Auto merge of #10034 - rilut:implement-elementsfrompoint, r=emilio

Implement Document#elementsFromPoint

Fixes #9859.

I'm trying to implement Document#elementsFromPoint, which I need to reuse the `get_nodes_under_mouse` and `mouse_over` function which have been removed a days ago in #9715. So I added it back while I'm not sure if my implementation is correct. Any advice will be greatly appreciated.

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components/layout/query.rs

@@ -20,6 +20,7 @@ use script::layout_interface::{ContentBoxResponse, ContentBoxesResponse, NodeGeo
 use script::layout_interface::{HitTestResponse, LayoutRPC, OffsetParentResponse};
 use script::layout_interface::{ResolvedStyleResponse, ScriptLayoutChan, MarginStyleResponse};
 use script_traits::LayoutMsg as ConstellationMsg;
+use script_traits::UntrustedNodeAddress;
 use sequential;
 use std::cmp::{min, max};
 use std::ops::Deref;
@@ -85,6 +86,24 @@ impl LayoutRPC for LayoutRPCImpl {
         }
     }
 
+    fn nodes_from_point(&self, point: Point2D<f32>) -> Vec<UntrustedNodeAddress> {
+        let point = Point2D::new(Au::from_f32_px(point.x), Au::from_f32_px(point.y));
+        let nodes_from_point_list = {
+            let &LayoutRPCImpl(ref rw_data) = self;
+            let rw_data = rw_data.lock().unwrap();
+            let result = match rw_data.display_list {
+                None => panic!("Tried to hit test without a DisplayList"),
+                Some(ref display_list) => display_list.hit_test(point),
+            };
+
+            result
+        };
+
+        nodes_from_point_list.iter()
+           .map(|metadata| metadata.node.to_untrusted_node_address())
+           .collect()
+    }
+
     fn node_geometry(&self) -> NodeGeometryResponse {
         let &LayoutRPCImpl(ref rw_data) = self;
         let rw_data = rw_data.lock().unwrap();

components/script/dom/document.rs

@@ -94,6 +94,7 @@ use net_traits::response::HttpsState;
 use net_traits::{AsyncResponseTarget, PendingAsyncLoad};
 use num::ToPrimitive;
 use script_thread::{MainThreadScriptChan, MainThreadScriptMsg, Runnable, ScriptChan};
+use script_traits::UntrustedNodeAddress;
 use script_traits::{AnimationState, MouseButton, MouseEventType, MozBrowserEvent};
 use script_traits::{ScriptMsg as ConstellationMsg, ScriptToCompositorMsg};
 use script_traits::{TouchEventType, TouchId};
@@ -1480,6 +1481,12 @@ impl Document {
 
         self.browsing_context.is_none() || !url_has_network_scheme(&self.url)
     }
+
+    pub fn nodes_from_point(&self, page_point: &Point2D<f32>) -> Vec<UntrustedNodeAddress> {
+        assert!(self.GetDocumentElement().is_some());
+
+        self.window.layout().nodes_from_point(*page_point)
+    }
 }
 
 #[derive(PartialEq, HeapSizeOf)]
@@ -2601,6 +2608,40 @@ impl DocumentMethods for Document {
             None => self.GetDocumentElement()
         }
     }
+
+    #[allow(unsafe_code)]
+    // https://drafts.csswg.org/cssom-view/#dom-document-elementsfrompoint
+    fn ElementsFromPoint(&self, x: Finite<f64>, y: Finite<f64>) -> Vec<Root<Element>> {
+        let x = *x as f32;
+        let y = *y as f32;
+        let point = &Point2D { x: x, y: y };
+        let window = window_from_node(self);
+        let viewport = window.window_size().unwrap().visible_viewport;
+
+        // Step 2
+        if x < 0.0 || y < 0.0 || x > viewport.width.get() || y > viewport.height.get() {
+            return vec!();
+        }
+
+        let js_runtime = unsafe { JS_GetRuntime(window.get_cx()) };
+
+        // Step 1 and Step 3
+        let mut elements: Vec<Root<Element>> = self.nodes_from_point(point).iter()
+            .flat_map(|&untrusted_node_address| {
+                let node = node::from_untrusted_node_address(js_runtime, untrusted_node_address);
+                Root::downcast::<Element>(node)
+        }).collect();
+
+        // Step 4
+        if let Some(root_element) = self.GetDocumentElement() {
+            if elements.last() != Some(&root_element) {
+                elements.push(root_element);
+            }
+        }
+
+        // Step 5
+        elements
+    }
 }
 
 fn is_scheme_host_port_tuple(url: &Url) -> bool {
@@ -2672,3 +2713,4 @@ pub enum FocusEventType {
     Focus,      // Element gained focus. Doesn't bubble.
     Blur,       // Element lost focus. Doesn't bubble.
 }
+

components/script/dom/webidls/Document.webidl

@@ -184,6 +184,7 @@ partial interface Document {
 // https://drafts.csswg.org/cssom-view/#dom-document-elementfrompoint
 partial interface Document {
   Element? elementFromPoint(double x, double y);
+  sequence<Element> elementsFromPoint(double x, double y);
 };
 
 // https://drafts.csswg.org/cssom/#extensions-to-the-document-interface

components/script/layout_interface.rs

@@ -113,6 +113,8 @@ pub trait LayoutRPC {
     fn offset_parent(&self) -> OffsetParentResponse;
     /// Query layout for the resolve values of the margin properties for an element.
     fn margin_style(&self) -> MarginStyleResponse;
+
+    fn nodes_from_point(&self, point: Point2D<f32>) -> Vec<UntrustedNodeAddress>;
 }
 
 #[derive(Clone)]

tests/wpt/include.ini

@@ -55,3 +55,5 @@ skip: true
   skip: false
 [WebIDL]
   skip: false
+[cssom-view]
+  skip: false

tests/wpt/metadata/cssom-view/elementsFromPoint.html.ini

@@ -0,0 +1,17 @@
+[elementsFromPoint.html]
+  type: testharness
+  [co-ordinates larger than the viewport from in iframe]
+    expected: FAIL
+
+  [SVG element at x,y]
+    expected: FAIL
+
+  [transformed element at x,y]
+    expected: FAIL
+
+  [no hit target at x,y]
+    expected: FAIL
+
+  [No viewport available]
+    expected: FAIL
+

tests/wpt/metadata/cssom-view/scrollingElement.html.ini

@@ -0,0 +1,5 @@
+[scrollingElement.html]
+  type: testharness
+  [Tests for scrollingElement]
+    expected: FAIL
+