[GSoC] KWin colour management

Daniel Nicoletti dantti12 at gmail.com
Thu Mar 22 12:54:49 GMT 2012

2012/3/22 Kai-Uwe Behrmann <ku.b at gmx.de>:
> Here my thoughts, why I think CM in Qt is not easily introduced during a
> minor Qt 5 release. [Preparation of CM for Qt 6 is a different story.]
> Lets hypothetical assume some effort is initiated to bring CM to Qt and that
> happens during Qt 5 life time. The new design says by default all content is
> considered sRGB, which is by itself reasonable. However existing
> applications will initially not know about that changed convention. There is
> currently no API to know that. They will play freestyle as before and colour
> correct to monitor space without knowing how to tell anything to Qt. These
> old style apps will colour correct to monitor and Qt will colour correct
> from sRGB to monitor as Qt does not better know. That is called double
> colour correction and would be a real design bug.
> The conflict is solveable by making the new drawing API incompatible with
> the old one, e.g. requiring a colour space argument. An other way is
> verbally declaring sRGB as the default colour space in Qt, which would be a
> major API change as well and only reasonable possible during major version
> change.
> Both is not easy before Qt 5. After the fist Qt 5 release a new drawing API
> could theoretically be introduced in parallel to the old one. But old Qt
> apps would then look inconsistent compared to ones using the new API. Not
> sure if that transition path would be a good option regarding code
> complexity. IMO best would be to wait for Qt 6 and then switch completely.

I'm sorry but you point is wrong here. Even if the real problem was
just API changing
and old applications getting unaware of that this is the easiest thing
to fix. When
people draw API they have this in mind and we don't need a whole new Qt just to
introduce a new feature, easy solution: QApplication::setColorCorrected(true);
Done! All old apps won't be color corrected since they don't set that
and all new
ones will be able to have this.

And I had only to think about it in 2 minutes, surely Qt devs will have a better

I'm not saying it's easy to add Color Correction to Qt, but API
additions is no excuse.

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