callout+infobox fixes

scss/westgate/_wiki-prose.scss

@@ -246,6 +246,12 @@
 	text-shadow: 0 0 10px rgba(194, 163, 90, 0.28);
 }
 
+.westgate-wiki .wiki-article-prose .wiki-callout::after,
+.westgate-wiki-compose .wiki-editor__content .wiki-callout::after {
+	mask-mode: alpha;
+	-webkit-mask-mode: alpha;
+}
+
 .westgate-wiki .wiki-article-prose :where(h1, h2, h3, h4),
 .westgate-wiki-compose .wiki-article-prose .ck.ck-editor__editable_inline.ck-content :where(h1, h2, h3, h4),
 .westgate-wiki-compose .ck.ck-editor__editable_inline.wiki-article-prose.ck-content :where(h1, h2, h3, h4) {

tests/wiki-callout-icon-theme.test.js

@@ -0,0 +1,45 @@
+const assert = require("assert");
+const fs = require("fs");
+const path = require("path");
+
+const stylesheet = fs.readFileSync(
+	path.join(__dirname, "..", "scss", "westgate", "_wiki-prose.scss"),
+	"utf8"
+);
+
+function ruleHasDeclaration(selector, declaration) {
+	const rulePattern = /([^{}]+)\{([^{}]*)\}/g;
+	let match;
+	while ((match = rulePattern.exec(stylesheet)) !== null) {
+		const selectors = match[1].split(",").map(value => value.trim());
+		const body = match[2];
+		if (selectors.includes(selector) && body.includes(declaration)) {
+			return true;
+		}
+	}
+	return false;
+}
+
+[
+	".westgate-wiki .wiki-article-prose .wiki-callout::after",
+	".westgate-wiki-compose .wiki-editor__content .wiki-callout::after",
+].forEach(selector => {
+	assert(
+		ruleHasDeclaration(selector, "mask-mode: alpha"),
+		`${selector} should force alpha mask rendering without changing the plugin's icon color`
+	);
+	assert(
+		ruleHasDeclaration(selector, "-webkit-mask-mode: alpha"),
+		`${selector} should force alpha mask rendering on WebKit/Blink mobile browsers`
+	);
+});
+
+assert(
+	!stylesheet.includes("--wiki-callout-icon-color"),
+	"The theme should not introduce new callout icon colors for this mobile rendering fix"
+);
+
+assert(
+	!stylesheet.includes(".wiki-callout::before"),
+	"The theme should not restyle the callout icon tile for this mobile rendering fix"
+);