fix: make draw.io built-in save button work

- Lift showSaveDialog state to DiagramContext for sharing between components
- Add onSave handler to DrawIoEmbed that opens the save dialog
- Add guard (isSavingRef) with 1s delay to prevent repeated save events from draw.io
- Add deprecation notice to custom download button tooltip

Closes #93, Closes #290

app/page.tsx

@@ -1,5 +1,5 @@
 "use client"
-import { useEffect, useRef, useState } from "react"
+import { useCallback, useEffect, useRef, useState } from "react"
 import { DrawIoEmbed } from "react-drawio"
 import type { ImperativePanelHandle } from "react-resizable-panels"
 import ChatPanel from "@/components/chat-panel"
@@ -21,6 +21,8 @@ export default function Home() {
         onDrawioLoad,
         resetDrawioReady,
         saveDiagramToStorage,
+        showSaveDialog,
+        setShowSaveDialog,
     } = useDiagram()
     const [isMobile, setIsMobile] = useState(false)
     const [isChatVisible, setIsChatVisible] = useState(true)
@@ -30,6 +32,24 @@ export default function Home() {
     const [closeProtection, setCloseProtection] = useState(false)
 
     const chatPanelRef = useRef<ImperativePanelHandle>(null)
+    const isSavingRef = useRef(false)
+
+    // Reset saving flag when dialog closes (with delay to ignore lingering save events from draw.io)
+    useEffect(() => {
+        if (!showSaveDialog && isSavingRef.current) {
+            const timeout = setTimeout(() => {
+                isSavingRef.current = false
+            }, 1000)
+            return () => clearTimeout(timeout)
+        }
+    }, [showSaveDialog])
+
+    // Handle save from draw.io's built-in save button
+    const handleDrawioSave = useCallback(() => {
+        if (isSavingRef.current) return
+        isSavingRef.current = true
+        setShowSaveDialog(true)
+    }, [setShowSaveDialog])
 
     // Load preferences from localStorage after mount
     useEffect(() => {
@@ -155,6 +175,7 @@ export default function Home() {
                                     ref={drawioRef}
                                     onExport={handleDiagramExport}
                                     onLoad={onDrawioLoad}
+                                    onSave={handleDrawioSave}
                                     baseUrl={drawioBaseUrl}
                                     urlParameters={{
                                         ui: drawioUi,

components/chat-input.tsx

@@ -155,12 +155,16 @@ export function ChatInput({
     minimalStyle = false,
     onMinimalStyleChange = () => {},
 }: ChatInputProps) {
-    const { diagramHistory, saveDiagramToFile } = useDiagram()
+    const {
+        diagramHistory,
+        saveDiagramToFile,
+        showSaveDialog,
+        setShowSaveDialog,
+    } = useDiagram()
     const textareaRef = useRef<HTMLTextAreaElement>(null)
     const fileInputRef = useRef<HTMLInputElement>(null)
     const [isDragging, setIsDragging] = useState(false)
     const [showClearDialog, setShowClearDialog] = useState(false)
-    const [showSaveDialog, setShowSaveDialog] = useState(false)
 
     // Allow retry when there's an error (even if status is still "streaming" or "submitted")
     const isDisabled =
@@ -401,7 +405,7 @@ export function ChatInput({
                             size="sm"
                             onClick={() => setShowSaveDialog(true)}
                             disabled={isDisabled}
-                            tooltipContent="Save diagram"
+                            tooltipContent="Save diagram (deprecated: use Save button in upper right corner of draw.io)"
                             className="h-8 w-8 p-0 text-muted-foreground hover:text-foreground"
                         >
                             <Download className="h-4 w-4" />

contexts/diagram-context.tsx

@@ -27,6 +27,8 @@ interface DiagramContextType {
     isDrawioReady: boolean
     onDrawioLoad: () => void
     resetDrawioReady: () => void
+    showSaveDialog: boolean
+    setShowSaveDialog: (show: boolean) => void
 }
 
 const DiagramContext = createContext<DiagramContextType | undefined>(undefined)
@@ -38,6 +40,7 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
         { svg: string; xml: string }[]
     >([])
     const [isDrawioReady, setIsDrawioReady] = useState(false)
+    const [showSaveDialog, setShowSaveDialog] = useState(false)
     const hasCalledOnLoadRef = useRef(false)
     const drawioRef = useRef<DrawIoEmbedRef | null>(null)
     const resolverRef = useRef<((value: string) => void) | null>(null)
@@ -309,6 +312,8 @@ export function DiagramProvider({ children }: { children: React.ReactNode }) {
                 isDrawioReady,
                 onDrawioLoad,
                 resetDrawioReady,
+                showSaveDialog,
+                setShowSaveDialog,
             }}
         >
             {children}