How to change the color of a ComboBox using win32 API

Question

A ComboBox has its color in white when created. I want to change is appearance so that it is colored (not the backgrouond color). I am using native winapi and don't know how to do it. I googled and I could find examples of changing the background color by handling the WM_CTLCOLORLISTBOX but that is not what I want. I also have the hint from google that I should subclass the ComboBox and handle the WM_NCPAINT message, but there is just no example the can achieve the effect I want. I have been battling this for few days with no luck. Any help is appreciated.

What's wrong with WM_CTLCOLORLISTBOX ? Does it not work? (That's entirely possible, I don't know for sure as I myself use ownerdraw, and that might be your best option here although it's more work, obviously). But forget that Google hint, that's way wrong. — Paul Sanders
That's a combobox, not listbox. The style is either drop-down or drop-list, I can't tell. Do you want to redraw the button section in one style, and leave the drop-down list in a different style? — Barmak Shemirani
@Paul, I meant the Green part of the combo, not the dropdown part of it. WCM_CTLCOLORLISTBOX allows the change of the dropdown of it. — simon
@Paul, the suggested link does not apply to my question as it is about how to color the seleted item in the dropdown list. What I want is to paint the button (the green) part of it in the image above. I've also tried ownerdraw control but no luck. Much appreciate if you could share a relevant example. — simon

Barmak Shemirani Barmak Shemirani · Accepted Answer · 2018-06-15T05:03:08

If Visual Style is enabled you can subclass the combobox and override WM_PAINT. This works only for CBS_DROPDOWNLIST (resource editor calls it "Drop List"). You have to manually draw a drop down arrow.

#include <Windows.h>
#include <CommCtrl.h>

#pragma comment(lib, "Comctl32.lib")

LRESULT CALLBACK ComboProc(HWND hwnd, UINT msg, WPARAM wParam,
    LPARAM lParam, UINT_PTR uIdSubClass, DWORD_PTR)
{
    switch(msg)
    {
    case WM_PAINT:
    {
        DWORD style = GetWindowLongPtr(hwnd, GWL_STYLE);
        if(!(style & CBS_DROPDOWNLIST))
            break;

        RECT rc;
        GetClientRect(hwnd, &rc);

        PAINTSTRUCT ps;
        auto hdc = BeginPaint(hwnd, &ps);
        auto bkcolor = RGB(80, 140, 0);
        auto brush = CreateSolidBrush(bkcolor);
        auto pen = CreatePen(PS_SOLID, 1, RGB(128, 128, 128));
        auto oldbrush = SelectObject(hdc, brush);
        auto oldpen = SelectObject(hdc, pen);
        SelectObject(hdc, (HFONT)SendMessage(hwnd, WM_GETFONT, 0, 0));
        SetBkColor(hdc, bkcolor);
        SetTextColor(hdc, RGB(255, 255, 255));

        Rectangle(hdc, 0, 0, rc.right, rc.bottom);

        if(GetFocus() == hwnd)
        {
            RECT temp = rc;
            InflateRect(&temp, -2, -2);
            DrawFocusRect(hdc, &temp);
        }

        int index = SendMessage(hwnd, CB_GETCURSEL, 0, 0);
        if(index >= 0)
        {
            int buflen = SendMessage(hwnd, CB_GETLBTEXTLEN, index, 0);
            TCHAR *buf = new TCHAR[(buflen + 1)];
            SendMessage(hwnd, CB_GETLBTEXT, index, (LPARAM)buf);
            rc.left += 5;
            DrawText(hdc, buf, -1, &rc, DT_EDITCONTROL|DT_LEFT|DT_VCENTER|DT_SINGLELINE);
            delete[]buf;
        }

        SelectObject(hdc, oldpen);
        SelectObject(hdc, oldbrush);
        DeleteObject(brush);
        DeleteObject(pen);

        EndPaint(hwnd, &ps);
        return 0;
    }

    case WM_NCDESTROY:
    {
        RemoveWindowSubclass(hwnd, ComboProc, uIdSubClass);
        break;
    }

    }

    return DefSubclassProc(hwnd, msg, wParam, lParam);
}

Usage:

INT_PTR CALLBACK DialogProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lParam)
{
    static HBRUSH hbrBkgnd = CreateSolidBrush(RGB(0, 255, 0));
    switch(msg)
    {
    case WM_INITDIALOG:
    {
        HWND hcombo = GetDlgItem(hwnd, IDC_COMBO1);
        SetWindowSubclass(hcombo, ComboProc, 0, 0);
        ...
        break;
    }
    ...
}

How to change the color of a ComboBox using win32 API

1 Answers