Add image usability checks to drawImage()

components/script/canvas_state.rs

@@ -388,6 +388,14 @@ impl CanvasState {
                 self.draw_offscreen_canvas(&canvas, htmlcanvas, sx, sy, sw, sh, dx, dy, dw, dh)
             },
             CanvasImageSource::HTMLImageElement(ref image) => {
+                // https://html.spec.whatwg.org/multipage/#drawing-images
+                // 2. Let usability be the result of checking the usability of image.
+                // 3. If usability is bad, then return (without drawing anything).
+                if !image.is_usable()? {
+                    return Ok(());
+                }
+
+                // TODO(pylbrecht): is it possible for image.get_url() to return None after the usability check?
                 // https://html.spec.whatwg.org/multipage/#img-error
                 // If the image argument is an HTMLImageElement object that is in the broken state,
                 // then throw an InvalidStateError exception

components/script/dom/htmlimageelement.rs

@@ -13,7 +13,7 @@ use crate::dom::bindings::codegen::Bindings::HTMLImageElementBinding::HTMLImageE
 use crate::dom::bindings::codegen::Bindings::MouseEventBinding::MouseEventMethods;
 use crate::dom::bindings::codegen::Bindings::NodeBinding::NodeBinding::NodeMethods;
 use crate::dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
-use crate::dom::bindings::error::Fallible;
+use crate::dom::bindings::error::{Error, Fallible};
 use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::refcounted::Trusted;
 use crate::dom::bindings::reflector::DomObject;
@@ -164,6 +164,26 @@ impl HTMLImageElement {
     pub fn get_url(&self) -> Option<ServoUrl> {
         self.current_request.borrow().parsed_url.clone()
     }
+    // https://html.spec.whatwg.org/multipage/#check-the-usability-of-the-image-argument
+    pub fn is_usable(&self) -> Fallible<bool> {
+        // If image has an intrinsic width or intrinsic height (or both) equal to zero, then return bad.
+        match &self.current_request.borrow().image {
+            Some(image) => {
+                if image.width == 0 || image.height == 0 {
+                    return Ok(false);
+                }
+            },
+            None => return Ok(false),
+        }
+
+        match self.current_request.borrow().state {
+            // If image's current request's state is broken, then throw an "InvalidStateError" DOMException.
+            State::Broken => Err(Error::InvalidState),
+            State::CompletelyAvailable => Ok(true),
+            // If image is not fully decodable, then return bad.
+            State::PartiallyAvailable | State::Unavailable => Ok(false),
+        }
+    }
 }
 
 /// The context required for asynchronously loading an external image.

tests/wpt/metadata/2dcontext/drawing-images-to-the-canvas/drawimage_html_image.html.ini

@@ -1,8 +1,5 @@
 [drawimage_html_image.html]
   type: testharness
-  [Draw 100x100 image to 100x100 canvas at 0,0.]
-    expected: FAIL
-
   [Test scenario 12: sx = -20, sy = -20, sw = 50, sh = 50, dx = 20, dy = 20, dw = 125, dh = 125 --- Pixel 70,99 should be light purple.]
     expected: FAIL