Auto merge of #20012 - alexfjw:avoid_Window-GetComputedStyle_when_che…

…cking_for_display-none, r=emilio

Avoid `Window::GetComputedStyle` when checking for `display: none`

<!-- Please describe your changes on the following line: -->
Refactored Window::GetComputedStyle to use Element::Style.

Not sure which tests are relevant, but I've ran the dom, fetch & 2dcontext wpt tests. They don't seem to give errors.

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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 #19885.

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- [x] These changes do not require tests because it's a refactoring task

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components/script/dom/canvasrenderingcontext2d.rs

@@ -9,15 +9,13 @@ use canvas_traits::canvas::{RadialGradientStyle, RepetitionStyle, byte_swap_and_
 use cssparser::{Parser, ParserInput, RGBA};
 use cssparser::Color as CSSColor;
 use dom::bindings::cell::DomRefCell;
-use dom::bindings::codegen::Bindings::CSSStyleDeclarationBinding::CSSStyleDeclarationMethods;
 use dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding;
 use dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::CanvasFillRule;
 use dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::CanvasImageSource;
 use dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::CanvasLineCap;
 use dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::CanvasLineJoin;
 use dom::bindings::codegen::Bindings::CanvasRenderingContext2DBinding::CanvasRenderingContext2DMethods;
 use dom::bindings::codegen::Bindings::ImageDataBinding::ImageDataMethods;
-use dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
 use dom::bindings::codegen::UnionTypes::StringOrCanvasGradientOrCanvasPattern;
 use dom::bindings::error::{Error, ErrorResult, Fallible};
 use dom::bindings::inheritance::Castable;
@@ -27,6 +25,7 @@ use dom::bindings::root::{Dom, DomRoot, LayoutDom};
 use dom::bindings::str::DOMString;
 use dom::canvasgradient::{CanvasGradient, CanvasGradientStyle, ToFillOrStrokeStyle};
 use dom::canvaspattern::CanvasPattern;
+use dom::element::Element;
 use dom::globalscope::GlobalScope;
 use dom::htmlcanvaselement::HTMLCanvasElement;
 use dom::imagedata::ImageData;
@@ -543,18 +542,11 @@ impl CanvasRenderingContext2D {
                         Some(ref canvas) => &**canvas,
                     };
 
-                    let window = window_from_node(canvas);
+                    let canvas_element = canvas.upcast::<Element>();
 
-                    let style = window.GetComputedStyle(canvas.upcast(), None);
-
-                    let element_not_rendered =
-                        !canvas.upcast::<Node>().is_in_doc() ||
-                        style.GetPropertyValue(DOMString::from("display")) == "none";
-
-                    if element_not_rendered {
-                        Ok(RGBA::new(0, 0, 0, 255))
-                    } else {
-                        self.parse_color(&style.GetPropertyValue(DOMString::from("color")))
+                    match canvas_element.style() {
+                        Some(ref s) if canvas_element.has_css_layout_box() => Ok(s.get_color().color),
+                        _ => Ok(RGBA::new(0, 0, 0, 255))
                     }
                 },
                 _ => Err(())

components/script/dom/element.rs

@@ -350,14 +350,14 @@ impl Element {
 
     /// style will be `None` for elements in a `display: none` subtree. otherwise, the element has a
     /// layout box iff it doesn't have `display: none`.
-    fn style(&self) -> Option<Arc<ComputedValues>> {
+    pub fn style(&self) -> Option<Arc<ComputedValues>> {
         window_from_node(self).style_query(
             self.upcast::<Node>().to_trusted_node_address()
         )
     }
 
     // https://drafts.csswg.org/cssom-view/#css-layout-box
-    fn has_css_layout_box(&self) -> bool {
+    pub fn has_css_layout_box(&self) -> bool {
         self.style()
             .map_or(false, |s| !s.get_box().clone_display().is_none())
     }

components/script/script_thread.rs

@@ -25,7 +25,6 @@ use devtools_traits::{ScriptToDevtoolsControlMsg, WorkerId};
 use devtools_traits::CSSError;
 use document_loader::DocumentLoader;
 use dom::bindings::cell::DomRefCell;
-use dom::bindings::codegen::Bindings::CSSStyleDeclarationBinding::CSSStyleDeclarationMethods;
 use dom::bindings::codegen::Bindings::DocumentBinding::{DocumentMethods, DocumentReadyState};
 use dom::bindings::codegen::Bindings::EventBinding::EventInit;
 use dom::bindings::codegen::Bindings::TransitionEventBinding::TransitionEventInit;
@@ -1955,7 +1954,7 @@ impl ScriptThread {
         node.dirty(NodeDamage::NodeStyleDamaged);
 
         if let Some(el) = node.downcast::<Element>() {
-            if &*window.GetComputedStyle(el, None).Display() == "none" {
+            if !el.has_css_layout_box() {
                 return;
             }
         }