Improve behavior of cpp editor tool bar

The parse context drop down was taking a content based, fixed amount of
space in the editor tool bar, without being shrinkable.

That was especially bad if you have a long project / target name. When
working with a small window / split, the outline drop down would be
dropped from the tool bar.

This patch makes the parse context drop down shrinkable (with a small
minimum size), and gives the outline drop down a slightly higher
priority for getting tool bar space.

Task-number: QTCREATORBUG-19386
Change-Id: I87e3ee2e411a43b1f398ffd24fe5608e4df02af6
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/cppeditor/cppparsecontext.cpp

@@ -134,6 +134,11 @@ ParseContextWidget::ParseContextWidget(ParseContextModel &parseContextModel, QWi
     : QComboBox(parent)
     , m_parseContextModel(parseContextModel)
 {
+    setSizeAdjustPolicy(QComboBox::AdjustToContents);
+    QSizePolicy policy = sizePolicy();
+    policy.setHorizontalStretch(1);
+    policy.setHorizontalPolicy(QSizePolicy::Maximum);
+    setSizePolicy(policy);
     // Set up context menu with a clear action
     setContextMenuPolicy(Qt::ActionsContextMenu);
     m_clearPreferredAction = new QAction(tr("Clear Preferred Parse Context"), this);
@@ -170,5 +175,16 @@ void ParseContextWidget::syncToModel()
     CppEditorWidget::updateWidgetHighlighting(this, isPreferred);
 }
 
+QSize ParseContextWidget::minimumSizeHint() const
+{
+    // QComboBox always returns the same from sizeHint() and minimumSizeHint().
+    // We want sizeHint() to be the preferred and maximum size
+    // (horizontalPolicy == Maximum), but want it to be shrinkable, which is not the case
+    // if the minimumSizeHint() is the same as sizeHint()
+    QSize size = QComboBox::minimumSizeHint();
+    size.setWidth(120);
+    return size;
+}
+
 } // namespace Internal
 } // namespace CppEditor