Fix issue 14198: [Dark Mode] Improve visual contrast of the Group Headers in ListView control in dark by SimonZhao888 · Pull Request #14406 · dotnet/winforms

SimonZhao888 · 2026-03-18T08:26:34Z

Fixes #14198

Proposed changes

In Dark Mode, the ListView's internal theme has been switched from "Explorer" to "ItemsView" to ensure alignment with the column headers.
After the Handle is created, call the new method UpdateDarkModeGroupTextColors() to set the group header and footer text colors using LVM_SETGROUPMETRICS.
Add CDRF_NOTIFYITEMDRAW to enable the native control to send CDDS_ITEMPREPAINT notifications for group items.
Added a 'group' branch to CDDS_ITEMPREPAINT: In dark mode, return CDRF_SKIPDEFAULT to skip native group painting, and cache clrTextBk and uItemState in a dictionary for use during the overlay phase.
In Dark Mode, force the HDC text color to equal ForeColor, and set the group text of the header control to use clrTextBk.

Customer Impact

Improve visual contrast of the Group Headers in ListView control in dark.

Regression?

No

Risk

Min

Screenshots

Before

After

2026-05-15.103056.mp4

Test environment(s)

11.0.100-preview.5.26227.104

…ders in ListView control in dark

Copilot

Pull request overview

This PR targets WinForms ListView dark mode rendering by improving the visual contrast of group headers (and related group text) when groups are enabled.

Changes:

Adds custom dark-mode rendering logic for group header text, chevron, subtitle, and footer.
Adjusts custom-draw flags and text color handling to receive group-related draw notifications and control group text colors.
Updates the applied dark-mode theme identifier for the ListView/ColumnHeader to use the ItemsView theme.

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Copilot

Pull request overview

Improves ListView group header readability in dark mode by adjusting theming/custom-draw behavior and adding an overlay render pass to redraw group header/subtitle/footer with higher-contrast styling.

Changes:

Add dark-mode overlay drawing for group header/subtitle/footer and a custom chevron/underline rendering path.
Adjust ListView custom draw flags/colors so group custom-draw notifications are raised and native group text is suppressed in dark mode.
Switch the applied dark-mode theme identifier to DarkMode_ItemsView and attempt to configure group text colors via LVM_SETGROUPMETRICS.

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LeafShi1 · 2026-03-24T09:02:38Z

Please consider Copilot's suggestion and complete the PR description

SimonZhao888 · 2026-03-25T01:41:58Z

Please consider Copilot's suggestion and complete the PR description

I'm trying to add a selected overlay to a Group Item in Dark Mode.

SimonZhao888 · 2026-05-15T02:40:40Z

/azp run

azure-pipelines · 2026-05-15T02:40:49Z

Azure Pipelines successfully started running 1 pipeline(s).

Copilot

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 6 comments.

+        int centerX = headerRect.Right - 9;
+        int centerY = headerTextRect.Top + (headerTextRect.Height / 2) + 1;
+
+        Rectangle nativeChevronRect = new(
+            headerRect.Right - 28,
+            headerRect.Top,
+            28,
+            headerRect.Height);
+        using (Brush backgroundBrush = new SolidBrush(backgroundColor))
+        {
+            g.FillRectangle(backgroundBrush, nativeChevronRect);
+        }
+
+        Point[] points = collapsed
+            ? [new Point(centerX - 3, centerY - 5), new Point(centerX + 2, centerY), new Point(centerX - 3, centerY + 5)]
+            : [new Point(centerX - 5, centerY - 2), new Point(centerX, centerY + 3), new Point(centerX + 5, centerY - 2)];
+
+        using Pen chevronPen = new(chevronColor, 2.6f)
+        {
+            StartCap = Drawing.Drawing2D.LineCap.Round,
+            EndCap = Drawing.Drawing2D.LineCap.Round,
+            LineJoin = Drawing.Drawing2D.LineJoin.Round
+        };
+
+        g.DrawLines(chevronPen, points);


+        COLORREF textColor = (COLORREF)ColorTranslator.ToWin32(ForeColor);
+        COLORREF headerColor = (COLORREF)ColorTranslator.ToWin32(BackColor);
+        LVGROUPMETRICS groupMetrics = new()
+        {
+            cbSize = (uint)sizeof(LVGROUPMETRICS),
+            mask = LVGMF_TEXTCOLOR,
+            crHeader = headerColor,
+            crFooter = textColor
+        };
+
+        PInvokeCore.SendMessage(this, LVM_SETGROUPMETRICS, (WPARAM)0, ref groupMetrics);


+                ? Color.FromArgb(64, 90, 150, 255)
+                : (isHovered ? Color.FromArgb(28, 255, 255, 255) : Color.Empty);


+            int interactionBottom = headerRect.Bottom;
+            if (!string.IsNullOrEmpty(group.Subtitle))
+            {
+                interactionBottom = headerRect.Top + Font.Height + verticalSpacing + Font.Height + headerVerticalPadding;
+            }
+
+            if (!string.IsNullOrEmpty(group.Footer) && (collapsed || group.Items.Count == 0))
+            {
+                int subtitleOffset = string.IsNullOrEmpty(group.Subtitle) ? 1 : 2;
+                int collapsedFooterY = headerRect.Top + (Font.Height * subtitleOffset) + footerCollapsedAdditionalOffset;
+                interactionBottom = Math.Min(interactionBottom, Math.Max(headerRect.Top, collapsedFooterY - LogicalToDeviceUnits(1)));
+            }
+
+            Rectangle interactionRect = Rectangle.Intersect(
+                groupRect,
+                new Rectangle(
+                    groupRect.Left,
+                    headerRect.Top,
+                    groupRect.Width,
+                    Math.Max(0, interactionBottom - headerRect.Top)));
+


+                    int oldHoveredGroupId = _darkModeHoveredGroupId;
+                    int hoveredGroupId = GetDarkModeGroupHeaderHitId();
+                    if (_darkModeHoveredGroupId != hoveredGroupId)
+                    {
+                        _darkModeHoveredGroupId = hoveredGroupId;
+                        InvalidateDarkModeGroupHeader(oldHoveredGroupId);
+                        InvalidateDarkModeGroupHeader(_darkModeHoveredGroupId);
+                    }


+                    // Suppress native hover processing in dark mode group overlay mode.
+                    // Native hover invalidates group headers while mouse moves over grouped content,
+                    // causing repaint jitter.
+                    LVHITTESTINFO lvhi = SetupHitTestInfo();
+                    bool isMouseOverItem = (int)PInvokeCore.SendMessage(this, PInvoke.LVM_HITTEST, (WPARAM)0, ref lvhi) >= 0;
+                    bool allowNativeHover = isMouseOverItem || HoverSelection || HotTracking;
+
+                    if (!allowNativeHover)
+                    {
+                        Capture = false;
+                        return;
+                    }


LeafShi1

Please consider Copilot's suggestions and the test case updates.

LeafShi1

Several potential issues found

LeafShi1 · 2026-05-15T07:18:09Z

+        public COLORREF crHeader;
+        public COLORREF crFooter;
+    }
+


Hardcoded colors are not theme-aware

Color.FromArgb(120, 180, 255) (header), Color.FromArgb(80, 170, 255) (chevron), Color.FromArgb(64, 90, 150, 255) (selected overlay), and Color.FromArgb(28, 255, 255, 255) (hover overlay) are all hardcoded magic values. These should at minimum be extracted as named static readonly constants for maintainability. Ideally they should come from system/theme colors or be configurable — if the system dark mode palette changes in a future Windows version, these will look wrong.

LeafShi1 · 2026-05-15T07:18:09Z

+                HWND header = (HWND)PInvokeCore.SendMessage(this, PInvoke.LVM_GETHEADER);
+                if (!header.IsNull)
+                {
+                    PInvokeCore.GetWindowRect(header, out RECT headerRect);


Chevron drawing is not DPI-aware

In this method, several pixel values are not scaled via LogicalToDeviceUnits():

centerX = headerRect.Right - 9 and centerY offset +1

The native chevron cover rect uses a hardcoded width of 28

Chevron point offsets (3, 5, 2) and pen width (2.6f) are raw pixel values

dividerTextSpacing = 6 is unscaled

The parent method (DrawDarkModeGroupSubtitleAndFooterOverlay) correctly uses LogicalToDeviceUnits() for padding/spacing. On high-DPI displays (200%+), the chevron will appear undersized and mispositioned relative to the DPI-scaled header text.

LeafShi1 · 2026-05-15T07:18:09Z

+            {
+                return background;
+            }
+


Duplicated layout logic between drawing and hit-testing

The interaction rect computation here (headerVerticalPadding, verticalSpacing, footerCollapsedAdditionalOffset, interactionBottom calculation) is duplicated nearly identically in TryGetDarkModeGroupInteractionRect further below. If any layout constant or formula changes, both locations must be updated in sync — this is fragile. Consider extracting a shared helper that computes the layout metrics once.

LeafShi1 · 2026-05-15T07:18:09Z

+                    {
+                        Capture = false;
+                        return;
+                    }


Suppressing base.WndProc for WM_MOUSEMOVE may have side effects

When !allowNativeHover, the code sets Capture = false and returns, completely bypassing base.WndProc(ref m). This means other mouse-move processing (accessibility notifications, tooltip tracking, drag detection) will be skipped. Could this cause subtle regressions for drag-and-drop or accessibility scenarios? It might be safer to only suppress the specific hover invalidation rather than skipping the entire base message processing.

LeafShi1 · 2026-05-15T07:18:09Z

+                    textColor = nmlvcd->clrTextBk;
+                }
+                else
+                {


Using clrTextBk as text color is semantically confusing

textColor = nmlvcd->clrTextBk;

This reads the background color field and uses it as the text color. Even if this works due to how the native control populates these fields for group items, it's surprising to readers and fragile if the native behavior changes. A comment explaining why the background color field contains the desired text color value would help future maintainers.

Fix issue 14198: [Dark Mode] Improve visual contrast of the Group Hea…

418a4fb

…ders in ListView control in dark

SimonZhao888 requested a review from Copilot March 18, 2026 08:26

SimonZhao888 requested a review from a team as a code owner March 18, 2026 08:26

github-actions Bot added the area-DarkMode Issues relating to Dark Mode feature label Mar 18, 2026

SimonZhao888 changed the title ~~Fix issue 14198: [Dark Mode] Improve visual contrast of the Group Hea…~~ Fix issue 14198: [Dark Mode] Improve visual contrast of the Group Headers in ListView control in dark Mar 18, 2026

dotnet-policy-service Bot assigned SimonZhao888 Mar 18, 2026

Copilot started reviewing on behalf of SimonZhao888 March 18, 2026 08:27 View session

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SimonZhao888 requested a review from Copilot March 19, 2026 02:20

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Simon Zhao (BEYONDSOFT CONSULTING INC) added 3 commits March 26, 2026 13:51

Adjust codes

951a261

Add mask layer effect

f913bc7

Add Hover effect

f05bde8

SimonZhao888 marked this pull request as draft March 26, 2026 08:47

dotnet-policy-service Bot added the draft draft PR label Mar 26, 2026

Add comment to the new method

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SimonZhao888 marked this pull request as ready for review May 15, 2026 02:40

SimonZhao888 requested review from KlausLoeffelmann, LeafShi1, Copilot and ricardobossan May 15, 2026 02:40

Copilot started reviewing on behalf of SimonZhao888 May 15, 2026 02:41 View session

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dotnet-policy-service Bot removed the draft draft PR label May 15, 2026

LeafShi1 reviewed May 15, 2026

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		? Color.FromArgb(64, 90, 150, 255)
		: (isHovered ? Color.FromArgb(28, 255, 255, 255) : Color.Empty);

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LeafShi1 commented Mar 24, 2026

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