CmdPal: Add a dock (#45824)

Add support for a "dock" window in CmdPal. The dock is a toolbar powered
by the `APPBAR` APIs. This gives you a persistent region to display
commands for quick shortcuts or glanceable widgets.

The dock can be pinned to any side of the screen.
The dock can be independently styled with any of the theming controls
cmdpal already has
The dock has three "regions" to pin to - the "start", the "center", and
the "end".
Elements on the dock are grouped as "bands", which contains a set of
"items". Each "band" is one atomic unit. For example, the Media Player
extension produces 4 items, but one _band_.
The dock has only one size (for now)
The dock will only appear on your primary display (for now)

This PR includes support for pinning arbitrary top-level commands to the
dock - however, we're planning on replacing that with a more universal
ability to pin any command to the dock or top level. (see #45191). This
is at least usable for now.

This is definitely still _even more preview_ than usual PowerToys
features, but it's more than usable. I'd love to get it out there and
start collecting feedback on where to improve next. I'll probably add a
follow-up issue for tracking the remaining bugs & nits.

closes #45201

---------

Co-authored-by: Niels Laute <niels.laute@live.nl>

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Settings/DockSettings.cs

@@ -0,0 +1,172 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Text.Json.Serialization;
+using Microsoft.UI;
+using Windows.UI;
+
+namespace Microsoft.CmdPal.UI.ViewModels.Settings;
+
+#pragma warning disable SA1402 // File may only contain a single type
+
+/// <summary>
+/// Settings for the Dock. These are settings for _the whole dock_. Band-specific
+/// settings are in <see cref="DockBandSettings"/>.
+/// </summary>
+public class DockSettings
+{
+    public DockSide Side { get; set; } = DockSide.Top;
+
+    public DockSize DockSize { get; set; } = DockSize.Small;
+
+    public DockSize DockIconsSize { get; set; } = DockSize.Small;
+
+    // <Theme settings>
+    public DockBackdrop Backdrop { get; set; } = DockBackdrop.Acrylic;
+
+    public UserTheme Theme { get; set; } = UserTheme.Default;
+
+    public ColorizationMode ColorizationMode { get; set; }
+
+    public Color CustomThemeColor { get; set; } = Colors.Transparent;
+
+    public int CustomThemeColorIntensity { get; set; } = 100;
+
+    public int BackgroundImageOpacity { get; set; } = 20;
+
+    public int BackgroundImageBlurAmount { get; set; }
+
+    public int BackgroundImageBrightness { get; set; }
+
+    public BackgroundImageFit BackgroundImageFit { get; set; }
+
+    public string? BackgroundImagePath { get; set; }
+
+    // </Theme settings>
+    // public List<string> PinnedCommands { get; set; } = [];
+    public List<DockBandSettings> StartBands { get; set; } = [];
+
+    public List<DockBandSettings> CenterBands { get; set; } = [];
+
+    public List<DockBandSettings> EndBands { get; set; } = [];
+
+    public bool ShowLabels { get; set; } = true;
+
+    [JsonIgnore]
+    public IEnumerable<(string ProviderId, string CommandId)> AllPinnedCommands =>
+        StartBands.Select(b => (b.ProviderId, b.CommandId))
+        .Concat(CenterBands.Select(b => (b.ProviderId, b.CommandId)))
+        .Concat(EndBands.Select(b => (b.ProviderId, b.CommandId)));
+
+    public DockSettings()
+    {
+        // Initialize with default values
+        // PinnedCommands = [
+        //     "com.microsoft.cmdpal.winget"
+        // ];
+        StartBands.Add(new DockBandSettings
+        {
+            ProviderId = "com.microsoft.cmdpal.builtin.core",
+            CommandId = "com.microsoft.cmdpal.home",
+        });
+        StartBands.Add(new DockBandSettings
+        {
+            ProviderId = "WinGet",
+            CommandId = "com.microsoft.cmdpal.winget",
+            ShowLabels = false,
+        });
+
+        EndBands.Add(new DockBandSettings
+        {
+            ProviderId = "PerformanceMonitor",
+            CommandId = "com.microsoft.cmdpal.performanceWidget",
+        });
+        EndBands.Add(new DockBandSettings
+        {
+            ProviderId = "com.microsoft.cmdpal.builtin.datetime",
+            CommandId = "com.microsoft.cmdpal.timedate.dockBand",
+        });
+    }
+}
+
+/// <summary>
+/// Settings for a specific dock band. These are per-band settings stored
+/// within the overall <see cref="DockSettings"/>.
+/// </summary>
+public class DockBandSettings
+{
+    public required string ProviderId { get; set; }
+
+    public required string CommandId { get; set; }
+
+    /// <summary>
+    /// Gets or sets whether titles are shown for items in this band.
+    /// If null, falls back to dock-wide ShowLabels setting.
+    /// </summary>
+    public bool? ShowTitles { get; set; }
+
+    /// <summary>
+    /// Gets or sets whether subtitles are shown for items in this band.
+    /// If null, falls back to dock-wide ShowLabels setting.
+    /// </summary>
+    public bool? ShowSubtitles { get; set; }
+
+    /// <summary>
+    /// Gets or sets a value for backward compatibility. Maps to ShowTitles.
+    /// </summary>
+    [System.Text.Json.Serialization.JsonIgnore]
+    public bool? ShowLabels
+    {
+        get => ShowTitles;
+        set => ShowTitles = value;
+    }
+
+    /// <summary>
+    /// Resolves the effective value of <see cref="ShowTitles"/> for this band.
+    /// If this band doesn't have a specific value set, we'll fall back to the
+    /// dock-wide setting (passed as <paramref name="defaultValue"/>).
+    /// </summary>
+    public bool ResolveShowTitles(bool defaultValue) => ShowTitles ?? defaultValue;
+
+    /// <summary>
+    /// Resolves the effective value of <see cref="ShowSubtitles"/> for this band.
+    /// If this band doesn't have a specific value set, we'll fall back to the
+    /// dock-wide setting (passed as <paramref name="defaultValue"/>).
+    /// </summary>
+    public bool ResolveShowSubtitles(bool defaultValue) => ShowSubtitles ?? defaultValue;
+
+    public DockBandSettings Clone()
+    {
+        return new()
+        {
+            ProviderId = this.ProviderId,
+            CommandId = this.CommandId,
+            ShowTitles = this.ShowTitles,
+            ShowSubtitles = this.ShowSubtitles,
+        };
+    }
+}
+
+public enum DockSide
+{
+    Left = 0,
+    Top = 1,
+    Right = 2,
+    Bottom = 3,
+}
+
+public enum DockSize
+{
+    Small,
+    Medium,
+    Large,
+}
+
+public enum DockBackdrop
+{
+    Transparent,
+    Acrylic,
+}
+
+#pragma warning restore SA1402 // File may only contain a single type