How to determine the size of the button portion of a Windows radio button

Question

I'm drawing old school (unthemed - themed radios are a whole other problem) radio buttons myself using DrawFrameControl:

DrawFrameControl(dc, &rectRadio, DFC_BUTTON, isChecked() ? DFCS_BUTTONRADIO | DFCS_CHECKED : DFCS_BUTTONRADIO);

I've never been able to figure out a sure fire way to figure out what to pass for the RECT. I've been using a 12x12 rectangle but I'de like Windows to tell me the size of a radio button.

DrawFrameControl seems to scale the radio button to fit the rect I pass so I have to be close to the "right" size of the radio looks off from other (non-owner drawn) radios on the screen.

Anyone know how to do this?

Answer 1

This page shows some sizing guidelines for controls. Note that the sizes are given in both DLU (dialog units) and pixels, depending on whether you are placing the control on a dialog or not:

http://msdn.microsoft.com/en-us/library/aa511279.aspx#controlsizing

I thought the GetSystemMetrics API might return the standard size for some of the common controls, but I didn't find anything. There might be a common control specific API to determine sizing.