Migrate Planner + FitsViewer callbacks to signal bus (Phase 3)

- PlannerTab: replace OnBuildSchedule with BuildScheduleSignal
- FitsViewer: replace OnExit/OnToggleFullscreen/OnPlateSolve with
  RequestExitSignal/ToggleFullscreenSignal/PlateSolveSignal
- VkImageRenderer: zero callback properties remaining
- Add signal types to GuiSignals.cs

All action callbacks now flow through the signal bus.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: sebgod

src/TianWen.UI.Abstractions/GuiSignals.cs

@@ -19,3 +19,12 @@ namespace TianWen.UI.Abstractions;
 
 /// <summary>Update profile data (filter config, OTA props, etc.).</summary>
 public readonly record struct UpdateProfileSignal(ProfileData Data);
+
+/// <summary>Build the observation schedule from pinned targets.</summary>
+public readonly record struct BuildScheduleSignal;
+
+/// <summary>Toggle fullscreen mode.</summary>
+public readonly record struct ToggleFullscreenSignal;
+
+/// <summary>Request plate solving the current image.</summary>
+public readonly record struct PlateSolveSignal;

src/TianWen.UI.FitsViewer/Program.cs

@@ -82,8 +82,10 @@
 var ctx = VulkanContext.Create(sdlWindow.Instance, sdlWindow.Surface, (uint)pixW, (uint)pixH);
 var renderer = new VkRenderer(ctx, (uint)pixW, (uint)pixH);
 
+var bus = new SignalBus();
 var imageRenderer = new VkImageRenderer(renderer, (uint)pixW, (uint)pixH)
 {
+    Bus = bus,
     DpiScale = sdlWindow.DisplayScale,
     CelestialObjectDB = celestialObjectDB
 };
@@ -150,24 +152,24 @@
 
     OnPostFrame = () =>
     {
+        bus.ProcessPending();
         state.NeedsRedraw = false;
     }
 };
 
-// Wire app-level callbacks that need loop/window references
-imageRenderer.OnExit = () => loop.Stop();
-imageRenderer.OnToggleFullscreen = () => sdlWindow.ToggleFullscreen();
-imageRenderer.OnPlateSolve = () =>
+// Signal subscriptions for app-level actions
+bus.Subscribe<RequestExitSignal>(_ => loop.Stop());
+bus.Subscribe<ToggleFullscreenSignal>(_ => sdlWindow.ToggleFullscreen());
+bus.Subscribe<PlateSolveSignal>(_ =>
 {
     if (document is not null && !state.IsPlateSolving && !document.IsPlateSolved)
     {
         var factory = sp.GetRequiredService<TianWen.Lib.Astrometry.PlateSolve.IPlateSolverFactory>();
         backgroundTask = ViewerActions.PlateSolveAsync(document, state, factory, cts.Token);
     }
-    return Task.CompletedTask;
-};
+});
 
-// OnKeyDown wired separately — imageRenderer.HandleKeyDown handles F11 via OnToggleFullscreen
+// OnKeyDown wired separately — imageRenderer.HandleKeyDown handles F11 via signal bus
 loop.OnKeyDown = (inputKey, inputModifier) =>
 {
     imageRenderer.HandleKeyDown(inputKey, inputModifier);

src/TianWen.UI.Gui/Program.cs

@@ -102,8 +102,8 @@
 });
 Task? plannerTask = null;
 
-// Wire tab callbacks that need DI/profile access
-guiRenderer.PlannerTab.OnBuildSchedule = () =>
+// Signal subscription for building the schedule
+bus.Subscribe<BuildScheduleSignal>(signal =>
 {
     if (appState.ActiveProfile is null) return;
     var transform = TransformFactory.FromProfile(appState.ActiveProfile, external.TimeProvider, out _);
@@ -125,7 +125,7 @@
             availableFilters: availableFilters is { Count: > 0 } ? availableFilters : null,
             opticalDesign: opticalDesign);
     }
-};
+});
 
 if (appState.ActiveProfile is not null)
 {

src/TianWen.UI.Gui/VkPlannerTab.cs

@@ -53,8 +53,6 @@ public sealed class VkPlannerTab : VkTabBase
         /// <summary>Reference to the planner state from the last Render call.</summary>
         private PlannerState? _state;
 
-        /// <summary>Callback for building the schedule (needs profile/transform). Set by the host.</summary>
-        public Action? OnBuildSchedule { get; set; }
 
         // Layout rects computed during Render, used by hit testing
         private RectF32 _targetListRect;
@@ -616,7 +614,7 @@ public override bool HandleKeyDown(InputKey key, InputModifier modifiers)
                     return true;
 
                 case InputKey.S:
-                    OnBuildSchedule?.Invoke();
+                    PostSignal(new BuildScheduleSignal());
                     return true;
 
                 default:

src/TianWen.UI.Shared/VkImageRenderer.cs

@@ -42,14 +42,6 @@ public sealed class VkImageRenderer : PixelWidgetBase<VulkanContext>, IDisposabl
     /// <summary>Reference to the document from the last Render call.</summary>
     private AstroImageDocument? _document;
 
-    /// <summary>Callback for plate solving (needs DI). Set by the host.</summary>
-    public Func<Task>? OnPlateSolve { get; set; }
-
-    /// <summary>Callback for app exit. Set by the host.</summary>
-    public Action? OnExit { get; set; }
-
-    /// <summary>Callback for fullscreen toggle. Set by the host.</summary>
-    public Action? OnToggleFullscreen { get; set; }
 
     /// <summary>
     /// DPI scale factor. Set from framebuffer size / window size ratio.
@@ -1537,10 +1529,10 @@ public override bool HandleKeyDown(InputKey key, InputModifier modifiers)
         switch (key)
         {
             case InputKey.Escape:
-                OnExit?.Invoke();
+                PostSignal(new RequestExitSignal());
                 return true;
             case InputKey.F11:
-                OnToggleFullscreen?.Invoke();
+                PostSignal(new ToggleFullscreenSignal());
                 return true;
             case InputKey.T:
                 ViewerActions.ToggleStretch(state);
@@ -1593,7 +1585,7 @@ public override bool HandleKeyDown(InputKey key, InputModifier modifiers)
                 }
                 return true;
             case InputKey.P:
-                OnPlateSolve?.Invoke();
+                PostSignal(new PlateSolveSignal());
                 return true;
             case InputKey.F:
                 ViewerActions.ZoomToFit(state);