# WinUI 3 migration plan

**Started:** 2026-05-12 (overnight)
**Status:** in flight — scaffold + redesigned MainWindow + theme system landed,
runtime activation blocked, view-model wiring not yet started.

The full plan for replatforming TeamsISO from WPF / .NET 8 to WinUI 3 /
Windows App SDK 1.6 LTS. The redesigned UI per the approved shape brief
(PRODUCT.md, DESIGN.md, the 2026-05-12 chat transcript) lands as the new
TeamsISO.App.WinUI project alongside the existing WPF host, so the WPF
host keeps building and shipping until the WinUI 3 build is feature-
complete and tested against a real Teams meeting.

## Why two projects instead of in-place rewrite

The WPF and WinUI 3 XAML dialects look similar but diverge in enough
places (resource URIs, DataGrid availability, WindowChrome vs AppWindow,
DispatcherTimer vs DispatcherQueueTimer, pack:// vs ms-appx:///, ThemeResource
vs DynamicResource semantics) that an in-place rewrite would break the
working WPF host for hours-to-days. Coexisting both projects means:

1. `dotnet build TeamsISO.Windows.slnf` keeps producing a working WPF .exe
   throughout the migration.
2. Each WinUI 3 view can be migrated and verified independently.
3. The engine layer (TeamsISO.Engine, TeamsISO.Engine.NdiInterop) and the
   view-models (TeamsISO.App/ViewModels/) are **shared** via ProjectReference.
   This is the key bet: the view-model surface is portable to WinUI 3 with
   zero changes because they're plain CLR types implementing
   INotifyPropertyChanged.
4. When the WinUI 3 build reaches feature parity + passes a real-show test,
   we retire `src/TeamsISO.App` and the WinUI 3 project becomes the only
   shipping host.

## Architectural decisions (locked)

| Decision | Choice | Rationale |
|---|---|---|
| Framework | Windows App SDK 1.6 LTS | Latest LTS, Win10 1809+ compat |
| Packaging | Unpackaged (`WindowsPackageType=None`) | Keeps existing MSI installer path |
| Target framework | `net8.0-windows10.0.19041.0` | WindowsAppSDK 1.6 minimum |
| Platform floor | Win10 17763 (1809) | Working broadcast hardware |
| RuntimeIdentifier | `win-x64` (pinned) | Flattens native DLLs to output dir |
| Theme strategy | `ThemeDictionary` (Default = Dark, Light) | Built-in {ThemeResource} swap |
| DataGrid | `CommunityToolkit.WinUI.UI.Controls.DataGrid 7.1.2` | Only maintained free option |
| View-model | Reuse from TeamsISO.App via ProjectReference | Zero porting cost |
| Window chrome | `AppWindow.TitleBar.ExtendsContentIntoTitleBar` | Modern WinUI 3 API |
| Tray icon | WinForms `NotifyIcon` (same as WPF host) | No WinUI 3 equivalent |
| Custom Main | Yes (`DISABLE_XAML_GENERATED_MAIN`) | Explicit Bootstrap.TryInitialize |

## Phases

### Phase 1 — Scaffold (done)

- [x] `src/TeamsISO.App.WinUI/` project created with WindowsAppSDK 1.6
- [x] `Themes/Tokens.xaml` with Dark + Light ThemeDictionaries
- [x] `Themes/Controls.xaml` with Button hierarchy + typographic ramp
- [x] `App.xaml` + `App.xaml.cs` minimal startup
- [x] `Program.cs` custom Main with Bootstrap.TryInitialize
- [x] Assets copied (Inter.ttf, JetBrainsMono.ttf, dragon-mark.png, icon)
- [x] Solution updated (.sln + .slnf paths backslash-normalized)
- [x] `dotnet build TeamsISO.Windows.slnf -c Debug` is clean

### Phase 2 — MainWindow shell (done)

- [x] 64px left rail with brand mark + nav buttons + status puck
- [x] 44px custom title bar with absorbed live pills + theme toggle
- [x] Section header (Participants count + filter + actions + primary)
- [x] Participants list (ItemsRepeater + DataTemplate, mock data)
- [x] Conditional in-call control bar
- [x] Slim status bar at bottom
- [x] Theme toggle wires Window.Content.RequestedTheme + title-bar colors

### Phase 3 — Runtime activation (blocked, next priority)

The compiled .exe shows "TeamsISO.exe - This application could not be
started" before Main() runs. COREHOST_TRACE confirms .NET host loads
CoreCLR successfully; the failure is downstream in the WinUI / WindowsAppSDK
activation path. Suspected causes (in priority order):

1. **Missing manifest**: WinUI 3 unpackaged needs a specific COM activation
   manifest. Our custom `app.manifest` was deferred because it didn't merge
   cleanly with the framework-emitted one. Reintroduce with proper
   `uap:VisualElements`.
2. **Microsoft.WindowsDesktop.App framework reference**: runtimeconfig.json
   includes `Microsoft.WindowsDesktop.App 8.0.0`, which WinUI 3 doesn't
   want. The .NET SDK adds it implicitly from the `-windows` target
   framework moniker. Try `<EnableMsixTooling>true</EnableMsixTooling>`
   + remove from frameworks list.
3. **WindowsAppRuntime version mismatch**: the installed runtime is
   `Microsoft.WindowsAppRuntime.1.6 (6000.519.329.0)`. Bootstrap.TryInitialize
   should accept any 1.6.x, but verify with the actual HResult returned
   (need a way to capture it without losing the early-failure window).
4. **Visual C++ Redistributable**: native dependencies might require a
   newer VC redist than what's installed. Check WindowsAppSDK 1.6's
   redist requirements.

**Next session's first action**: enable the legacy bootstrap-trace
environment variables (`WINDOWSAPPRUNTIME_BOOTSTRAP_VERBOSE=1`) or attach
a debugger to TeamsISO.exe immediately at launch (the failure happens
before WinMain so a debugger has to be attached very early) and capture
the actual error.

### Phase 4 — View-model wiring

Once runtime activation succeeds, hook the WinUI host into the existing
view-model layer:

- [ ] `MainViewModel` instantiated by `App.OnLaunched` (mirror WPF
      App.xaml.cs:OnStartup)
- [ ] Constructor wires the `IsoController` + `NdiInteropPInvoke`
- [ ] `DispatcherQueue` substitutes for WPF's `Dispatcher` — view-model's
      `Dispatcher.InvokeAsync` calls need adapting to
      `DispatcherQueue.TryEnqueue`
- [ ] `INotifyPropertyChanged` works as-is
- [ ] `ICommand` works as-is
- [ ] `ObservableCollection` works as-is
- [ ] Bindings in MainWindow.xaml updated from {Binding ...} to {x:Bind ...}
      where possible (compile-time-checked, slightly faster)

### Phase 5 — DataGrid migration

Replace the placeholder `ItemsRepeater` with
`CommunityToolkit.WinUI.UI.Controls.DataGrid`:

- [ ] Column definitions: avatar+name+codec, signal+lock, audio meter,
      output-name, ISO toggle
- [ ] Row template with active-speaker cyan-left-border trigger
- [ ] Selection mode = single
- [ ] Right-click context menu (open preview, custom name, restart ISO)
- [ ] Sort: JoinOrder / Alphabetical / OnlineFirst / LoudestFirst (matches
      `UIPreferences.SortMode`)

### Phase 6 — Secondary windows

- [ ] Settings drawer (`SettingsDrawer.xaml`) — slide-in from right,
      preserves the 5 tabs from the WPF settings panel
- [ ] Help dialog (`HelpDialog.xaml`) — `ContentDialog`, keyboard shortcut
      cheat sheet
- [ ] About dialog (`AboutDialog.xaml`) — version, logs path, update check
- [ ] Onboarding (`OnboardingWindow.xaml`) — first-launch only, three panes
- [ ] Notes viewer (`NotesViewer.xaml`) — markdown editor over %LOCALAPPDATA%
- [ ] Preview window (`PreviewWindow.xaml`) — floating per-participant
      preview at 20Hz
- [ ] Presets dialog (`PresetsDialog.xaml`) — `ContentDialog` with the
      save/load/duplicate/export/import row

### Phase 7 — Hardening

- [ ] Single-instance mutex + bring-to-front (port from WPF `App.xaml.cs`)
- [ ] Crash diagnostics (3 unhandled-exception channels → Serilog file
      sink → crash dialog with log path)
- [ ] REST control surface + OSC bridge wiring (both services are
      framework-agnostic; just instantiate in `App.OnLaunched`)
- [ ] Tray icon (port `TrayIconHost.cs` — WinForms.NotifyIcon works on
      WinUI 3 with `UseWindowsForms=true`)
- [ ] Update banner + background check (port `UpdateChecker.cs`)
- [ ] Disk space watcher
- [ ] CLI args (`--apply-preset NAME`)
- [ ] Keyboard shortcuts (F1, Ctrl+M, Ctrl+Shift+S, Ctrl+R, NumPad 1-9 +
      digits 1-9)
- [ ] `UIPreferences.Theme` field added, persistence on theme toggle

### Phase 8 — Tests + verification

- [ ] Build the WinUI 3 project in `TeamsISO.App.Tests` (currently targets
      `net8.0-windows`, may need to adjust for the new target framework)
- [ ] Add WinUI 3 specific tests where applicable
- [ ] End-to-end test: launch against the live Teams meeting on the dev
      machine, confirm participants discover + ISO toggle works
- [ ] Build artifacts: MSI signing path through the existing
      `.forgejo/workflows/release.yml`

### Phase 9 — Retire WPF host

- [ ] `dotnet sln remove src/TeamsISO.App/TeamsISO.App.csproj`
- [ ] Delete `src/TeamsISO.App/` directory
- [ ] Update README.md and CHANGELOG.md
- [ ] Tag v1.0.0 (the original v1.0 cut moves to v0.9; v1.0 = first WinUI
      3 release)

## Risk register

| Risk | Mitigation |
|---|---|
| Activation failure not resolvable | Pivot to WinUI 3 packaged (MSIX) mode; the existing MSI workflow has to change but it's not the end of the world |
| `Dispatcher` → `DispatcherQueue` semantics differ | Wrap with a small `IDispatcher` interface in the engine layer; both hosts provide an impl |
| Custom WPF-style WindowChrome can't fully reproduce in AppWindow API | Accept a slightly different drag-region shape; the title-bar buttons API gives us close-button colors and click handling |
| WebView2 + WindowsAppSDK version conflicts | Pin WebView2 explicitly in the .csproj |
| CommunityToolkit DataGrid 7.x maintenance ending | Plan a fallback to `WinUI.TableView` 1.4.x as a contingency |
| Performance regression on the participants table (thumbnails at 20Hz × N rows) | Profile early; if needed, use `Win2D` for the audio meter and signal indicator |

## What I'm NOT doing

- Replacing the engine layer
- Touching the NDI native interop
- Changing the control surface protocol (REST/WebSocket/OSC)
- Migrating tests right now (Phase 8)
- Adding new product features (anything not in the redesign brief stays
  for a follow-on release)
