perf(style): make GlobalStyleScope.StackHandle GC-free via counter scope

HellionChat/Ui/StyleEngine/GlobalStyleScope.cs

@@ -1,5 +1,4 @@
 using Dalamud.Bindings.ImGui;
-using Dalamud.Interface.Utility.Raii;
 using HellionChat.Themes;
 using HellionChat.Util;
 
@@ -33,6 +32,13 @@ internal static class GlobalStyleScope
         var childBgWithAlpha = ResolveChildBgAlpha(c.ChildBg, windowOpacity);
 
         var stack = new StackHandle();
+        // Hard contract: every push must be balanced by a pop. The pushes below
+        // are pure, practically non-throwing ImGui calls, but if one ever threw
+        // mid-stack we must still pop what we pushed before the exception escapes,
+        // or the global style stack stays corrupt for every other window this
+        // frame. Dispose then rethrow.
+        try
+        {
             stack.PushStyleVar(ImGuiStyleVar.WindowRounding, l.WindowRounding);
             stack.PushStyleVar(ImGuiStyleVar.ChildRounding, l.ChildRounding);
             stack.PushStyleVar(ImGuiStyleVar.PopupRounding, l.PopupRounding);
@@ -87,6 +93,12 @@ internal static class GlobalStyleScope
             stack.PushColorAbgr(ImGuiCol.Separator, a.Border);
             stack.PushColorAbgr(ImGuiCol.SeparatorHovered, a.PrimaryLight);
             stack.PushColorAbgr(ImGuiCol.SeparatorActive, a.Primary);
+        }
+        catch
+        {
+            stack.Dispose();
+            throw;
+        }
 
         return stack;
     }
@@ -101,24 +113,46 @@ internal static class GlobalStyleScope
         return (themeChildBgRgba & 0xFFFFFF00u) | childBgAlpha;
     }
 
+    // Counter-based scope: pushes go straight onto the global ImGui style
+    // stack and we only remember how many of each kind we pushed. Dispose
+    // pops them in one batched PopStyleColor(count)/PopStyleVar(count) call.
+    // This replaces the old List<IDisposable> + per-push boxed ImRaii structs
+    // (44 allocations/frame) with two ints — zero per-frame GC. Every style
+    // var pushed here is a single-float var, so PopStyleVar(count) is valid;
+    // both colour paths funnel into one PushStyleColor, so one colour counter
+    // covers them. Symmetry is the whole contract: the pop counts must equal
+    // the push counts or the global stack corrupts for every other window.
     private sealed class StackHandle : IDisposable
     {
-        private readonly List<IDisposable> _items = new(64);
+        private int _colorCount;
+        private int _styleVarCount;
 
-        internal void PushColor(ImGuiCol slot, uint rgba) =>
-            _items.Add(ImRaii.PushColor(slot, ColourUtil.RgbaToAbgr(rgba)));
+        internal void PushColor(ImGuiCol slot, uint rgba)
+        {
+            ImGui.PushStyleColor(slot, ColourUtil.RgbaToAbgr(rgba));
+            _colorCount++;
+        }
 
-        internal void PushColorAbgr(ImGuiCol slot, uint abgr) =>
-            _items.Add(ImRaii.PushColor(slot, abgr));
+        internal void PushColorAbgr(ImGuiCol slot, uint abgr)
+        {
+            ImGui.PushStyleColor(slot, abgr);
+            _colorCount++;
+        }
 
-        internal void PushStyleVar(ImGuiStyleVar var, float value) =>
-            _items.Add(ImRaii.PushStyle(var, value));
+        internal void PushStyleVar(ImGuiStyleVar var, float value)
+        {
+            ImGui.PushStyleVar(var, value);
+            _styleVarCount++;
+        }
 
         public void Dispose()
         {
-            for (var i = _items.Count - 1; i >= 0; i--)
-                _items[i].Dispose();
-            _items.Clear();
+            if (_styleVarCount > 0)
+                ImGui.PopStyleVar(_styleVarCount);
+            if (_colorCount > 0)
+                ImGui.PopStyleColor(_colorCount);
+            _styleVarCount = 0;
+            _colorCount = 0;
         }
     }
 }