TreeModel: Introduce a TreeItem::indexInParent() convenience function

To shorten user code and hide the ugly const_cast.

Change-Id: I798bd105932004ea17cb95b243fc38ccfcda0a2c
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/libs/utils/treemodel.cpp

@@ -766,6 +766,11 @@ int TreeItem::level() const
     return l;
 }
 
+int TreeItem::indexInParent() const
+{
+    return m_parent ? m_parent->m_children.indexOf(const_cast<TreeItem *>(this)) : -1;
+}
+
 QModelIndex TreeItem::index() const
 {
     QTC_ASSERT(m_model, return QModelIndex());

src/libs/utils/treemodel.h

@@ -65,6 +65,7 @@ public:
     int level() const;
 
     int childCount() const { return m_children.size(); }
+    int indexInParent() const;
     TreeItem *childAt(int index) const;
     QVector<TreeItem *> children() const { return m_children; }
     QModelIndex index() const;

src/plugins/clangstaticanalyzer/clangstaticanalyzerdiagnosticmodel.cpp

@@ -272,7 +272,7 @@ QVariant ExplainingStepItem::data(int column, int role) const
     case ClangStaticAnalyzerDiagnosticModel::DiagnosticRole:
         return QVariant::fromValue(static_cast<DiagnosticItem *>(parent())->diagnostic());
     case Qt::DisplayRole: {
-        const int row = parent()->children().indexOf(const_cast<ExplainingStepItem *>(this)) + 1;
+        const int row = indexInParent() + 1;
         const int padding = static_cast<int>(std::log10(parent()->childCount()))
                 - static_cast<int>(std::log10(row));
         return QString::fromLatin1("%1%2: %3")

src/plugins/projectexplorer/projectwindow.cpp

@@ -361,7 +361,7 @@ void ProjectWindow::deregisterProject(Project *project)
 void ProjectWindow::startupProjectChanged(Project *project)
 {
     if (ProjectItem *projectItem = itemForProject(project)) {
-        int index = projectItem->parent()->children().indexOf(projectItem);
+        int index = projectItem->indexInParent();
         QTC_ASSERT(index != -1, return);
         m_projectSelection->setCurrentIndex(index);
         m_selectorModel->rootItem()->m_currentProjectIndex = index;

src/plugins/valgrind/xmlprotocol/errorlistmodel.cpp

@@ -278,7 +278,7 @@ QVariant FrameItem::data(int column, int role) const
     case ErrorListModel::ErrorRole:
         return QVariant::fromValue(getErrorItem()->error());
     case Qt::DisplayRole: {
-        const int row = parent()->children().indexOf(const_cast<FrameItem *>(this)) + 1;
+        const int row = indexInParent() + 1;
         const int padding = static_cast<int>(std::log10(parent()->childCount()))
                 - static_cast<int>(std::log10(row));
         return QString::fromLatin1("%1%2: %3")