Form With Shadow

roshihans

I have a form and a png image file (with a transparent shadow in its border) and what I want is to make a drop shadow effect on the form. I know there are CS_DROPSHADOW solution for this, but I think it doesn't look too good. So I create a "fake" form using CreateWindowEx (via DllImport), and draw the png image file into the fake form.

void CreateFakeForm()
{
WNDCLASSEX wndClsEx = new WNDCLASSEX();
wndClsEx.Init();
wndClsEx.style = CS_VREDRAW | CS_HREDRAW;
wndClsEx.lpfnWndProc = m_DefWndProcDelegate;
wndClsEx.cbClsExtra = 0;
wndClsEx.cbWndExtra = 0;
wndClsEx.hInstance = GetModuleHandle(null);
wndClsEx.hIcon = IntPtr.Zero;
wndClsEx.hIconSm = IntPtr.Zero;
wndClsEx.hCursor = IntPtr.Zero;
wndClsEx.hbrBackground = IntPtr.Zero;
wndClsEx.lpszClassName = m_WndClsName;
wndClsEx.lpszMenuName = null;

        bool success = RegisterClassEx(ref wndClsEx) != 0;

        UInt32 dwExStyle = WS\_EX\_LAYERED |
            WS\_EX\_TRANSPARENT |
            WS\_EX\_NOACTIVATE |
            WS\_EX\_LEFT;
        UInt32 dwStyle = WS\_VISIBLE | WS\_OVERLAPPED;
        
        FakeWndHandle = CreateWindowEx(dwExStyle
            , m\_WndClsName
            , null
            , dwStyle
            , X
            , Y
            , PngImg.Width
            , PngImg.Height
            , MainFormHandle
            , IntPtr.Zero
            , GetModuleHandle(null)
            , IntPtr.Zero
            );

}

The problem is my fake form always in the topmost position. Is there a way to put the fake form behind the main form? In other words, how do I set z-order between the main form and the fake form so that the fake form placed at the bottom of the Z order? How to hide the fake form whenever the main form minimized or maximized, and move or resize the fake form whenever the main form moved or resized? Thanks.

Saksida Bojan

Why don't you override CreateParams instead of creating FakeWindow? This example overrides default border and replace it with AERO. to get WS_ numbers, go to your Windows SDK and look under window.h for decleration

protected override CreateParams CreateParams
{
get
{
CreateParams cp = base.CreateParams;
unchecked
{
cp.Style |= (int)0x80000000; // WS_POPUP
cp.Style |= 0x40000; // WS_THICKFRAME
}
return cp;
}
}

roshihans

Thanks for the reply, I'm using Windows XP, so I think there are no WS_ for AERO.

Saksida Bojan

when i said WS_ i meant WS_EX_NOACTIVATE and other. The one I post was uses AERO. It isn't limited for aero. It has all same as unmanaged code

roshihans

When you say override CreateParams, did you refer to the main form's CreateParams? But then, where do I draw the png image files into?. Sorry, but I'm new in this so I'm still confused.

Saksida Bojan

for painting try look into OnPaint event or you can even ovverride

roshihans wrote:

When you say override CreateParams, did you refer to the main form's CreateParams?

That is correct

roshihans

Saksida Bojan wrote:

for painting try look into OnPaint event or you can even ovverride

I thought if I paint form's border with a transparent-shadow background (using png file), it will not become transparent unless I set the main form transparent too. And how to paint the shadow into the border which is located in non-client area?

Saksida Bojan

roshihans wrote:

And how to paint the shadow into the border which is located in non-client area?

Special 'Graphics' Objects to Draw Anywhere on your Window[^]

roshihans wrote:

it will not become transparent unless I set the main form transparent too

To enable Form transparecy you need to enable transparent color.

this.SetStyle(ControlStyles.SupportsTransparentBackColor | ControlStyles.DoubleBuffer, true);

roshihans

Thanks a lot for your help. I will try your suggestion

roshihans

Saksida Bojan wrote:

this.SetStyle(ControlStyles.SupportsTransparentBackColor | ControlStyles.DoubleBuffer, true);

It seems that SetStyle only applied in client area. I can't make the non-client area transparent. Any suggestion?

Saksida Bojan

In a book i am reading, this is formula for getting transparecy displayColor = sourceColor × alpha / 255 + backgroundColor × (255 - alpha) / 255 ImageTraverser[^] This link is very good. Create a snapshot and you can get pixel. Image.GetPixel is super slow, this example is very fast.

So Sereyboth

how can i use the function 'CreateFakeForm'? could you give me the full project? I 1 2 create a nice shadow behind a customized form... Thanks