servo: Merge #15821 - Implement ImageData constructors #15671 -- 1 (from montrivo:ImDataConstructors); r=Ms2ger

<!-- Please describe your changes on the following line: -->
Implement ImageData constructors
* new constructors in the imagedata.rs file
* modification of the ImageData::new method
* new method ImageData::from_vec
* new wpt test file imagedata.html

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes affect #15671  (github issue number if applicable).

<!-- Either: -->
- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

Source-Repo: https://github.com/servo/servo
Source-Revision: 5bfa87a8e27e125fced2c8824e3ce784f8dc5405

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : c2dae4fb25b6bc9915a30f93721364af10596407

servo/components/script/dom/imagedata.rs

@@ -5,6 +5,7 @@
 use core::nonzero::NonZero;
 use dom::bindings::codegen::Bindings::ImageDataBinding;
 use dom::bindings::codegen::Bindings::ImageDataBinding::ImageDataMethods;
+use dom::bindings::error::{Fallible, Error};
 use dom::bindings::js::Root;
 use dom::bindings::reflector::{Reflector, reflect_dom_object};
 use dom::globalscope::GlobalScope;
@@ -28,14 +29,7 @@ pub struct ImageData {
 impl ImageData {
     #[allow(unsafe_code)]
     pub fn new(global: &GlobalScope, width: u32, height: u32, mut data: Option<Vec<u8>>) -> Root<ImageData> {
-        let imagedata = box ImageData {
-            reflector_: Reflector::new(),
-            width: width,
-            height: height,
-            data: Heap::default(),
-        };
         let len = width * height * 4;
-
         unsafe {
             let cx = global.get_cx();
             rooted!(in (cx) let mut js_object = ptr::null_mut());
@@ -47,11 +41,88 @@ impl ImageData {
                 None => CreateWith::Length(len),
             };
             Uint8ClampedArray::create(cx, data, js_object.handle_mut()).unwrap();
-            (*imagedata).data.set(js_object.get());
+            Self::new_with_jsobject(global, width, Some(height), Some(js_object.get())).unwrap()
+        }
+    }
+
+    #[allow(unsafe_code)]
+    unsafe fn new_with_jsobject(global: &GlobalScope,
+                                width: u32,
+                                mut opt_height: Option<u32>,
+                                opt_jsobject: Option<*mut JSObject>)
+                                -> Fallible<Root<ImageData>> {
+        assert!(opt_jsobject.is_some() || opt_height.is_some());
+
+        if width == 0 {
+            return Err(Error::IndexSize);
         }
 
-        reflect_dom_object(imagedata,
-                           global, ImageDataBinding::Wrap)
+        // checking jsobject type and verifying (height * width * 4 == jsobject.byte_len())
+        if let Some(jsobject) = opt_jsobject {
+            let cx = global.get_cx();
+            typedarray!(in(cx) let array_res: Uint8ClampedArray = jsobject);
+            let mut array = try!(array_res
+                .map_err(|_| Error::Type("Argument to Image data is not an Uint8ClampedArray".to_owned())));
+
+            let byte_len = array.as_slice().len() as u32;
+            if byte_len % 4 != 0 {
+                return Err(Error::InvalidState);
+            }
+
+            let len = byte_len / 4;
+            if width == 0 || len % width != 0 {
+                return Err(Error::IndexSize);
+            }
+
+            let height = len / width;
+            if opt_height.map_or(false, |x| height != x) {
+                return Err(Error::IndexSize);
+            } else {
+                opt_height = Some(height);
+            }
+        }
+
+        let height = opt_height.unwrap();
+        if height == 0 {
+            return Err(Error::IndexSize);
+        }
+
+        let imagedata = box ImageData {
+            reflector_: Reflector::new(),
+            width: width,
+            height: height,
+            data: Heap::default(),
+        };
+
+        if let Some(jsobject) = opt_jsobject {
+            (*imagedata).data.set(jsobject);
+        } else {
+            let len = width * height * 4;
+            let cx = global.get_cx();
+            rooted!(in (cx) let mut array = ptr::null_mut());
+            Uint8ClampedArray::create(cx, CreateWith::Length(len), array.handle_mut()).unwrap();
+            (*imagedata).data.set(array.get());
+        }
+
+        Ok(reflect_dom_object(imagedata, global, ImageDataBinding::Wrap))
+    }
+
+    // https://html.spec.whatwg.org/multipage/#pixel-manipulation:dom-imagedata-3
+    #[allow(unsafe_code)]
+    pub fn Constructor(global: &GlobalScope, width: u32, height: u32) -> Fallible<Root<Self>> {
+        unsafe { Self::new_with_jsobject(global, width, Some(height), None) }
+    }
+
+    // https://html.spec.whatwg.org/multipage/#pixel-manipulation:dom-imagedata-4
+    #[allow(unsafe_code)]
+    #[allow(unused_variables)]
+    pub unsafe fn Constructor_(cx: *mut JSContext,
+                               global: &GlobalScope,
+                               jsobject: *mut JSObject,
+                               width: u32,
+                               opt_height: Option<u32>)
+                               -> Fallible<Root<Self>> {
+        Self::new_with_jsobject(global, width, opt_height, Some(jsobject))
     }
 
     #[allow(unsafe_code)]

servo/components/script/dom/webidls/ImageData.webidl

@@ -9,9 +9,9 @@
  * You are granted a license to use, reproduce and create derivative works of this document.
  */
 
-//[Constructor(unsigned long sw, unsigned long sh),
-//Constructor(Uint8ClampedArray data, unsigned long sw, optional unsigned long sh),
-[Exposed=(Window,Worker)]
+[Constructor(unsigned long sw, unsigned long sh),
+ Constructor(/* Uint8ClampedArray */ object data, unsigned long sw, optional unsigned long sh),
+ Exposed=(Window,Worker)]
 interface ImageData {
   //[Constant]
   readonly attribute unsigned long width;