Merge pull request #512 from kchadha/skin-empty-image-data

Add Support for Empty Skins

src/BitmapSkin.js

@@ -56,7 +56,7 @@ class BitmapSkin extends Skin {
      */
     // eslint-disable-next-line no-unused-vars
     getTexture (scale) {
-        return this._texture;
+        return this._texture || super.getTexture();
     }
 
     /**
@@ -78,6 +78,10 @@ class BitmapSkin extends Skin {
      * @fires Skin.event:WasAltered
      */
     setBitmap (bitmapData, costumeResolution, rotationCenter) {
+        if (!bitmapData.width || !bitmapData.height) {
+            super.setEmptyImageData();
+            return;
+        }
         const gl = this._renderer.gl;
 
         // Preferably bitmapData is ImageData. ImageData speeds up updating

src/SVGSkin.js

@@ -66,6 +66,10 @@ class SVGSkin extends Skin {
      */
     // eslint-disable-next-line no-unused-vars
     getTexture (scale) {
+        if (!this._svgRenderer.canvas.width || !this._svgRenderer.canvas.height) {
+            return super.getTexture();
+        }
+
         // The texture only ever gets uniform scale. Take the larger of the two axes.
         const scaleMax = scale ? Math.max(Math.abs(scale[0]), Math.abs(scale[1])) : 100;
         const requestedScale = Math.min(scaleMax / 100, this._maxTextureScale);
@@ -108,6 +112,12 @@ class SVGSkin extends Skin {
             // updating Silhouette and is better handled by more browsers in
             // regards to memory.
             const canvas = this._svgRenderer.canvas;
+
+            if (!canvas.width || !canvas.height) {
+                super.setEmptyImageData();
+                return;
+            }
+
             const context = canvas.getContext('2d');
             const textureData = context.getImageData(0, 0, canvas.width, canvas.height);
 

src/Skin.js

@@ -140,7 +140,7 @@ class Skin extends EventEmitter {
      */
     // eslint-disable-next-line no-unused-vars
     getTexture (scale) {
-        return null;
+        return this._emptyImageTexture;
     }
 
     /**
@@ -171,6 +171,38 @@ class Skin extends EventEmitter {
      */
     updateSilhouette () {}
 
+    /**
+     * Set the contents of this skin to an empty skin.
+     * @fires Skin.event:WasAltered
+     */
+    setEmptyImageData () {
+        // Free up the current reference to the _texture
+        this._texture = null;
+
+        if (!this._emptyImageData) {
+            // Create a transparent pixel
+            this._emptyImageData = new ImageData(1, 1);
+
+            // Create a new texture and update the silhouette
+            const gl = this._renderer.gl;
+
+            const textureOptions = {
+                auto: true,
+                wrap: gl.CLAMP_TO_EDGE,
+                src: this._emptyImageData
+            };
+
+            // Note: we're using _emptyImageTexture here instead of _texture
+            // so that we can cache this empty texture for later use as needed.
+            // this._texture can get modified by other skins (e.g. BitmapSkin
+            // and SVGSkin, so we can't use that same field for caching)
+            this._emptyImageTexture = twgl.createTexture(gl, textureOptions);
+        }
+
+        this._silhouette.update(this._emptyImageData);
+        this.emit(Skin.Events.WasAltered);
+    }
+
     /**
      * Does this point touch an opaque or translucent point on this skin?
      * Nearest Neighbor version