# Controls — index

The phase-2 carved pieces of what used to be one monolithic `MainWindow.xaml`
(1,681 lines → a 123-line shell). Each is a `UserControl` in the `ytLive.Controls`
namespace, extracted one roll-back commit at a time (refactor-commit-12..18).
See [`schema.md`](../schema.md) for the memory-map conventions.

| File | Purpose |
|------|---------|
| `BottomBar.xaml(.cs)` | Footer (Row 3): stream stats (bitrate/fps/dropped/duration/health), resolution dropdown (gear menu moved up to TopBar 2026-09-22) |
| `HealthBanner.xaml(.cs)` | Row 1 status banner + the 7 value→visibility converters live in the app theme, not here |
| `TopBar.xaml(.cs)` | Row 0 session surface (2026-09-22 redesign): brand + gear menu (left), one segmented REC|ON-AIR mode switch + world actions (Record: Start Recording · Stream: Go Live + Test) + reality line while running (dot/word/elapsed) + End (center), account zone — Sign In or avatar w/ Change Account/Logout context menu (right). `RefreshAvatar()`, `GearButton_Click` |
| `PreviewPane.xaml(.cs)` | Row 1 Col 1 center: the 1920×1080 `OverlayCanvas`/`SelectionOverlay`/`BrandFlashLayer`/`SocialBarElement`, text pull-out drawer, and the live-controls row (TRAX / game / mic meters + sliders + speakers + socials) |
| `SceneThumbnailStrip.xaml(.cs)` | Row 0 scene-picker strip (`ItemsControl` over `Scenes`), staged-red / live-green border highlight |
| `LeftPanel.xaml(.cs)` | Row 1 Col 0 left panel: edit mode → layers+properties; live → YouTube chat. Source add/edit/remove, list drag-to-reorder, snapshot revert-accept |
| `OverlayHost.xaml(.cs)` | Root-grid overlay dialogs: Settings / Report Bug / Feature Request / About (+ licenses + license-key entry). `BackToAbout_Click` lives here |
| `SceneThumbnailStrip.xaml.cs` | Code-behind for the strip above |
| `LeftPanel.xaml.cs` | Code-behind for the panel above |

## Window ↔ control contract

The shell (`MainWindow.xaml(.cs)`) wires up each control and routes the few
cross-cutting calls through it:

- Ctor finds each control by `x:Name` (`TopBar`, `PreviewPane`, `LeftPanel`)
  AFTER `InitializeComponent`, **before** any method touches it (null-ref guard).
- `_previewPane.IsClickInsidePreview/Drawer` + `_leftPanel.IsClickInside` →
  deselection guard in `Window_PreviewMouseLeftButtonDown`.
- `_previewPane.UpdateSelectionOverlay(bool)` + `_leftPanel.OnSelectionChanged(vm)`
  → selection/edit-mode routing from the VM's `SelectedElement` change.
- `_topBar.RefreshAvatar()` on `IsConnected`/`AccountAvatarUrl` change.
- Handlers in moved controls cast `(DataContext as MainViewModel)` — controls
  inherit the window's DataContext; never pass the VM through a property.

## Gotchas learned the hard way

- **A UserControl cannot see `Window.Resources`** (StaticResource resolves by
  element lookup, so it stops at the control boundary). The 7 converters
  (`BoolToVis`, `InverseBoolToVis`, `NotNullToVis`, `NullToVis`, `HiddenBoolToVis`,
  `EnumToBool`, `AllTrueToVis`) were promoted from `MainWindow.Resources` into
  `Themes/Controls.xaml` (see [`Themes/index.md`](../Themes/index.md)).
- **Moved XAML can lose its namespace**: a block cut from MainWindow carries no
  root xmlns, so any `models:`/`Helpers:` ref in it breaks the build with
  `MC2000: Value cannot be null (key)`. Declare `xmlns:models` / `xmlns:Helpers`
  on each control's root (LeftPanel hit this).
- **Name-looked-up host stubs must stay in the window**, not a control:
  `WebViewHostPanel` (ctor `InitWebView2(WebViewHostPanel)`) and `ToastArea`
  (`NotificationService.InArea("ToastArea")`) are resolved by name from the
  window root — so `OverlayHost` deliberately leaves them as thin window-root
  children (Commit 18). Since the 2026-09-14 composition-capture redesign only
  `ToastArea` remains — `WebViewHostPanel` is deleted (web sources no longer
  host a multiline XAML control; `InitWebView2()` runs from `MainWindow_Loaded`
  with no panel argument).
- When cutting visual wrappers, don't drop the outer `Border`'s
  background/glow/margin — Commit 15 initially lost the preview's outer border
  and had to restore it same-commit.

Related: [`ViewModels/index.md`](../ViewModels/index.md) (MainViewModel the
controls bind to), [`Themes/index.md`](../Themes/index.md) (styles/converters),
[`Helpers/index.md`](../Helpers/index.md) (ViewModelBase, converters), the
`MainWindow.xaml` shell at repo root that hosts these.