CComboBoxEx in dark mode (with Dropdown style) in MFC

Question

I am trying to implement a dark mode for my application, by using DarkMode_Explorer / DarkMode_CFD etc. I have handled OnCtlColor and set the theme using SetWindowTheme.

If my CComboBoxEx is a DropList then it renderings properly. But when I set it to Downdown it looks odd:

Using a standard CComboBox renders properly for both modes.

I wanted to use the CComboBoxEx because it made it easier to get at the edit control and set it as numeric. I realise I can do it old-style with CComboBox. But it would be nice to continue using this control.

Steps to reproduce

1. Add a CComBoxEx control to your dialog and set it as Dropdown.
2. Configure your application / dialog to use dark mode.
3. Apply the theme to the combo:

pComboBoxEx->SetWindowTheme(theme);
auto pComboEdit = pComboBoxEx->GetEditCtrl();
if (pComboEdit && pComboEdit->GetSafeHwnd())
{
	SetWindowTheme(pComboEdit->GetSafeHwnd(), L"DarkMode_CFD", nullptr);
}

// Get the underlying ComboBox control so that we can get the ListBox handle
auto pComboBox = pComboBoxEx->GetComboBoxCtrl();
if (pComboBox)
{
	COMBOBOXINFO cbi{};
	cbi.cbSize = sizeof(COMBOBOXINFO);
	if (GetComboBoxInfo(pComboBox->GetSafeHwnd(), &cbi) && cbi.hwndList)
	{
		SetWindowTheme(cbi.hwndList, L"DarkMode_Explorer", nullptr);
		// The scrollbars are now set correctly, but the ListBox background is still white.
	}
}

4. Handle WM_CTLCOLOR (I am including all I am using in my project):

const auto backColour = parentIsChild ? DarkModeTools::kDarkSheetBackgroundColor
	: DarkModeTools::kDarkBackgroundColor;
switch (nCtlColor)
{
case CTLCOLOR_STATIC: // Static text
	pDC->SetBkColor(backColour);
	if (pControl->IsWindowEnabled())
	{
		pDC->SetTextColor(kDarkTextColor);
	}
	else
	{
		pDC->SetTextColor(::GetSysColor(COLOR_GRAYTEXT));
	}
	break;
case CTLCOLOR_DLG: // Dialog background
case CTLCOLOR_SCROLLBAR: // Scrollbars
case CTLCOLOR_EDIT: // Edit control
case CTLCOLOR_LISTBOX: // Listbox
case CTLCOLOR_MSGBOX:
	pDC->SetTextColor(kDarkTextColor);
	pDC->SetBkColor(backColour);
	break;
case CTLCOLOR_BTN: // Buttons
default:
	// You can add specific cases here if needed
	break;
}

Hat should be enough to replicate the issue.

Answer 1

Hi,

I can't change the color of scrollbar using the sample code.

I edited the drawing of CTLCOLOR_LISTBOX

	case CTLCOLOR_LISTBOX:
	{
		pDC->SetTextColor (RGB (250, 250, 250));
		static CBrush brush (RGB (0, 0, 0));
		return brush;
	}

Best regards,

Minxin Yu

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