refactor(canvas): getDrawioSrc takes the editor's source, and CanvasStage can be given one

components/canvas/canvas-stage.tsx

@@ -3,7 +3,12 @@ import { DrawioFrame } from "@/components/canvas/drawio-frame"
 import { useLocale } from "@/components/canvas/locale-context"
 import { useDiagram } from "@/contexts/diagram-context"
 import { useDictionary } from "@/hooks/use-dictionary"
-import { DRAWIO_CSS, getDrawioSrc } from "@/lib/drawio/drawio-config"
+import {
+    DRAWIO_CSS,
+    type DrawioSource,
+    getDrawioSrc,
+    webDrawioSource,
+} from "@/lib/drawio/drawio-config"
 import { keepCenter, refitIfRecent } from "@/lib/drawio/editor-bridge"
 import { i18n, type Locale } from "@/lib/i18n/config"
 import { STORAGE_KEYS } from "@/lib/storage"
@@ -28,6 +33,7 @@ export function CanvasStage({
     style,
     hideOverlays = false,
     overlay,
+    drawioSource,
     waitForSavedLocale = false,
 }: {
     className?: string
@@ -36,6 +42,9 @@ export function CanvasStage({
     hideOverlays?: boolean
     /** Rendered over the canvas once draw.io is ready */
     overlay?: (size: CanvasSize) => React.ReactNode
+    /** Where the editor comes from; none: the web app's own copy (the MCP
+     * shell passes what its server configured) */
+    drawioSource?: DrawioSource
     /** Web app: the page is about to switch to the language picked last
      * time (useSavedLocale in the workspace); do not load draw.io in the
      * URL's language meanwhile */
@@ -74,11 +83,10 @@ export function CanvasStage({
                 return
             }
         }
-        const isElectron = !!(window as { electronAPI?: unknown }).electronAPI
         // The theme class is set before the page renders; the settings store
         // may not have read it yet
         const dark = document.documentElement.classList.contains("dark")
-        setSrc(getDrawioSrc({ lang, isElectron, dark }))
+        setSrc(getDrawioSrc(drawioSource ?? webDrawioSource(lang), dark))
     }, [lang])
 
     // A new iframe starts over: draw.io reports load and access again
@@ -94,8 +102,7 @@ export function CanvasStage({
         if (editorAccess !== false || !src) return
         const startedDark = new URL(src).searchParams.get("dark") === "1"
         if (startedDark === isDark) return
-        const isElectron = !!(window as { electronAPI?: unknown }).electronAPI
+        setSrc(getDrawioSrc(drawioSource ?? webDrawioSource(lang), isDark))
-        setSrc(getDrawioSrc({ lang, isElectron, dark: isDark }))
     }, [isDark, editorAccess, lang, src])
 
     useEffect(() => {

lib/drawio/drawio-config.ts

@@ -6,28 +6,49 @@ import { BLANK_MXFILE } from "@/packages/mcp-server/src/pages.ts"
 const EXTERNAL_DRAWIO_URL = process.env.NEXT_PUBLIC_DRAWIO_BASE_URL || ""
 
 /**
- * URL of the draw.io editor iframe. By default this is the copy bundled in
+ * Where the editor comes from and how it starts. The web app fills it from
- * public/drawio, served from our own origin.
+ * its build settings (webDrawioSource); the MCP's canvas shell from the
+ * config its server writes into the page.
  */
-export function getDrawioSrc({
+export interface DrawioSource {
-    lang,
+    /** The editor page: the bundled copy's index.html on this origin, or an
-    isElectron,
+     * external draw.io (cross-origin, limited features) */
-    dark,
+    editorUrl: string
-}: {
+    /** draw.io theme (its ui parameter); none: draw.io's default and the
-    lang: Locale
+     * user's own pick */
-    isElectron: boolean
+    ui?: string
-    dark: boolean
+    /** Language in draw.io's naming ("zh-tw"); none: draw.io's own pick */
-}): string {
+    lang?: string
-    // index.html: Next.js does not serve directory indexes
+    /** No calls to external services (the desktop app) */
-    const base =
+    offline?: boolean
-        EXTERNAL_DRAWIO_URL ||
+}
-        `${window.location.origin}${getAssetUrl("/drawio/index.html")}`
+
-    const url = new URL(base)
+/**
+ * The web app's editor: the copy in public/drawio, served from our own
+ * origin (index.html, as Next.js serves no directory indexes), or
+ * NEXT_PUBLIC_DRAWIO_BASE_URL; the simple theme in the page's language.
+ */
+export function webDrawioSource(lang: Locale): DrawioSource {
+    const isElectron = !!(window as { electronAPI?: unknown }).electronAPI
+    return {
+        editorUrl: EXTERNAL_DRAWIO_URL || getAssetUrl("/drawio/index.html"),
+        ui: "simple",
+        // draw.io names Traditional Chinese "zh-tw"
+        lang: lang === "zh-Hant" ? "zh-tw" : lang,
+        offline: isElectron && !EXTERNAL_DRAWIO_URL,
+    }
+}
+
+/** URL of the draw.io editor iframe */
+export function getDrawioSrc(source: DrawioSource, dark: boolean): string {
+    const url = new URL(source.editorUrl, window.location.href)
     const params: Record<string, string> = {
         embed: "1",
         proto: "json",
         configure: "1",
-        ui: "simple",
+    }
+    if (source.ui) params.ui = source.ui
+    Object.assign(params, {
         spin: "0",
         libraries: "0",
         noSaveBtn: "1",
@@ -36,11 +57,9 @@ export function getDrawioSrc({
         // draw.io's own dark mode (switched in place later when the editor
         // can be driven directly)
         dark: dark ? "1" : "0",
-        // draw.io names Traditional Chinese "zh-tw"
+    })
-        lang: lang === "zh-Hant" ? "zh-tw" : lang,
+    if (source.lang) params.lang = source.lang
-    }
+    if (source.offline) params.offline = "1"
-    // No calls to external services from the desktop app
-    if (isElectron && !EXTERNAL_DRAWIO_URL) params.offline = "1"
     for (const [key, value] of Object.entries(params)) {
         url.searchParams.set(key, value)
     }