Add support for using system skia

[jopejoe1]

I'm currently working on packaging skia-python for NixOS and i want to compile it against our version of skia. This patch makes it possible for me to-do that.

[HinTak]

No, it does not. I actually do this kind of thing for myself while doing the monthly pulls, and the static libraries needs to be compiled with -rtti, etc. Otherwise it will build and link, but show runtime errors at load time. Convince yourself by actually running your copy of skia-python built your way.

FWIW, my build script to do it separately, and the monthly releases of shared and static libraries, are at:
https://github.com/HinTak/skia-building-fun

[HinTak]

And why are you modifying the non-NixOS code, also? You don't need to touch the apple or Windows code, really.

[HinTak]

Just launch python, (into the REPL prompt), then type import skia and see if you can load it.

[HinTak]

I'll let this go through CI, but I am not convinced it will pass... anyway, let's see.

[HinTak]

You'll need a bit more change to setup.py if you use your own libskia, since it inter-depends on freetype / harfbuzz /libjpeg which we bundled in the public wheels. I have the local diff in my private repo, but since it isn't a config usable by a random person who doesn't know how they interdepend, I haven't posted it, nor ever intend to. Anyway, give import skia a try and see if it can convince you not to do this.

[jopejoe1]

I mainly build it as a dependencies for building noto-font (which did build after this patch), but i did not test it standalone, but doing the import like you said indeed fails with an import error.

ImportError: /nix/store/kc6api80a4zxv2bqyxxk7kxbc9qwsva1-skia-124-unstable-2024-05-22/lib/libsvg.so: undefined symbol: _Z11SkStrSearchPKPKciS0_m

And why are you modifying the non-NixOS code, also? You don't need to touch the apple or Windows code, really.

We also have MacOS support and are working on getting windows support (very early states (mainly cross))

Will need to do a more in dpeth look into this will draft the pr till then.

[HinTak]

import skia (or equivalent from skia import ...) is the first line of any python script using skia-python... so if it doesn't work, it means you mis-built it :-). It is a lesson I learned last summer.