A supposedly patent-free suggestion/solution to the curious subpixel rendering in Fedora

Callum Lerwick seg at haxxed.com
Fri Mar 27 21:46:34 UTC 2009


On Fri, 2009-03-27 at 15:14 -0500, Jud Craft wrote:
> I didn't know myself for sure whether it [Qt's filter code] was
> patent-infringing.  But I did know:
> 
> 1.  Fedora tries not to ship patented technologies.

A bit oversimplified. I remember reading some kind of patent guideline a
while back, probably from spot, but googling and searching the wiki
isn't bringing it up. Basically since pretty much everything is
patented, "not shipping patented technology" isn't feasible. Instead
it's a judgement call, we avoid patents who's owners are known to be
actively seeking licensing fees or are otherwise sue happy. We can't
avoid them all and still have a product to ship.

> 2.  Fedora took subpixel filtering (due to its possible infringement)
> out of the desktop stack.

Where is this coming from? Are you confusing subpixel filtering with
hinting? They're two different things.

> 3.  Qt has its own separate filtering code.
> 4.  Fedora did NOT remove the Qt subpixel filters.
> 
> Hence I began to wonder if A) Qt's filtering technique was considered
> as non-infringing, and B) if so, why not just use that for the rest of
> the X stack?

Near as I can tell, filtering isn't the problem. MS seems to have a
patent on the very idea of subpixel font rendering, it doesn't matter
what you do to filter the color fringing away.

> (after all, I am not a lawyer, but I thought certainly Fedora was
> on good legal ground)

There's no winning when it comes to software patents. Everyone is a
criminal.
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