Create window without titlebar, with resizable border and without bogus 6px white stripe

Question

I want a window without title bar but with resizable frames and shadow. This can easily be achieved by removing WS_CAPTION and adding WS_THICKFRAME, however, since Windows 1

Answer 1

Just to expand on this a little; in order to remove the white stripe one just has to remove the corresponding value from the first rect in NCCALCSIZE. pywin32 code would be:

    if msg == WM_NCCALCSIZE:
        if wParam:
            res = CallWindowProc(
                wndProc, hWnd, msg, wParam, lParam
            )
            sz = NCCALCSIZE_PARAMS.from_address(lParam)
            sz.rgrc[0].top -= 6 # remove 6px top border!
            return res

Answer 2

Change the style of dialog.

LONG lStyle = GetWindowLong(hwnd, GWL_STYLE);
lStyle |= WS_THICKFRAME; // 6px white stripe cause of this.
lStyle = lStyle & ~WS_CAPTION;

Answer 3

That's not a bug. In Windows 10 the borders on left/right/bottom are transparent. The top border is not transparent. You should leave it as is. Probably nobody will complain.

To change it, you must modify the non-client area. This is rather difficult in Windows Vista and above. See Custom Window Frame Using DWM for reference.

• Find border thickness

• Use DwmExtendFrameIntoClientArea to get access to non-client area

• Use BeginBufferedPaint to draw opaque color over non-client area

Windows 10 example:

(See the next example for compatibility with Windows Vista, 7, 8)

//requires Dwmapi.lib and UxTheme.lib
#include <Windows.h>
#include <Dwmapi.h>

void my_paint(HDC hdc, RECT rc)
{
    HBRUSH brush = CreateSolidBrush(RGB(0, 128, 0));
    FillRect(hdc, &rc, brush);
    DeleteObject(brush);
}

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    static RECT border_thickness;

    switch (uMsg)
    {
    case WM_CREATE:
    {
        //find border thickness
        SetRectEmpty(&border_thickness);
        if (GetWindowLongPtr(hwnd, GWL_STYLE) & WS_THICKFRAME)
        {
            AdjustWindowRectEx(&border_thickness, GetWindowLongPtr(hwnd, GWL_STYLE) & ~WS_CAPTION, FALSE, NULL);
            border_thickness.left *= -1;
            border_thickness.top *= -1;
        }
        else if (GetWindowLongPtr(hwnd, GWL_STYLE) & WS_BORDER)
        {
            SetRect(&border_thickness, 1, 1, 1, 1);
        }

        MARGINS margins = { 0 };
        DwmExtendFrameIntoClientArea(hwnd, &margins);
        SetWindowPos(hwnd, NULL, 0, 0, 0, 0, SWP_SHOWWINDOW | SWP_NOMOVE | SWP_NOSIZE | SWP_FRAMECHANGED);
        break;
    }

    case WM_PAINT:
    {
        PAINTSTRUCT ps;
        HDC hdc = BeginPaint(hwnd, &ps);

        RECT rc = ps.rcPaint;
        BP_PAINTPARAMS params = { sizeof(params), BPPF_NOCLIP | BPPF_ERASE };
        HDC memdc;
        HPAINTBUFFER hbuffer = BeginBufferedPaint(hdc, &rc, BPBF_TOPDOWNDIB, &params, &memdc);

        my_paint(memdc, rc);

        BufferedPaintSetAlpha(hbuffer, &rc, 255);
        EndBufferedPaint(hbuffer, TRUE);

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

    case WM_NCACTIVATE:
        return 0;

    case WM_NCCALCSIZE:
        if (lParam)
        {
            NCCALCSIZE_PARAMS* sz = (NCCALCSIZE_PARAMS*)lParam;
            sz->rgrc[0].left += border_thickness.left;
            sz->rgrc[0].right -= border_thickness.right;
            sz->rgrc[0].bottom -= border_thickness.bottom;
            return 0;
        }
        break;

    case WM_NCHITTEST:
    {
        //do default processing, but allow resizing from top-border
        LRESULT result = DefWindowProc(hwnd, uMsg, wParam, lParam);
        if (result == HTCLIENT)
        {
            POINT pt = { GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam) };
            ScreenToClient(hwnd, &pt);
            if (pt.y < border_thickness.top) return HTTOP;
        }
        return result;
    }

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;

    }
    return DefWindowProc(hwnd, uMsg, wParam, lParam);
}

int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE, PWSTR, int)
{
    const wchar_t CLASS_NAME[] = L"Sample Window Class";

    WNDCLASS wc = {};
    wc.lpfnWndProc = WindowProc;
    wc.hInstance = hInstance;
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.lpszClassName = CLASS_NAME;
    RegisterClass(&wc);

    CreateWindowEx(0, CLASS_NAME,   NULL,
        WS_VISIBLE | WS_THICKFRAME | WS_POPUP,
        10, 10, 600, 400, NULL, NULL, hInstance, NULL);

    MSG msg = {};
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return 0;
}

For compatibility with Windows Vista/7/8 use this procedure instead. This will paint over left/top/bottom borders as well as top border. This window will appear as a simple rectangle, with resizing borders:

//for Windows Vista, 7, 8, 10
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    static RECT border_thickness;

    switch (uMsg)
    {
    case WM_CREATE:
    {
        //find border thickness
        SetRectEmpty(&border_thickness);
        if (GetWindowLongPtr(hwnd, GWL_STYLE) & WS_THICKFRAME)
        {
            AdjustWindowRectEx(&border_thickness, GetWindowLongPtr(hwnd, GWL_STYLE) & ~WS_CAPTION, FALSE, NULL);
            border_thickness.left *= -1;
            border_thickness.top *= -1;
        }
        else if (GetWindowLongPtr(hwnd, GWL_STYLE) & WS_BORDER)
        {
            SetRect(&border_thickness, 1, 1, 1, 1);
        }

        MARGINS margins = { 0 };
        DwmExtendFrameIntoClientArea(hwnd, &margins);
        SetWindowPos(hwnd, NULL, 0, 0, 0, 0, SWP_SHOWWINDOW | SWP_NOMOVE | SWP_NOSIZE | SWP_FRAMECHANGED);
        break;
    }

    case WM_PAINT:
    {
        PAINTSTRUCT ps;
        HDC hdc = BeginPaint(hwnd, &ps);

        RECT rc = ps.rcPaint;
        BP_PAINTPARAMS params = { sizeof(params), BPPF_NOCLIP | BPPF_ERASE };
        HDC memdc;
        HPAINTBUFFER hbuffer = BeginBufferedPaint(hdc, &rc, BPBF_TOPDOWNDIB, &params, &memdc);

        my_paint(memdc, rc);

        BufferedPaintSetAlpha(hbuffer, &rc, 255);
        EndBufferedPaint(hbuffer, TRUE);

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

    case WM_NCACTIVATE:
        return 0;

    case WM_NCCALCSIZE:
        if (lParam)
            return 0;

    case WM_NCHITTEST:
    {
        POINT pt = { GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam) };
        ScreenToClient(hwnd, &pt);
        RECT rc;
        GetClientRect(hwnd, &rc);
        enum {left=1, top=2, right=4, bottom=8};
        int hit = 0;
        if (pt.x < border_thickness.left) hit |= left;
        if (pt.x > rc.right - border_thickness.right) hit |= right;
        if (pt.y < border_thickness.top) hit |= top;
        if (pt.y > rc.bottom - border_thickness.bottom) hit |= bottom;

        if (hit & top && hit & left) return HTTOPLEFT;
        if (hit & top && hit & right) return HTTOPRIGHT;
        if (hit & bottom && hit & left) return HTBOTTOMLEFT;
        if (hit & bottom && hit & right) return HTBOTTOMRIGHT;
        if (hit & left) return HTLEFT;
        if (hit & top) return HTTOP;
        if (hit & right) return HTRIGHT;
        if (hit & bottom) return HTBOTTOM;

        return HTCLIENT;
    }

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;

    }
    return DefWindowProc(hwnd, uMsg, wParam, lParam);
}