Auto merge of #21628 - paavininanda:Current-pixel-density, r=jdm

Current pixel density

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix a subset of #11416.

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- [x] There are tests for these changes OR

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components/script/dom/htmlimageelement.rs

@@ -706,7 +706,7 @@ impl HTMLImageElement {
     }
 
     /// Step 13-17 of html.spec.whatwg.org/multipage/#update-the-image-data
-    fn prepare_image_request(&self, url: &ServoUrl, src: &DOMString) {
+    fn prepare_image_request(&self, url: &ServoUrl, src: &DOMString, selected_pixel_density: f64) {
         match self.image_request.get() {
             ImageRequestPhase::Pending => {
                 if let Some(pending_url) = self.pending_request.borrow().parsed_url.clone() {
@@ -731,15 +731,18 @@ impl HTMLImageElement {
                             // TODO: queue a task to restart animation, if restart-animation is set
                             return
                         }
+                        pending_request.current_pixel_density = Some(selected_pixel_density);
                         self.image_request.set(ImageRequestPhase::Pending);
                         self.init_image_request(&mut pending_request, &url, &src);
                     },
                     (_, State::Broken) | (_, State::Unavailable) => {
                         // Step 17
+                        current_request.current_pixel_density = Some(selected_pixel_density);
                         self.init_image_request(&mut current_request, &url, &src);
                     },
                     (_, _) => {
                         // step 17
+                        pending_request.current_pixel_density = Some(selected_pixel_density);
                         self.image_request.set(ImageRequestPhase::Pending);
                         self.init_image_request(&mut pending_request, &url, &src);
                     },
@@ -755,12 +758,9 @@ impl HTMLImageElement {
         let window = document.window();
         let task_source = window.dom_manipulation_task_source();
         let this = Trusted::new(self);
-        let src = match self.select_image_source() {
-            Some(src) => {
-                // Step 8
-                // TODO: Handle pixel density.
-                src.0
-            },
+        let (src, pixel_density) = match self.select_image_source() {
+            // Step 8
+            Some(data) => data,
             None => {
                 // Step 9.
                 // FIXME(nox): Why are errors silenced here?
@@ -816,7 +816,7 @@ impl HTMLImageElement {
         match parsed_url {
             Ok(url) => {
                 // Step 13-17
-                self.prepare_image_request(&url, &src);
+                self.prepare_image_request(&url, &src, pixel_density);
             },
             Err(_) => {
                 // Step 12.1-12.5.
@@ -1231,6 +1231,9 @@ pub trait LayoutHTMLImageElementHelpers {
     #[allow(unsafe_code)]
     unsafe fn image_url(&self) -> Option<ServoUrl>;
 
+    #[allow(unsafe_code)]
+    unsafe fn image_density(&self) -> Option<f64>;
+
     fn get_width(&self) -> LengthOrPercentageOrAuto;
     fn get_height(&self) -> LengthOrPercentageOrAuto;
 }
@@ -1246,6 +1249,11 @@ impl LayoutHTMLImageElementHelpers for LayoutDom<HTMLImageElement> {
         (*self.unsafe_get()).current_request.borrow_for_layout().parsed_url.clone()
     }
 
+    #[allow(unsafe_code)]
+    unsafe fn image_density(&self) -> Option<f64> {
+        (*self.unsafe_get()).current_request.borrow_for_layout().current_pixel_density.clone()
+    }
+
     #[allow(unsafe_code)]
     fn get_width(&self) -> LengthOrPercentageOrAuto {
         unsafe {
@@ -1350,20 +1358,22 @@ impl HTMLImageElementMethods for HTMLImageElement {
 
     // https://html.spec.whatwg.org/multipage/#dom-img-naturalwidth
     fn NaturalWidth(&self) -> u32 {
-        let ref metadata = self.current_request.borrow().metadata;
+        let request = self.current_request.borrow();
+        let pixel_density = request.current_pixel_density.unwrap_or(1f64);
 
-        match *metadata {
-            Some(ref metadata) => metadata.width,
+        match request.metadata {
+            Some(ref metadata) => (metadata.width as f64 / pixel_density) as u32,
             None => 0,
         }
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-img-naturalheight
     fn NaturalHeight(&self) -> u32 {
-        let ref metadata = self.current_request.borrow().metadata;
+        let request = self.current_request.borrow();
+        let pixel_density = request.current_pixel_density.unwrap_or(1f64);
 
-        match *metadata {
-            Some(ref metadata) => metadata.height,
+        match request.metadata {
+            Some(ref metadata) => (metadata.height as f64 / pixel_density) as u32,
             None => 0,
         }
     }

components/script/dom/node.rs

@@ -1030,6 +1030,7 @@ pub trait LayoutNodeHelpers {
     fn text_content(&self) -> String;
     fn selection(&self) -> Option<Range<usize>>;
     fn image_url(&self) -> Option<ServoUrl>;
+    fn image_density(&self) -> Option<f64>;
     fn canvas_data(&self) -> Option<HTMLCanvasData>;
     fn svg_data(&self) -> Option<SVGSVGData>;
     fn iframe_browsing_context_id(&self) -> Option<BrowsingContextId>;
@@ -1173,6 +1174,15 @@ impl LayoutNodeHelpers for LayoutDom<Node> {
         }
     }
 
+    #[allow(unsafe_code)]
+    fn image_density(&self) -> Option<f64> {
+        unsafe {
+            self.downcast::<HTMLImageElement>()
+                .expect("not an image!")
+                .image_density()
+        }
+    }
+
     fn canvas_data(&self) -> Option<HTMLCanvasData> {
         self.downcast::<HTMLCanvasElement>()
             .map(|canvas| canvas.data())