fix: adopted stylesheets (#2785)

Author: niklasvh

src/dom/document-cloner.ts

@@ -2,12 +2,14 @@ import {Bounds} from '../css/layout/bounds';
 import {
     isBodyElement,
     isCanvasElement,
+    isCustomElement,
     isElementNode,
     isHTMLElementNode,
     isIFrameElement,
     isImageElement,
     isScriptElement,
     isSelectElement,
+    isSlotElement,
     isStyleElement,
     isSVGElementNode,
     isTextareaElement,
@@ -63,7 +65,7 @@ export class DocumentCloner {
             throw new Error('Cloned element does not have an owner document');
         }
 
-        this.documentElement = this.cloneNode(element.ownerDocument.documentElement) as HTMLElement;
+        this.documentElement = this.cloneNode(element.ownerDocument.documentElement, false) as HTMLElement;
     }
 
     toIFrame(ownerDocument: Document, windowSize: Bounds): Promise<HTMLIFrameElement> {
@@ -160,6 +162,17 @@ export class DocumentCloner {
             }
         }
 
+        if (isCustomElement(clone)) {
+            return this.createCustomElementClone(clone);
+        }
+
+        return clone;
+    }
+
+    createCustomElementClone(node: HTMLElement): HTMLElement {
+        const clone = document.createElement('html2canvascustomelement');
+        copyCSSStyles(node.style, clone);
+
         return clone;
     }
 
@@ -231,7 +244,20 @@ export class DocumentCloner {
         return clonedCanvas;
     }
 
-    cloneNode(node: Node): Node {
+    appendChildNode(clone: HTMLElement | SVGElement, child: Node, copyStyles: boolean): void {
+        if (
+            !isElementNode(child) ||
+            (!isScriptElement(child) &&
+                !child.hasAttribute(IGNORE_ATTRIBUTE) &&
+                (typeof this.options.ignoreElements !== 'function' || !this.options.ignoreElements(child)))
+        ) {
+            if (!this.options.copyStyles || !isElementNode(child) || !isStyleElement(child)) {
+                clone.appendChild(this.cloneNode(child, copyStyles));
+            }
+        }
+    }
+
+    cloneNode(node: Node, copyStyles: boolean): Node {
         if (isTextNode(node)) {
             return document.createTextNode(node.data);
         }
@@ -260,16 +286,22 @@ export class DocumentCloner {
             const counters = this.counters.parse(new CSSParsedCounterDeclaration(this.context, style));
             const before = this.resolvePseudoContent(node, clone, styleBefore, PseudoElementType.BEFORE);
 
-            for (let child = node.firstChild; child; child = child.nextSibling) {
-                if (
-                    !isElementNode(child) ||
-                    (!isScriptElement(child) &&
-                        !child.hasAttribute(IGNORE_ATTRIBUTE) &&
-                        (typeof this.options.ignoreElements !== 'function' || !this.options.ignoreElements(child)))
-                ) {
-                    if (!this.options.copyStyles || !isElementNode(child) || !isStyleElement(child)) {
-                        clone.appendChild(this.cloneNode(child));
+            if (isCustomElement(node)) {
+                copyStyles = true;
+            }
+
+            for (
+                let child = node.shadowRoot ? node.shadowRoot.firstChild : node.firstChild;
+                child;
+                child = child.nextSibling
+            ) {
+                if (isElementNode(child) && isSlotElement(child) && typeof child.assignedNodes === 'function') {
+                    const assignedNodes = child.assignedNodes() as ChildNode[];
+                    if (assignedNodes.length) {
+                        assignedNodes.forEach((assignedNode) => this.appendChildNode(clone, assignedNode, copyStyles));
                     }
+                } else {
+                    this.appendChildNode(clone, child, copyStyles);
                 }
             }
 
@@ -284,7 +316,10 @@ export class DocumentCloner {
 
             this.counters.pop(counters);
 
-            if (style && (this.options.copyStyles || isSVGElementNode(node)) && !isIFrameElement(node)) {
+            if (
+                (style && (this.options.copyStyles || isSVGElementNode(node)) && !isIFrameElement(node)) ||
+                copyStyles
+            ) {
                 copyCSSStyles(style, clone);
             }
 

src/dom/node-parser.ts

@@ -131,3 +131,5 @@ export const isScriptElement = (node: Element): node is HTMLScriptElement => nod
 export const isTextareaElement = (node: Element): node is HTMLTextAreaElement => node.tagName === 'TEXTAREA';
 export const isSelectElement = (node: Element): node is HTMLSelectElement => node.tagName === 'SELECT';
 export const isSlotElement = (node: Element): node is HTMLSlotElement => node.tagName === 'SLOT';
+// https://html.spec.whatwg.org/multipage/custom-elements.html#valid-custom-element-name
+export const isCustomElement = (node: Element): node is HTMLElement => node.tagName.indexOf('-') > 0;

tests/reftests/webcomponents/autonomous-custom-element.js

@@ -40,6 +40,10 @@ class AutonomousCustomElement extends HTMLElement {
         wrapper.appendChild(img);
         wrapper.appendChild(info);
     }
+
+    connectedCallback() {
+        this.shadowRoot.adoptedStyleSheets = [sheet];
+    }
 }
 
 customElements.define('autonomous-custom-element', AutonomousCustomElement);

tests/reftests/webcomponents/webcomponents.html

@@ -3,10 +3,11 @@
 <head>
     <title>Web components tests</title>
     <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
+    <script>
+        const sheet = new CSSStyleSheet();
+        sheet.replaceSync('* { color: red !important; }')
+    </script>
     <script type="text/javascript" src="../../test.js"></script>
-    <style>
-
-    </style>
 </head>
 <body>
 <div>