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Rendering

Freshness: 2026-08-05 · commit c77517c · covers Controls/, Animations/, Composition/, Converters/, Themes/

Template equivalent: frontend.

Everything the user sees. Two stacks meet here — WPF for layout and chrome, Windows.UI.Composition for the live window previews. They are bridged by CompositionHost, an HwndHost.

Capture stack — StageManager.Composition

File Lines Role
CaptureSession.cs 584 one live window → one composition visual tree
D3DDeviceHolder.cs 211 shared D3D11 device + IDirect3DDevice, device-lost recovery
CompositionHost.cs 130 HwndHost child window with WS_EX_NOREDIRECTIONBITMAP; Root visual setter
CompositorFactory.cs 65 per-thread Compositor + DesktopWindowTarget
DispatcherQueueHelper.cs 57 CreateDispatcherQueueController so WPF's thread can host a compositor
Interop/CompositionInterop.cs 73 ICompositorInterop, ICompositorDesktopInterop, ICompositionDrawingSurfaceInterop
Interop/Direct3DInterop.cs 75 CreateDirect3D11DeviceFromDXGIDevice, IDirect3DDxgiInterfaceAccess
Interop/GraphicsCaptureItemInterop.cs 69 IGraphicsCaptureItemInterop.CreateForWindow

CaptureSession visual tree

Three layers, because Composition only foreshortens a child visual's 3D rotation — perspective must sit alone on an ancestor.

_rootContainer  ContainerVisual   TransformMatrix = pure perspective, M34 = -1/depth
   └ _content   ContainerVisual   TransformMatrix = affine (shear, scale, translate)
      └ _sprite SpriteVisual      RotationAngle about Y, brush = capture surface
                                  GeometricClip = rounded rect

Public setters, all idempotent and dirty-checked by callers:

Start()  Pause()  Resume()  Dispose()
SetVisualSize(hwndPixels, basePixels)
SetTransformMatrix(Matrix4x4)      -> _content
SetSpriteRotationY(degrees)        -> _sprite
SetPerspective(depthPx)            -> _rootContainer
SetOpacity(float)  SetCornerRadius(radiusPx, sizePx)
RootVisual : Visual?    event TargetClosed

Pause/Resume take a per-HWND SemaphoreSlim with a non-blocking Wait(0); contention defers to the threadpool. This is deliberate — a blocking wait on the UI thread during WM_CLOSE deadlocks, and disposing a WinRT session inside an input-synchronous message pump throws RPC_E_CANTCALLOUT_ININPUTSYNCCALL (0x8001010D), which is unhandleable. See Controls/CompositionThumbnail.ShutdownAll.

Tiles — StageManager.Controls

File Lines Role
CompositionThumbnail.xaml.cs 640 the sidebar tile; owns a CaptureSession, solves tile geometry
IconOverlayManager.cs 458 per-scene app icons and labels in layered windows
IconOverlayWindow.xaml.cs 73 one layered, click-through overlay window
LayeredOverlayWindowBase.cs 45 `WS_EX_LAYERED

CompositionThumbnail — geometry authority

Dependency properties: PreviewHandle, CornerRadius, TopEdgeDegrees, BottomEdgeDegrees, MirrorScale, MirrorOpacity.

Constants:

Name Value Meaning
TrayTiltDegrees 2.0 resting shear of a sidebar tile
PerspectiveDepthPx 220.0 vanishing distance; fixed for tile and flying card alike
HoverHeadroom 0.30 per-side HWND inflation (1.6× total) so the near edge isn't clipped

SolveEdgeAngles(topDeg, bottomDeg, baseHeightPx) -> (shearDeg, spriteRotationDeg) is the single source of truth for the trapezoid. Given the two requested edge slopes it splits them into a shear component and a convergence component, then inverts Q = H·tan(θ)/(2·depth) for θ. Because θ is solved against the live height, the look is size- and DPI-independent.

Both ApplyTransform (resting tile) and LiveCardHost.SetEdgeShape (flying card) call it. Nothing else may compute a rotation angle.

Static shutdown registry: s_live + s_shuttingDown, drained by ShutdownAll() from MainWindow.OnClosing. OnIsVisibleChanged, OnUnloaded and StartCaptureIfReady all early-out once the flag is set.

Visual lending: BorrowRootVisual() / ReturnRootVisual() let an animation take the tile's visual and give it back. Session is exposed for the same purpose.

Motion — StageManager.Animations

File Lines Role
DragDropManager.cs 285 stage → sidebar drag; BufferWidthLogical = 120.0
LiveCardHost.cs 226 flying card backed by a real capture session
SceneTransitionAnimator.cs 178 drives the overlay animation, owns TransitionOverlayWindow
DragGhostWindow.cs 141 layered ghost window during a stage drag
SidebarDragGhost.cs 100 sidebar → stage ghost
DebugZoneOverlay.cs 73 visualises drag zones when enabled
PlaceholderFactory.cs 48 static fallback card
BorderCard.cs 43 IFlyingCard that draws a plain border, no capture
Anim.cs 35 DoubleAnimation factory — To, From, Storyboard (target/property pre-bound)
IFlyingCard.cs 22 Update(baseRect, skewDegrees), SetVisible, Release

IFlyingCard has three implementations: LiveCardHost (real frames), BorderCard, and the PlaceholderFactory output. Callers never branch on which.

LiveCardHost

Two flavours: borrowed (TryBorrow takes a tile's running session; Release returns the visual) and owned (TryCreateOwned starts a fresh session for a window with no tile, e.g. the outgoing scene; Release disposes it).

Mount states SetPerspective(PerspectiveDepthPx) once. Update then calls SetEdgeShape, which re-solves the trapezoid against the card's current height every frame. Owned cards carry _restTop/_restBottomEdgeDegrees == 0 and take an early-out to a plain shear.

Why the re-solve exists: the card previously kept the rotation the tile solved for a ~200 px sprite while growing to ~1 600 px. Q scales with H, so the perspective divide ran away — one vertical edge scaled ~1.85×, the other ~0.69×, a 2.7:1 trapezoid taller than the display.

WPF surface

File Role
MainWindow.xaml sidebar ItemsControl, Grid ItemsPanel, tray NotifyIcon, context menu
Animations/TransitionOverlayWindow.xaml full-screen transparent canvas that hosts flying cards
Controls/CompositionThumbnail.xaml grid + CompositionHost placement
Controls/IconOverlayWindow.xaml icon/label layer
Themes/{DarkColors,LightColors,TrayMenuTheme}.xaml resource dictionaries swapped by ThemeManager
Converters/IndexToOffsetMarginConverter.cs per-row sidebar offset
Converters/IndexToZIndexConverter.cs stacking order within a scene

Tiles use HorizontalAlignment="Left" — WPF's default Stretch centres a fixed-width child, which left tiles of differing widths ragged.

Two window-level tricks

Sidebar hit-test. CompositionThumbnail.xaml:12,23 set Background="#01000000". The sidebar is a layered top-level window, so it must register non-zero alpha at tile locations or WindowFromPoint falls through to whatever is behind it. Alpha 1/255 is invisible and sufficient.

Sidebar parking. MainWindow.ApplyWindowMode (:1329) moves the sidebar to Left = -Width in WindowMode.OffScreen. Opacity = 0 alone would stop DWM compositing the tiles; parking keeps frames flowing. Slide-in animates Left back to 0 on hover — the edge trigger is e.Data.X <= 44 (:1429). WindowMode.Flyover sets Topmost.

The transition overlay carries WS_EX_TOOLWINDOW | WS_EX_TRANSPARENT so it stays out of Alt-Tab and never intercepts clicks.

Constraints

  • Every capture visual belongs to the compositor of the thread that created it. Cross-thread mounting throws; CompositorFactory is per-thread for this reason.
  • HwndHost children do not clip to WPF layout. Hence HoverHeadroom inflation instead of overflow.
  • Device loss is recovered inside D3DDeviceHolder; sessions rebuild their frame pool on Resume.
  • .NET 10 WPF removed PlaneProjection — noted at Animations/BorderCard.cs:13 and Animations/PlaceholderFactory.cs:24. There is no framework route back to 3D tilt.