[webkit-dev] Replacing Cairo in WebKit with Skia

[Dominik Röttsches]

Hi,

Thanks for taking on this effort and the technical investigation that went
into this!

One question I had asked on X: Does this have implications for font format
support: Will WebKitGTK/WPE with Skia support COLRv1 fonts through Skia?
Will it also support the Fontations Rust backend of Skia, that's in
development?

Thanks,

Dominik




On Fri, Feb 2, 2024 at 4:49 PM Carlos Garcia Campos via webkit-dev <
webkit-dev at lists.webkit.org> wrote:

> Hi WebKittens,
>
> At Igalia we have spent some time exploring different options to
> replace the Cairo 2D rendering library in the GTK and WPE ports (we
> even tried rolling our own library). Recently we decided to try Skia
> and we have successfully integrated it in the WPE port. Right now we
> can compile WebKit with Skia linked statically, as part of the CMake
> build, and run a number benchmarks. This has allowed us to compare the
> Skia GPU and CPU renderers with the existing Cairo one in different
> devices.
>
> The results are very promising: benchmarks are faster than Cairo's CPU
> rendering, specially with Skia's GPU renderer. The improvement varies
> for each device, but in any case it is already clear that the change is
> a net positive on every configuration we have tested. Additionally, the
> integration in the build system is well isolated: importing Skia under
> Source/ThirdParty there is no need for any additional dependencies,
> patching Skia has not been needed, and the changes in WebKit are
> limited to code from the WPE port.
>
> After talking to teams from Google, Sony, Apple and RedHat during this
> week, everyone thinks using Skia will be a great improvement for the
> GTK, WPE, PlayStation and WinCairo ports. Therefore, we would like to
> start upstreaming what we have to the WebKit repository and continue
> the work there.
>
> Points we need to consider:
>
>     - Skia is licensed under the BSD 3-Clause “New” license, which
> should be compatible with WebKit's.
>
>     - The Skia source tree would add about 170MiB to the repository
> under Source/ThirdParty. For the sake of comparison, libwebrtc weighs
> 367MiB and ANGLE 73MiB.
>
>     - We plan to update Skia frequently following Google's
> recommendation. We have already agreed with the Skia maintainers to
> stay in contact and will explore integrating an automated system to
> test updates. We have also discussed Skia's security policy with
> Google, and we will have a procedure in place to incorporate security
> fixes, the latest when we start making releases using Skia.
>
>     - We cannot promise a timeline at the moment but expect refactors
> in the GTK and WPE ports after the initial integration. We have big
> plans for rearchitecting the rendering pipeline to better take
> advantage of GPUs, and we hope we can get rid of some complex code
> while at it.
>
> Please let us know if you have any questions, we plan to do this job
> sooner rather than later if there are no objections. We are very
> excited about this move since we really think it will be a great step
> ahead for the non Apple ports of WebKit, allowing the project to grow
> even bigger and stronger.
>
> Best regards,
>
> - The Igalia team
>
> --
> Carlos Garcia Campos
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> webkit-dev at lists.webkit.org
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>
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