Add image usability checks to drawImage()

1 files changed, 21 insertions, 1 deletions

diff --git a/components/script/dom/htmlimageelement.rs b/components/script/dom/htmlimageelement.rs
index 59238ca6545..1cfecef1728 100644
--- a/components/script/dom/htmlimageelement.rs
+++ b/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.