bug#616: #616 - 23.0.60; Emacs.app does not support SVG file type - Emacs bug report logs

[Adrian Robert]

> If I set the Emacs background to black, they look transparent but
> that's of course an illusion.  I tried several approaches to make it
> work, but did not succeed.  I hope that someone else does.
>
> ...
>
> +#elif defined (HAVE_NS)
> +      background.pixel = FRAME_BACKGROUND_PIXEL (f);
> ...

The NS port doesn't use FRAME_BACKGROUND_PIXEL.  One approach would be  
to get FRAME_BACKGROUND_COLOR (an NSColor) and extract its RGB info.   
Did you try this and it didn't work either?

Note that simply leaving in the alpha information should also work, as  
the NS image code (ns_put_pixel()) supports alpha.  Did you try  
#ifdef'ing out all of the code in that function that hacks away SVG's  
alpha information?  I'd say this is the preferred solution.  But if  
that doesn't work, here is some code that would use the frame  
background color (I'd try but don't have librsvg set up on my machine.)

float r, g, b, a;
NSColor *col = FRAME_BACKGROUND_COLOR(f);
if (![[col colorSpaceName] isEqualToString: NSNamedColorSpace])
  col = [col colorUsingColorSpaceName: NSCalibratedRGBColorSpace];
[col getRed: &r green: &g blue: &b alpha: &a];
background.red = r * 256;
background.green = g * 256;
background.blue = b * 256;