ElyMark: the print page is staged off the window thread (M-14)

paper::stage takes the background executor and inlines images, reads
the style sheet and writes the page there. A gpui test checks nothing
is written before the executor runs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/ely-mark/src/export.rs

@@ -15,7 +15,7 @@ use ely_ui::{commands, i18n::text};
 use ely_web_content::{Event, WebView};
 use gpui::{
     AnyElement, App, AppContext as _, Context, Entity, IntoElement as _, ParentElement as _,
-    Subscription, Window,
+    Subscription, Task, Window,
 };
 use serde_json::Value;
 
@@ -62,7 +62,7 @@ pub struct Lost {
 }
 
 impl Lost {
-    fn of(images: Vec<String>, rendered: &Value) -> Lost {
+    pub fn of(images: Vec<String>, rendered: &Value) -> Lost {
         let diagrams = rendered["failed"].as_array().into_iter().flatten();
         let formulas = rendered["formulas"].as_array().into_iter().flatten();
         Lost {
@@ -280,19 +280,15 @@ impl Desk {
                 "html",
                 move |rendered, cx: &mut App| {
                     let staged = work.join(format!("print-{n}.html"));
-                    let writing = staged.clone();
+                    let page = match rendered {
+                        Ok(rendered) => {
+                            let print = paper::Print { folder, style, name, page: staged.clone() };
+                            paper::stage(cx.background_executor(), rendered, print)
+                        }
+                        Err(why) => Task::ready(Err(io::Error::other(why))),
+                    };
                     cx.spawn(async move |cx| {
-                        // Images inline and the page writes off the window thread.
-                        let page = cx
-                            .background_spawn(async move {
-                                rendered.map_err(io::Error::other).and_then(|rendered| {
-                                    let (html, images) = paper::Marked::read(&rendered)?.inline(&folder);
-                                    let style = format!("<style>{}</style>", std::fs::read_to_string(&style)?);
-                                    std::fs::write(&writing, paper::page(&name, &style, &html))?;
-                                    Ok(Lost::of(images, &rendered))
-                                })
-                            })
-                            .await;
+                        let page = page.await;
                         in_window(&desk, cx, |desk, window, cx| match page {
                             Ok(lost) => {
                                 let job = Job {

apps/ely-mark/src/paper.rs

@@ -85,6 +85,28 @@ fn kind(path: &Path) -> &'static str {
     }
 }
 
+/// What the print page is made of.
+pub struct Print {
+    pub folder: std::path::PathBuf,
+    pub style: std::path::PathBuf,
+    pub name: String,
+    pub page: std::path::PathBuf,
+}
+
+/// Writes the print page off the window thread, images inline.
+pub fn stage(
+    background: &gpui::BackgroundExecutor,
+    rendered: serde_json::Value,
+    print: Print,
+) -> gpui::Task<std::io::Result<crate::export::Lost>> {
+    background.spawn(async move {
+        let (html, images) = Marked::read(&rendered)?.inline(&print.folder);
+        let style = format!("<style>{}</style>", std::fs::read_to_string(&print.style)?);
+        std::fs::write(&print.page, page(&print.name, &style, &html))?;
+        Ok(crate::export::Lost::of(images, &rendered))
+    })
+}
+
 /// The page's HTML; image `src` values replaced by numbered tokens.
 #[derive(Clone, Debug, Default)]
 pub struct Marked {
@@ -222,6 +244,31 @@ mod tests {
         assert!(Marked::read(&serde_json::json!({ "html": "<p>" })).is_err());
     }
 
+    #[gpui::test]
+    fn the_print_page_is_written_off_the_window_thread(cx: &mut gpui::TestAppContext) {
+        let dir = tempfile::tempdir().expect("a temp dir");
+        std::fs::write(dir.path().join("a.png"), b"png").expect("an image");
+        std::fs::write(dir.path().join("export.css"), "p {}").expect("a style");
+        let rendered = serde_json::json!({
+            "html": "<p>hi</p><img src=\"T0\"><img src=\"T1\">",
+            "token": "T",
+            "images": ["a.png", "gone.png"],
+            "failed": [3],
+        });
+        let print = Print {
+            folder: dir.path().into(),
+            style: dir.path().join("export.css"),
+            name: "notes".into(),
+            page: dir.path().join("print-1.html"),
+        };
+        let staging = stage(&cx.executor(), rendered, print);
+        assert!(!dir.path().join("print-1.html").exists(), "staged on the window thread");
+        let lost = cx.foreground_executor().block_test(staging).expect("staged");
+        let written = std::fs::read_to_string(dir.path().join("print-1.html")).expect("the page");
+        assert!(written.contains("<style>p {}</style>") && written.contains("data:image/png;base64,cG5n"));
+        assert_eq!(format!("{lost:?}"), r#"Lost { images: ["gone.png"], diagrams: [3], formulas: [] }"#);
+    }
+
     #[test]
     fn titles_escape() {
         assert!(page("a<b>&", "", "").contains("<title>a&lt;b&gt;&amp;</title>"));

tasks/BUGS.md

@@ -74,7 +74,7 @@
 - [x] M-11 页面把搜索词写进应用日志 — 控制台的文字与来源都可由文档伪造，只记行号；页面自己的诊断经 elyQuery；R1 前缀可伪造、R2 data 来源、R3 sourceURL、R4 编码路径与目录、R5 缺回归测试：已补并经变异核对（五轮上限，未再审）
 - [x] M-12 浏览器创建完成前 `WebView` 已释放，浏览器泄漏 — 浏览器在泵里同步建好即登记，视图要么在建前已走、要么有浏览器可关；webprobe 加建前丢弃与 0–27 毫秒丢弃，35 页都在保持前释放（审查 4 轮）
 - [x] M-13 编辑器构建失败时页面空白且不上报 — 可视建不成退回源码并告知，两者都建不成即报失败、留下文字、模式请求重建、不留容器；新测 mark-broken.mjs（审查 2 轮）
-- [ ] M-14 `render_pdf` 在界面线程内嵌图片并写文件
+- [x] M-14 `render_pdf` 在界面线程内嵌图片并写文件 — 打印页的内嵌、读样式与写入经 paper::stage 在后台执行，GPUI 单测证明执行器运行前未写（审查 2 轮）
 - [ ] M-15 打印与导出 PDF 的暂存页执行文档里的脚本
 - [ ] G-01 打开“文件历史”或“逐行追溯”后，中间区不再响应任何别的选择
 - [ ] G-02 进行中操作读取失败被吞掉；`git am` 冲突无提示条无错误

tasks/reviews/M-14-r1.md

@@ -0,0 +1,3 @@
+FAIL
+
+apps/ely-mark/src/export.rs:287 — 缺少 M-14 的后台暂存回归测试。具体失败场景：把此处 `background_spawn(...).await` 改回前台直接执行，图片内嵌、样式读取及暂存页写入重新阻塞界面，现有测试仍全绿。本轮在隔离副本中编译并运行该变异：Windows 的 22 项适用测试、WSL 的全部 24 项测试均通过；现有 `mark-output.sh` 只检查输出及打印作业，没有线程或界面响应断言。额外的 GPUI 暂存片段探针在当前代码上通过六种成功、失败场景，在该变异上明确报出 `staging ran on foreground`，证明现有测试漏掉了本项针对的行为（UX-05、PERF-02）。修复方向：补充执行实际暂存调度路径的 GPUI 回归测试，验证耗时准备在后台执行、结果交回前台处理，撤掉后台调度时必须失败。证据：`.work/M-14-r1/{windows,linux}-foreground-mutant-tests.log`、`{windows,linux}-staging-{current,foreground-mutant}-tests.log`。探针副本及其独立构建目录已删除；未运行 macOS 窗口测试。

tasks/reviews/M-14-r2.md

@@ -0,0 +1 @@
+PASS