godot/modules/mono/config.py
Ignacio Roldán Etcheverry 124fbf95f8 C#: Move marshaling logic and generated glue to C#
We will be progressively moving most code to C#.
The plan is to only use Mono's embedding APIs to set things at launch.
This will make it much easier to later support CoreCLR too which
doesn't have rich embedding APIs.

Additionally the code in C# is more maintainable and makes it easier
to implement new features, e.g.: runtime codegen which we could use to
avoid using reflection for marshaling everytime a field, property or
method is accessed.

SOME NOTES ON INTEROP

We make the same assumptions as GDNative about the size of the Godot
structures we use. We take it a bit further by also assuming the layout
of fields in some cases, which is riskier but let's us squeeze out some
performance by avoiding unnecessary managed to native calls.

Code that deals with native structs is less safe than before as there's
no RAII and copy constructors in C#. It's like using the GDNative C API
directly. One has to take special care to free values they own.
Perhaps we could use roslyn analyzers to check this, but I don't know
any that uses attributes to determine what's owned or borrowed.

As to why we maily use pointers for native structs instead of ref/out:
- AFAIK (and confirmed with a benchmark) ref/out are pinned
  during P/Invoke calls and that has a cost.
- Native struct fields can't be ref/out in the first place.
- A `using` local can't be passed as ref/out, only `in`. Calling a
  method or property on an `in` value makes a silent copy, so we want
  to avoid `in`.

REGARDING THE BUILD SYSTEM

There's no longer a `mono_glue=yes/no` SCons options. We no longer
need to build with `mono_glue=no`, generate the glue and then build
again with `mono_glue=yes`. We build only once and generate the glue
(which is in C# now).
However, SCons no longer builds the C# projects for us. Instead one
must run `build_assemblies.py`, e.g.:
```sh
%godot_src_root%/modules/mono/build_scripts/build_assemblies.py \
        --godot-output-dir=%godot_src_root%/bin \
        --godot-target=release_debug`
```
We could turn this into a custom build target, but I don't know how
to do that with SCons (it's possible with Meson).

OTHER NOTES

Most of the moved code doesn't follow the C# naming convention and
still has the word Mono in the names despite no longer dealing with
Mono's embedding APIs. This is just temporary while transitioning,
to make it easier to understand what was moved where.
2022-08-22 03:35:59 +02:00

69 lines
2.1 KiB
Python

supported_platforms = ["windows", "macos", "linuxbsd", "server", "android", "haiku", "javascript", "ios"]
def can_build(env, platform):
return not env["arch"].startswith("rv")
def get_opts(platform):
from SCons.Variables import BoolVariable, PathVariable
default_mono_static = platform in ["ios", "javascript"]
default_mono_bundles_zlib = platform in ["javascript"]
return [
PathVariable(
"mono_prefix",
"Path to the Mono installation directory for the target platform and architecture",
"",
PathVariable.PathAccept,
),
PathVariable(
"mono_bcl",
"Path to a custom Mono BCL (Base Class Library) directory for the target platform",
"",
PathVariable.PathAccept,
),
BoolVariable("mono_static", "Statically link Mono", default_mono_static),
BoolVariable("build_cil", "Build C# solutions", True),
BoolVariable(
"copy_mono_root", "Make a copy of the Mono installation directory to bundle with the editor", True
),
# TODO: It would be great if this could be detected automatically instead
BoolVariable(
"mono_bundles_zlib", "Specify if the Mono runtime was built with bundled zlib", default_mono_bundles_zlib
),
]
def configure(env):
platform = env["platform"]
if platform not in supported_platforms:
raise RuntimeError("This module does not currently support building for this platform")
env.add_module_version_string("mono")
if env["mono_bundles_zlib"]:
# Mono may come with zlib bundled for WASM or on newer version when built with MinGW.
print("This Mono runtime comes with zlib bundled. Disabling 'builtin_zlib'...")
env["builtin_zlib"] = False
thirdparty_zlib_dir = "#thirdparty/zlib/"
env.Prepend(CPPPATH=[thirdparty_zlib_dir])
def get_doc_classes():
return [
"CSharpScript",
"GodotSharp",
]
def get_doc_path():
return "doc_classes"
def is_enabled():
# The module is disabled by default. Use module_mono_enabled=yes to enable it.
return False