GSoC CM collaboration

Olivier Galibert galibert at
Mon Mar 3 12:52:02 PST 2008

On Mon, Mar 03, 2008 at 08:29:24PM +0100, Tomas Carnecky wrote:
> Olivier Galibert wrote:
> >On Mon, Mar 03, 2008 at 06:59:50PM +0100, Tomas Carnecky wrote:
> >>It adds additional costs, that's true, but so does if every toolkit does 
> >>the transformation on its own!
> >
> >*Way* less in the toolkit, though.  Look at your screen, and think
> >about the number of color lookups the toolkit would have to do
> >compared to the number of pixels in the window.
> Given the fact that the newer gtk engines use OpenGL (don't know about 
> Qt), and if they were to implement the conversion they'd be using 
> shaders (you don't want to render the UI, copy it to system memory, 
> perform the conversion, and copy it back to the video card), then no, it 
> would cost about the same on a gnome desktop.

You're making my point here.  You want the newer gtk engines to
integrate the color conversion in their opengl pipeline.  And anyway
you want to render the UI using colors/color ramps you've already done
the lookup on.  That's the point of doing it in the toolkit, you have
a higher-level point of view allowing to collapse operations.

> Part of the GSoC project I could do some performance measurement to see 
> how much faster the conversion on CPU vs. shaders is, how big the 
> difference is on a normal desktop etc.

That wouldn't tell you how much faster it is to do it at a higher

> >Well, if you want to do it on for the windows which care, your job is
> >already done.  The applications which do care about CM already manage
> >it internally.  No need to add anything else in the server or the
> So applications that _do_ care about colors already manage them, so 
> really, where's the problem?
> ... it was my impression that Kai-Uwe wanted to have this color 
> management integrated X, in a way so that all applications could profit 
> from it. So I'm proposing a solution that is as far down on the stack as 
> possible, in a place where all applications would automatically profit 
> from it, no matter which toolkit they are using.

But if it isn't painless, since it's only for "unimportant"
applications, it will just be turned off.  Me, I'd like something I
can leave on without caring.  Do you want your work to be used only by
a micro-minority?


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