Merge pull request #30 from igagen/master

Change withImage to tryLoadImage returning Maybe to handle failure

Author: paf31

docs/Graphics/Canvas.md

@@ -65,10 +65,10 @@ Opaque object describing a gradient.
 canvasElementToImageSource :: CanvasElement -> CanvasImageSource
 ```
 
-#### `withImage`
+#### `tryLoadImage`
 
 ``` purescript
-withImage :: forall eff. String -> (CanvasImageSource -> Eff eff Unit) -> Eff eff Unit
+tryLoadImage :: forall eff. String -> (Maybe CanvasImageSource -> Eff (canvas :: Canvas | eff) Unit) -> Eff (canvas :: Canvas | eff) Unit
 ```
 
 Wrapper for asynchronously loading a image file by path and use it in callback, e.g. drawImage

src/Graphics/Canvas.js

@@ -5,16 +5,21 @@ exports.canvasElementToImageSource = function(e) {
     return e;
 };
 
-exports.withImage = function (src) {
-  return function(f) {
-        return function () {
-            var img = new Image();
-            img.src = src;
-            img.addEventListener("load", function() {
-                f(img)();
-            }, false);
-
-            return {};
+exports.tryLoadImageImpl = function (src) {
+  return function(e) {
+        return function(f) {
+            return function () {
+                var img = new Image();
+                img.src = src;
+                img.addEventListener("load", function() {
+                    f(img)();
+                }, false);
+                img.addEventListener("error", function(error) {
+                    e();
+                }, false);
+
+                return {};
+            }
         }
     };
 };

src/Graphics/Canvas.purs

@@ -84,7 +84,7 @@ module Graphics.Canvas
   , restore
   , withContext
 
-  , withImage
+  , tryLoadImage
   , getImageData
   , putImageData
   , putImageDataFull
@@ -139,8 +139,12 @@ foreign import data CanvasGradient :: *
 
 foreign import canvasElementToImageSource :: CanvasElement -> CanvasImageSource
 
+foreign import tryLoadImageImpl :: forall eff. String -> Eff (canvas :: Canvas | eff) Unit -> (CanvasImageSource -> Eff (canvas :: Canvas | eff) Unit) -> Eff (canvas :: Canvas | eff) Unit
+
 -- | Wrapper for asynchronously loading a image file by path and use it in callback, e.g. drawImage
-foreign import withImage :: forall eff. String -> (CanvasImageSource -> Eff eff Unit) -> Eff eff Unit
+tryLoadImage :: forall eff. String -> (Maybe CanvasImageSource -> Eff (canvas :: Canvas | eff) Unit) -> Eff (canvas :: Canvas | eff) Unit
+tryLoadImage path k = tryLoadImageImpl path (k Nothing) (k <<< Just)
+
 
 foreign import getCanvasElementByIdImpl ::
   forall r eff. Fn3 String