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Fix issue 14772: Button hosted on a TabPage does not use the Windows accent-colored focus indicator with VisualStylesMode = NET11 #14860

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Fix issue 14772: Button hosted on a TabPage does not use the Windows accent-colored focus indicator with VisualStylesMode = NET11 #14860

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14 changes: 11 additions & 3 deletions src/System.Windows.Forms/System/Windows/Forms/Control.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -899,10 +899,18 @@ public virtual partial VisualStylesMode VisualStylesMode

VisualStylesMode oldEffectiveValue = EffectiveVisualStylesMode;

// Inherit was requested explicitly, or the requested value matches the ambient (parent) value:
// drop any local override so the value is inherited again.
bool hadLocalOverride = Properties.TryGetValue(
s_visualStylesModeProperty,
out VisualStylesMode existingRawValue)
&& existingRawValue != VisualStylesMode.Inherit;

// Inherit always clears the local override. Setting to the ambient (parent) value clears only when
// transitioning an existing local override back to ambient.
if (value == VisualStylesMode.Inherit
|| (ParentInternal is { } parent && parent.ResolvedVisualStylesMode == value))
|| (hadLocalOverride
&& existingRawValue != value
&& ParentInternal is { } parent
&& parent.ResolvedVisualStylesMode == value))
{
Properties.RemoveValue(s_visualStylesModeProperty);
}
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36 changes: 26 additions & 10 deletions ...ms/System/Windows/Forms/Controls/Buttons/ButtonInternal/DarkMode/ButtonDarkModeAdapter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -85,24 +85,40 @@ private Color GetButtonBackColor(PushButtonState state)
{
Color backColor;

if (Control.BackColor != Forms.Control.DefaultBackColor)
// Net11 default buttons must always use the accent-driven palette, even when BackColor is set.
if (_modern && Control.IsDefault)
{
backColor = ButtonDarkModeRenderer.GetBackgroundColor(
state,
Control.IsDefault,
Control.BackColor);
isDefault: true,
customBaseColor: Color.Empty);
}
else
{
bool hasExplicitBackColor = Control.ShouldSerializeBackColor();
bool hasUsableAmbientBackColor = _modern
&& !Control.BackColor.HasTransparency()

@LeafShi1 LeafShi1 Aug 11, 2026

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This change makes a Classic button ignore a non-default BackColor inherited from its parent. Before this PR, Control.BackColor—including an ambient value—was passed to the renderer whenever it differed from DefaultBackColor. After this change, ambient colors are accepted only when _modern is true. Consequently, a Classic button on a custom-colored container now renders with the default palette instead of the inherited color. This appears to be a behavioral regression and contradicts the PR description that the Classic path retains its original behavior.

&& Control.BackColor != Forms.Control.DefaultBackColor;

if (IsHighContrastHighlighted())
if (hasExplicitBackColor || hasUsableAmbientBackColor)
{
backColor = ButtonDarkModeRenderer.GetBackgroundColor(
state,
Control.IsDefault,
Control.BackColor);
}
else
{
backColor = SystemColors.HighlightText;
backColor = ButtonDarkModeRenderer.GetBackgroundColor(
state,
Control.IsDefault,
customBaseColor: Color.Empty);
}
}
else

if (IsHighContrastHighlighted())
{
backColor = ButtonDarkModeRenderer.GetBackgroundColor(
state,
Control.IsDefault,
customBaseColor: Color.Empty);
backColor = SystemColors.HighlightText;
}

if (_animateBackgroundColors)
Expand Down
156 changes: 155 additions & 1 deletion src/test/unit/System.Windows.Forms/System/Windows/Forms/ButtonVisualStylesTests.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
// Licensed to the .NET Foundation under one or more agreements.
// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

#nullable disable
Expand Down Expand Up @@ -121,6 +121,71 @@ public void ModernGlyphControl_ThemedTabPage_PaintsOpaqueBackground(Type control
Assert.Equal(255, actual.GetPixel(control.Width - 2, 2).A);
}

[WinFormsTheory]
[InlineData(false)]
[InlineData(true)]
public void Button_ModernDefaultState_UsesAccent_WhenHostedOnContainer(bool hostedOnTabPage)
{
if (!Application.RenderWithVisualStyles)
{
return;
}

using Form form = new() { VisualStylesMode = VisualStylesMode.Net11 };
using Button button = new()
{
FlatStyle = FlatStyle.Standard,
Size = new Size(120, 32),
Text = string.Empty,
VisualStylesMode = VisualStylesMode.Inherit
};

if (hostedOnTabPage)
{
using TabControl tabControl = new() { Size = new Size(180, 120) };
using TabPage tabPage = new()
{
Size = tabControl.Size,
UseVisualStyleBackColor = true
};

tabPage.Controls.Add(button);
tabControl.TabPages.Add(tabPage);
form.Controls.Add(tabControl);
form.AcceptButton = button;
form.CreateControl();
tabControl.CreateControl();
tabPage.CreateControl();
button.CreateControl();

using Bitmap actual = new(button.Width, button.Height);
button.DrawToBitmap(actual, new Rectangle(Point.Empty, button.Size));

Color expected = ModernButtonColorMath.GetDefaultButtonColor(
Application.SystemVisualSettings.AccentColor,
VisualStyles.PushButtonState.Normal);
Color center = actual.GetPixel(button.Width / 2, button.Height / 2);

Assert.Equal(expected.ToArgb(), center.ToArgb());
return;
}

form.Controls.Add(button);
form.AcceptButton = button;
form.CreateControl();
button.CreateControl();

using Bitmap bitmap = new(button.Width, button.Height);
button.DrawToBitmap(bitmap, new Rectangle(Point.Empty, button.Size));

Color expectedColor = ModernButtonColorMath.GetDefaultButtonColor(
Application.SystemVisualSettings.AccentColor,
VisualStyles.PushButtonState.Normal);
Color actualColor = bitmap.GetPixel(button.Width / 2, button.Height / 2);

Assert.Equal(expectedColor.ToArgb(), actualColor.ToArgb());
}

[WinFormsFact]
public void Button_VisualStylesMode_ChangedToNet11_Invalidates()
{
Expand Down Expand Up @@ -509,6 +574,72 @@ public void ModernButtonColorMath_ExplicitBackColorIsTheRenderedBase()
button.FlatAppearance.MouseOverBackColor);
}

[WinFormsFact]
public void ButtonDarkModeAdapter_NonNet11_ExplicitBackColor_DefaultStatePreservesBackColor()
{
using Button button = new()
{
FlatStyle = FlatStyle.Standard,
VisualStylesMode = VisualStylesMode.Classic,
BackColor = Color.FromArgb(10, 20, 30)
};
button.NotifyDefault(true);

ButtonInternal.ButtonDarkModeAdapter adapter = new(button);
dynamic accessor = adapter.TestAccessor.Dynamic;

Color actual = (Color)accessor.GetButtonBackColor(VisualStyles.PushButtonState.Normal);

Assert.Equal(button.BackColor, actual);
}

[WinFormsFact]
public void ButtonDarkModeAdapter_ClassicInNet11Hierarchy_ExplicitBackColor_DefaultStatePreservesBackColor()
{
using Form form = new() { VisualStylesMode = VisualStylesMode.Net11 };
using Button button = new()
{
FlatStyle = FlatStyle.Standard,
VisualStylesMode = VisualStylesMode.Classic,
BackColor = Color.FromArgb(10, 20, 30)
};
form.Controls.Add(button);
form.AcceptButton = button;
button.NotifyDefault(true);

ButtonInternal.ButtonDarkModeAdapter adapter = new(button);
dynamic accessor = adapter.TestAccessor.Dynamic;

Color actual = (Color)accessor.GetButtonBackColor(VisualStyles.PushButtonState.Normal);

Assert.Equal(button.BackColor, actual);
}

[WinFormsFact]
public void ButtonDarkModeAdapter_ClassicInNet11Hierarchy_InheritedBackColor_DoesNotUseAmbientAsCustomBase()
{
using Form form = new()
{
VisualStylesMode = VisualStylesMode.Net11,
BackColor = Color.FromArgb(31, 63, 95)
};
using Button button = new()
{
FlatStyle = FlatStyle.Standard,
VisualStylesMode = VisualStylesMode.Classic,
UseVisualStyleBackColor = true
};
form.Controls.Add(button);
button.NotifyDefault(true);

ButtonInternal.ButtonDarkModeAdapter adapter = new(button);
dynamic accessor = adapter.TestAccessor.Dynamic;

Color actual = (Color)accessor.GetButtonBackColor(VisualStyles.PushButtonState.Normal);

Assert.NotEqual(form.BackColor, actual);
}

[WinFormsFact]
public void ModernButtonDarkModeRenderer_CornerRadiusDependsOnFocusAndDefaultState()
{
Expand Down Expand Up @@ -545,6 +676,29 @@ public void ModernButtonDarkModeRenderer_ModernStateDefaultsUseAccentAndExplicit
Assert.Equal(Color.Blue, renderer.GetBackgroundColor(VisualStyles.PushButtonState.Hot, false, Color.Empty));
}

[WinFormsTheory]
[InlineData(VisualStyles.PushButtonState.Normal)]
[InlineData(VisualStyles.PushButtonState.Hot)]
[InlineData(VisualStyles.PushButtonState.Pressed)]
public void ButtonDarkModeAdapter_Net11_DefaultStateWithExplicitBackColor_UsesAccent(
VisualStyles.PushButtonState state)
{
using Button button = new()
{
FlatStyle = FlatStyle.Standard,
VisualStylesMode = VisualStylesMode.Net11,
BackColor = Color.FromArgb(16, 48, 80)
};
button.NotifyDefault(true);
ButtonInternal.ButtonDarkModeAdapter adapter = new(button);
dynamic accessor = adapter.TestAccessor.Dynamic;
Color accent = Application.SystemVisualSettings.AccentColor;

Color actual = (Color)accessor.GetButtonBackColor(state);

Assert.Equal(ModernButtonColorMath.GetDefaultButtonColor(accent, state), actual);
}

[WinFormsTheory]
[InlineData(FlatStyle.Standard, 96)]
[InlineData(FlatStyle.Standard, 144)]
Expand Down
19 changes: 19 additions & 0 deletions src/test/unit/System.Windows.Forms/System/Windows/Forms/ControlTests.VisualStylesMode.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -193,6 +193,25 @@ public void Control_VisualStylesMode_AmbientBehaviorTest()
Assert.Equal(VisualStylesMode.Classic, child.EffectiveVisualStylesModeAccessor);
}

[WinFormsFact]
public void Control_VisualStylesMode_FirstSetToAmbientValue_PreservesLocalOverride()
{
using SubControlWithVisualStyles parent = new()
{
VisualStylesMode = VisualStylesMode.Classic
};
using SubControlWithVisualStyles child = new();
parent.Controls.Add(child);

child.VisualStylesMode = VisualStylesMode.Classic;
Assert.Equal(VisualStylesMode.Classic, child.VisualStylesMode);

parent.VisualStylesMode = VisualStylesMode.Net11;

Assert.Equal(VisualStylesMode.Classic, child.VisualStylesMode);
Assert.Equal(VisualStylesMode.Classic, child.EffectiveVisualStylesModeAccessor);
}

[WinFormsFact]
public void Control_VisualStylesMode_ReparentingToDifferentMode_RaisesChanged()
{
Expand Down
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