make transformations undoable/redoable

area.js

@@ -546,6 +546,10 @@ var DrawingArea = new Lang.Class({
             this._redisplay();
         }
         
+        if (duplicate)
+            // For undo, ignore both the transformations inherited from the duplicated element
+            // and the current transformation.
+            this.grabbedElement.makeAllTransformationsNotUndoable();
         
         this.motionHandler = this.connect('motion-event', (actor, event) => {
             if (this.spaceKeyPressed)
@@ -907,18 +911,36 @@ var DrawingArea = new Lang.Class({
     deleteLastElement: function() {
         this._stopAll();
         this.elements.pop();
+        
+        if (this.elements.length)
+            this.elements[this.elements.length - 1].resetUndoneTransformations();
+        
         this._redisplay();
     },
     
     undo: function() {
-        if (this.elements.length > 0)
+        if (!this.elements.length)
+            return;
+        
+        let success = this.elements[this.elements.length - 1].undoTransformation();
+        if (!success) {
             this.undoneElements.push(this.elements.pop());
+            if (this.elements.length)
+                this.elements[this.elements.length - 1].resetUndoneTransformations();
+        }
+        
         this._redisplay();
     },
     
     redo: function() {
-        if (this.undoneElements.length > 0)
+        let success = false;
+        
+        if (this.elements.length)
+            success = this.elements[this.elements.length - 1].redoTransformation();
+            
+        if (!success && this.undoneElements.length > 0)
             this.elements.push(this.undoneElements.pop());
+        
         this._redisplay();
     },
     

elements.js

@@ -458,7 +458,7 @@ const _DrawingElement = new Lang.Class({
                 return;
                 
             let center = this._getOriginalCenter();
-            this.transformations[0] = { type: Transformations.ROTATION,
+            this.transformations[0] = { type: Transformations.ROTATION, notUndoable: true,
                                         angle: getAngle(center[0], center[1], points[points.length - 1][0], points[points.length - 1][1], x, y) };
             
         } else if (this.shape == Shapes.ELLIPSE && transform) {
@@ -467,7 +467,7 @@ const _DrawingElement = new Lang.Class({
             
             points[2] = [x, y];
             let center = this._getOriginalCenter();
-            this.transformations[0] = { type: Transformations.ROTATION,
+            this.transformations[0] = { type: Transformations.ROTATION, notUndoable: true,
                                         angle: getAngle(center[0], center[1], center[0] + 1, center[1], x, y) };
             
         } else if (this.shape == Shapes.POLYGON || this.shape == Shapes.POLYLINE) {
@@ -586,6 +586,42 @@ const _DrawingElement = new Lang.Class({
         }
     },
     
+    undoTransformation: function() {
+        if (this.transformations && this.transformations.length) {
+            // Do not undo initial transformations (transformations made during the drawing step).
+            if (this.lastTransformation.notUndoable)
+                return false;
+            
+            if (!this._undoneTransformations)
+                this._undoneTransformations = [];
+            this._undoneTransformations.push(this.transformations.pop());
+            
+            return true;
+        }
+        
+        return false;
+    },
+    
+    redoTransformation: function() {
+        if (this._undoneTransformations && this._undoneTransformations.length) {
+            if (!this.transformations)
+                this.transformations = [];
+            this.transformations.push(this._undoneTransformations.pop());
+            
+            return true;
+        }
+        
+        return false;
+    },
+    
+    resetUndoneTransformations: function() {
+        delete this._undoneTransformations;
+    },
+    
+    makeAllTransformationsNotUndoable: function() {
+        this.transformations.forEach(transformation => transformation.notUndoable = true);
+    },
+    
     // The figure rotation center before transformations (original).
     // this.textWidth is computed during Cairo building.
     _getOriginalCenter: function() {