closes #278 Text marker should follow undo actions

app/src/processing/app/CaretAwareUndoableEdit.java

@@ -0,0 +1,77 @@
+package processing.app;
+
+import processing.app.syntax.JEditTextArea;
+
+import javax.swing.undo.CannotRedoException;
+import javax.swing.undo.CannotUndoException;
+import javax.swing.undo.UndoableEdit;
+
+public class CaretAwareUndoableEdit implements UndoableEdit {
+
+  private final UndoableEdit undoableEdit;
+  private final int caretPosition;
+
+  public CaretAwareUndoableEdit(UndoableEdit undoableEdit, JEditTextArea textArea) {
+    this.undoableEdit = undoableEdit;
+    this.caretPosition = textArea.getCaretPosition();
+  }
+
+  @Override
+  public void undo() throws CannotUndoException {
+    undoableEdit.undo();
+  }
+
+  @Override
+  public boolean canUndo() {
+    return undoableEdit.canUndo();
+  }
+
+  @Override
+  public void redo() throws CannotRedoException {
+    undoableEdit.redo();
+  }
+
+  @Override
+  public boolean canRedo() {
+    return undoableEdit.canRedo();
+  }
+
+  @Override
+  public void die() {
+    undoableEdit.die();
+  }
+
+  @Override
+  public boolean addEdit(UndoableEdit undoableEdit) {
+    return this.undoableEdit.addEdit(undoableEdit);
+  }
+
+  @Override
+  public boolean replaceEdit(UndoableEdit undoableEdit) {
+    return this.undoableEdit.replaceEdit(undoableEdit);
+  }
+
+  @Override
+  public boolean isSignificant() {
+    return undoableEdit.isSignificant();
+  }
+
+  @Override
+  public String getPresentationName() {
+    return undoableEdit.getPresentationName();
+  }
+
+  @Override
+  public String getUndoPresentationName() {
+    return undoableEdit.getUndoPresentationName();
+  }
+
+  @Override
+  public String getRedoPresentationName() {
+    return undoableEdit.getRedoPresentationName();
+  }
+
+  public int getCaretPosition() {
+    return caretPosition;
+  }
+}

app/src/processing/app/Editor.java

@@ -137,7 +137,7 @@ public class Editor extends JFrame implements RunnerListener {
   JMenuItem undoItem, redoItem;
   protected UndoAction undoAction;
   protected RedoAction redoAction;
-  UndoManager undo;
+  LastUndoableEditAwareUndoManager undo;
   // used internally, and only briefly
   CompoundEdit compoundEdit;
 
@@ -1344,6 +1344,10 @@ public class Editor extends JFrame implements RunnerListener {
         //System.out.println("Unable to undo: " + ex);
         //ex.printStackTrace();
       }
+      if (undo.getLastUndoableEdit() != null && undo.getLastUndoableEdit() instanceof CaretAwareUndoableEdit) {
+        CaretAwareUndoableEdit undoableEdit = (CaretAwareUndoableEdit) undo.getLastUndoableEdit();
+        textarea.setCaretPosition(undoableEdit.getCaretPosition() - 1);
+      }
       updateUndoState();
       redoAction.updateRedoState();
     }
@@ -1383,6 +1387,10 @@ public class Editor extends JFrame implements RunnerListener {
         //System.out.println("Unable to redo: " + ex);
         //ex.printStackTrace();
       }
+      if (undo.getLastUndoableEdit() != null && undo.getLastUndoableEdit() instanceof CaretAwareUndoableEdit) {
+        CaretAwareUndoableEdit undoableEdit = (CaretAwareUndoableEdit) undo.getLastUndoableEdit();
+        textarea.setCaretPosition(undoableEdit.getCaretPosition());
+      }
       updateRedoState();
       undoAction.updateUndoState();
     }
@@ -1664,7 +1672,7 @@ public class Editor extends JFrame implements RunnerListener {
               compoundEdit.addEdit(e.getEdit());
 
             } else if (undo != null) {
-              undo.addEdit(e.getEdit());
+              undo.addEdit(new CaretAwareUndoableEdit(e.getEdit(), textarea));
               undoAction.updateUndoState();
               redoAction.updateRedoState();
             }

app/src/processing/app/LastUndoableEditAwareUndoManager.java

@@ -0,0 +1,31 @@
+package processing.app;
+
+import javax.swing.undo.CannotRedoException;
+import javax.swing.undo.CannotUndoException;
+import javax.swing.undo.UndoManager;
+import javax.swing.undo.UndoableEdit;
+
+public class LastUndoableEditAwareUndoManager extends UndoManager {
+
+  private UndoableEdit lastUndoableEdit;
+
+  public LastUndoableEditAwareUndoManager() {
+    this.lastUndoableEdit = null;
+  }
+
+  @Override
+  public synchronized void undo() throws CannotUndoException {
+    lastUndoableEdit = super.editToBeUndone();
+    super.undo();
+  }
+
+  @Override
+  public synchronized void redo() throws CannotRedoException {
+    lastUndoableEdit = super.editToBeRedone();
+    super.redo();
+  }
+
+  public UndoableEdit getLastUndoableEdit() {
+    return lastUndoableEdit;
+  }
+}

app/src/processing/app/SketchCode.java

@@ -27,7 +27,7 @@ package processing.app;
 import java.io.*;
 
 import javax.swing.text.Document;
-import javax.swing.undo.*;
+
 import static processing.app.I18n._;
 
 
@@ -55,7 +55,7 @@ public class SketchCode {
    * Editor.undo will be set to this object when this code is the tab
    * that's currently the front.
    */
-  private UndoManager undo = new UndoManager();
+  private LastUndoableEditAwareUndoManager undo = new LastUndoableEditAwareUndoManager();
 
   // saved positions from last time this tab was used
   private int selectionStart;
@@ -221,7 +221,7 @@ public class SketchCode {
   }
   
   
-  public UndoManager getUndo() {
+  public LastUndoableEditAwareUndoManager getUndo() {
     return undo;
   }