CMFCButton as a radio button

David Webber 136

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

David Lowndes 4,716 Reputation points

2020-09-10T14:41:38.443+00:00

Does it work any better if you use an icon (with transparency) rather than a bitmap?
David Lowndes 4,716 Reputation points

2020-09-10T14:44:16.673+00:00

There's a comment here that you suggests using LR_CREATEDIBSECTION when you load the bitmap.
Castorix31 85,706 Reputation points

2020-09-12T08:43:17.763+00:00
CMFCButton is an Owner-Drawn button
You can see the source in afxbutton.cpp (I have it in
E:\Program Files\Microsoft Visual Studio\2019\Enterprise\VC\Tools\MSVC\14.25.28610\atlmfc\src\mfc)

in particular

void CMFCButton::SetImageInternal(HBITMAP hBitmapCold, BOOL bAutoDestroy, HBITMAP hBitmapHot, BOOL bMap3dColors, BOOL bChecked, HBITMAP hBitmapDisabled)

where it sets the transparent color at :

image.SetTransparentColor(bMap3dColorsCurr ? RGB(192, 192, 192) : bAlpha ?(COLORREF) -1 : GetGlobalData()->clrBtnFace);
David Webber 136 Reputation points

2020-09-12T10:36:01.94+00:00

It isn't 'owner-draw' in the traditional sense that it has the 'owner-draw' flag set in its properties.

For this reason I can set it to be a push-like radio button in the DIALOG (radio buttons can't apparently have the owner-draw property) and by setting it as CMFCButton in the MFC CDialogEx, I can get a radio button with both an image and text (as CMFCButton does that).

But the process of drawing the image so that its background matches the button face has some subtle nuances rooted in the behaviour of

void CMFCButton::SetImageInternal(HBITMAP hBitmapCold, BOOL bAutoDestroy, HBITMAP hBitmapHot, BOOL bMap3dColors, BOOL bChecked, HBITMAP hBitmapDisabled)

This depends no only on the parameter bMap3dColors, but also on the bits-per-pixel of the bitmap. I'm just in the process of cataloguing it. I'll report on the results, probably with another question!

Dave

2 answers

David Webber 136 Reputation points

2020-09-10T21:30:50.23+00:00

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
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David Lowndes 4,716 Reputation points

2020-09-10T21:49:57.327+00:00

As a sanity check, have you tried using an icon or bitmap produced with VS?
That would hopefully tell you whether the issue is with CMFCButton::SetImage or a quirk of how you're producing the bitmaps.

David Webber 136 Reputation points

2020-09-11T19:47:15.43+00:00

Thanks for this David. Some results:

There are 3 columns of 3 radio buttons, each connected to a CMFCButton.
The bitmaps in cols 1 & 2 are 16colours using only black and RGB(192,192,192).

Column1 images use CMFCButton.SetImage( BITMAP-RESOURCE_ID ).
It works perfectly.

Column 2 does it in two steps:
HBITMAP hBmp = ::LoadImage( ... IMAGE_BITMAP ... fuLoad );
CMFCButton::SetImage( hBmp, TRUE, NULL, bMap3dColours, NULL );

with parameters:

top: ( fuLoad, bMap3dColours ) = (LR_CREATEDIBSECTION, TRUE)
middle: ( fuLoad, bMap3dColours ) = (LR_CREATEDIBSECTION, FALSE)
bottom: ( fuLoad, bMap3dColours ) = (LR_LOADMAP3DCOLORS|LR_CREATEDIBSECTION, TRUE)

Only the top one works!

Column 3: draws an EMF file on a screen-compatible HBITMAP and then does
CMFCButton::SetImage( hBmp, TRUE, NULL, bMap3dColours, NULL );

top: bMap3dColours = TRUE
middle bMap3dColours = FALSE

Neither works. Annoying!

Dave

David Lowndes 4,716 Reputation points

2020-09-11T21:46:55.323+00:00

So presumably it's some quirk of how you're producing the bitmap - but I don't know what it might be to offer any advice.

David Webber 136 Reputation points

2020-09-11T22:48:00.273+00:00

Nevertheless I think you have helped to lead me to the answer :-)

In the small print for LR_LOADMAP3DCOLORS it says "Do not use this option if you are loading a bitmap with a color depth greater than 8bpp."

Now in creating, and drawing on, a bitmap which is compatible with the screen, I have presumably created a bitmap with 24 or 32 bits per pixel! If I assume that the CMFCButton::SetImage( hBitmap,...) does essentially the same as ::LoadImage( hBitmap,...), then there's no guarantee it will work on a screen-compatible bitmap!

What I need to do is look up the actual colour of the button face, and use that as the background of my image. I assume that is possible using the 'themes'. Don't now how yet, but That must be the way to go!

Thanks again for your input!

Dave
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David Webber 136 Reputation points

2020-09-12T16:06:49.813+00:00

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
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David Lowndes 4,716 Reputation points

2020-09-12T23:15:13.773+00:00

That's great Dave, thanks for letting us know you've sussed it.
If you think the documentation could do with mentioning something, please send your feedback in on it.

Jeanine Zhang-MSFT 9,766 Reputation points Microsoft Vendor

2020-09-14T01:19:31.577+00:00

@David Webber , I am glad you have got your solution and thanks for your sharing, I would appreciate it if you mark them as answer and this will be beneficial to other community.
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CMFCButton as a radio button

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