Enable DataGridView dark mode theming via AppContext switch by LeafShi1 · Pull Request #14267 · dotnet/winforms

LeafShi1 · 2026-02-04T10:11:14Z

Fixes #14266

Proposed changes

Introduce an AppContext quirk switch System.Windows.Forms.DataGridViewDarkModeTheming (exposed via LocalAppContextSwitches / AppContextSwitches) to control whether DataGridView uses dark-mode-specific theming, defaulting to enabled for .NET 10 and allowing apps to opt out.
Add ApplyDarkModeTheming in DataGridView and call it only when dark mode is active and the new switch is enabled, centralizing the dark palette (background, gridlines, header/row colors) for high contrast on dark backgrounds.
Update DataGridView painting logic for several cell types—core cells, checkbox cells, combo box cells, and column header cells (sort glyphs)—to use adjusted colors and rendering that remain legible and visually correct in dark mode.
Improve DataGridViewLinkCell in dark mode by using shared LinkUtilities link colors (aligned with LinkLabel’s dark colors) and ensuring selected links render with appropriate selection foreground color for sufficient contrast.
Keep existing light-mode/legacy behavior unchanged when the AppContext switch is disabled, so existing applications can retain their current appearance without code changes.

Customer Impact

Users get a DataGridView that automatically renders with readable, high-contrast colors in dark mode by default, while app developers can still opt out via an AppContext switch to preserve existing light-themed behavior if needed.

Regression?

No

Risk

Minimal

Screenshots

Before

After

Test methodology

Manually

Test environment(s)

11.0.0-preview.2.26080.101

Microsoft Reviewers: Open in CodeFlow

codecov · 2026-02-05T08:07:18Z

Codecov Report

❌ Patch coverage is 4.61538% with 248 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.16791%. Comparing base (9b546b7) to head (dcf698f).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #14267         +/-   ##
===================================================
- Coverage   77.18395%   77.16791%   -0.01604%     
===================================================
  Files           3279        3279                 
  Lines         645138      645263        +125     
  Branches       47730       47755         +25     
===================================================
- Hits          497943      497936          -7     
- Misses        143503      143631        +128     
- Partials        3692        3696          +4

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production	`52.03815% <4.61538%> (-0.02504%)`	⬇️
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…Dark Mode.

…com/LeafShi1/winforms into Issue_14266_Add_DarkThemeExtensions

…Color.get' and 'set' to public API

Copilot

Pull request overview

This PR introduces dark mode theming for the DataGridView control via an AppContext switch (System.Windows.Forms.DataGridViewDarkModeTheming), defaulting to enabled for .NET 10+. The changes provide better visual appearance and contrast in dark mode while preserving opt-out capability for backward compatibility.

Changes:

Added AppContext switch to control DataGridView dark mode theming, with inheritance through style system
Implemented dark mode rendering for multiple cell types including link cells, combo box cells, checkbox cells, and column header sort glyphs
Added shared dark mode link colors to LinkUtilities for consistent link rendering across the DataGridView

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 31 comments.

Show a summary per file

File	Description
src/System.Windows.Forms.Primitives/src/System/LocalAppContextSwitches/LocalAppContextSwitches.cs	Added DataGridViewDarkModeTheming switch with .NET 10+ default
src/System.Windows.Forms/System/Windows/Forms/Controls/Labels/LinkUtilities.cs	Added dark mode color constants for links
src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewLinkCell.cs	Implemented dark mode link colors with proper selection handling
src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewComboBoxCell.DataGridViewComboBoxCellRenderer.cs	Added dark mode rendering for combo box dropdown and readonly buttons
src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewColumnHeaderCell.cs	Refactored sort glyph rendering to support solid white glyphs in dark mode
src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewCheckBoxCell.cs	Switched to CheckBoxRenderer.DrawCheckBoxWithVisualStyles for dark mode support
src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewCellStyle.cs	Added SortGlyphColor property to allow customization of sort arrow color
src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewCell.cs	Enhanced GetContrastedColors to provide better contrast in dark mode
src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridView.Methods.cs	Added ApplyDarkModeTheming method and integration in OnHandleCreated
src/System.Windows.Forms/PublicAPI.Unshipped.txt	Documented new SortGlyphColor public API

Copilot · 2026-02-12T10:06:27Z

...ows/Forms/Controls/DataGridView/DataGridViewComboBoxCell.DataGridViewComboBoxCellRenderer.cs

+                using var brush = new SolidBrush(Color.FromArgb(45, 45, 45));
+                g.FillRectangle(brush, bounds);
+
+                // Draw border
+                using var pen = new Pen(Color.FromArgb(100, 100, 100));
+                g.DrawRectangle(pen, bounds.X, bounds.Y, bounds.Width - 1, bounds.Height - 1);


The hardcoded Color.FromArgb(45, 45, 45) and Color.FromArgb(100, 100, 100) magic numbers should be replaced with named constants. These same values appear in ToolStripSystemDarkModeRenderer. Consider extracting these common dark mode colors to a shared location (such as a DarkModeColors class) to ensure consistency across controls and improve maintainability.

Copilot · 2026-02-12T10:06:27Z

...tem.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewColumnHeaderCell.cs

+            // In Dark Mode with quirk enabled, use a solid white glyph for better visibility
+            if (Application.IsDarkModeEnabled && AppContextSwitches.DataGridViewDarkModeTheming)
+            {
+                darkColor = Color.White;
+                lightColor = Color.White;


The SortGlyphColor property from cellStyle is inherited in BuildInheritedColumnHeaderCellStyle but is never actually used in the painting logic. The sort glyph rendering code hardcodes Color.White for dark mode on line 1011-1012 instead of checking if cellStyle.SortGlyphColor is set. The code should check cellStyle.SortGlyphColor first and only fall back to Color.White if it's Color.Empty, allowing users to customize the sort glyph color.

Suggested change

// In Dark Mode with quirk enabled, use a solid white glyph for better visibility

if (Application.IsDarkModeEnabled && AppContextSwitches.DataGridViewDarkModeTheming)

{

darkColor = Color.White;

lightColor = Color.White;

// In Dark Mode with quirk enabled, prefer SortGlyphColor when set, otherwise use solid white glyph for better visibility

if (Application.IsDarkModeEnabled && AppContextSwitches.DataGridViewDarkModeTheming)

{

Color sortGlyphColor = cellStyle.SortGlyphColor;

if (sortGlyphColor == Color.Empty)

{

sortGlyphColor = Color.White;

}

darkColor = sortGlyphColor;

lightColor = sortGlyphColor;

Copilot · 2026-02-12T10:06:28Z

src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridView.Methods.cs

+        Color onSurface = SystemColors.WindowText;
+        Color headerBg = SystemColors.ControlDarkDark;
+        Color headerFg = SystemColors.ActiveCaptionText;
+        Color selectionBg = Color.FromArgb(0x33, 0x66, 0xCC);


The magic numbers Color.FromArgb(0x33, 0x66, 0xCC) for selectionBg should be replaced with a named constant to improve code clarity and maintainability. Consider defining this as a constant like DarkModeSelectionBackground.

Copilot · 2026-02-12T10:06:28Z

src/System.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewCell.cs

+        else if (Application.IsDarkModeEnabled)
+        {
+            // In Dark Mode, use higher contrast colors for better visibility.
+            // For dark backgrounds, we need lighter colors that stand out.
+            darkColor = darkDistance < ContrastThreshold
+                ? ControlPaint.Light(baseline, 0.5f)
+                : SystemColors.ControlLight;
+
+            lightColor = lightDistance < ContrastThreshold
+                ? ControlPaint.LightLight(baseline)
+                : SystemColors.ControlLightLight;
+        }


The GetContrastedColors method now checks Application.IsDarkModeEnabled and returns dark-mode-optimized colors for all DataGridView cells, but it does not verify the AppContextSwitches.DataGridViewDarkModeTheming switch. This means border rendering and other uses of GetContrastedColors will apply dark mode logic even if the user has opted out via the AppContext switch. If the intent is that opting out of the quirk should preserve all existing light-mode behavior, then GetContrastedColors should also check the AppContext switch. Alternatively, if general dark mode color improvements are intended to apply regardless of the quirk, this should be clarified in the PR description.

Copilot · 2026-02-12T10:06:28Z

...ows/Forms/Controls/DataGridView/DataGridViewComboBoxCell.DataGridViewComboBoxCellRenderer.cs

+            if (Application.IsDarkModeEnabled)
+            {
+                InitializeRenderer(ComboBoxDropDownButtonElement, (int)state);
+            }


The DataGridViewComboBoxCellRenderer methods DrawDropDownButton and DrawReadOnlyButton check Application.IsDarkModeEnabled but do not verify the AppContextSwitches.DataGridViewDarkModeTheming switch. This means dark mode rendering will be applied even if the user has opted out via the AppContext switch. Both dark mode conditions should check both Application.IsDarkModeEnabled AND AppContextSwitches.DataGridViewDarkModeTheming to respect the opt-out mechanism.

Copilot · 2026-02-12T10:06:34Z

...tem.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewColumnHeaderCell.cs

+                            g.DrawLine(penControlDark,
+                                sortGlyphLocation.X,
+                                sortGlyphLocation.Y + 1,
+                                sortGlyphLocation.X + s_sortGlyphWidth / 2 - 1,


Possible loss of precision: any fraction will be lost.

Copilot · 2026-02-12T10:06:34Z

...tem.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewColumnHeaderCell.cs

+                            g.DrawLine(penControlDark,
+                                sortGlyphLocation.X + 1,
+                                sortGlyphLocation.Y + 1,
+                                sortGlyphLocation.X + s_sortGlyphWidth / 2 - 1,


Possible loss of precision: any fraction will be lost.

Copilot · 2026-02-12T10:06:34Z

...tem.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewColumnHeaderCell.cs

+                            g.DrawLine(penControlLightLight,
+                                sortGlyphLocation.X,
+                                sortGlyphLocation.Y + 1,
+                                sortGlyphLocation.X + s_sortGlyphWidth / 2 - 1,


Possible loss of precision: any fraction will be lost.

Copilot · 2026-02-12T10:06:34Z

...tem.Windows.Forms/System/Windows/Forms/Controls/DataGridView/DataGridViewColumnHeaderCell.cs

+                            g.DrawLine(penControlLightLight,
+                                sortGlyphLocation.X + 1,
+                                sortGlyphLocation.Y + 1,
+                                sortGlyphLocation.X + s_sortGlyphWidth / 2 - 1,


Possible loss of precision: any fraction will be lost.

Copilot · 2026-02-12T10:06:35Z

...ystem.Windows.Forms.Primitives/src/System/LocalAppContextSwitches/LocalAppContextSwitches.cs

+        if (framework.Version.Major >= 10)
+        {
+            // Behavior changes added in .NET 10
+
+            if (switchName == DataGridViewDarkModeThemingSwitchName)
+            {
+                return true;
+            }
+        }


These 'if' statements can be combined.

Add theming API and improve selection/grid readability

cbb3bcc

github-actions bot added the needs-area-label label Feb 4, 2026

dotnet-policy-service bot assigned LeafShi1 Feb 4, 2026

dotnet-policy-service bot added the draft draft PR label Feb 4, 2026

Update DarkThemePalette

0466578

LeafShi1 and others added 2 commits February 9, 2026 17:55

Update the sorting icon in the column headers so it appears white in …

0e46f9d

…Dark Mode.

Remove unnecessary line break in DataGridViewColumnHeaderCell

20ce8c5

github-actions bot added area-controls-DataGridView and removed needs-area-label labels Feb 10, 2026

LeafShi1 added 3 commits February 10, 2026 15:40

Update ComboBoxCell and CheckBoxCell

cc7aa78

Merge branch 'Issue_14266_Add_DarkThemeExtensions' of https://github.…

f9dd611

…com/LeafShi1/winforms into Issue_14266_Add_DarkThemeExtensions

Add quirk AppContextSwitches.DataGridViewDarkModeTheming

2af28f4

LeafShi1 changed the title ~~Add theming API and improve selection/grid readability~~ Enable DataGridView dark mode theming via AppContext switch Feb 12, 2026

Declared Symbol 'System.Windows.Forms.DataGridViewCellStyle.SortGlyph…

dcf698f

…Color.get' and 'set' to public API

LeafShi1 marked this pull request as ready for review February 12, 2026 09:54

LeafShi1 requested a review from a team as a code owner February 12, 2026 09:54

LeafShi1 requested review from KlausLoeffelmann, Copilot and merriemcgaw February 12, 2026 09:56

Copilot started reviewing on behalf of LeafShi1 February 12, 2026 09:56 View session

Copilot AI reviewed Feb 12, 2026

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-            // In Dark Mode with quirk enabled, use a solid white glyph for better visibility
-            if (Application.IsDarkModeEnabled && AppContextSwitches.DataGridViewDarkModeTheming)
-            {
-                darkColor = Color.White;
-                lightColor = Color.White;
+            // In Dark Mode with quirk enabled, prefer SortGlyphColor when set, otherwise use solid white glyph for better visibility
+            if (Application.IsDarkModeEnabled && AppContextSwitches.DataGridViewDarkModeTheming)
+            {
+                Color sortGlyphColor = cellStyle.SortGlyphColor;
+                if (sortGlyphColor == Color.Empty)
+                {
+                    sortGlyphColor = Color.White;
+                }
+                darkColor = sortGlyphColor;
+                lightColor = sortGlyphColor;

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Proposed changes

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