Draw to QImage instead of QPixmap. When rendering is done, it's converted

wonder · wonder · commit d0943b807e01 · 2006-03-19T11:20:23.000Z
to QPixmap for fast onscreen drawing. git-svn-id: http://svn.osgeo.org/qgis/trunk@5063 c8812cc2-4d05-0410-92ff-de0c093fc19c
diff --git a/src/gui/qgsmapcanvasmap.cpp b/src/gui/qgsmapcanvasmap.cpp
@@ -42,14 +42,22 @@ void QgsMapCanvasMap::resize(QSize size)
 
 void QgsMapCanvasMap::render()
 {
-  mPixmap.fill(mBgColor);
+  // use temporary image for rendering
+  QImage image(size(), QImage::Format_RGB32);
   
-  QPainter paint(&mPixmap);
+  image.fill(mBgColor.rgb());
+
+  QPainter paint;
+  paint.begin(&image);
 
   // antialiasing
   if (mAntiAliasing)
     paint.setRenderHint(QPainter::Antialiasing);
   
   mRender->render(&paint);
 
+  paint.end();
+  
+  // convert QImage to QPixmap to acheive faster drawing on screen
+  mPixmap = QPixmap::fromImage(image);
 }
