fix(viewer): keep the image src until a closed Viewer is released

Viewer.js rebuilds its item list from images that still have a src. On
close, the src was removed before the viewer cleanup ran, so a pending
view found no items and threw "c is undefined" (WebKit and Firefox).
With Viewer.js, the src is now removed after the viewer is destroyed,
once its pending view settles.

The recorded-run history test passed 40 of 40 runs in WebKit and in
Firefox.

tests/js/workspace-media-viewer.test.js

@@ -164,18 +164,22 @@ test('an inline Viewer still loading its image is destroyed only after it has vi
     const f = mountedDom(), parentScope = createScope(), controller = borrowedController(), items = [occurrenceMedia('1',1,'c')];
     const instances = [];
     // Viewer.js's inline destroy() leaves an in-flight view running; its callback then needs a live instance.
-    f.win.Viewer = class { constructor(node,options) { this.options = options; this.destroyed = 0; this.viewed = false; instances.push(this); }
+    f.win.Viewer = class { constructor(node,options) { this.node = node; this.options = options; this.destroyed = 0; this.viewed = false; instances.push(this); }
         destroy() { this.destroyed++; } resize() {} };
     const globals = {ResizeObserver:globalThis.ResizeObserver, requestAnimationFrame:globalThis.requestAnimationFrame, cancelAnimationFrame:globalThis.cancelAnimationFrame};
     Object.assign(globalThis, {ResizeObserver:class { observe() {} disconnect() {} }, requestAnimationFrame:() => 1, cancelAnimationFrame() {}});
     const view = module.createMediaViewer({container:f.container,parentScope,inspectionController:controller,adapter,sender:{open(){}}});
     try {
         view.open({items,selectedKey:'c'.repeat(64)});
-        const [loading] = instances;
+        const [loading] = instances, image = loading.node, removed = [];
+        image.removeAttribute = key => removed.push(key);
         f.walk(f.container,n => n.attributes['aria-label'] === 'Close preview')[0].fire('click');
         assert.equal(loading.destroyed, 0, 'not destroyed while its image view is pending');
+        // Viewer.js lists only images that still have a src; the pending view needs it.
+        assert.deepEqual(removed, [], 'the image keeps its src while the view is pending');
         loading.viewed = true; loading.options.viewed.call(loading);
         assert.equal(loading.destroyed, 1, 'destroyed once its pending view settles');
+        assert.deepEqual(removed, ['src'], 'the src is released after the viewer');
         loading.options.viewed.call(loading);
         assert.equal(loading.destroyed, 1, 'never destroyed twice');
 

web/js/workspace/media-viewer.mjs

@@ -129,13 +129,19 @@ export function createMediaViewer({container,parentScope,inspectionController,se
             } else {
                 node.alt = selected.filename;node.decoding = 'async';
                 node.hidden = !!window.Viewer;
-                if (!window.Viewer) mediaLocal.listen(node,'load',() => {if (current()) session.ready(key);});
-                mediaLocal.cleanup(() => node.removeAttribute('src'));
+                // With Viewer.js the src is released after the viewer (see release below).
+                if (!window.Viewer) {
+                    mediaLocal.listen(node,'load',() => {if (current()) session.ready(key);});
+                    mediaLocal.cleanup(() => node.removeAttribute('src'));
+                }
             }
             node.src = url.href;media.append(node);
             if (!selected.is_video && window.Viewer) {
                 let fitFrame = 0, fitWidth, fitHeight, viewSettled = false, released = false, fallback = 0;
-                const release = () => { if (released) return; released = true; clearTimeout(fallback); instance.destroy(); };
+                const release = () => {
+                    if (released) return;
+                    released = true;clearTimeout(fallback);instance.destroy();node.removeAttribute('src');
+                };
                 const scheduleFit = () => {
                     if (!current() || fitFrame) return;
                     fitFrame = requestAnimationFrame(() => {
@@ -157,7 +163,8 @@ export function createMediaViewer({container,parentScope,inspectionController,se
                 viewer = instance;mediaLocal.cleanup(() => {
                     observer.disconnect();cancelAnimationFrame(fitFrame);
                     // Inline Viewer.js keeps viewing a still-loading image after destroy(), and that view
-                    // then reads the destroyed list; destroy once the view settles, fails or times out.
+                    // rebuilds its list from images that still have a src; keep both until the view
+                    // settles, fails or times out.
                     if (viewSettled) { release(); return; }
                     node.addEventListener('error',release,{once:true});
                     fallback = setTimeout(release,PENDING_VIEW_DESTROY_MS);