Feature : add onion skin option

New option in application settings : onion skin.
You can choose the overlay to display now :
- no overlay
- onion skin (default)
- layer preview (previous default)

Available in Application Settings panel.

Only one overlay can be used at the same time.
The onion skin overlay is driven by a new OnionSkinRenderer maanged by the
drawing.

The drawing controller is responsible for instanciating and 'choosing' the
overlay renderer.

When switching to a new overlay, other overlays are cleared and flushed
(they cache their rendering frame, flush empties the cache).

NB : flush is only available on LayersRenderer and OnionSkinRenderer for
now.

src/css/style.css

@@ -136,12 +136,14 @@ body {
   background: url(../img/canvas_background/lowcont_dark_canvas_background.png) repeat;
 }
 
-.layers-canvas {
+.layers-canvas,
+.canvas.onion-skin-canvas {
   opacity: 0.2;
 }
 
 .canvas.canvas-overlay,
-.canvas.layers-canvas {
+.canvas.layers-canvas,
+.canvas.onion-skin-canvas {
   position: absolute;
   top: 0;
   left: 0;
@@ -157,7 +159,8 @@ body {
 .canvas.layers-below-canvas  {z-index:  7;}
 .canvas.drawing-canvas       {z-index:  8;}
 .canvas.layers-above-canvas  {z-index:  9;}
-.canvas.canvas-overlay       {z-index: 10;}
+.canvas.onion-skin-canvas    {z-index: 10;}
+.canvas.canvas-overlay       {z-index: 11;}
 
 /**
  * Animated preview styles.

src/js/Constants.js

@@ -19,6 +19,10 @@ var Constants = {
   DEFAULT_PEN_COLOR : '#000000',
   TRANSPARENT_COLOR : 'rgba(0, 0, 0, 0)',
 
+  OVERLAY_ONION_SKIN : 'onion-skin',
+  OVERLAY_LAYER_PREVIEW : 'layer-preview',
+  OVERLAY_DISABLED : 'no-overlay',
+
   NO_PALETTE_ID : '__no-palette',
   CURRENT_COLORS_PALETTE_ID : '__current-colors',
   MANAGE_PALETTE_ID : '__manage-palettes',

src/js/controller/DrawingController.js

@@ -32,13 +32,15 @@
 
     this.overlayRenderer = new pskl.rendering.frame.CachedFrameRenderer(this.container, renderingOptions, ["canvas-overlay"]);
     this.renderer = new pskl.rendering.frame.CachedFrameRenderer(this.container, renderingOptions, ["drawing-canvas"]);
+    this.onionSkinRenderer = new pskl.rendering.OnionSkinRenderer(this.container, renderingOptions, piskelController);
     this.layersRenderer = new pskl.rendering.layer.LayersRenderer(this.container, renderingOptions, piskelController);
 
     this.compositeRenderer = new pskl.rendering.CompositeRenderer();
     this.compositeRenderer
       .add(this.overlayRenderer)
       .add(this.renderer)
-      .add(this.layersRenderer);
+      .add(this.layersRenderer)
+      .add(this.onionSkinRenderer);
 
     // State of drawing controller:
     this.isClicked = false;
@@ -111,6 +113,12 @@
   ns.DrawingController.prototype.onUserSettingsChange_ = function (evt, settingsName, settingsValue) {
     if(settingsName == pskl.UserSettings.SHOW_GRID) {
       console.warn('DrawingController:onUserSettingsChange_ not implemented !');
+    } else if (settingsName == pskl.UserSettings.OVERLAY) {
+      this.onionSkinRenderer.clear();
+      this.onionSkinRenderer.flush();
+      this.layersRenderer.clear();
+      this.layersRenderer.flush();
+      this.render();
     }
   };
 
@@ -311,7 +319,13 @@
       this.overlayFrame = pskl.model.Frame.createEmptyFromFrame(currentFrame);
     }
 
+    var overlaySetting = pskl.UserSettings.get(pskl.UserSettings.OVERLAY);
+    if (overlaySetting === Constants.OVERLAY_ONION_SKIN) {
+      this.onionSkinRenderer.render();
+    } else if (overlaySetting === Constants.OVERLAY_LAYER_PREVIEW) {
       this.layersRenderer.render();
+    }
+
     this.renderer.render(currentFrame);
     this.overlayRenderer.render(this.overlayFrame);
   };

src/js/controller/settings/ApplicationSettingsController.js

@@ -18,9 +18,9 @@
     $('#grid-width').val(gridWidth);
     $('#grid-width').change(this.onGridWidthChange.bind(this));
 
-    var tiledPreview = pskl.UserSettings.get(pskl.UserSettings.TILED_PREVIEW);
-    $('#tiled-preview').prop('checked', tiledPreview);
-    $('#tiled-preview').change(this.onTiledPreviewChange.bind(this));
+    var overlay = pskl.UserSettings.get(pskl.UserSettings.OVERLAY);
+    $('#overlay').val(overlay);
+    $('#overlay').change(this.onOverlayChange.bind(this));
 
     // Handle canvas background changes:
     $('#background-picker-wrapper').click(this.onBackgroundClick.bind(this));
@@ -31,9 +31,9 @@
     pskl.UserSettings.set(pskl.UserSettings.GRID_WIDTH, parseInt(width, 10));
   };
 
-  ns.ApplicationSettingsController.prototype.onTiledPreviewChange = function (evt) {
-    var checked = $('#tiled-preview').prop('checked');
-    pskl.UserSettings.set(pskl.UserSettings.TILED_PREVIEW, checked);
+  ns.ApplicationSettingsController.prototype.onOverlayChange = function (evt) {
+    var overlay = $('#overlay').val();
+    pskl.UserSettings.set(pskl.UserSettings.OVERLAY, overlay);
   };
 
   ns.ApplicationSettingsController.prototype.onBackgroundClick = function (evt) {

src/js/rendering/OnionSkinRenderer.js

@@ -0,0 +1,77 @@
+(function () {
+  var ns = $.namespace('pskl.rendering');
+
+  ns.OnionSkinRenderer = function (container, renderingOptions, piskelController) {
+    pskl.rendering.CompositeRenderer.call(this);
+
+    this.piskelController = piskelController;
+
+    // Do not use CachedFrameRenderers here, since the caching will be performed in the render method of LayersRenderer
+    this.renderer = new pskl.rendering.frame.FrameRenderer(container, renderingOptions, ["onion-skin-canvas"]);
+
+    this.add(this.renderer);
+
+    this.serializedRendering = '';
+  };
+
+  pskl.utils.inherit(pskl.rendering.OnionSkinRenderer, pskl.rendering.CompositeRenderer);
+
+  ns.OnionSkinRenderer.prototype.render = function () {
+    var offset = this.getOffset();
+    var size = this.getDisplaySize();
+    var layers = this.piskelController.getLayers();
+    var currentFrameIndex = this.piskelController.getCurrentFrameIndex();
+
+    var frames = [];
+    this.addFrameAtIndexToArray_(currentFrameIndex - 1, frames);
+    this.addFrameAtIndexToArray_(currentFrameIndex + 1, frames);
+
+    var serializedRendering = [
+      this.getZoom(),
+      this.getGridWidth(),
+      offset.x,
+      offset.y,
+      size.width,
+      size.height,
+      frames.map(function (f) {
+        return f.getHash();
+      }).join('-'),
+      layers.length
+    ].join("-");
+
+
+    if (this.serializedRendering != serializedRendering) {
+      this.serializedRendering = serializedRendering;
+
+      if (frames.length > 0) {
+        this.clear();
+        var mergedFrame = pskl.utils.FrameUtils.merge(frames);
+        this.renderer.render(mergedFrame);
+      }
+    }
+  };
+
+  ns.OnionSkinRenderer.prototype.addFrameAtIndexToArray_ = function (frameIndex, frames) {
+    var layer = this.piskelController.getCurrentLayer();
+    if (this.piskelController.hasFrameAt(frameIndex)) {
+      frames.push(layer.getFrameAt(frameIndex));
+    }
+  };
+
+  /**
+   * See @pskl.rendering.frame.CachedFrameRenderer
+   * Same issue : FrameRenderer setDisplaySize destroys the canvas
+   * @param {Number} width
+   * @param {Number} height
+   */
+  ns.OnionSkinRenderer.prototype.setDisplaySize = function (width, height) {
+    var size = this.getDisplaySize();
+    if (size.width !== width || size.height !== height) {
+      this.superclass.setDisplaySize.call(this, width, height);
+    }
+  };
+
+  ns.OnionSkinRenderer.prototype.flush = function () {
+    this.serializedRendering = '';
+  };
+})();

src/js/rendering/layer/LayersRenderer.js

@@ -58,7 +58,6 @@
     }
   };
 
-
   /**
    * See @pskl.rendering.frame.CachedFrameRenderer
    * Same issue : FrameRenderer setDisplaySize destroys the canvas
@@ -78,4 +77,8 @@
     });
     return pskl.utils.FrameUtils.merge(frames);
   };
+
+  ns.LayersRenderer.prototype.flush = function () {
+    this.serializedRendering = '';
+  };
 })();

src/js/utils/UserSettings.js

@@ -6,12 +6,14 @@
     CANVAS_BACKGROUND : 'CANVAS_BACKGROUND',
     SELECTED_PALETTE : 'SELECTED_PALETTE',
     TILED_PREVIEW : 'TILED_PREVIEW',
+    OVERLAY : 'OVERLAY',
 
     KEY_TO_DEFAULT_VALUE_MAP_ : {
       'GRID_WIDTH' : 0,
       'CANVAS_BACKGROUND' : 'lowcont-dark-canvas-background',
       'SELECTED_PALETTE' : Constants.CURRENT_COLORS_PALETTE_ID,
-      'TILED_PREVIEW' : false
+      'TILED_PREVIEW' : false,
+      'OVERLAY' : Constants.OVERLAY_ONION_SKIN
     },
 
     /**

src/piskel-script-list.js

@@ -60,6 +60,7 @@
   "js/rendering/CompositeRenderer.js",
   "js/rendering/layer/LayersRenderer.js",
   "js/rendering/frame/FrameRenderer.js",
+  "js/rendering/OnionSkinRenderer.js",
   "js/rendering/frame/TiledFrameRenderer.js",
   "js/rendering/frame/CachedFrameRenderer.js",
   "js/rendering/CanvasRenderer.js",

src/templates/settings/application.html

@@ -29,6 +29,18 @@
       <option value="4">Enabled - 4px wide</option>
     </select>
   </div>
+
+  <div class="settings-title">
+    Overlay:
+  </div>
+  <div class="settings-item">
+    <label for="overlay">Display :</label>
+    <select id="overlay">
+      <option value="no-overlay">No overlay</option>
+      <option value="onion-skin">Onion skin</option>
+      <option value="layer-preview">Layer preview</option>
+    </select>
+  </div>
   <!-- <div class="settings-item">
     <label for="tiled-preview">Display tiled preview :</label>
     <input type="checkbox" value="1" id="tiled-preview" name="tiled-preview-checkbox"/>