Restore the canvas even when a PNG export fails

export() resized the canvas, changed its scale and offset, and only
restored them after the blob came back. Anything that threw in between —
most plausibly toBlob on a workflow large enough to exceed the browser's
canvas limit, which is exactly the workflow someone wants a PNG of — left
the user's view stuck at export dimensions until they reloaded.

restoreState() now runs in a finally, followed by a redraw.

The GuLuLu yes/no callbacks also swallowed the rejection, so the failure
looked like the button simply doing nothing. They now go through a wrapper
that logs and shows a toast naming the canvas limit as the likely cause.

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Changelog
 
 ## [未发布 Unreleased]
+- 修复 Workflow PNG 导出失败时画布视图被留在导出状态、只能刷新页面才能恢复的问题；导出失败现在也会明确提示（大工作流可能超出浏览器画布上限），不再静默无反应
+- Fixed a failed Workflow PNG export leaving the canvas stuck in its export state until the page was reloaded; failures are now reported instead of silently doing nothing (a very large workflow can exceed the browser's canvas limit)
 - 给三个翻译节点的网络请求加上超时（连接 10 秒、读取 30 秒）。此前 requests 默认永不超时，对端连上却不回包会把整个工作流队列无限期堵死且无任何提示；百度翻译节点的网络异常也统一转成可读报错
 - Added timeouts to the three translator nodes (10s connect, 30s read). requests never times out by default, so a server that accepted the connection but never replied would block the whole workflow queue indefinitely with nothing reported; network failures in the Baidu node are now reported as readable errors too
 - 修复自定义图像保存节点把图片写到进程工作目录、并且无视 ComfyUI `--output-directory` 设置的问题；现在始终保存到 ComfyUI 的输出目录下的 `Custom_Save_Image` 子目录

README.md

@@ -9,6 +9,8 @@ This is a custom node utility package developed for ComfyUI. Initially created f
 ## 最新更新 / Last Update
 
 ### [未发布 Unreleased]
+- 修复 Workflow PNG 导出失败时画布视图被留在导出状态、只能刷新页面才能恢复的问题；导出失败现在也会明确提示（大工作流可能超出浏览器画布上限），不再静默无反应  
+- Fixed a failed Workflow PNG export leaving the canvas stuck in its export state until the page was reloaded; failures are now reported instead of silently doing nothing (a very large workflow can exceed the browser's canvas limit)  
 - 给三个翻译节点的网络请求加上超时（连接 10 秒、读取 30 秒）。此前 requests 默认永不超时，对端连上却不回包会把整个工作流队列无限期堵死且无任何提示；百度翻译节点的网络异常也统一转成可读报错  
 - Added timeouts to the three translator nodes (10s connect, 30s read). requests never times out by default, so a server that accepted the connection but never replied would block the whole workflow queue indefinitely with nothing reported; network failures in the Baidu node are now reported as readable errors too  
 - 修复自定义图像保存节点把图片写到进程工作目录、并且无视 ComfyUI `--output-directory` 设置的问题；现在始终保存到 ComfyUI 的输出目录下的 `Custom_Save_Image` 子目录  

web/workflowpng.js

@@ -69,11 +69,17 @@ class KayWorkflowImage {
 
     async export(includeWorkflow) {
         this.saveState();
-        this.updateView(this.getBounds());
-        const getDrawTextConfig = this.getDrawTextConfig;
-        app.canvas.draw(true, true);
-        const blob = await this.getBlob(includeWorkflow ? JSON.stringify(app.graph.serialize()) : undefined);
-        this.restoreState();
+        let blob;
+        try {
+            this.updateView(this.getBounds());
+            app.canvas.draw(true, true);
+            blob = await this.getBlob(includeWorkflow ? JSON.stringify(app.graph.serialize()) : undefined);
+        } finally {
+            // 必须无条件还原：updateView 会改掉画布的尺寸、缩放和偏移，
+            // 中途失败而不还原的话，用户的视图就一直停在导出用的状态，只能刷新页面。
+            this.restoreState();
+            app.canvas.draw(true, true);
+        }
         if (blob) this.download(blob);
     }
 
@@ -161,13 +167,29 @@ class KayWorkflowImage {
     }
 }
 
+async function runExport(includeWorkflow) {
+    try {
+        await new KayWorkflowImage().export(includeWorkflow);
+    } catch (e) {
+        console.error("[KayTool] Workflow PNG export failed:", e);
+        // 画布太大时 toBlob 会失败，这是最常见的原因，直接说清楚
+        app.extensionManager?.toast?.add?.({
+            severity: "error",
+            summary: "Workflow PNG",
+            detail: `Export failed: ${e?.message || e}. A very large workflow can exceed the browser's canvas limit.`,
+            life: 8000,
+        });
+    }
+}
+
 function exportWorkflowPNG() {
     showNotification({
         message: `GuLuLu: 你需要把工作流信息嵌入到PNG中吗？啊？Do you need to embed Workflow information into PNG? *GuLuLu~Gulu*`,
         bgColor: "#fff3cd",
         size: "medium",
-        onYes: () => new KayWorkflowImage().export(true),
-        onNo: () => new KayWorkflowImage().export(false)
+        // 回调里的异常没人接，会被静默吞掉，用户只看到「没反应」。
+        onYes: () => runExport(true),
+        onNo: () => runExport(false)
     });
 }