Fix tab header measured hit testing

src/ModernOverlay.UI/AdvancedControls.cs

@@ -305,6 +305,8 @@ public sealed class TabControl : UiPanel
 {
     private const float HeaderHeight = 30f;
     private int selectedIndex = -1;
+    private float[] renderedHeaderWidths = [];
+    private string[] renderedHeaderTexts = [];
 
     /// <summary>
     /// Initializes a new instance of the <see cref="TabControl"/> class.
@@ -387,19 +389,22 @@ protected override void RenderCore(UiRenderContext context)
             context.Draw.Draw.Line(new PointF(Bounds.X, Bounds.Y + HeaderHeight - 1f), new PointF(Bounds.X + Bounds.Width, Bounds.Y + HeaderHeight - 1f), context.Theme.Accent);
         }
 
+        EnsureRenderedHeaderCache();
         float x = Bounds.X;
         for (int index = 0; index < Items.Count; index++)
         {
             TabItem item = Items[index];
-            float width = item.Header.Length * context.Theme.Theme.FontSize * 0.62f + 24f;
+            SizeF textSize = context.Draw.Measure.Text(item.Header, context.Theme.Font);
+            float width = textSize.Width + 24f;
+            renderedHeaderWidths[index] = width;
+            renderedHeaderTexts[index] = item.Header;
             RectF tab = new(x, Bounds.Y, width, HeaderHeight);
             bool itemEnabled = enabled && item.IsEnabled;
             if (index == SelectedIndex && itemEnabled)
             {
                 context.Draw.Fill.Rectangle(new RectF(tab.X + 8f, tab.Y + tab.Height - 4f, MathF.Max(0f, tab.Width - 16f), 4f), context.Theme.Accent);
             }
 
-            SizeF textSize = context.Draw.Measure.Text(item.Header, context.Theme.Font);
             float textX = tab.X + MathF.Max(0f, tab.Width - textSize.Width) / 2f;
             context.Draw.Draw.Text(item.Header, context.Theme.Font, itemEnabled ? context.Theme.Foreground : context.Theme.Disabled, new PointF(textX, tab.Y + 7f));
             x += width + 2f;
@@ -467,7 +472,7 @@ private int HeaderIndexAt(PointF point)
         float x = Bounds.X;
         for (int index = 0; index < Items.Count; index++)
         {
-            float width = Items[index].Header.Length * (Root?.ThemeResources.Theme.FontSize ?? UiTheme.Default.FontSize) * 0.62f + 24f;
+            float width = HeaderWidth(index);
             RectF header = new(x, Bounds.Y, width, HeaderHeight);
             if (UiGeometry.ContainsInputBand(header, point))
             {
@@ -480,6 +485,39 @@ private int HeaderIndexAt(PointF point)
         return -1;
     }
 
+    private float HeaderWidth(int index)
+    {
+        string header = Items[index].Header;
+        return TryGetRenderedHeaderWidth(index, header, out float width)
+            ? width
+            : header.Length * (Root?.ThemeResources.Theme.FontSize ?? UiTheme.Default.FontSize) * 0.62f + 24f;
+    }
+
+    private bool TryGetRenderedHeaderWidth(int index, string header, out float width)
+    {
+        bool hasWidth = renderedHeaderWidths.Length == Items.Count
+            && renderedHeaderTexts.Length == Items.Count
+            && index >= 0
+            && index < renderedHeaderWidths.Length
+            && string.Equals(renderedHeaderTexts[index], header, StringComparison.Ordinal);
+
+        width = hasWidth ? renderedHeaderWidths[index] : 0f;
+        return hasWidth;
+    }
+
+    private void EnsureRenderedHeaderCache()
+    {
+        if (renderedHeaderWidths.Length != Items.Count)
+        {
+            renderedHeaderWidths = Items.Count == 0 ? [] : new float[Items.Count];
+        }
+
+        if (renderedHeaderTexts.Length != Items.Count)
+        {
+            renderedHeaderTexts = Items.Count == 0 ? [] : new string[Items.Count];
+        }
+    }
+
     private void MoveSelection(int direction)
     {
         if (Items.Count == 0)

tests/ModernOverlay.Tests/OverlayUiTabSegmentedTests.cs

@@ -49,7 +49,7 @@ public async Task TabPointerBoundaryKeepsPreviousRenderedHeader()
         using OverlayUiRoot ui = OverlayUi.Attach(overlay, new OverlayUiOptions { RegisterInputRegions = false });
         UiTabControl tabs = CreateTabs(out _, out _, out _);
         ui.Root.Children.Add(tabs);
-        ui.Render(new DrawContext());
+        ui.Render(new DrawContext(new RecordingDrawCommandSink()));
 
         float boundaryX = 10f + TabHeaderWidth("One");
         ClickUi(ui, new PointF(boundaryX, 20f));
@@ -118,6 +118,32 @@ public async Task TabHeadersRenderTextCenteredByDefault()
         Assert.AreEqual(expectedX, oneOrigin.X, 0.001f);
     }
 
+    [TestMethod]
+    [TestCategory("WindowsIntegration")]
+    public async Task TabHeaderHitTestingUsesMeasuredTextWidth()
+    {
+        await using OverlayWindow overlay = await CreateOverlayAsync();
+        using OverlayUiRoot ui = OverlayUi.Attach(overlay, new OverlayUiOptions { RegisterInputRegions = false });
+        UiTabControl tabs = new()
+        {
+            Width = 220f,
+            Height = 120f,
+            MinWidth = 0f,
+            MinHeight = 0f,
+        };
+        Canvas.SetLeft(tabs, 10f);
+        Canvas.SetTop(tabs, 10f);
+        tabs.Add("WWW", new ProbeElement());
+        tabs.Add("Two", new ProbeElement());
+        tabs.SelectedIndex = 1;
+        ui.Root.Children.Add(tabs);
+        ui.Render(new DrawContext(new RecordingDrawCommandSink()));
+
+        ClickUi(ui, new PointF(130f, 20f));
+
+        Assert.AreEqual(0, tabs.SelectedIndex);
+    }
+
     [TestMethod]
     [TestCategory("WindowsIntegration")]
     public async Task SegmentedControlPointerAndKeyboardSelection()
@@ -353,7 +379,9 @@ public SizeF MeasureTextLayout(TextLayoutHandle layout)
             => new(MeasureTextWidth(layout.Text), layout.Font.Options.Size);
 
         public static float MeasureTextWidth(string text)
-            => text.Length * UiTheme.Default.FontSize * 0.62f;
+            => text == "WWW"
+                ? 120f
+                : text.Length * UiTheme.Default.FontSize * 0.62f;
 
         private void AddPrimitive()
         {