fix: release the large page preview when closed

.github/workflows/build.yml

@@ -40,6 +40,7 @@ jobs:
           node t12-remote.js
           node t13-upload-retry.js
           node t14-preview-files.js
+          node t15-page-view.js
 
   windows:
     name: Windows installer

Source code/server/public/app.js

@@ -908,6 +908,7 @@ function openPageView(n) {
 function closePageView() {
   viewPage = 0;
   $("pageView").hidden = true;
+  $("pvStage").innerHTML = "";
 }
 
 function renderPageView() {

Source code/tests/README.md

@@ -18,6 +18,8 @@ websites (`fake-web.js`) on spare ports, so nothing else needs to be running.
     node t13-upload-retry.js  "Print this?" screen: a stuck upload is sent again, then shows an error
     node t14-preview-files.js  the preview library is sent gzipped to browsers that can take it
 
+    node t15-page-view.js    closing the large page preview frees its image; reopening the same page works
+
 These run on Linux/macOS. The Windows-only parts (the Task Scheduler task,
 the installer) are covered by manual checks on Windows and Mac.
 t4, t5 and t6 need a real network card: on a machine with only

Source code/tests/t15-page-view.js

@@ -0,0 +1,33 @@
+// Closing the large page view releases its image, and the same page can reopen.
+const fs = require("fs"), path = require("path"), vm = require("vm"), assert = require("assert");
+let n = 0; const ok = (c, m) => { assert(c, m); n++; console.log("  ok -", m); };
+const src = fs.readFileSync(path.join(__dirname, "../server/public/app.js"), "utf8");
+const code = src.slice(src.indexOf("function openPageView("), src.indexOf("function setupPageView("));
+function element() {
+  return {
+    children: [], style: {}, hidden: true, clientWidth: 600,
+    appendChild(child) { this.children.push(child); },
+    set innerHTML(value) { this.children = []; },
+  };
+}
+const ids = Object.fromEntries(["pageView", "pvStage", "pvTitle", "pvChoose", "pvPrev", "pvNext"].map(id => [id, element()]));
+const draws = [];
+const box = {
+  viewPage: 0, MAX_THUMBS: 100, $: id => ids[id],
+  document: { createElement: element }, window: { innerHeight: 800 },
+  activeEntry: () => ({ pdf: {}, pageCount: 2, pageSizes: {}, chosen: new Set([1]) }),
+  placeOnPaper: () => ({ ratio: 595 / 842, left: 0, top: 0, width: 1, height: 1 }),
+  drawPageInto(entry, page, holder) { draws.push(page); holder.appendChild(element()); },
+};
+vm.runInNewContext(code, box);
+for (const page of [1, 1, 2]) {
+  box.openPageView(page);
+  ok(!ids.pageView.hidden && box.viewPage === page, "opens page " + page);
+  ok(ids.pvStage.children.length === 1 && draws.at(-1) === page, "renders the requested page");
+  box.closePageView();
+  ok(ids.pageView.hidden && box.viewPage === 0, "hides and resets the view");
+  ok(ids.pvStage.children.length === 0, "releases the large preview subtree");
+}
+box.closePageView();
+ok(ids.pvStage.children.length === 0, "closing an already closed view is harmless");
+console.log(n + " checks passed");