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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,68 +1,54 @@ | ||
| let FRAME: HTMLIFrameElement | null = null; | ||
| import { HTML_PROPERTIES } from "./html-properties"; | ||
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|
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| /** | ||
| * Given an element, returns any attributes that have a cause a visual change. | ||
| * This works by copying the element to an iframe without any styles and | ||
| * testing the computed styles while toggling the attributes. | ||
| * This works by checking against a whitelist of known visual properties, and | ||
| * their related attribute name. | ||
| */ | ||
| export function getVisualAttributes(el: Element) { | ||
| let visualAttributes: Array<{ name: string; value: string }> | null = null; | ||
| const document = el.ownerDocument!; | ||
| FRAME = FRAME || document.createElement("iframe"); | ||
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| document.body.appendChild(FRAME); | ||
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| const contentDocument = FRAME.contentDocument!; | ||
| const contentWindow = contentDocument.defaultView!; | ||
| const clone = contentDocument.importNode(el, false); | ||
| const { attributes } = clone; | ||
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| contentDocument.body.appendChild(clone); | ||
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| const defaultStyles = contentWindow.getComputedStyle(clone); | ||
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| for (let i = attributes.length; i--; ) { | ||
| const attr = attributes[i]; | ||
|
|
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| if (attr.name === "style") { | ||
| continue; | ||
| let visualAttributes: Array<{ | ||
| name: string; | ||
| value: string | boolean | null; | ||
| }> | null = null; | ||
| if (!el.namespaceURI || el.namespaceURI === "http://www.w3.org/1999/xhtml") { | ||
| // For HTML elements we look at a whitelist of properties and compare against the default value. | ||
| const defaults = el.ownerDocument!.createElement(el.localName); | ||
|
|
||
| for (const prop in HTML_PROPERTIES) { | ||
| const { alias, tests } = HTML_PROPERTIES[ | ||
| prop as keyof typeof HTML_PROPERTIES | ||
| ]; | ||
| const name = alias || prop; | ||
| const value = el[prop]; | ||
|
|
||
| if (value !== defaults[prop]) { | ||
| for (const test of tests) { | ||
| if (test(el)) { | ||
| (visualAttributes || (visualAttributes = [])).push({ name, value }); | ||
| break; | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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| clone.removeAttributeNode(attr); | ||
|
|
||
| if ( | ||
| !computedStylesEqual(defaultStyles, contentWindow.getComputedStyle(clone)) | ||
| ) { | ||
| (visualAttributes || (visualAttributes = [])).push({ | ||
| name: attr.name, | ||
| value: attr.value | ||
| }); | ||
| } else { | ||
| // For other namespaces we assume all attributes are visual, except for a blacklist. | ||
| const { attributes } = el; | ||
|
|
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| for (let i = 0, len = attributes.length; i < len; i++) { | ||
| const { name, value } = attributes[i]; | ||
|
|
||
| if ( | ||
| !( | ||
| (el.localName === "a" && /^(?:xmlns:)?href$/i.test(name)) || | ||
| /^(?:class|id|style|lang|target|xmlns(?::.+)?|xlink:(?!href).+|xml:(?:lang|base)|on*|aria-*|data-*)$/i.test( | ||
| name | ||
| ) | ||
| ) | ||
| ) { | ||
| (visualAttributes || (visualAttributes = [])).push({ name, value }); | ||
| } | ||
| } | ||
|
|
||
| clone.setAttributeNode(attr); | ||
| } | ||
|
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| contentDocument.body.removeChild(clone); | ||
| document.body.removeChild(FRAME); | ||
|
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| return visualAttributes; | ||
| } | ||
|
|
||
| /** | ||
| * Checks if two CSSStyleDeclarations have the same styles applied. | ||
| */ | ||
| function computedStylesEqual(a: CSSStyleDeclaration, b: CSSStyleDeclaration) { | ||
| if (a.length !== b.length) { | ||
| return false; | ||
| } | ||
|
|
||
| for (let i = a.length; i--; ) { | ||
| const name = a[i]; | ||
|
|
||
| if (a[name] !== b[name]) { | ||
| return false; | ||
| } | ||
| } | ||
|
|
||
| return true; | ||
| } |
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