Add PDF state persistence

src-tauri/assets/viewer/viewer.js

@@ -33,8 +33,11 @@ const zoomLabel     = document.getElementById("zoom-label");
 const pageIndicator = document.getElementById("page-indicator");
 
 // ── Global state ─────────────────────────────────────────────────────────────
-const refId = new URLSearchParams(location.search).get("ref_id") || "";
-const DPR   = window.devicePixelRatio || 1;
+const params         = new URLSearchParams(location.search);
+const refId          = params.get("ref_id") || "";
+const savedZoom      = parseFloat(params.get("zoom"));      // NaN if absent
+const savedScrollTop = parseFloat(params.get("scroll_top")); // NaN if absent
+const DPR            = window.devicePixelRatio || 1;
 
 let pdfDoc          = null;
 let pageManager     = null;
@@ -61,12 +64,13 @@ function refreshPageIndicator() {
   pageIndicator.textContent = cur + " / " + pageManager.numPages;
 }
 
-async function fitToWidth() {
+async function fitToPage() {
   if (!pdfDoc) return 1.0;
-  const page  = await pdfDoc.getPage(1);
-  const vp    = page.getViewport({ scale: 1.0 });
-  const avail = container.clientWidth - 40;
-  return Math.max(0.1, Math.min(5.0, avail / vp.width));
+  const page   = await pdfDoc.getPage(1);
+  const vp     = page.getViewport({ scale: 1.0 });
+  const scaleW = (container.clientWidth  - 40) / vp.width;
+  const scaleH = (container.clientHeight - 40) / vp.height;
+  return Math.max(0.1, Math.min(5.0, Math.min(scaleW, scaleH)));
 }
 
 function scrollToPage(pageNum) {
@@ -103,7 +107,7 @@ async function renderPage(pageNum, scale, gen) {
     const bitmap = offscreen.transferToImageBitmap();
     pageManager?.onRendered(pageNum, gen, bitmap);
     refreshPageIndicator();
-    setStatus("Ready");
+    if (pageManager?.allRendered) setStatus("Ready");
   } catch (e) {
     if (e?.name !== "RenderingCancelledException") {
       console.warn("[viewer] render error page", pageNum, e);
@@ -113,6 +117,11 @@ async function renderPage(pageNum, scale, gen) {
   }
 }
 
+function sendViewerState() {
+  if (!bridge || !zoomController) return;
+  bridge.postViewerState(refId, zoomController.scale, container.scrollTop);
+}
+
 // ── Visibility change callback (called by ViewportTracker) ───────────────────
 function onVisibilityChange(bufferSet, visibleSet) {
   currentBufferSet  = bufferSet;
@@ -145,9 +154,12 @@ async function load() {
       viewports.push({ width: vp.width, height: vp.height });
     }
 
-    // 3. Compute initial fit-to-width scale
-    const avail        = container.clientWidth - 40;
-    const initialScale = Math.max(0.1, Math.min(5.0, avail / viewports[0].width));
+    // 3. Compute initial scale: use saved zoom if available, else fit full page
+    const fittedScale = Math.max(0.1, Math.min(5.0, Math.min(
+      (container.clientWidth  - 40) / viewports[0].width,
+      (container.clientHeight - 40) / viewports[0].height,
+    )));
+    const initialScale = (savedZoom > 0) ? Math.max(0.1, Math.min(5.0, savedZoom)) : fittedScale;
 
     // 4. PageManager — creates placeholder divs
     pageManager = new PageManager(
@@ -160,11 +172,14 @@ async function load() {
       container, pageManager.pageWrappers, onVisibilityChange,
     );
 
-    // 6. ZoomController
+    // 6. ZoomController — send state after each debounced re-render
     zoomController = new ZoomController(
       container,
       pageManager,
-      (newScale, bufferSet, visibleSet) => pageManager.onScaleChange(newScale, bufferSet, visibleSet),
+      (newScale, bufferSet, visibleSet) => {
+        pageManager.onScaleChange(newScale, bufferSet, visibleSet);
+        sendViewerState();
+      },
       () => ({ bufferSet: currentBufferSet, visibleSet: currentVisibleSet }),
       zoomLabel,
       initialScale,
@@ -182,19 +197,29 @@ async function load() {
     document.getElementById("btn-zoom-in").addEventListener("click",
       () => zoomController.applyScale(zoomController.scale * 1.25));
     document.getElementById("btn-zoom-fit").addEventListener("click",
-      async () => zoomController.applyScale(await fitToWidth()));
+      async () => zoomController.applyScale(await fitToPage()));
 
     // Keyboard shortcuts + keydown forwarding to parent
     document.addEventListener("keydown", ev => {
       if (ev.target.tagName === "INPUT") return;
       if (ev.key === "+" || ev.key === "=") { ev.preventDefault(); zoomController.applyScale(zoomController.scale * 1.25); }
       if (ev.key === "-")                   { ev.preventDefault(); zoomController.applyScale(zoomController.scale / 1.25); }
-      if (ev.key === "0")                   { ev.preventDefault(); fitToWidth().then(s => zoomController.applyScale(s)); }
+      if (ev.key === "0")                   { ev.preventDefault(); fitToPage().then(s => zoomController.applyScale(s)); }
       bridge.forwardKeydown(ev);
     });
 
-    // Scroll → update page indicator
-    container.addEventListener("scroll", refreshPageIndicator, { passive: true });
+    // Scroll → update page indicator + debounced state save
+    let _scrollSaveTimer = null;
+    container.addEventListener("scroll", () => {
+      refreshPageIndicator();
+      if (_scrollSaveTimer) clearTimeout(_scrollSaveTimer);
+      _scrollSaveTimer = setTimeout(sendViewerState, 500);
+    }, { passive: true });
+
+    // Restore saved scroll position (rAF ensures layout is ready)
+    if (savedScrollTop > 0) {
+      requestAnimationFrame(() => { container.scrollTop = savedScrollTop; });
+    }
 
     // Lifecycle: tab hidden → free caches; tab visible → re-reconcile
     document.addEventListener("visibilitychange", () => {