CMFCButton as a radio button

Question

I have just discovered that the 'Feature Pack' class CMFCButton allows me to have an image and text on push-like radio button. (Normally this would require it to be owner-draw, and radio buttons don't have the owner-draw possibility, so I'm quite excited about this.)

I have an hBitmap which (for the moment) looks like this:

I then set it in my CMFCButton derived class constructor with

	EnableWindowsTheming( TRUE );  
  
	BOOL       bAutoDestroy		= TRUE;  
	HBITMAP hBitmapHot		= NULL;  
	BOOL       bMap3dColors	= TRUE;  
	HBITMAP hBitmapDisabled	= NULL;  
	  
	SetImage( hBitmap, bAutoDestroy, hBitmapHot, bMap3dColors, hBitmapDisabled );  
  

and in use on the dialogue box it looks like:

The button background has become dark grey. It doesn't seem to matter what colour I draw the button background or whether bMap3dColors is TRUE or FALSE; the background always comes out the same grey colour! (I actually want the area to be the button background colour, but having failed at that, I made the bitmap background yellow to see what's happening. And discovered that my confusion seems to be at a deeper level.)

Can anyone tell me what I'm doing wrong?

Dave

Answer 1

Thanks @David Lowndes

I'm not actually loading a bitmap as such. To allow for high DPI I'm loading an EMF resource, drawing on a bitmap (of appropriate dpi-dependent size) in memory, and then giving it to my push-like radio button with CButton::SetBitmap(...) or, in particular CMFCButton::SetImage(...)

I've made some progress by doing this in OnInitDialog() rather than the button constructor. The grey has gone but it's still not mapping my input COLOR_BTNFACE=RGB(192,192,192) onto the button colour - empirically RGB(215,215,215). It's coming out as RGB(240,240,240). In fact CButton,and CMFCButton are both doing this, though I think only CMFCButton is documented as doing a mapping.

So I'm still puzzled.

Dave

Answer 2

I think I've cracked it!

CMFCButton::SetImage( hBitmap, ... bMap3dColors, ...)

If hBitmap is 32 bits-per-pixel then this function behaves very differently from other values. The source code is complicated, but makes a mention of (COLORREF)-1;

Now as far as I know COLORREF is only supposed to use the lowest three nybbles, and the high nybble should always be zero. But (COLORREF)-1 is of course 0xFFFFFFFF.

So I tried ::FillRect( ) with this COLORREF to draw my background on the bitmap, before drawing my image from the EMF resource. And it works. CMFCImage::SetImage( hBitmap,...) treats it as a transparent background! Irrespective, I think, of bMap3dColors.

Thanks to you on this thread for your comments which definitely helped point me in the right direction!

Dave