zoom persistenz

web/app.js

@@ -126,10 +126,11 @@ async function loadPdf(index) {
   }
   loadedIndex = index;
 
+  const previousZoom = pdfViewer ? pdfViewer.zoom : 1;
   if (pdfViewer) {
     pdfViewer.destroy();
   }
-  pdfViewer = new PdfViewer(pdfContainer);
+  pdfViewer = new PdfViewer(pdfContainer, { initialZoom: previousZoom });
   viewer.classList.remove("loaded");
   pdfMessage.hidden = false;
   pdfMessage.textContent = "Loading PDF\u2026";

web/pdf_viewer.js

@@ -6,7 +6,7 @@ const ZOOM_MAX = 5;
 const ZOOM_STEP = 1.2; // multiplicative
 
 class PdfViewer {
-  constructor(container) {
+  constructor(container, options = {}) {
     this.container = container;
     this.generation = 0;
     this.loadingTask = null;
@@ -15,12 +15,18 @@ class PdfViewer {
     this.renderTasks = new Set();
     this.lastUrl = null;
     this.lastSize = null;
-    this.zoom = 1; // multiplier on fit-to-width (1 = fit width)
+    // multiplier on fit-to-width (1 = fit width); can be seeded from the
+    // previous viewer instance so zoom survives switching documents
+    this.zoom = Math.min(
+      ZOOM_MAX,
+      Math.max(ZOOM_MIN, options.initialZoom ?? 1),
+    );
     this._lastRenderWidth = 0;
     this._resizeTimer = null;
     this._zoomTimer = null;
     this.resizeObserver = null;
     this._createDOM();
+    this._updateZoomLabel();
     this._observeResize();
   }