feat(文件管理): 添加已打开文件状态标记及相应逻辑

引入hasOpenedFile状态标记，用于跟踪用户是否已打开或操作过文件
- 修改欢迎界面显示逻辑，仅在无内容且未打开文件时显示
- 调整保存/另存为/新建场景等操作的权限判断
- 更新标题栏显示逻辑，支持已打开文件但无内容的场景
- 在文件拖放、加载等操作时自动标记文件打开状态

src/App.vue

@@ -59,6 +59,7 @@ const state = reactive({
   showOpenSceneDialog: false,
   pendingScenePath: null as string | null,
   pendingAction: null as 'close' | 'openScene' | null,
+  hasOpenedFile: false, // 标记是否已打开过文件或添加过内容
 });
 
 // Computed title
@@ -71,6 +72,12 @@ const hasContent = computed(() => {
   return sceneManager.elements.value.length > 0;
 });
 
+// Check if should show welcome overlay
+// Only show when: no content AND no file has been opened/used
+const showWelcome = computed(() => {
+  return !hasContent.value && !state.hasOpenedFile;
+});
+
 // Selection box state
 const selectionBox = reactive({
   visible: false,
@@ -125,7 +132,9 @@ function getContextMenuItems(): MenuItem[] {
   items.push({ label: '', action: () => {}, separator: true });
   
   // File operations
-  const canSave = hasContent.value;
+  // 允许保存：有内容 或 已打开文件（可以保存空文件）
+  const canSave = hasContent.value || state.hasOpenedFile;
+  const canCreateNew = hasContent.value || state.hasOpenedFile;
   
   items.push(
     {
@@ -148,7 +157,7 @@ function getContextMenuItems(): MenuItem[] {
       action: () => handleNew(),
       shortcut: 'Ctrl+N',
       checked: false,
-      disabled: !canSave,
+      disabled: !canCreateNew,
     }
   );
   
@@ -212,6 +221,9 @@ async function handleCanvasInitialized() {
   try {
     const loaded = await sceneService.loadOnStartup();
     if (loaded) {
+      // 标记已打开文件
+      state.hasOpenedFile = true;
+      
       // Sync renderer and view transform after loading
       canvasViewRef.value?.syncRendererElements();
       canvasViewRef.value?.syncViewTransform();
@@ -305,6 +317,9 @@ async function handleTauriFileDrop(paths: string[], dropX: number, dropY: number
   // Handle image files
   if (imageFiles.length === 0) return;
   
+  // 标记已开始使用场景，防止删除元素后显示欢迎界面
+  state.hasOpenedFile = true;
+  
   // Record state for undo
   const currentState = sceneManager.getState();
   historyManager.record(currentState.elements, currentState.viewTransform);
@@ -335,6 +350,9 @@ async function loadSceneFromPath(path: string) {
   try {
     const success = await sceneService.loadFromPath(path);
     if (success) {
+      // 标记已打开文件，防止删除元素后显示欢迎界面
+      state.hasOpenedFile = true;
+      
       canvasViewRef.value?.syncRendererElements();
       canvasViewRef.value?.syncViewTransform();
       canvasViewRef.value?.getRenderer()?.requestRender();
@@ -355,8 +373,12 @@ async function loadSceneFromPath(path: string) {
 async function handleConfirmOpenScene() {
   state.showOpenSceneDialog = false;
   if (state.pendingScenePath) {
+    // 从指定路径加载（拖放文件）
     await loadSceneFromPath(state.pendingScenePath);
     state.pendingScenePath = null;
+  } else {
+    // 通过对话框选择文件（Ctrl+L）
+    await performLoad();
   }
 }
 
@@ -553,8 +575,8 @@ function handleGlobalAction(action: string, data: unknown) {
 // ============================================
 
 async function handleSave() {
-  // Don't save if no content
+  // 允许保存：有内容 或 已打开文件（可以保存空文件）
-  if (!hasContent.value) return;
+  if (!hasContent.value && !state.hasOpenedFile) return;
   
   try {
     const success = await sceneService.save();
@@ -567,8 +589,8 @@ async function handleSave() {
 }
 
 async function handleSaveAs() {
-  // Don't save if no content
+  // 允许另存为：有内容 或 已打开文件（可以保存空文件）
-  if (!hasContent.value) return;
+  if (!hasContent.value && !state.hasOpenedFile) return;
   
   try {
     const success = await sceneService.saveAs();
@@ -581,6 +603,29 @@ async function handleSaveAs() {
 }
 
 async function handleLoad() {
+  // 如果有未保存的更改，显示提示对话框
+  if (state.isDirty && (hasContent.value || state.hasOpenedFile)) {
+    state.pendingAction = 'openScene';
+    state.pendingScenePath = null; // null 表示通过对话框选择文件
+    state.showUnsavedDialog = true;
+    return;
+  }
+  
+  // 如果有内容但没有未保存更改，显示确认对话框
+  if (hasContent.value || state.hasOpenedFile) {
+    state.pendingScenePath = null;
+    state.showOpenSceneDialog = true;
+    return;
+  }
+  
+  // 没有内容，直接打开
+  await performLoad();
+}
+
+/**
+ * 实际执行加载操作
+ */
+async function performLoad() {
   try {
     // Record state for undo before loading
     const currentState = sceneManager.getState();
@@ -588,6 +633,9 @@ async function handleLoad() {
     
     const success = await sceneService.load();
     if (success) {
+      // 标记已打开文件，防止显示欢迎界面
+      state.hasOpenedFile = true;
+      
       // Sync renderer and view transform after loading
       canvasViewRef.value?.syncRendererElements();
       canvasViewRef.value?.syncViewTransform();
@@ -619,14 +667,18 @@ async function handleBrowseFiles() {
 }
 
 function handleNew() {
-  // Don't create new scene if already empty
+  // Don't create new scene if already empty and no file opened
-  if (!hasContent.value) return;
+  if (!hasContent.value && !state.hasOpenedFile) return;
   
-  // Record state for undo
+  // Record state for undo if there's content
+  if (hasContent.value) {
     const currentState = sceneManager.getState();
     historyManager.record(currentState.elements, currentState.viewTransform);
+  }
   
   sceneService.newScene();
+  // 重置标志，允许显示欢迎界面
+  state.hasOpenedFile = false;
   canvasViewRef.value?.syncRendererElements();
 }
 
@@ -1005,8 +1057,14 @@ async function executePendingAction() {
   
   if (action === 'close') {
     await forceCloseWindow();
-  } else if (action === 'openScene' && scenePath) {
+  } else if (action === 'openScene') {
+    if (scenePath) {
+      // 从指定路径加载（拖放文件）
       await loadSceneFromPath(scenePath);
+    } else {
+      // 通过对话框选择文件（Ctrl+L）
+      await performLoad();
+    }
   }
 }
 
@@ -1140,6 +1198,7 @@ onUnmounted(() => {
       :always-on-top="state.alwaysOnTop"
       :is-dirty="state.isDirty"
       :has-content="hasContent"
+      :has-opened-file="state.hasOpenedFile"
       @minimize="minimizeWindow"
       @maximize="toggleFullscreen"
       @close="closeWindow"
@@ -1156,9 +1215,10 @@ onUnmounted(() => {
       @file-drop="handleFileDrop"
     />
 
-    <!-- Welcome Overlay (when scene is empty) -->
+    <!-- Welcome Overlay (when scene is empty and no file opened) -->
     <WelcomeOverlay
-      v-if="state.isInitialized && !hasContent"
+      v-if="state.isInitialized && showWelcome"
+      :key="'welcome-' + hasContent + '-' + state.hasOpenedFile"
       @browse="handleBrowseFiles"
       @help="state.showHelp = true"
     />

src/components/CanvasView.vue

@@ -502,6 +502,7 @@ async function handleDelete() {
   if (sceneManager.getSelectedCount() > 0) {
     recordState();
     sceneManager.deleteSelected();
+    sceneService.markDirty();
     await syncRendererElements();
     // Force render update
     renderer?.requestRender();

src/components/TitleBar.vue

@@ -10,6 +10,7 @@ const props = defineProps<{
   alwaysOnTop?: boolean;
   isDirty?: boolean;
   hasContent?: boolean;
+  hasOpenedFile?: boolean;
 }>();
 
 const emit = defineEmits<{
@@ -133,7 +134,7 @@ onUnmounted(() => {
       @mousedown="handleDragStart"
     >
       <span class="title-bar__title">
-        <template v-if="hasContent">{{ isDirty ? '*' : '' }}{{ title || 'Untitled' }}</template>
+        <template v-if="hasContent || hasOpenedFile">{{ isDirty ? '*' : '' }}{{ title || 'Untitled' }}</template>
       </span>
     </div>