On Feb 22, 2007, at 10:35 PM, Aaron Reichow wrote:

> John and the list-
>
> There has to be a way to do this on OS X!  I'm hoping that John or  
> someone else on the list might be willing to tackle it or be  
> willing to tell me where to look myself.  I'm quite handy with  
> anything in Smalltalk, but when it comes to the workings of the VM  
> or FFI calls into C I'm lost.
>
> It seems that this should be pretty easy to implement, if only  
> because a) Mac OS X can do transparency too and b) the Windows  
> version manages to be implemented in a measly ~5 pages of code,  
> looking at the fileout.  When you actually file it in, it's a tiny  
> bit of code, relatively.  It uses FFI to work its magic and doesn't  
> require a plugin.  As you see if you download the zip below, it was  
> created for Squeak 3.0, however I've used it on newer Squeaks (at  
> least up to 3.6, possibly 3.7 IIRC) with no problems or patches.

Have you fiddled with
http://www.smalltalkconsulting.com/html/squeakinfoplist.html

SqueakWindowHasTitle
SqueakWindowType
SqueakWindowAttribute



kOverlayWindowClass

     Identifies an overlay window, which is a completely transparent  
window positioned above all other windows. Overlay windows are  
intended as a replacement for the pre-Carbon practice of drawing  
directly into the Window Manager port. By creating a full-screen  
overlay window and drawing into it, you can draw over any window in  
any application without disturbing the contents of the windows  
beneath your drawing. Overlay windows have a default handler for  
kEventWindowPaint that uses CGContextClearRect to clear the overlay  
window's alpha channel to zero. This ensures the initial transparency  
of the window.


If you don't set
SqueakWindowAttribute
to all zeros, then you'll crash because I don't check for window  
failure open,and by setting kOverlayWindowClass to 14 you must have  
the right attributes.
Likely you should code a FFI call to

WindowAttributes GetAvailableWindowAttributes (
    WindowClass inClass
);

likely you could also code a FFI call to
OSStatus SetWindowClass (
    WindowRef window,
    WindowClass inClass
);

and

OSStatus ChangeWindowAttributes (
    WindowRef window,
    WindowAttributes setTheseAttributes,
    WindowAttributes clearTheseAttributes
);

Both Sophie and Croquet have lots of FFI calls you can look at for  
examples.


Lastly I believe I drag the data out of the squeak display buffer  
using kCGImageAlphaNoneSkipFirst
in sqMacWindowUniversal.c

I guess I could make this a info.plist and let people figure out what  
they want.
I suspect you'll need a new vm and set thing to kCGImageAlphaFirst or  
kCGImageAlphaPremultipliedFirst
Oh and likely it might different for macIntel.

Anyway you'll need to test some things before a vm change, then let  
me know


kCGImageAlphaFirst
The alpha component is stored in the most significant bits of each  
pixel. For example, non-premultiplied ARGB.

kCGImageAlphaLast
The alpha component is stored in the least significant bits of each  
pixel. For example, non-premultiplied RGBA.

kCGImageAlphaNone
There is no alpha channel. If the total size of the pixel is greater  
than the space required for the number of color components in the  
color space, the least significant bits are ignored. This value is  
equivalent to kCGImageAlphaNoneSkipLast.

kCGImageAlphaNoneSkipFirst
There is no alpha channel. If the total size of the pixel is greater  
than the space required for the number of color components in the  
color space, the most significant bits are ignored.

kCGImageAlphaOnly
There is no color data, only an alpha channel.

kCGImageAlphaNoneSkipLast
There is no alpha channel. If the total size of the pixel is greater  
than the space required for the number of color components in the  
color space, the least significant bits are ignored. This value is  
equivalent to kCGImageAlphaNone.

kCGImageAlphaPremultipliedFirst
The alpha component is stored in the most significant bits of each  
pixel and the color components have already been multiplied by this  
alpha value. For example, premultiplied ARGB.

kCGImageAlphaPremultipliedLast
The alpha component is stored in the least significant bits of each  
pixel and the color components have already been multiplied by this  
alpha value. For example, premultiplied RGBA.






--
======================================================================== 
===
John M. McIntosh <johnmci at smalltalkconsulting.com>
Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com
======================================================================== 
===