[composer] Fix item rotation so that rotation occurs around item center

nyalldawson · nyalldawson · commit 41365d850162 · 2013-12-30T20:00:56.000+11:00
diff --git a/src/app/composer/qgscomposeritemwidget.cpp b/src/app/composer/qgscomposeritemwidget.cpp
@@ -504,7 +504,7 @@ void QgsComposerItemWidget::on_mItemRotationSpinBox_valueChanged( double val )
   if ( mItem )
   {
     mItem->beginCommand( tr( "Item rotation changed" ), QgsComposerMergeCommand::ItemRotation );
-    mItem->setItemRotation( val );
+    mItem->setItemRotation( val, true );
     mItem->update();
     mItem->endCommand();
   }
diff --git a/src/core/composer/qgscomposeritem.cpp b/src/core/composer/qgscomposeritem.cpp
@@ -486,8 +486,6 @@ void QgsComposerItem::setSceneRect( const QRectF& rectangle )
 
   QRectF newRect( 0, 0, newWidth, newHeight );
   QGraphicsRectItem::setRect( newRect );
-  //rotate item around its centre point
-  setTransformOriginPoint( QPointF( rect().width() / 2.0, rect().height() / 2.0 ) );
   setPos( xTranslation, yTranslation );
 
   emit sizeChanged();
@@ -712,8 +710,21 @@ void QgsComposerItem::setRotation( double r )
   setItemRotation( r );
 }
 
-void QgsComposerItem::setItemRotation( double r )
+void QgsComposerItem::setItemRotation( double r, bool adjustPosition )
 {
+  if ( adjustPosition )
+  {
+    //adjustPosition set, so shift the position of the item so that rotation occurs around item center
+    //create a line from the centrepoint of the rect() to its origin, in scene coordinates
+    QLineF refLine = QLineF( mapToScene( QPointF( rect().width() / 2.0, rect().height() / 2.0 ) ) , mapToScene( QPointF( 0 , 0 ) ) );
+    //rotate this line by the current rotation angle
+    refLine.setAngle( refLine.angle() - r + mItemRotation );
+    //get new end point of line - this is the new item position
+    QPointF rotatedReferencePoint = refLine.p2();
+    setPos( rotatedReferencePoint );
+    emit sizeChanged();
+  }
+
   if ( r > 360 )
   {
     mItemRotation = (( int )r ) % 360;
@@ -723,8 +734,7 @@ void QgsComposerItem::setItemRotation( double r )
     mItemRotation = r;
   }
 
-  //rotate item around its centre point
-  setTransformOriginPoint( QPointF( rect().width() / 2.0, rect().height() / 2.0 ) );
+  setTransformOriginPoint( 0, 0 );
   QGraphicsItem::setRotation( mItemRotation );
 
   emit itemRotationChanged( r );
diff --git a/src/core/composer/qgscomposeritem.h b/src/core/composer/qgscomposeritem.h
@@ -320,9 +320,12 @@ class CORE_EXPORT QgsComposerItem: public QObject, public QGraphicsRectItem
     virtual void setRotation( double r );
 
     /**Sets the item rotation
+      @param r item rotation in degrees
+      @param adjustPosition set to true if item should be shifted so that rotation occurs
+       around item center. If false, rotation occurs around item origin
       @note this method was added in version 2.1
     */
-    virtual void setItemRotation( double r );
+    virtual void setItemRotation( double r, bool adjustPosition = false );
 
     void repaint();
 

Original file line number	Diff line number	Diff line change
`@@ -504,7 +504,7 @@ void QgsComposerItemWidget::on_mItemRotationSpinBox_valueChanged( double val )`
`504`	`504`	`if ( mItem )`
`505`	`505`	`{`
`506`	`506`	`mItem->beginCommand( tr( "Item rotation changed" ), QgsComposerMergeCommand::ItemRotation );`
`507`		`- mItem->setItemRotation( val );`
	`507`	`+ mItem->setItemRotation( val, true );`
`508`	`508`	`mItem->update();`
`509`	`509`	`mItem->endCommand();`
`510`	`510`	`}`