Prevent Win32 from drawing a classic title bar

Question

I wanted to add a nice shadow to my borderless form, and the best way I found for this with minimal performance loss is to use DwmExtendFrameIntoClientArea . However, it seems that this forces Windows to draw the classic title bar above the window, but it does not work (i.e., Glitch is just graphic).

This is the code I'm using:

int v = (int) DWMNCRENDERINGPOLICY.DWMNCRP_ENABLED;
NativeApi.DwmSetWindowAttribute(Handle, DwmWindowAttribute.NCRENDERING_POLICY, ref v, sizeof(int));
int enable = 0;
NativeApi.DwmSetWindowAttribute(Handle, DwmWindowAttribute.ALLOW_NCPAINT, ref enable, sizeof(int));
MARGINS margins = new MARGINS() {
    leftWidth = 0,
    topHeight = 0,
    rightWidth = 0,
    bottomHeight = 1
};
NativeApi.DwmExtendFrameIntoClientArea(Handle, ref margins);

I tried to set ALLOW_NCPAINTto 1, and even tried to return 0 when the window receives WM_NCPAINTwithout a call DefWndProc, but that didn't matter.

Is there any way to solve this strange problem when using DwmExtendFrameIntoClientArea?

Answer 1

@Erik Philips, , , , . CreateParams:

/// <summary>
/// Gets the parameters that define the initial window style.
/// </summary>
protected override CreateParams CreateParams {
    get {
        CreateParams cp = base.CreateParams;
        if (!DesignMode) {
            cp.ClassStyle |= (int) ClassStyle.DoubleClicks;
            cp.Style |= unchecked((int) (WindowStyle.Popup | WindowStyle.SystemMenu | WindowStyle.ClipChildren | WindowStyle.ClipSiblings));
            cp.ExStyle |= (int) ExtendedWindowStyle.Layered;
        }
        return cp;
    }
}

| cp.Style:

protected override CreateParams CreateParams {
    get {
        CreateParams cp = base.CreateParams;
        if (!DesignMode) {
            cp.ClassStyle |= (int) ClassStyle.DoubleClicks;
            cp.Style = unchecked((int) (WindowStyle.Popup | WindowStyle.SystemMenu | WindowStyle.ClipChildren | WindowStyle.ClipSiblings));
            cp.ExStyle |= (int) ExtendedWindowStyle.Layered;
        }
        return cp;
    }
}

, , -, WinForms WS_BORDER , FormBorderStyle None.