[needs-docs] Use alt modifier to reverse zoom behaviour

Previously shift-modifier was used to change zoom in to out, and
zoom out to in. This commit changes it to the more common alt
modifier.

src/gui/qgscomposerview.cpp

@@ -290,7 +290,7 @@ void QgsComposerView::mousePressEvent( QMouseEvent* e )
 
     case Zoom:
     {
-      if ( !( e->modifiers() & Qt::ShiftModifier ) )
+      if ( !( e->modifiers() & Qt::AltModifier ) )
       {
         //zoom in action
         startMarqueeZoom( scenePoint );
@@ -1706,7 +1706,7 @@ void QgsComposerView::keyPressEvent( QKeyEvent * e )
     {
       //both control and space pressed
       //set cursor to zoom in/out depending on shift key status
-      QPixmap myZoomQPixmap = QPixmap(( const char ** )(( e->modifiers() & Qt::ShiftModifier ) ? zoom_out : zoom_in ) );
+      QPixmap myZoomQPixmap = QPixmap(( const char ** )(( e->modifiers() & Qt::AltModifier ) ? zoom_out : zoom_in ) );
       QCursor zoomCursor = QCursor( myZoomQPixmap, 7, 7 );
       viewport()->setCursor( zoomCursor );
     }
@@ -1740,8 +1740,8 @@ void QgsComposerView::keyPressEvent( QKeyEvent * e )
       mTemporaryZoomStatus = QgsComposerView::Active;
       mPreviousTool = mCurrentTool;
       setCurrentTool( Zoom );
-      //set cursor to zoom in/out depending on shift key status
-      QPixmap myZoomQPixmap = QPixmap(( const char ** )(( e->modifiers() & Qt::ShiftModifier ) ? zoom_out : zoom_in ) );
+      //set cursor to zoom in/out depending on alt key status
+      QPixmap myZoomQPixmap = QPixmap(( const char ** )(( e->modifiers() & Qt::AltModifier ) ? zoom_out : zoom_in ) );
       QCursor zoomCursor = QCursor( myZoomQPixmap, 7, 7 );
       viewport()->setCursor( zoomCursor );
       return;
@@ -1750,10 +1750,10 @@ void QgsComposerView::keyPressEvent( QKeyEvent * e )
 
   if ( mCurrentTool == QgsComposerView::Zoom )
   {
-    //using the zoom tool, respond to changes in shift key status and update mouse cursor accordingly
+    //using the zoom tool, respond to changes in alt key status and update mouse cursor accordingly
     if ( ! e->isAutoRepeat() )
     {
-      QPixmap myZoomQPixmap = QPixmap(( const char ** )(( e->modifiers() & Qt::ShiftModifier ) ? zoom_out : zoom_in ) );
+      QPixmap myZoomQPixmap = QPixmap(( const char ** )(( e->modifiers() & Qt::AltModifier ) ? zoom_out : zoom_in ) );
       QCursor zoomCursor = QCursor( myZoomQPixmap, 7, 7 );
       viewport()->setCursor( zoomCursor );
     }
@@ -1939,10 +1939,10 @@ void QgsComposerView::keyReleaseEvent( QKeyEvent * e )
   }
   else if ( mCurrentTool == QgsComposerView::Zoom )
   {
-    //if zoom tool is active, respond to changes in the shift key status and update cursor accordingly
+    //if zoom tool is active, respond to changes in the alt key status and update cursor accordingly
     if ( ! e->isAutoRepeat() )
     {
-      QPixmap myZoomQPixmap = QPixmap(( const char ** )(( e->modifiers() & Qt::ShiftModifier ) ? zoom_out : zoom_in ) );
+      QPixmap myZoomQPixmap = QPixmap(( const char ** )(( e->modifiers() & Qt::AltModifier ) ? zoom_out : zoom_in ) );
       QCursor zoomCursor = QCursor( myZoomQPixmap, 7, 7 );
       viewport()->setCursor( zoomCursor );
     }

src/gui/qgsmaptoolzoom.cpp

@@ -84,7 +84,7 @@ void QgsMapToolZoom::canvasReleaseEvent( QgsMapMouseEvent* e )
     return;
 
   bool zoomOut = mZoomOut;
-  if ( e->modifiers() & Qt::ShiftModifier )
+  if ( e->modifiers() & Qt::AltModifier )
     zoomOut = !zoomOut;
 
   // We are not really dragging in this case. This is sometimes caused by