QMacStyle: smooth QMenu corners for real

It's been for years that QMenu's rounded corners in qmacstyle_mac were
done via QWidget::setMask(QRegion). Unfortunately, QRegion mask does not
work well with retina displays and also does not support translucency.
That's why in this change we explicitly make QMenu's background
transparent and then draw a rectangle with rounded corners in
QMacStyle::drawPrimitive(PE_PanelMenu). This not only gives much better
result than the mask-based approach, but also de-HIThemes QMenu.

As a consequence, QComboBoxPrivateContainer doesn't get any mask from
QMacStyle anymore. Therefore, when the mask is empty, we need to paint
PE_PanelMenu before invoking QFrame's paint event handler.

Made-with: Gabriel de Dietrich <gabriel.dedietrich@qt.io>
Change-Id: Ia9236176113f23b86e45507fa6ddf77236084ce3
Reviewed-by: Oleg Yadrov <oleg.yadrov@qt.io>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@qt.io>

1 files changed, 14 insertions, 0 deletions

diff --git a/src/widgets/widgets/qcombobox.cpp b/src/widgets/widgets/qcombobox.cpp
index 1338a496e6..9afb4b3ae6 100644
--- a/src/widgets/widgets/qcombobox.cpp
+++ b/src/widgets/widgets/qcombobox.cpp
@@ -428,6 +428,20 @@ void QComboBoxPrivateContainer::resizeEvent(QResizeEvent *e)
     QFrame::resizeEvent(e);
 }
 
+void QComboBoxPrivateContainer::paintEvent(QPaintEvent *e)
+{
+    QStyleOptionComboBox cbOpt = comboStyleOption();
+    if (combo->style()->styleHint(QStyle::SH_ComboBox_Popup, &cbOpt, combo)
+            && mask().isEmpty()) {
+        QStyleOption opt;
+        opt.initFrom(this);
+        QPainter p(this);
+        style()->drawPrimitive(QStyle::PE_PanelMenu, &opt, &p, this);
+    }
+
+    QFrame::paintEvent(e);
+}
+
 void QComboBoxPrivateContainer::leaveEvent(QEvent *)
 {
 // On Mac using the Mac style we want to clear the selection