Increase accuracy of various Web APIs (#2946)

src/platform_impl/web/web_sys/canvas.rs

@@ -28,6 +28,7 @@ pub struct Canvas {
     common: Common,
     id: WindowId,
     pub has_focus: Arc<AtomicBool>,
+    pub is_intersecting: Option<bool>,
     on_touch_start: Option<EventListenerHandle<dyn FnMut(Event)>>,
     on_touch_end: Option<EventListenerHandle<dyn FnMut(Event)>>,
     on_focus: Option<EventListenerHandle<dyn FnMut(FocusEvent)>>,
@@ -97,6 +98,7 @@ impl Canvas {
             },
             id,
             has_focus: Arc::new(AtomicBool::new(false)),
+            is_intersecting: None,
             on_touch_start: None,
             on_touch_end: None,
             on_blur: None,
@@ -134,11 +136,29 @@ impl Canvas {
 
     pub fn position(&self) -> LogicalPosition<f64> {
         let bounds = self.common.raw.get_bounding_client_rect();
-
-        LogicalPosition {
+        let mut position = LogicalPosition {
             x: bounds.x(),
             y: bounds.y(),
+        };
+
+        let document = self.window().document().expect("Failed to obtain document");
+
+        if document.contains(Some(self.raw())) {
+            let style = self
+                .window()
+                .get_computed_style(self.raw())
+                .expect("Failed to obtain computed style")
+                // this can't fail: we aren't using a pseudo-element
+                .expect("Invalid pseudo-element");
+            if style.get_property_value("display").unwrap() != "none" {
+                position.x += super::style_size_property(&style, "border-left-width")
+                    + super::style_size_property(&style, "padding-left");
+                position.y += super::style_size_property(&style, "border-top-width")
+                    + super::style_size_property(&style, "padding-top");
+            }
         }
+
+        position
     }
 
     pub fn old_size(&self) -> PhysicalSize<u32> {