Enable touch for the map canvas on windows

Author: NathanW2

src/gui/qgsmapcanvas.cpp

@@ -129,6 +129,13 @@ QgsMapCanvas::QgsMapCanvas( QWidget * parent, const char *name )
   connect( QgsProject::instance(), SIGNAL( writeProject( QDomDocument & ) ),
            this, SLOT( writeProject( QDomDocument & ) ) );
   mMap->resize( size() );
+
+#ifdef Q_OS_WIN
+  // Enable touch event on Windows.
+  // Qt on Windows needs to be told it can take touch events or else it ignores them.
+  grabGesture(Qt::PinchGesture);
+  viewport()->setAttribute(Qt::WA_AcceptTouchEvents);
+#endif
 } // QgsMapCanvas ctor