Changing a Window’s Shape

In most newsgroups that have something to do with Windows programming there are postings on how to change window’s shape. I thought that there must be an article about this here, and when I didn’t find one, I decided to write one myself.

In reality changing window’s shape is very easy to do, although most people think that it’s an extremely hard procedure. In this article I will explain how to create a window that will be a circle instead of a rectangle shape.

There are two functions that change window’s shape: CWnd::SetWindowRgn() and win32’s SetWindowRgn(). I will use the CWnd::SetWindowRgn(), but u can use the one you like more.

The function declaration looks like this:
int SetWindowRgn( HRGN hRgn, BOOL bRedraw );

The return value is zero if function fails or nonzero otherwise(at least it says so in Microsoft documentation). The first parameter is the CRgn, a region of a window, and the second parameter is a BOOL value that allows u to redraw the window. All you have to do is to create a CRgn variable, and pass the parametr to the SetWindowRgn function. That’s all.

Here is the source code you have to add to your application in order to make a window be a circle shape.

CRgn MyRgn;
MyRgn.CreateEllipticRgn(0, 0, 100, 100);
SetWindowRgn(MyRgn, TRUE);

That’s it. I can add just one more thing. If you create a button or another window without a title bar, you can skip this paragraph. If the window has a title bar, I advise you to read this. The thing is, that with most regions at least part of a title bar will not be drawn. From my point of view, the optimal decision is to create a window with a style that won’t have a title bar, and then implement the title bar functions yourself. It sounds hard, but it’s much easier then dealing with a regular title bar.

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