test(selftest): add GlobalStyleScope GC-reserve alloc probe

HellionChat/Plugin.cs

@@ -409,6 +409,7 @@ public sealed class Plugin : IAsyncDalamudPlugin
                 new SelfTests.HonorificHeaderRenderStep(this),
                 new SelfTests.AboutIntegrationsStatusStep(this),
                 new SelfTests.PerformanceBaselineStep(this),
+                new SelfTests.GlobalStyleScopeAllocStep(this),
                 new SelfTests.MainWindowFocusOpacityStep(this),
                 new SelfTests.MainWindowFlagsStep(this),
                 new SelfTests.SenderNameReformatStep(this),

HellionChat/SelfTests/GlobalStyleScopeAllocStep.cs

@@ -0,0 +1,61 @@
+using System;
+using Dalamud.Bindings.ImGui;
+using Dalamud.Plugin.SelfTest;
+using HellionChat.Ui.StyleEngine;
+
+namespace HellionChat.SelfTests;
+
+// GC-reserve probe for the v1.9.0 B4a refactor: GlobalStyleScope.Push runs
+// once per draw frame, so its StackHandle must allocate nothing. Before the
+// counter rewrite it boxed 44 ImRaii structs + a List per frame; after, it
+// holds two ints and pushes straight onto the ImGui stack. This step drives a
+// real Push()->Dispose() cycle and asserts the per-thread allocation delta is
+// ~0 (not a non-null-handle check — feedback_hellion_chat_fontmanager_push_trap).
+// A warm-up cycle pays the one-time JIT/first-touch cost so the measured cycle
+// reflects steady state, matching the real per-frame hot path.
+internal sealed class GlobalStyleScopeAllocStep : ISelfTestStep
+{
+    // Headroom for incidental managed noise (GC bookkeeping, boxing inside
+    // ImGui bindings we do not control). The pre-fix path allocated ~1-2 KB
+    // per cycle (44 boxes + List), so anything under this threshold proves
+    // the StackHandle itself stopped allocating. Tighten only if a future
+    // binding upgrade removes all incidental noise.
+    private const long AllocBudgetBytes = 256;
+
+    private readonly Plugin _plugin;
+
+    public GlobalStyleScopeAllocStep(Plugin plugin)
+    {
+        _plugin = plugin;
+    }
+
+    public string Name => "Hellion Chat - GlobalStyleScope GC reserve";
+
+    public SelfTestStepResult RunStep()
+    {
+        var registry = _plugin.ThemeRegistry;
+        var theme = registry.Active;
+        var opacity = Plugin.Config.WindowOpacity;
+
+        // Warm-up: JIT the Push/Dispose path + first-touch any lazy ImGui
+        // stack growth, so the measured cycle is steady-state only.
+        GlobalStyleScope.Push(theme, registry, opacity).Dispose();
+
+        var before = GC.GetAllocatedBytesForCurrentThread();
+        GlobalStyleScope.Push(theme, registry, opacity).Dispose();
+        var delta = GC.GetAllocatedBytesForCurrentThread() - before;
+
+        if (delta > AllocBudgetBytes)
+        {
+            ImGui.Text(
+                $"GlobalStyleScope.Push allocated {delta} bytes/cycle "
+                    + $"(budget {AllocBudgetBytes}) — StackHandle is not GC-free."
+            );
+            return SelfTestStepResult.Fail;
+        }
+
+        return SelfTestStepResult.Pass;
+    }
+
+    public void CleanUp() { }
+}