[composer] Add zoomToExtent for QgsComposerMap, allows easily fitting…

… a set extent into the map item without altering the item's shape

python/core/composer/qgscomposermap.sip

@@ -129,9 +129,24 @@ class QgsComposerMap : QgsComposerItem
     /**Sets new scale and changes only mExtent*/
     void setNewScale( double scaleDenominator, bool forceUpdate = true );
 
-    /**Sets new Extent and changes width, height (and implicitely also scale)*/
+    /**Sets new extent for the map. This method may change the width or height of the map
+     * item to ensure that the extent exactly matches the specified extent, with no
+     * overlap or margin. This method implicitly alters the map scale.
+     * @param extent new extent for the map
+     * @see zoomToExtent
+    */
     void setNewExtent( const QgsRectangle& extent );
 
+    /**Zooms the map so that the specified extent is fully visible within the map item.
+     * This method will not change the width or height of the map, and may result in
+     * an overlap or margin from the specified extent. This method implicitly alters the
+     * map scale.
+     * @param extent new extent for the map
+     * @see setNewExtent
+     * @note added in QGIS 2.5
+    */
+    void zoomToExtent( const QgsRectangle& extent );
+
     /**Sets new Extent for the current atlas preview and changes width, height (and implicitely also scale).
       Atlas preview extents are only temporary, and are regenerated whenever the atlas feature changes
     */

src/app/composer/qgscomposermapwidget.cpp

@@ -447,37 +447,8 @@ void QgsComposerMapWidget::on_mSetToMapCanvasExtentButton_clicked()
 
   QgsRectangle newExtent = mComposerMap->composition()->mapSettings().visibleExtent();
 
-  //Make sure the width/height ratio is the same as in current composer map extent.
-  //This is to keep the map item frame and the page layout fixed
-  QgsRectangle currentMapExtent = *( mComposerMap->currentMapExtent() );
-  double currentWidthHeightRatio = currentMapExtent.width() / currentMapExtent.height();
-  double newWidthHeightRatio = newExtent.width() / newExtent.height();
-
-  if ( currentWidthHeightRatio < newWidthHeightRatio )
-  {
-    //enlarge height of new extent, ensuring the map center stays the same
-    double newHeight = newExtent.width() / currentWidthHeightRatio;
-    double deltaHeight = newHeight - newExtent.height();
-    newExtent.setYMinimum( newExtent.yMinimum() - deltaHeight / 2 );
-    newExtent.setYMaximum( newExtent.yMaximum() + deltaHeight / 2 );
-  }
-  else
-  {
-    //enlarge width of new extent, ensuring the map center stays the same
-    double newWidth = currentWidthHeightRatio * newExtent.height();
-    double deltaWidth = newWidth - newExtent.width();
-    newExtent.setXMinimum( newExtent.xMinimum() - deltaWidth / 2 );
-    newExtent.setXMaximum( newExtent.xMaximum() + deltaWidth / 2 );
-  }
-
-  //fill text into line edits
-  mXMinLineEdit->setText( QString::number( newExtent.xMinimum() ) );
-  mXMaxLineEdit->setText( QString::number( newExtent.xMaximum() ) );
-  mYMinLineEdit->setText( QString::number( newExtent.yMinimum() ) );
-  mYMaxLineEdit->setText( QString::number( newExtent.yMaximum() ) );
-
   mComposerMap->beginCommand( tr( "Map extent changed" ) );
-  mComposerMap->setNewExtent( newExtent );
+  mComposerMap->zoomToExtent( newExtent );
   mComposerMap->endCommand();
 }
 

src/core/composer/qgscomposermap.cpp

@@ -710,6 +710,46 @@ void QgsComposerMap::setNewExtent( const QgsRectangle& extent )
   updateItem();
 }
 
+void QgsComposerMap::zoomToExtent( const QgsRectangle &extent )
+{
+  QgsRectangle newExtent = extent;
+  //Make sure the width/height ratio is the same as the current composer map extent.
+  //This is to keep the map item frame size fixed
+  double currentWidthHeightRatio = currentMapExtent()->width() / currentMapExtent()->height();
+  double newWidthHeightRatio = newExtent.width() / newExtent.height();
+
+  if ( currentWidthHeightRatio < newWidthHeightRatio )
+  {
+    //enlarge height of new extent, ensuring the map center stays the same
+    double newHeight = newExtent.width() / currentWidthHeightRatio;
+    double deltaHeight = newHeight - newExtent.height();
+    newExtent.setYMinimum( newExtent.yMinimum() - deltaHeight / 2 );
+    newExtent.setYMaximum( newExtent.yMaximum() + deltaHeight / 2 );
+  }
+  else
+  {
+    //enlarge width of new extent, ensuring the map center stays the same
+    double newWidth = currentWidthHeightRatio * newExtent.height();
+    double deltaWidth = newWidth - newExtent.width();
+    newExtent.setXMinimum( newExtent.xMinimum() - deltaWidth / 2 );
+    newExtent.setXMaximum( newExtent.xMaximum() + deltaWidth / 2 );
+  }
+
+  if ( *currentMapExtent() == newExtent )
+  {
+    return;
+  }
+  *currentMapExtent() = newExtent;
+
+  //recalculate data defined scale and extents, since that may override extent
+  refreshMapExtents();
+
+  mCacheUpdated = false;
+  updateItem();
+  emit itemChanged();
+  emit extentChanged();
+}
+
 void QgsComposerMap::setNewAtlasFeatureExtent( const QgsRectangle& extent )
 {
   if ( mAtlasFeatureExtent != extent )

src/core/composer/qgscomposermap.h

@@ -172,9 +172,24 @@ class CORE_EXPORT QgsComposerMap : public QgsComposerItem
     /**Sets new scale and changes only mExtent*/
     void setNewScale( double scaleDenominator, bool forceUpdate = true );
 
-    /**Sets new Extent and changes width, height (and implicitely also scale)*/
+    /**Sets new extent for the map. This method may change the width or height of the map
+     * item to ensure that the extent exactly matches the specified extent, with no
+     * overlap or margin. This method implicitly alters the map scale.
+     * @param extent new extent for the map
+     * @see zoomToExtent
+    */
     void setNewExtent( const QgsRectangle& extent );
 
+    /**Zooms the map so that the specified extent is fully visible within the map item.
+     * This method will not change the width or height of the map, and may result in
+     * an overlap or margin from the specified extent. This method implicitly alters the
+     * map scale.
+     * @param extent new extent for the map
+     * @see setNewExtent
+     * @note added in QGIS 2.5
+    */
+    void zoomToExtent( const QgsRectangle& extent );
+
     /**Sets new Extent for the current atlas preview and changes width, height (and implicitely also scale).
       Atlas preview extents are only temporary, and are regenerated whenever the atlas feature changes
     */