Review Request: Rectangular and square gradient support

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This review has been submitted with commit da3f0d1bbbd5f254634dffe743973bf2e4acc0ba by Lukáš Tvrdý to branch master.

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On Oct. 10, 2011, 1:24 p.m., Lukáš Tvrdý wrote:
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> (Updated Oct. 10, 2011, 1:24 p.m.)
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> 
> Review request for Calligra, Jan Hambrecht and Thorsten Zachmann.
> 
> 
> Description
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> 
> Bugs: displays gradient of shapes from bug https://bugs.kde.org/show_bug.cgi?id=274909
> Ellipsoid gradient is missing so far.
> 
> This patch adds support for ODF gradient style rectangular and square.
> 
> First I was trying to integrate gradients into KoGradientBackground, but shortly I noticed
> that it is crashing as the editing tools require QGradient and are tied to it. So some abstraction
> and re-factoring will be needed to support of creation and editing of the constructed ODF gradients.
> 
> Then I decided to introduce new class KoOdfGradientBackground which is not editable and integrate nicely.
> 
> Saving and loading of gradients work.
> 
> The gradients have many options like position, rotation, border. So far square gradients support 
> all of them, though rotation of gradient is showing some artifacts, small pixels, I was not able to fix them. 
> Rectangular type does not support rotation. 
> 
> Rotation would probably require to compute the gradient per pixel, which might be slow. I was trying to use QPainter and combination of QGradient and 
> clipping to create the gradients effectively. I found inspiration here http://ariya.ofilabs.com/2011/06/rectangular-gradient.html
> for square gradient.Rectangular gradient was done in similar way.
> 
> There was some problem with alias when rendering the gradients. First I was trying to solve it by supersampling,
> then I wanted to use the exact size of the shape in pixels (without zooming). Then I ended up to compute
> the pixel size of the shape on the canvas. 
> 
> There are two possibilities: to add new parameter KoViewConverter to paint method of the KoShapeBackground,
> in the patch you can see it is not that much effort. Zagge was in a favor to not to add that parameter and 
> he was suggesting to use QPainter's matrix as that one already includes the zooming information.
> 
> The patch includes the changes needed to include KoViewConverter, I will drop them if the preferred 
> way is to use paint's QPainter matrix, which so far works as needed.
> 
> Square gradients in words
> http://wstaw.org/m/2011/10/05/plasma-desktopoo2237.jpg
> 
> Rectangular gradients in words
> http://wstaw.org/m/2011/10/05/plasma-desktopLg2237.jpg
> 
> 
> Diffs
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> 
>   libs/flake/CMakeLists.txt dad0c9a 
>   libs/flake/KoOdfGradientBackground.h PRE-CREATION 
>   libs/flake/KoOdfGradientBackground.cpp PRE-CREATION 
>   libs/flake/KoShape.cpp 6b07e7c 
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> Diff: http://git.reviewboard.kde.org/r/102780/diff/diff
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> 
> Testing
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> I'm going to test it with cstester, I don't expect any regressions as the code handles previously non-handled ODF gradients.
> 
> 
> Thanks,
> 
> Lukáš Tvrdý
> 
>

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