Move to Meson Build System

[AesaraB]

Completes #1229

Two arguments from setup.py catch our interest, they contain other commands and do everything needed to create a running instance of MyPaint:

1. build
2. managed_install

Build(build)

• Inherits distutils' build, which itself inherits Command
• 1. BuildConfig(Command)
• 2. build_ext
• 3. build_py
• 4. build_clib
  • build C/C++ libraries used by Python extensions
• 5. build_scripts
  • "build" scripts (copy and fixup #! line)
• 6. BuildTranslations(Command)

managed_install

TBD

Other setuptools/distutils Features

• Dependencies

[AesaraB]

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Dependencies

Meson can check for dependencies, this is what we've checked so far:

• python
• gtk3
• pygobject
• lcms
• json-c
• gettext
• librsvg2
• numpy
• pycairo

[AesaraB]

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build_py

Inherits distutils' Command

This is probably the simplest step in the build process. It copies files from two directories, gui/ and lib/

List of files copied by build_py: build_py.txt

gui/

There are four "file types" in this directory. From what I gather, build_py just copies it all

• *.glade
• *.py
• *.xml
• directories

lib/

There are four "files types" in this directory. build_py only copies all *.py files, including ones in subdirectores.

• *.hpp
• *.cpp
• *.py
• directories

The pattern?

There are two potential matching strategies for the pattern we see: additive, or subtractive.

1. Additive: *.glade, *.py, *.xml are copied to the build directory
2. Subtractive: All files that aren't *.hpp or *.cpp are copied to the build directory

Translating to Meson

You can't glob files in meson like you can in setuptools/distutils. Obviously this has implications for how we compile C/C++ files, but it also poses an issue for build_py.

We can either:

1. Individually specify all the lib/*.py files in meson.build,
   • This may create an arduously long meson.build file.
2. Separate C/C++ files from python files in lib/, or
3. Create a script to glob these files and modify meson.build for us.
   • I'm not sure how different this is in practice to option 1.

[AesaraB]

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BuildConfig(Command)

Inherits distutils' Command

Concept

• lib/config.py is a file created from a template.
• The template (which will get filled in with information we provide) is config.py.in
• The substituted information comes in the form of a dict
• instantiate_template() takes a template and substitution dictionary as arguments to create to create an output file (lib/config.py)

Translating to Meson

Meson does out of source builds, meaning that lib/config.py will not exist in the the source directory, but rather the build directory.

[AesaraB]

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build_ext

The gist of this class is that it basically takes in a list of C++ files alongside a list of flags and uses swig to compile them to the build directory.

Output of build_ext: build_ext.txt

[jtojnar]

Yeah, I would expect something like https://github.com/linux-nvme/libnvme/blob/bff7dda7e2a0f883d0b89e23fed725c916de3e61/libnvme/meson.build#L29-L45 to work.

[eli-schwartz]

Lexer error:

meson.build:47:16: ERROR: Double quotes are not supported. Use single quotes.
if system_os == "darwin"
                ^

[eli-schwartz]

I think this has to go in src/meson.build (or src/lib/meson.build), since all the paths are in src/lib/* and it will be painful as-is.

[eli-schwartz]

Just output it to mypaintlib_wrapper.cpp, exact paths don't really matter for a .cpp file anyway.

[AesaraB]

@eli-schwartz I appreciate your review, but the latest commit was half copied and pasted code that I was yet to fully translate. Nonetheless, you have made some useful suggestions, which I'll add in when I can sit down and look at them more closely.

[eli-schwartz]

Ahh, gotcha. :)

(I have selfish reasons for having a small interest in seeing mypaint be compiled by meson, as it's currently a pain to handle diverging expectations of PEP 517 vs traditional setup.py usage and packagers are being strongly encouraged to only use PEP 517, which doesn't work here. So I figured any small help I could provide might make that transition happen faster. Please do feel free to ask me for help.)

[AesaraB]

@eli-schwartz I'm tremendously grateful for your interest in improving MyPaint -- thank you for your offer of help.

Would you mind if I call you in to be a reviewer at the final stages of the draft?

[eli-schwartz]

I'd be thrilled to. :)