int pos = editor->position();
     unsigned token = T_EOF_SYMBOL;
 
@@ -649,6 +655,14 @@ bool CppCodeCompletion::triggersCompletion(TextEditor::ITextEditable *editor)
         }
 
         return true;
+    } else {
+        // Trigger completion after at least three characters of a name have been typed
+        const int startOfName = findStartOfName(pos);
+        if (pos - startOfName > 2) {
+            const QChar firstCharacter = editor->characterAt(startOfName);
+            if (firstCharacter.isLetter() || firstCharacter == QLatin1Char('_'))
+                return true;
+        }
     }
 
     return false;
@@ -1751,6 +1765,8 @@ bool CppCodeCompletion::typedCharCompletes(const TextEditor::CompletionItem &ite
 
 void CppCodeCompletion::complete(const TextEditor::CompletionItem &item, QChar typedChar)
 {
+    m_shouldRestartCompletion = false; // Enabled for specific cases
+
     Symbol *symbol = 0;
 
     if (item.data.isValid()) {
@@ -1780,10 +1796,13 @@ void CppCodeCompletion::complete(const TextEditor::CompletionItem &item, QChar t
             typedChar = QChar();
     } else if (m_completionOperator == T_STRING_LITERAL || m_completionOperator == T_ANGLE_STRING_LITERAL) {
         toInsert = item.text;
-        if (!toInsert.endsWith(QLatin1Char('/')))
+        if (!toInsert.endsWith(QLatin1Char('/'))) {
             extraChars += QLatin1Char((m_completionOperator == T_ANGLE_STRING_LITERAL) ? '>' : '"');
-        else if (typedChar == QLatin1Char('/')) // Eat the slash
-            typedChar = QChar();
+        } else {
+            m_shouldRestartCompletion = true;  // Re-trigger for subdirectory
+            if (typedChar == QLatin1Char('/')) // Eat the slash
+                typedChar = QChar();
+        }
     } else {
         toInsert = item.text;
 
@@ -1867,6 +1886,12 @@ void CppCodeCompletion::complete(const TextEditor::CompletionItem &item, QChar t
             --cursorOffset;
     }
 
+    if (!extraChars.isEmpty() && extraChars.length() + cursorOffset > 0) {
+        const QChar c = extraChars.at(extraChars.length() - 1 + cursorOffset);
+        if (c == QLatin1Char('.') || c == QLatin1Char('('))
+            m_shouldRestartCompletion = true;
+    }
+
     // Avoid inserting characters that are already there
     for (int i = 0; i < extraChars.length(); ++i) {
         const QChar a = extraChars.at(i);

src/plugins/cpptools/cppcodecompletion.h

@@ -72,6 +72,7 @@ public:
 
     TextEditor::ITextEditable *editor() const;
     int startPosition() const;
+    bool shouldRestartCompletion();
     QList<TextEditor::CompletionItem> getCompletions();
     bool supportsEditor(TextEditor::ITextEditable *editor);
     bool triggersCompletion(TextEditor::ITextEditable *editor);
@@ -144,6 +145,7 @@ private:
     CppModelManager *m_manager;
     TextEditor::ITextEditable *m_editor;
     int m_startPosition;     // Position of the cursor from which completion started
+    bool m_shouldRestartCompletion;
 
     bool m_forcedCompletion;
     unsigned m_completionOperator;