Show the image picker instantly, with no backdrop (#14709)

Remove the carousel's fade and geometry transitions, hold the reveal until every visible preview has decoded and two frames have pre-rendered (falling back to revealing anyway after 400ms), and drop the fullscreen scrim and its theme tokens so the picker sits directly on the desktop. Only Escape is accepted before the picker is visible.

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

@@ -174,4 +174,88 @@ assert(
     /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'
 )
+assert(
+  !/Behavior on (opacity|x|y|width|height)/.test(imagePickerQml) && !imagePickerQml.includes('NumberAnimation'),
+  'image picker appears instantly with no fade or geometry transitions'
+)
+assertEqual((imagePickerQml.match(/layoutSettled = true/g) || []).length, 1, 'image picker settles its layout in exactly one place')
+assert(
+  /readonly property bool previewSettled: !thumbnailPath \|\| previewReady/.test(imagePickerQml) &&
+    /onPreviewSettledChanged: if \(previewSettled\) root\.maybeReveal\(\)/.test(imagePickerQml) &&
+    /function allPreviewsSettled\(\) \{[\s\S]*?for \(var i = 0; i < imageCards\.count; i\+\+\) \{[\s\S]*?if \(!item \|\| !item\.previewSettled\) return false[\s\S]*?return true/.test(imagePickerQml) &&
+    /function maybeReveal\(\) \{\s*if \(!allPreviewsSettled\(\) \|\| renderedFrames < 2\) return[\s\S]*?Qt\.callLater\(function\(\) \{\s*if \(root\.allPreviewsSettled\(\) && root\.renderedFrames >= 2\) root\.settleReveal\(\)/.test(imagePickerQml) &&
+    /function settleReveal\(\) \{\s*if \(!opened \|\| !imagesLoaded \|\| layoutSettled \|\| imageArray\.length === 0\) return\s*layoutSettled = true\s*focusPicker\(\)/.test(imagePickerQml),
+  'image picker reveals only once every visible preview has loaded'
+)
+assert(
+  /id: card\s*visible: root\.opened && root\.imagesLoaded && root\.imageArray\.length > 0\s*opacity: root\.layoutSettled \? 1 : 0/.test(imagePickerQml) &&
+    /FrameAnimation \{\s*running: root\.opened && !root\.layoutSettled && root\.renderedFrames < 2\s*onTriggered: \{\s*root\.renderedFrames \+= 1\s*root\.maybeReveal\(\)/.test(imagePickerQml) &&
+    /if \(!allPreviewsSettled\(\) \|\| renderedFrames < 2\) return/.test(imagePickerQml) &&
+    /MouseArea \{ anchors\.fill: parent; enabled: root\.layoutSettled; onClicked: \{\} \}/.test(imagePickerQml),
+  'image picker pre-renders hidden for two frames so its first visible frame is complete'
+)
+assert(
+  !imagePickerQml.includes('color: root.scrim') && !/property color scrim:/.test(imagePickerQml),
+  'image picker shows no fullscreen scrim wash behind the carousel'
+)
+const colorQml = fs.readFileSync(path.join(root, 'shell/Commons/Color.qml'), 'utf8')
+const shellTpl = fs.readFileSync(path.join(root, 'default/themed/shell.toml.tpl'), 'utf8')
+const pickerSection = shellTpl.slice(shellTpl.indexOf('[image-picker]'), shellTpl.indexOf('\n[', shellTpl.indexOf('[image-picker]') + 1))
+assert(
+  !colorQml.includes('image-picker.scrim') && !pickerSection.includes('scrim'),
+  'image picker scrim theme tokens are gone with the backdrop'
+)
+assert(
+  /Timer \{\s*interval: 400\s*running: root\.opened && root\.imagesLoaded && !root\.layoutSettled && root\.imageArray\.length > 0\s*onTriggered: root\.settleReveal\(\)/.test(imagePickerQml),
+  'image picker reveals anyway after a short wait if a preview stalls'
+)
+assert(
+  /if \(!root\.layoutSettled\) \{\s*if \(event\.key === Qt\.Key_Escape\) \{\s*root\.cancel\(\)\s*event\.accepted = true\s*\}\s*return\s*\}/.test(imagePickerQml) &&
+    imagePickerQml.indexOf('if (!root.layoutSettled) {') < imagePickerQml.indexOf('if (root.filterText) {'),
+  'image picker only accepts Escape before it is visible'
+)
+
+// Run the QML reveal guards themselves, the way the loadRows handler above
+// runs, against mocked delegates in each state the gate must decide.
+const revealFns = [
+  imagePickerQml.match(/function allPreviewsSettled\(\) \{[\s\S]*?\n  \}/)[0],
+  imagePickerQml.match(/function settleReveal\(\) \{[\s\S]*?\n  \}/)[0],
+  imagePickerQml.match(/function maybeReveal\(\) \{[\s\S]*?\n  \}/)[0]
+].join('\n')
+function revealContext(settledFlags, frames) {
+  const ctx = {
+    opened: true,
+    imagesLoaded: true,
+    layoutSettled: false,
+    renderedFrames: frames,
+    imageArray: settledFlags.map(() => ({})),
+    focused: 0,
+    Qt: { callLater(callback) { callback() } }
+  }
+  const items = settledFlags.map(previewSettled => ({ previewSettled }))
+  ctx.imageCards = { count: items.length, itemAt(i) { return items[i] } }
+  ctx.focusPicker = () => { ctx.focused += 1 }
+  ctx.root = ctx
+  require('vm').runInNewContext(revealFns, ctx)
+  return ctx
+}
+let reveal = revealContext([true, true], 2)
+reveal.maybeReveal()
+assert(reveal.layoutSettled && reveal.focused === 1, 'reveal settles and focuses once every preview is settled and frames presented')
+reveal = revealContext([true, false], 2)
+reveal.maybeReveal()
+assert(!reveal.layoutSettled, 'an unsettled preview holds the reveal')
+reveal = revealContext([true, true], 1)
+reveal.maybeReveal()
+assert(!reveal.layoutSettled, 'reveal waits for presented frames')
+reveal = revealContext([], 2)
+reveal.maybeReveal()
+assert(!reveal.layoutSettled, 'reveal waits while no cards are rendered')
+reveal = revealContext([false], 0)
+reveal.settleReveal()
+assert(reveal.layoutSettled, 'fallback settle reveals despite a stalled preview')
+reveal = revealContext([true], 2)
+reveal.opened = false
+reveal.settleReveal()
+assert(!reveal.layoutSettled, 'settle does nothing once the picker is closed')
 JS