feat(plugins): let a plugin set its own icon (#1761)

A plugin can set `icon` (and `icon-dark`) in plugin.toml. The SVGs go through the existing sanitiser (16 KiB each), ship with the package, and show in Settings › Plugins (list rows and detail header) and the marketplace, whose index entries carry them; the IDE sanitises index icons again and drops unsafe ones.

IDEs before plugin API 1.2 refuse a manifest with `icon`, so Manifest::needs_api refuses one whose engines.openidea still admits them (check and install), keeping the index from offering such a package to older IDEs.

Closes #1732

Co-authored-by: arnaud-ritti <[email protected]>

src/features/plugins/pluginIcon.ts

@@ -0,0 +1,53 @@
+import type { PluginIcon } from "@/bindings";
+import { registerExternalIcons } from "@/ui/icons";
+
+// ponytail: never unregistered; bounded by the distinct icons seen this session.
+const registered = new Set<string>();
+
+/** FNV-1a: a short key for an icon's markup. */
+function hash(text: string): string {
+  let h = 0x811c9dc5;
+  for (let i = 0; i < text.length; i++) h = Math.imul(h ^ text.charCodeAt(i), 0x01000193);
+  return (h >>> 0).toString(16);
+}
+
+const ROOT_ONLY = new Set(["viewBox", "width", "height", "id", "version"]);
+
+/**
+ * `Icon` keeps only the root's viewBox and draws on `fill="none"`: move the
+ * root's other attributes onto a group, with SVG's default black fill.
+ */
+function standalone(svg: string): string {
+  const open = svg.indexOf("<svg");
+  const start = svg.indexOf(">", open) + 1;
+  const end = svg.lastIndexOf("</svg>");
+  if (open < 0 || start <= open || end < start) return svg;
+  const tag = svg.slice(open, start);
+  const inherited = [...tag.matchAll(/\s([\w:-]+)="[^"]*"/g)]
+    .filter((m) => !ROOT_ONLY.has(m[1] ?? "") && !m[1]?.startsWith("xmlns"))
+    .map((m) => m[0])
+    .join("");
+  const fill = /\sfill="/.test(inherited) ? "" : ' fill="#000"';
+  return `${tag}<g${fill}${inherited}>${svg.slice(start, end)}</g></svg>`;
+}
+
+/**
+ * The icon name of a plugin's own icon, else the generic one. Names follow the
+ * markup, so copies of a plugin with different icons (marketplace, local) keep
+ * their own; plugin ids have no `/`, so no id yields another's name or `_dark`.
+ */
+export function pluginIconName(pluginId: string, icon: PluginIcon | null | undefined): string {
+  if (!icon) return "plugin";
+  const name = `ext:pluginIcon/${pluginId}/${hash(`${icon.light}\n${icon.dark ?? ""}`)}`;
+  if (registered.has(name)) return name;
+  registered.add(name);
+  registerExternalIcons(
+    icon.dark
+      ? [
+          [name, standalone(icon.light)],
+          [`${name}_dark`, standalone(icon.dark)],
+        ]
+      : [[name, standalone(icon.light)]],
+  );
+  return name;
+}