Add initial support for background shorthand property (#277)

Siteimprove · Jun 25, 2020 · ae2b659 · ae2b659
1 parent eb78e06
commit ae2b659
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Showing 3 changed files with 21 additions and 8 deletions.
diff --git a/packages/alfa-style/src/property.ts b/packages/alfa-style/src/property.ts
@@ -198,6 +198,7 @@ export namespace Property {
 
     type Registered = typeof Registered;
     const Registered = {
+      background: Background.Shorthand,
       overflow: Overflow.Shorthand,
     };
 

diff --git a/packages/alfa-style/src/property/background.ts b/packages/alfa-style/src/property/background.ts
@@ -15,6 +15,7 @@ import {
 } from "@siteimprove/alfa-css";
 import { Iterable } from "@siteimprove/alfa-iterable";
 import { Parser } from "@siteimprove/alfa-parser";
+import { Record } from "@siteimprove/alfa-record";
 
 import * as css from "@siteimprove/alfa-css";
 
@@ -33,6 +34,9 @@ export namespace Background {
     export type Computed = RGB<Percentage, Percentage> | Current | System;
   }
 
+  /**
+   * @see https://drafts.csswg.org/css-backgrounds/#background-color
+   */
   export const Color: Property<
     Color.Specified,
     Color.Computed
@@ -66,6 +70,9 @@ export namespace Background {
     >;
   }
 
+  /**
+   * @see https://drafts.csswg.org/css-backgrounds/#background-image
+   */
   export const Image: Property<Image.Specified, Image.Computed> = Property.of(
     List.of([Keyword.of("none")], ", "),
     map(
@@ -91,6 +98,19 @@ export namespace Background {
         )
       )
   );
+
+  /**
+   * @see https://drafts.csswg.org/css-backgrounds/#background
+   */
+  export const Shorthand = Property.Shorthand.of(
+    ["background-image", "background-color"],
+    map(Color.parse, (color) => {
+      return Record.of({
+        "background-color": color,
+        "background-image": Image.initial as Image.Specified,
+      });
+    })
+  );
 }
 
 function resolveImage(image: Image, style: Style) {

diff --git a/packages/alfa-style/src/style.ts b/packages/alfa-style/src/style.ts
@@ -56,10 +56,6 @@ export class Style implements Serializable {
       const { name, value } = declaration;
 
       if (Property.isName(name)) {
-        if (this._cascaded.has(name)) {
-          continue;
-        }
-
         const property = Property.get(name);
 
         for (const result of parse(property, value)) {
@@ -72,10 +68,6 @@ export class Style implements Serializable {
 
         for (const result of parseShorthand(shorthand, value)) {
           for (const [name, value] of result) {
-            if (this._cascaded.has(name)) {
-              continue;
-            }
-
             this._cascaded.set(name, Value.of(value, Option.of(declaration)));
           }
         }