Add rotation member to QgsMapCanvasMap, use for handling paint event

Fixes the regression with pre-rendering user feedback for
non-rotated maps. The glitch is still there for rotated maps
but that's not a regression.

See http://hub.qgis.org/issues/11811

Author: Sandro Santilli

src/gui/qgsmapcanvas.cpp

@@ -724,7 +724,7 @@ void QgsMapCanvas::rendererJobFinished()
     p.end();
 
     QgsRectangle rect = mSettings.visibleExtent();
-    mMap->setContent( img, rect );
+    mMap->setContent( img, rect, mSettings.rotation() );
   }
 
   // now we are in a slot called from mJob - do not delete it immediately

src/gui/qgsmapcanvasmap.cpp

@@ -23,7 +23,7 @@
 #include <QPainter>
 
 QgsMapCanvasMap::QgsMapCanvasMap( QgsMapCanvas* canvas )
-    : QgsMapCanvasItem( canvas )
+    : QgsMapCanvasItem( canvas ), mRotation(0.0)
 {
   setZValue( -10 );
 }
@@ -32,8 +32,9 @@ QgsMapCanvasMap::~QgsMapCanvasMap()
 {
 }
 
-void QgsMapCanvasMap::setContent( const QImage& image, const QgsRectangle& rect )
+void QgsMapCanvasMap::setContent( const QImage& image, const QgsRectangle& rect, double rotation )
 {
+  mRotation = rotation;
   mImage = image;
 
   // For true retro fans: this is approximately how the graphics looked like in 1990
@@ -47,9 +48,28 @@ void QgsMapCanvasMap::setContent( const QImage& image, const QgsRectangle& rect
 void QgsMapCanvasMap::paint( QPainter* painter )
 {
   int w = qRound( boundingRect().width() ) - 2, h = qRound( boundingRect().height() ) - 2; // setRect() makes the size +2 :-(
+  int wi = mImage.width();
+  int hi = mImage.height();
+
+  double ar = h ? double(w)/h : 0.0; // aspect ratio of bounding rect
+  double ari = hi ? double(wi)/hi : 0.0; // aspect ratio of image
+  double ard = fabs(ari-ar); // aspect ratio difference
+
+#if 0
+  QgsDebugMsg( QString( "XXXX img %1,%2 (%3) item %4,%5 (%6) ardiff %7" )
+    .arg( wi ).arg( hi ).arg( ari )
+    .arg( w ).arg( h ).arg( ar )
+    .arg ( ard )
+  );
+#endif
+
   if ( mImage.size() != QSize( w, h ) )
   {
-    QgsDebugMsg( QString( "map paint DIFFERENT SIZE: img %1,%2  item %3,%4" ).arg( mImage.width() ).arg( mImage.height() ).arg( w ).arg( h ) );
+    QgsDebugMsg( QString( "map paint DIFFERENT SIZE: img %1,%2  item %3,%4" ).arg( wi ).arg( hi ).arg( w ).arg( h ) );
+  }
+
+  if ( mRotation )
+  {
     int tX = ( w - mImage.width() ) / 2.0;
     int tY = ( h - mImage.height() ) / 2.0;
     int fX = 0;

src/gui/qgsmapcanvasmap.h

@@ -41,7 +41,8 @@ class GUI_EXPORT QgsMapCanvasMap : public QgsMapCanvasItem  // public QObject, p
     ~QgsMapCanvasMap();
 
     //! @note added in 2.4
-    void setContent( const QImage& image, const QgsRectangle& rect );
+    //! @note rotation parameter added in 2.8
+    void setContent( const QImage& image, const QgsRectangle& rect, double rotation=0.0 );
 
     //! @note added in 2.4
     QImage contentImage() const { return mImage; }
@@ -75,6 +76,8 @@ class GUI_EXPORT QgsMapCanvasMap : public QgsMapCanvasItem  // public QObject, p
   private:
 
     QImage mImage;
+
+    double mRotation;
 };
 
 #endif