CmdPal: Add slideshow background mode and rotation settings by Error0229 · Pull Request #46452 · microsoft/PowerToys

Error0229 · 2026-03-24T00:52:14Z

Summary of the Pull Request

Add a dedicated Slideshow background mode in CmdPal appearance settings
Add slideshow folder path, change interval (on activation / 1 / 10 / 30 / 60 min), and shuffle settings
Add slideshow rotation engine in ThemeService — rotates on hide so next activation shows new image
Shuffle uses Fisher-Yates algorithm to guarantee every image is shown before any repeats
Add BackgroundImagePathResolver utility with 13 unit tests
Fix a settings crash by guarding against empty preview image paths

PR Checklist

Closes: CmdPal: Support background image rotation from a folder #45879
Communication: This is a community contribution for my own feature request (CmdPal: Support background image rotation from a folder #45879). Happy to adjust the approach based on team feedback.
Tests: Added/updated and all pass
Localization: All end-user-facing strings can be localized
Dev docs: N/A — no new module or public API surface
New binaries: N/A — no new binaries added
Documentation updated: N/A — internal feature addition, no external docs change needed

Detailed Description of the Pull Request / Additional comments

New mode: Slideshow

ColorizationMode.Slideshow is added alongside the existing Image mode. Both modes share tint/opacity/blur/fit controls, but have separate path controls — single-image uses a file picker (BackgroundImagePath), slideshow uses a folder picker (BackgroundImageSlideshowFolderPath).

Rotation engine

ThemeService maintains internal state to track the current slideshow image. Rotation triggers on: folder changed, current file deleted, or activation after the configured interval elapsed. Supports both shuffle and sequential (alphabetical wrap-around) ordering.

Shuffle algorithm

Uses Fisher-Yates to pre-shuffle the full index array, then walks through it with a cursor. When the deck is exhausted, reshuffles — with the last-shown image swapped away from position 0 to avoid repeats at deck boundaries. This guarantees every image is shown exactly once before any image repeats.

Rotation timing

MainWindow.HideWindow() calls RefreshThemeForActivation() before hiding, so the image swaps while invisible — no flicker on next activation.

Settings

New JSON keys (additive, no migration needed):

BackgroundImageSlideshowFolderPath (string)
BackgroundImageChangeIntervalMinutes (int, default 0 = on activation only)
BackgroundImageShuffle (bool, default true)

Validation Steps Performed

Built src/modules/cmdpal/Microsoft.CmdPal.UI with tools/build/build.cmd (Debug/x64) — 0 errors
Built and ran BackgroundImagePathResolverTests (13/13 passed)
Manually validated CmdPal settings flow for Image vs Slideshow modes
Validated on-hide rotation behavior
Verified shuffle covers all images before repeating

…t#45879) Add a dedicated Slideshow background mode in CmdPal appearance settings with folder-based image rotation, configurable interval, and shuffle. - Add ColorizationMode.Slideshow enum value - Add slideshow folder path, change interval, and shuffle settings - Add slideshow rotation engine in ThemeService (sequential/shuffle, interval-based, rotate-on-hide so next activation shows new image) - Add BackgroundImagePathResolver utility with unit tests (13 tests) - Add folder picker and slideshow controls to AppearancePage - Fix settings crash on empty preview image paths - Add localized strings for all new UI elements Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Single-button StackPanel wrappers around the image picker and folder picker buttons serve no purpose. Use the Button directly as the SettingsCard content. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

…eImageUri Move the relative-path-to-absolute-URI logic out of the view model ternary chains into a dedicated helper. Both AppearanceSettingsViewModel and DockAppearanceSettingsViewModel now read as a simple null-check chain. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Error0229 · 2026-03-24T00:53:43Z

@microsoft-github-policy-service agree

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/AppearanceSettingsViewModel.cs

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.Designer.cs

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.resx

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Services/IThemeService.cs

src/modules/cmdpal/Microsoft.CmdPal.UI/MainWindow.xaml.cs

src/modules/cmdpal/Microsoft.CmdPal.UI/Strings/en-us/Resources.resw

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

michaeljolley · 2026-03-24T02:06:12Z

/azp run

azure-pipelines · 2026-03-24T02:06:22Z

Azure Pipelines successfully started running 1 pipeline(s).

Copilot

Pull request overview

Adds a new Slideshow background mode to CmdPal’s appearance settings, including folder selection and rotation behavior, so users can rotate background images from a directory instead of a single file.

Changes:

Introduces ColorizationMode.Slideshow plus new persisted settings for slideshow folder, change interval, and shuffle.
Updates settings UI to support slideshow selection (folder picker + interval/shuffle controls).
Adds BackgroundImagePathResolver utility (with unit tests) and wires it into theme/image preview paths.

Reviewed changes

Copilot reviewed 15 out of 16 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/ColorizationMode.cs	Adds `Slideshow` mode to the colorization enum.
src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/SettingsModel.cs	Persists slideshow folder, interval minutes, and shuffle flag.
src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Services/IThemeService.cs	Adds `RefreshThemeForActivation()` hook for summon-time refresh behavior.
src/modules/cmdpal/Microsoft.CmdPal.UI/Services/ThemeService.cs	Implements slideshow rotation/selection logic and integrates slideshow into theme snapshot generation.
src/modules/cmdpal/Microsoft.CmdPal.UI/MainWindow.xaml.cs	Triggers slideshow refresh before hiding to avoid visible swaps on next activation.
src/modules/cmdpal/Microsoft.CmdPal.UI/Settings/AppearancePage.xaml	Adds Slideshow option and slideshow-specific settings cards/controls.
src/modules/cmdpal/Microsoft.CmdPal.UI/Settings/AppearancePage.xaml.cs	Implements folder picker and forces mode switch when picking file/folder.
src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/AppearanceSettingsViewModel.cs	Adds slideshow settings bindings and preview image resolution logic.
src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/DockAppearanceSettingsViewModel.cs	Uses resolver-based URI creation for safer image preview resolution.
src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/MainWindowViewModel.cs	Applies theme snapshots on UI thread without always dispatching.
src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/BackgroundImagePathResolver.cs	New helper to resolve folder-vs-file paths, supported images, and safe image URIs.
src/modules/cmdpal/Tests/Microsoft.CmdPal.UI.ViewModels.UnitTests/BackgroundImagePathResolverTests.cs	Adds unit tests covering resolver behaviors (folder/file/URI cases).
src/modules/cmdpal/Microsoft.CmdPal.UI/Strings/en-us/Resources.resw	Adds localized strings for slideshow UI and interval/shuffle labels.
src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.resx	Adds localized string used by folder picker commit button.
src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.Designer.cs	Regenerates strongly-typed accessor for the new resx string.
.github/actions/spell-check/expect.txt	Adds “slideshow” to spelling allow-list and removes an unused entry.

Files not reviewed (1)

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Properties/Resources.Designer.cs: Language not supported

Copilot · 2026-03-24T18:47:25Z

src/modules/cmdpal/Microsoft.CmdPal.UI/Services/ThemeService.cs

+            return;
+        }
+
+        Interlocked.Exchange(ref _rotateMainBackgroundOnActivation, 1);


RefreshThemeForActivation() calls Reload() directly. Since Reload creates BitmapImage and swaps XAML resources, this should be marshaled onto the UI DispatcherQueue (or at least guard with _dispatcherQueue.HasThreadAccess). Otherwise any non-UI-thread caller of IThemeService.RefreshThemeForActivation could trigger thread-affinity crashes or undefined behavior.

Suggested change

Interlocked.Exchange(ref _rotateMainBackgroundOnActivation, 1);

Interlocked.Exchange(ref _rotateMainBackgroundOnActivation, 1);

// Ensure Reload runs on the UI thread, since it manipulates XAML resources and BitmapImage.

if (_dispatcherQueue is not null && !_dispatcherQueue.HasThreadAccess)

{

_dispatcherQueue.TryEnqueue(Reload);

return;

}

All current callers of RefreshThemeForActivation() run on the UI thread — HideWindow() is a UI event
handler, Initialize() runs during startup on UI thread, and RequestReload() fires via a DispatcherQueueTimer. Not a bug today, but the IThemeService interface doesn't document thread affinity. Happy to add a Debug.Assert(_dispatcherQueue.HasThreadAccess) guard or XML doc comment if the team thinks it's warranted.

Copilot · 2026-03-24T18:47:25Z

src/modules/cmdpal/Microsoft.CmdPal.UI/Services/ThemeService.cs

+        var files = BackgroundImagePathResolver.GetSupportedImageFiles(folderPath);
+        if (files.Count == 0)
+        {
+            ResetMainBackgroundImageState();
+            return null;


ResolveMainBackgroundImagePath enumerates and sorts the entire slideshow folder (GetSupportedImageFiles) during Reload(), which runs on the UI thread. With large folders or slow storage this can stall hide/summon and other theme reloads; consider caching the file list (and only refreshing when the folder changes or a rescan is needed) or moving the scan off the UI thread and applying the next image once available.

Acknowledged — GetSupportedImageFiles does synchronous EnumerateFiles + OrderBy + ToArray on the UI thread. For typical wallpaper folders (10-100 images) this is sub-millisecond on SSD. Adding caching would introduce invalidation complexity (file adds/deletes in the folder). Happy to add caching if the team considers it necessary

Copilot · 2026-03-24T18:47:26Z

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/AppearanceSettingsViewModel.cs

+    private string? GetEffectiveBackgroundPreviewPath()
+    {
+        return ColorizationMode switch
+        {
+            ColorizationMode.Slideshow => BackgroundImagePathResolver.ResolvePreviewImagePath(BackgroundImageSlideshowFolderPath),
+            _ => BackgroundImagePath,
+        };


GetEffectiveBackgroundPreviewPath() calls BackgroundImagePathResolver.ResolvePreviewImagePath(), which performs directory enumeration/sorting for folder paths. Because EffectiveBackgroundImageSource is a computed property used by bindings, this can introduce repeated synchronous disk I/O on the UI thread; consider resolving/caching the preview image path when BackgroundImageSlideshowFolderPath changes (and invalidating it when needed) rather than doing filesystem work in the getter path.

Suggested change

private string? GetEffectiveBackgroundPreviewPath()

{

return ColorizationMode switch

{

ColorizationMode.Slideshow => BackgroundImagePathResolver.ResolvePreviewImagePath(BackgroundImageSlideshowFolderPath),

_ => BackgroundImagePath,

};

// Cache for slideshow preview resolution to avoid repeated directory enumeration on the UI thread.

private string? _cachedSlideshowPreviewPath;

private string? _cachedSlideshowFolderPathForPreview;

private string? GetEffectiveBackgroundPreviewPath()

{

if (ColorizationMode == ColorizationMode.Slideshow)

{

var currentFolderPath = BackgroundImageSlideshowFolderPath;

if (string.Equals(currentFolderPath, _cachedSlideshowFolderPathForPreview, StringComparison.Ordinal)

&& _cachedSlideshowPreviewPath is not null)

{

return _cachedSlideshowPreviewPath;

}

var resolvedPath = BackgroundImagePathResolver.ResolvePreviewImagePath(currentFolderPath);

_cachedSlideshowFolderPathForPreview = currentFolderPath;

_cachedSlideshowPreviewPath = resolvedPath;

return resolvedPath;

}

return BackgroundImagePath;

This getter only runs while the settings page is visible, and ResolvePreviewImagePath picks the first file
from a typically small folder — the real-world cost is negligible. Leaving it uncached to keep behavior
correct and code simple

…trings Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

catol-abacus and others added 3 commits March 23, 2026 17:13

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chore: add 'slideshow' to spell-check expect list

1d6734e

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Error0229 force-pushed the feature/cmdpal-background-slideshow-45879 branch from f715528 to 1d6734e Compare March 24, 2026 01:18

michaeljolley added the Product-Command Palette Refers to the Command Palette utility label Mar 24, 2026

michaeljolley requested a review from Copilot March 24, 2026 18:40

Copilot started reviewing on behalf of michaeljolley March 24, 2026 18:41 View session

Copilot AI reviewed Mar 24, 2026

View reviewed changes

Merge upstream/main: resolve Resources.resw conflict with PinToDock s…

6982536

…trings Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

-        Interlocked.Exchange(ref _rotateMainBackgroundOnActivation, 1);
+        Interlocked.Exchange(ref _rotateMainBackgroundOnActivation, 1);
+        // Ensure Reload runs on the UI thread, since it manipulates XAML resources and BitmapImage.
+        if (_dispatcherQueue is not null && !_dispatcherQueue.HasThreadAccess)
+        {
+            _dispatcherQueue.TryEnqueue(Reload);
+            return;
+        }

-    private string? GetEffectiveBackgroundPreviewPath()
-    {
-        return ColorizationMode switch
-        {
-            ColorizationMode.Slideshow => BackgroundImagePathResolver.ResolvePreviewImagePath(BackgroundImageSlideshowFolderPath),
-            _ => BackgroundImagePath,
-        };
+    // Cache for slideshow preview resolution to avoid repeated directory enumeration on the UI thread.
+    private string? _cachedSlideshowPreviewPath;
+    private string? _cachedSlideshowFolderPathForPreview;
+    private string? GetEffectiveBackgroundPreviewPath()
+    {
+        if (ColorizationMode == ColorizationMode.Slideshow)
+        {
+            var currentFolderPath = BackgroundImageSlideshowFolderPath;
+            if (string.Equals(currentFolderPath, _cachedSlideshowFolderPathForPreview, StringComparison.Ordinal)
+                && _cachedSlideshowPreviewPath is not null)
+            {
+                return _cachedSlideshowPreviewPath;
+            }
+            var resolvedPath = BackgroundImagePathResolver.ResolvePreviewImagePath(currentFolderPath);
+            _cachedSlideshowFolderPathForPreview = currentFolderPath;
+            _cachedSlideshowPreviewPath = resolvedPath;
+            return resolvedPath;
+        }
+        return BackgroundImagePath;

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Summary of the Pull Request

PR Checklist

Detailed Description of the Pull Request / Additional comments

New mode: Slideshow

Rotation engine

Shuffle algorithm

Rotation timing

Settings

Validation Steps Performed

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Error0229 commented Mar 24, 2026

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