Clang: Fix completion position for clang and proposal

* Rename some members/functions to clarify their meaning.

* Ensure that the position for the proposal widget is at start of the
  identifer, so that the filter prefix will be found correctly in the
  GenericProposalWidget. For certain cases the completion were
  calculated but the widget was never shown:

  Case 1:

    void f()
    {
        <COMPLETION_CURSOR>
    }

  Case 2:

    void f()
    {
        st<COMPLETION_CURSOR>
    }

  Case 3:

    if (true)
      <COMPLETION_CURSOR>

  Case 4:

    foo. mem<COMPLETION_CURSOR>

Change-Id: Ie79e01e8a22f8ec306136ec4ccbfffd544edd573
Reviewed-by: Erik Verbruggen <erik.verbruggen@theqtcompany.com>

src/plugins/clangcodemodel/activationsequencecontextprocessor.cpp

@@ -46,8 +46,8 @@ ActivationSequenceContextProcessor::ActivationSequenceContextProcessor(const Cla
     : m_textCursor(assistInterface->textDocument()),
       m_assistInterface(assistInterface),
       m_positionInDocument(assistInterface->position()),
-      m_positionAfterOperator(m_positionInDocument),
-      m_positionBeforeOperator(m_positionAfterOperator)
+      m_startOfNamePosition(m_positionInDocument),
+      m_operatorStartPosition(m_positionInDocument)
 
 {
     m_textCursor.setPosition(m_positionInDocument);
@@ -65,19 +65,19 @@ const QTextCursor &ActivationSequenceContextProcessor::textCursor_forTestOnly()
     return m_textCursor;
 }
 
-int ActivationSequenceContextProcessor::positionAfterOperator() const
+int ActivationSequenceContextProcessor::startOfNamePosition() const
 {
-    return m_positionAfterOperator;
+    return m_startOfNamePosition;
 }
 
-int ActivationSequenceContextProcessor::positionBeforeOperator() const
+int ActivationSequenceContextProcessor::operatorStartPosition() const
 {
-    return m_positionBeforeOperator;
+    return m_operatorStartPosition;
 }
 
 void ActivationSequenceContextProcessor::process()
 {
-    skipeWhiteSpacesAndIdentifierBeforeCursor();
+    goBackToStartOfName();
     processActivationSequence();
 
     if (m_completionKind != CPlusPlus::T_EOF_SYMBOL) {
@@ -90,20 +90,21 @@ void ActivationSequenceContextProcessor::process()
         processSlashOutsideOfAString();
         processLeftParen();
         processPreprocessorInclude();
-        resetPositionForEOFCompletionKind();
     }
+
+    resetPositionsForEOFCompletionKind();
 }
 
 void ActivationSequenceContextProcessor::processActivationSequence()
 {
-    const auto activationSequence = m_assistInterface->textAt(m_positionInDocument - 3, 3);
+    const int nonSpacePosition = findStartOfNonSpaceChar(m_startOfNamePosition);
+    const auto activationSequence = m_assistInterface->textAt(nonSpacePosition - 3, 3);
     ActivationSequenceProcessor activationSequenceProcessor(activationSequence,
-                                                            m_positionInDocument,
+                                                            nonSpacePosition,
                                                             true);
 
     m_completionKind = activationSequenceProcessor.completionKind();
-    m_positionBeforeOperator = activationSequenceProcessor.position();
-
+    m_operatorStartPosition = activationSequenceProcessor.operatorStartPosition();
 }
 
 void ActivationSequenceContextProcessor::processStringLiteral()
@@ -221,27 +222,37 @@ void ActivationSequenceContextProcessor::processPreprocessorInclude()
     }
 }
 
-void ActivationSequenceContextProcessor::resetPositionForEOFCompletionKind()
+void ActivationSequenceContextProcessor::resetPositionsForEOFCompletionKind()
 {
     if (m_completionKind == CPlusPlus::T_EOF_SYMBOL)
-        m_positionBeforeOperator = m_positionInDocument;
+        m_operatorStartPosition = m_positionInDocument;
 }
 
-void ActivationSequenceContextProcessor::skipeWhiteSpacesAndIdentifierBeforeCursor()
+int ActivationSequenceContextProcessor::findStartOfNonSpaceChar(int startPosition)
 {
-    QTextDocument *document = m_assistInterface->textDocument();
+    int position = startPosition;
+    while (m_assistInterface->characterAt(position - 1).isSpace())
+        --position;
+    return position;
+}
 
-    const QRegExp findNonWhiteSpaceRegularExpression(QStringLiteral("[^\\s\\w]"));
+int ActivationSequenceContextProcessor::findStartOfName(int startPosition)
+{
+    int position = startPosition;
+    QChar character;
+    do {
+        character = m_assistInterface->characterAt(--position);
+    } while (character.isLetterOrNumber() || character == QLatin1Char('_'));
 
-    auto nonWhiteSpaceTextCursor = document->find(findNonWhiteSpaceRegularExpression,
-                                                  m_positionInDocument,
-                                                  QTextDocument::FindBackward);
+    return position + 1;
+}
 
-    if (!nonWhiteSpaceTextCursor.isNull()) {
-        m_positionInDocument = nonWhiteSpaceTextCursor.position();
-        m_positionAfterOperator = m_positionInDocument;
-        m_textCursor.setPosition(m_positionInDocument);
-    }
+void ActivationSequenceContextProcessor::goBackToStartOfName()
+{
+    m_startOfNamePosition = findStartOfName(m_positionInDocument);
+
+    if (m_startOfNamePosition != m_positionInDocument)
+        m_textCursor.setPosition(m_startOfNamePosition);
 }
 
 } // namespace Internal