Keep image picker work bounded for large theme collections

test/shell.d/image-picker-test.sh

@@ -42,6 +42,45 @@ assertEqual(picker.filteredPosition(images, 2, 'dark'), 1, 'image picker compute
 assertEqual(picker.selectedFilteredPosition(images, 2, 'dark'), 0, 'image picker selected filtered position falls back when selected is hidden')
 assertEqual(picker.nextSelectedIndexForFilter(images, 0, 'dark'), 1, 'image picker moves selection to first match when filter hides current item')
 
+class WindowModel {
+  constructor() { this.items = []; this.insertions = 0 }
+  get count() { return this.items.length }
+  get(i) { return this.items[i] }
+  remove(i) { this.items.splice(i, 1) }
+  insert(i, item) { this.items.splice(i, 0, { ...item }); this.insertions++ }
+  move(from, to) { this.items.splice(to, 0, this.items.splice(from, 1)[0]) }
+  setProperty(i, key, value) { this.items[i][key] = value }
+}
+
+for (const count of [0, 1, 200, 530, 10000]) {
+  const collection = Array.from({ length: count }, (_, i) => ({ filePath: `/themes/theme-${i}.png` }))
+  const indices = picker.matchingIndices(collection, '')
+  const model = new WindowModel()
+  for (const selected of [0, Math.min(1, count - 1), Math.floor(count / 2), count - 1]) {
+    const window = picker.visibleWindow(indices, selected, 16)
+    picker.syncWindow(model, window)
+    assertDeepEqual(model.items, window, `carousel window reconciles ${count} images at ${selected}`)
+    assert(model.count <= 33, `carousel bounds delegates for ${count} images`)
+    if (count) assert(window.some(item => item.imageIndex === selected && item.relativeIndex === 0), `carousel includes selection in ${count} images`)
+  }
+  const matches = picker.matchingIndices(collection, 'theme-19')
+  picker.syncWindow(model, picker.visibleWindow(matches, matches[0], 16))
+  assert(model.items.every(item => collection[item.imageIndex].filePath.includes('theme-19')), `carousel filters ${count} images`)
+  picker.syncWindow(model, picker.visibleWindow([], 0, 16))
+  assertEqual(model.count, 0, `carousel clears ${count} images when there are no matches`)
+}
+
+const windowModel = new WindowModel()
+const allIndices = Array.from({ length: 200 }, (_, i) => i)
+picker.syncWindow(windowModel, picker.visibleWindow(allIndices, 100, 16))
+const retained = windowModel.get(17)
+picker.syncWindow(windowModel, picker.visibleWindow(allIndices, 101, 16))
+assertEqual(windowModel.get(16), retained, 'carousel retains overlapping delegates when navigating')
+assertEqual(windowModel.insertions, 34, 'carousel creates only one new delegate for an adjacent selection')
+for (const radius of [1, 8, 16]) {
+  assertEqual(picker.visibleWindow(allIndices, 100, radius).length, radius * 2 + 1, `carousel scales its window to radius ${radius}`)
+}
+
 const imagePickerQml = fs.readFileSync(path.join(root, 'shell/plugins/image-picker/ImagePicker.qml'), 'utf8')
 assert(
   /function preloadRows[\s\S]*if \(opened \|\| requestActive\) return/.test(imagePickerQml),
@@ -74,7 +113,14 @@ assert(
   'image picker parks on OverlayWindow and takes the keyboard once images load'
 )
 assert(
-  /source: item\.sourceActivated && item\.thumbnailPath \? Util\.fileUrl\(item\.thumbnailPath\) : ""[\s\S]*asynchronous: false/.test(imagePickerQml),
-  'image picker loads activated thumbnails synchronously to avoid carousel flicker'
+  /model: visibleImages/.test(imagePickerQml) &&
+    /sourceSize: Qt\.size\(root\.expandedWidth, root\.expandedHeight\)/.test(imagePickerQml) &&
+    /asynchronous: true\s*cache: false/.test(imagePickerQml),
+  'image picker renders its window with bounded asynchronous decoding'
+)
+assert(
+  imagePickerQml.includes('(item.selected || root.neighborImagesEnabled)') &&
+    /onStatusChanged: if \(item.selected && \(status === Image.Ready \|\| status === Image.Error\)\) root.neighborImagesEnabled = true/.test(imagePickerQml),
+  'image picker prioritizes the selected preview and releases neighbors on success or failure'
 )
 JS