Optimize static wait presentation

docs/phase-a-slice-plan.md

@@ -1256,3 +1256,41 @@ and makes a committed alpha-zero ADV crop transparent. Focused model/raster test
 endpoint, identity modulation, and zero-opacity output. Validation: engine **134/134**, Godot build with
 zero warnings, matching windowed capture, and user manual confirmation that the box disappears fully and
 the controls retain their normal color while visible.
+
+### Godot window jitter / compositor performance investigation (2026-07-11)
+
+The visible window jitter is main-thread compositor pressure, not `FrameClock.Speed`, coroutine pacing,
+or GPU throughput. A bounded windowed run on the Vulkan backend (RTX 4080 SUPER, `--max-fps 60
+--print-fps`) sustained only **23–25 FPS / 40–43 ms per frame** while SC0000 approached its first ADV
+input wait. The retained frontend currently makes `ShouldRecomposite()` true throughout input waits,
+explicit sleeps, foreground waits, and text reveal. Each recomposite clears the 800x600 canvas, then for
+every visible layer calls `Image.GetData()`, runs the C# per-pixel inverse-affine rasterizer, calls
+`Image.SetData()`, and finally uploads the full canvas with `ImageTexture.Update()`. An unchanged input-wait
+screen therefore consumes the same expensive path every rendered frame; dragging the OS window stutters
+because this work runs on Godot's main thread.
+
+Continuous presentation itself is partly load-bearing: one-shot transitions, movies, and ambient cyclic
+channels must continue sampling `FrameClock` while active. The *unconditional* redraw implied by
+`IsWaiting`/`IsTextRevealing` is not. The existing gfx-change log showed real one-shot color changes through
+render frame 121, then no retained-object changes, while the separate steady-state FPS probe remained near
+23 FPS. A safe correction should preserve time-based presentation but distinguish dirty/static waits from
+active visual channels, and should avoid copying the full Godot `Image` out and back once per layer. Likely
+implementation boundaries are: (1) explicit compositor dirty generation plus an active-animation/movie
+query, and (2) one CPU backbuffer acquisition/update per recomposite or migration of ordinary layers to
+Godot/GPU-native drawing. Merely changing `--speed`, sleep/coroutine behavior, or the 60 FPS cap will not
+remove the underlying frame cost.
+
+**Quick win 1 implemented (2026-07-11).** `GfxState.HasActiveVisualPresentation(nowMs)` now reports
+only retained pixels that can change without another VM mutation: finite surface/one-shot channels plus
+visible spritesheet, color, and cyclic-rotation channels with positive periods. Godot consumes explicit
+presentation dirtiness once and otherwise recomposites only while that query is true. Entering input wait
+or `sleep` requests one publish so preceding retained writes remain visible; the wait/sleep state itself and
+ADV text reveal no longer rebuild the background. Movie frames retain their existing per-sample dirty
+publication. This preserves the clock, VM suspension model, active transitions, ambient animation, and
+movie lifecycle.
+
+Validation: the focused static-vs-ambient query regression brings the engine suite to **135/135**; Godot
+builds with zero warnings and threaded `SELFTEST OK`. A matching hidden-window Vulkan run capped at 60 FPS,
+using `--speed 8` only to reach the static state quickly, held **60 FPS / 16.66 ms per frame** for all eight
+reported samples, versus the pre-change 23-25 FPS. Buffer batching/source-pixel caching and rasterizer fast
+paths remain independent follow-ups.

engine/Age.Engine.Tests/GfxAnimationTests.cs

@@ -39,6 +39,33 @@ public class GfxAnimationTests
         Assert.True(o.RotationEnabled);
     }
 
+    [Fact]
+    public void ActiveVisualPresentation_ExcludesStaticWaits_ButIncludesAmbientChannels()
+    {
+        static GfxState VisibleObject()
+        {
+            var state = new GfxState();
+            state.SetSurface(1, 5, -1);
+            state.BindDraw(7, 1, 0, 0, 64, 64, 0, 0);
+            return state;
+        }
+
+        var unchanged = VisibleObject();
+        Assert.False(unchanged.HasActiveVisualPresentation(1000));
+
+        var spritesheet = VisibleObject();
+        spritesheet.SetSrcRect(7, 4, 1, 0, 800);
+        Assert.True(spritesheet.HasActiveVisualPresentation(1000));
+
+        var color = VisibleObject();
+        color.SetColorAnim(7, 1000, GfxState.PackColor(0x80, 0xff0000));
+        Assert.True(color.HasActiveVisualPresentation(1000));
+
+        var rotation = VisibleObject();
+        rotation.SetRotationCycle(7, 1000, (0, 0, 1));
+        Assert.True(rotation.HasActiveVisualPresentation(1000));
+    }
+
     [Fact]
     public void OneShotRotation_SharesMatrixClockAndMatchesNativeSample()
     {

engine/Age.Engine/Model/GfxState.cs

@@ -352,6 +352,21 @@ public sealed class GfxState
                                              o.RotationChannelEnabled || o.TranslationEnabled));
     }
 
+    /// <summary>Whether sampling the retained scene at a later frame can change its pixels without another
+    /// VM mutation. Includes finite presentation work plus the ambient channels that may remain active while
+    /// the interpreter is parked at an input wait. Static waits themselves are deliberately not animation.</summary>
+    public bool HasActiveVisualPresentation(long nowMs)
+    {
+        lock (_lock)
+            return _surfaceTransitions.Values.Any(t => TransitionProgress(t, nowMs) < 1.0) ||
+                   _objects.Values.Any(o => o.Visible &&
+                       (o.OneShotColorEnabled || o.ScaleEnabled || o.RotationChannelEnabled ||
+                        o.TranslationEnabled ||
+                        (o.SrcAnim && o.SrcPeriod > 0) ||
+                        (o.ColorAnim && o.ColorPeriod > 0) ||
+                        (o.RotationEnabled && o.RotationPeriodMs > 0)));
+    }
+
     /// <summary>Click completion affects only type-0 foreground transitions, never ambient object channels.</summary>
     public int CompleteForegroundTransitions(long nowMs)
     {

godot/GodotAdvHost.cs

@@ -105,6 +105,9 @@ public sealed class GodotAdvHost : IHost
     {
         Pages++;
         _main.CallDeferred("PageBreak");
+        // Publish retained mutations accumulated before the wait once. A static input wait is not itself a
+        // reason to rebuild the 800x600 background every frame; ambient channels are queried separately.
+        System.Threading.Interlocked.Exchange(ref _presentRequested, 1);
         IsWaiting = true;
         _timeline?.State("input-wait", new() { ["page"] = Pages });
         _gate.Wait();
@@ -167,6 +170,9 @@ public sealed class GodotAdvHost : IHost
             }
             _frameSignal.WaitOne(50);
         }
+        // The active query becomes false at the exact transition/movie endpoint. Publish that terminal sample
+        // once so the last visible frame cannot remain fractionally incomplete.
+        System.Threading.Interlocked.Exchange(ref _presentRequested, 1);
         IsTransitionWaiting = false;
         System.Threading.Interlocked.Exchange(ref _transitionStartedAtMs, -1);
         _foregroundGfx = null;
@@ -185,11 +191,12 @@ public sealed class GodotAdvHost : IHost
         System.Threading.Interlocked.Exchange(ref _presentRequested, 1);
     }
 
-    // Native retained-object writes are not front-buffer writes. The renderer publishes them only at an
-    // explicit present or while the interpreter is parked in a presentation-capable service boundary.
-    public bool ShouldRecomposite()
-        => IsWaiting || IsTransitionWaiting || IsSleeping || IsTextRevealing ||
-           System.Threading.Interlocked.Exchange(ref _presentRequested, 0) != 0;
+    // Native retained-object writes are not front-buffer writes. Publish explicit/service-boundary dirtiness
+    // once, then continue only while the sampled retained scene can actually change. Text reveal is a separate
+    // Godot Label; waiting/sleeping alone do not alter background pixels.
+    public bool ShouldRecomposite(GfxState gfx)
+        => System.Threading.Interlocked.Exchange(ref _presentRequested, 0) != 0 ||
+           gfx.HasActiveVisualPresentation(_clock.NowMs);
 
     public void Stop()
     {
@@ -218,6 +225,9 @@ public sealed class GodotAdvHost : IHost
         long ms = (long)System.Math.Clamp(duration * SleepScale, 0, 60_000);   // cap so a pathological script can't hang the window
         long deadline = _clock.NowMs + ms;
         _timeline?.State("sleep", new() { ["duration_ms"] = ms, ["deadline_ms"] = deadline });
+        // A sleep is a service boundary: make preceding retained writes visible once even when no animation
+        // channel is active during the hold.
+        System.Threading.Interlocked.Exchange(ref _presentRequested, 1);
         IsSleeping = true;
         while (_clock.NowMs < deadline)
         {

godot/Main.cs

@@ -222,7 +222,7 @@ public partial class Main : Godot.Control
         _timeline?.SetFrame(_timelineFrame, _clock.NowMs);
         _host?.PulseFrame();
         UpdateMovieFrames();
-        if (!_selftest && _vm != null && _host != null && _host.ShouldRecomposite())
+        if (!_selftest && _vm != null && _host != null && _host.ShouldRecomposite(_vm.Gfx))
             Recomposite();   // native publishes retained mutations only at present/service boundaries
         if (!_selftest && _host != null) UpdateAdvTextPresentation();
         // --shot-sequence: dump one PNG per frame across the opening so a time-based (paced) effect can be