My goal is to draw a Group Box that is not rectangular but instead has the corners cut away. I do not mean just clipping the corners, but rather have a continuous closed path where the corners are "indented." I want this to match the colors/style of the current theme.
I noticed on Windows XP that the Group Box has 1-pixel gray lines, but on Windows 7 there is a 3D effect created by having a gray line next to a white line (the white line on the interior except on the bottom where it's below the gray line).
You can get the color of the text label of a Group Box using something like this:
COLORREF cref;
GetThemeColor(hTheme, BP_GROUPBOX, GBS_NORMAL, TMT_TEXTCOLOR, &cref);
So, I'm trying to figure out how to get the color(s) and/or properties of the lines used in a Group Box, then (I hope to) be able to draw the lines I want matching the Group Box style by separately drawing each piece of the shape I want. I'm not sure what properties are used to describe the lines or if functions line DrawRect will draw the 3D effect with a suitable Pen. Is there a way to set a Pen to draw these 3D effects (2-shade parallel lines)?
Thanks.
The thing I always find unexpected about groupboxes is that they are really a style of buttons. (BS_GROUPBOX).
Themed groupboxes (XP and later with classic mode off) use theme part BP_GROUPBOX in VSCLASS_BUTTON. You can use the usual theme APIs to get and draw. If your Group box needs text you can use DrawThemeText.
There are APIs for drawing non-themed group boxes too (e.g. DrawEdge), but I don't remember the details and it's unlikely that you need them.
As usual, I will point out that reproducing the behaviour of controls is always harder than you think it is going to be.
Martyn