Fix updating map extent on resize

src/core/layout/qgslayoutitemmap.cpp

@@ -50,8 +50,7 @@ QgsLayoutItemMap::QgsLayoutItemMap( QgsLayout *layout )
 
   connect( this, &QgsLayoutItem::sizePositionChanged, this, [ = ]
   {
-    updateBoundingRect();
+    shapeChanged();
-    update();
   } );
 
 # if 0
@@ -945,6 +944,29 @@ void QgsLayoutItemMap::painterJobFinished()
   update();
 }
 
+void QgsLayoutItemMap::shapeChanged()
+{
+  // keep center as center
+  QgsPointXY oldCenter = mExtent.center();
+
+  double w = rect().width();
+  double h = rect().height();
+
+  // keep same width as before
+  double newWidth = mExtent.width();
+  // but scale height to match item's aspect ratio
+  double newHeight = newWidth * h / w;
+
+  mExtent = QgsRectangle::fromCenterAndSize( oldCenter, newWidth, newHeight );
+
+  //recalculate data defined scale and extents
+  refreshMapExtents();
+  updateBoundingRect();
+  invalidateCache();
+  emit changed();
+  emit extentChanged();
+}
+
 void QgsLayoutItemMap::connectUpdateSlot()
 {
   //connect signal from layer registry to update in case of new or deleted layers

src/core/layout/qgslayoutitemmap.h

@@ -507,6 +507,8 @@ class CORE_EXPORT QgsLayoutItemMap : public QgsLayoutItem
 
     void painterJobFinished();
 
+    void shapeChanged();
+
   private:
 
 
@@ -619,11 +621,6 @@ class CORE_EXPORT QgsLayoutItemMap : public QgsLayoutItem
     //! True if annotation items, rubber band, etc. from the main canvas should be displayed
     bool mDrawAnnotations = true;
 
-    /**
-     * Adjusts an extent rectangle to match the provided item width and height, so that extent
-     * center of extent remains the same */
-    void adjustExtentToItemShape( double itemWidth, double itemHeight, QgsRectangle &extent ) const;
-
     //! True if map is being controlled by an atlas
     bool mAtlasDriven = false;
     //! Current atlas scaling mode