Implement #_needsRedraw() mechanism in PaperScope and Project, to notify Views of redraws required by changes in appearance.

src/core/PaperScope.js

@@ -167,6 +167,15 @@ var PaperScope = this.PaperScope = Base.extend(/** @scope _global_ */{
 		delete PaperScope._scopes[this.id];
 	},
 
+	_needsRedraw: function() {
+		// Make sure we're not looping through the view list each time...
+		if (!this._redrawNotified) {
+			for (var i = this.views.length - 1; i >= 0; i--)
+				this.views[i]._redrawNeeded = true;
+			this._redrawNotified = true;
+		}
+	},
+
 	statics: {
 		_scopes: {},
 

src/item/Item.js

@@ -42,7 +42,12 @@ var Item = this.Item = Base.extend({
 	 * @param {ChangeFlag} flags describes what exactly has changed.
 	 */
 	_changed: function(flags) {
+		if (flags & ChangeFlag.APPEARANCE) {
+			if (this._project)
+				this._project._needsRedraw();
+		}
 		if (flags & ChangeFlag.GEOMETRY) {
+			// Clear cached bounds and position whenever geometry changes
 			delete this._bounds;
 			delete this._position;
 		}

src/item/Layer.js

@@ -58,7 +58,9 @@ var Layer = this.Layer = Group.extend({
 			if (deselect)
 				this.setSelected(false);
 			Base.splice(this._project.layers, null, this._index, 1);
-			this._project._changed(Change.HIERARCHY);
+			// Tell project we need a redraw. This is similar to _changed() 
+			// mechanism.
+			this._project._needsRedraw();
 			return true;
 		}
 		return false;

src/project/Project.js

@@ -57,10 +57,9 @@ var Project = this.Project = Base.extend({
 		this.activeLayer = new Layer();
 	},
 
-	_changed: function(flags) {
-		if (flags & ChangeFlag.GEOMETRY) {
-			// TODO: Mark as requireRedraw
-		}
+	_needsRedraw: function() {
+		if (this._scope)
+			this._scope._needsRedraw();
 	},
 
 	/**

src/ui/View.js

@@ -204,13 +204,15 @@ var View = this.View = Base.extend({
 		this._inverse = null;
 	},
 
-	draw: function() {
+	draw: function(checkRedraw) {
+		if (checkRedraw && !this._redrawNeeded)
+			return false;
 		if (this._stats)
 			this._stats.update();
 		// Initial tests conclude that clearing the canvas using clearRect
 		// is always faster than setting canvas.width = canvas.width
 		// http://jsperf.com/clearrect-vs-setting-width/7
-		var ctx =this._context,
+		var ctx = this._context,
 			bounds = this._viewBounds;
 		ctx.clearRect(bounds._x, bounds._y,
 				// TODO: +1... what if we have multiple views in one canvas? 
@@ -221,6 +223,10 @@ var View = this.View = Base.extend({
 		// Just draw the active project for now
 		this._scope.project.draw(ctx);
 		ctx.restore();
+		// Update _redrawNotified in PaperScope as soon as one view was drawn
+		this._redrawNeeded = false;
+		this._scope._redrawNotified = false;
+		return true;
 	},
 
 	activate: function() {