wxQt: Enable QPainter antialiasing by default.

src/qt/dc.cpp

@@ -83,6 +83,12 @@ void wxQtDCImpl::QtPreparePainter( )
         m_qtPainter->setBrush( wxBrush().GetHandle() );
         m_qtPainter->setFont( wxFont().GetHandle() );
 
+        if (m_qtPainter->device()->depth() > 1)
+        {
+            m_qtPainter->setRenderHints(QPainter::Antialiasing,
+                                        true);
+        }
+
         if (m_clipping)
         {
             m_qtPainter->setClipRegion( m_clippingRegion.GetHandle() );

src/qt/dcmemory.cpp

@@ -65,6 +65,12 @@ void wxMemoryDCImpl::DoSelect( const wxBitmap& bitmap )
         // start drawing on the intermediary device:
         m_ok = m_qtPainter->begin( m_qtPixmap );
 
+        if (m_qtPainter->device()->depth() > 1)
+        {
+            m_qtPainter->setRenderHints(QPainter::Antialiasing,
+                                        true);
+        }
+
         SetPen(m_pen);
         SetBrush(m_brush);
         SetFont(m_font);

src/qt/window.cpp

@@ -1361,6 +1361,12 @@ bool wxWindowQt::QtHandlePaintEvent ( QWidget *handler, QPaintEvent *event )
     // itself otherwise.
     const bool ok = m_qtPainter->begin( widget );
 
+    if (m_qtPainter->device()->depth() > 1)
+    {
+        m_qtPainter->setRenderHints(QPainter::Antialiasing,
+                                    true);
+    }
+
     if ( ok )
     {
         bool handled;