Center visible area to the selection when using mouse wheel to zoom in

and out

diylc/diylc-swing/src/org/diylc/swing/plugins/canvas/CanvasPlugin.java

@@ -1,24 +1,20 @@
 /*
-
+ * 
-    DIY Layout Creator (DIYLC).
+ * DIY Layout Creator (DIYLC). Copyright (c) 2009-2018 held jointly by the individual authors.
-    Copyright (c) 2009-2018 held jointly by the individual authors.
+ * 
-
+ * This file is part of DIYLC.
-    This file is part of DIYLC.
+ * 
-
+ * DIYLC is free software: you can redistribute it and/or modify it under the terms of the GNU
-    DIYLC is free software: you can redistribute it and/or modify
+ * General Public License as published by the Free Software Foundation, either version 3 of the
-    it under the terms of the GNU General Public License as published by
+ * License, or (at your option) any later version.
-    the Free Software Foundation, either version 3 of the License, or
+ * 
-    (at your option) any later version.
+ * DIYLC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
-
+ * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
-    DIYLC is distributed in the hope that it will be useful,
+ * Public License for more details.
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * 
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * You should have received a copy of the GNU General Public License along with DIYLC. If not, see
-    GNU General Public License for more details.
+ * <http://www.gnu.org/licenses/>.
-
+ */
-    You should have received a copy of the GNU General Public License
-    along with DIYLC.  If not, see <http://www.gnu.org/licenses/>.
-
-*/
 package org.diylc.swing.plugins.canvas;
 
 import java.awt.Dimension;
@@ -36,6 +32,7 @@ import java.awt.event.MouseAdapter;
 import java.awt.event.MouseEvent;
 import java.awt.event.MouseWheelEvent;
 import java.awt.event.MouseWheelListener;
+import java.awt.geom.Rectangle2D;
 import java.util.ArrayList;
 import java.util.EnumSet;
 import java.util.List;
@@ -275,23 +272,40 @@ public class CanvasPlugin implements IPlugIn, ClipboardOwner {
               plugInPort.setZoomLevel(newZoom = availableZoomLevels[i]);
             }
             
+            Rectangle2D selectionBounds = plugInPort.getSelectionBounds(true);
+            Rectangle visibleRect = scrollPane.getVisibleRect();
+            
+            JScrollBar horizontal = scrollPane.getHorizontalScrollBar();
+            JScrollBar vertical = scrollPane.getVerticalScrollBar();
+
+            if (selectionBounds == null) {
               // center to cursor
               Point desiredPos =
                   new Point((int) (1d * mousePos.x / oldZoom * newZoom), (int) (1d * mousePos.y / oldZoom * newZoom));
               int dx = desiredPos.x - mousePos.x;
               int dy = desiredPos.y - mousePos.y;              
-            JScrollBar horizontal = scrollPane.getHorizontalScrollBar();
               horizontal.setValue(horizontal.getValue() + dx);              
-            JScrollBar vertical = scrollPane.getVerticalScrollBar();
               vertical.setValue(vertical.getValue() + dy);
-          } if (e.isShiftDown()) {            
+            } else {
+              // center to selection
+              horizontal.setValue((int) (selectionBounds.getX() + selectionBounds.getWidth() / 2 - visibleRect
+                  .getWidth() / 2));
+              vertical.setValue((int) (selectionBounds.getY() + selectionBounds.getHeight() / 2 - visibleRect
+                  .getHeight() / 2));
+            }
+          }
+          if (e.isShiftDown()) {
             int iScrollAmount = e.getScrollAmount();
-            int iNewValue = horizontalScrollBar.getValue() + horizontalScrollBar.getBlockIncrement() * iScrollAmount * e.getWheelRotation();
+            int iNewValue =
+                horizontalScrollBar.getValue() + horizontalScrollBar.getBlockIncrement() * iScrollAmount
+                    * e.getWheelRotation();
             if (iNewValue <= horizontalScrollBar.getMaximum())
               horizontalScrollBar.setValue(iNewValue);
           } else {
             int iScrollAmount = e.getScrollAmount();
-            int iNewValue = verticalScrollBar.getValue() + verticalScrollBar.getBlockIncrement() * iScrollAmount * e.getWheelRotation();
+            int iNewValue =
+                verticalScrollBar.getValue() + verticalScrollBar.getBlockIncrement() * iScrollAmount
+                    * e.getWheelRotation();
             if (iNewValue <= verticalScrollBar.getMaximum())
               verticalScrollBar.setValue(iNewValue);
           }

diylc/diylc-swing/update.xml

@@ -1970,6 +1970,10 @@
 					<changeType>NEW_FEATURE</changeType>
 					<description>All file export actions (PNG, PDF, BOM...) take the current file name as a default</description>
 				</org.diylc.appframework.update.Change>
+				<org.diylc.appframework.update.Change>
+					<changeType>IMPROVEMENT</changeType>
+					<description>Center visible area to the selection when using mouse wheel to zoom in and out</description>
+				</org.diylc.appframework.update.Change>	
 				<org.diylc.appframework.update.Change>
 					<changeType>IMPROVEMENT</changeType>
 					<description>Change mouse cursor when in "Highlight Connected Areas" mode to avoid confusion</description>