- Moves interop functions to UnmanagedCallbacks struct that
contains the function pointers and is passed to C#.
- Implements UnmanagedCallbacksGenerator, a C# source generator that
generates the UnmanagedCallbacks struct in C# and the body for the
NativeFuncs methods (their implementation just calls the function
pointer in the UnmanagedCallbacks). The generated methods are needed
because .NET pins byref parameters of native calls, even if they are
'ref struct's, which don't need pinning. The generated methods use
`Unsafe.AsPointer` so that we can benefit from byref parameters
without suffering overhead of pinning.
Co-authored-by: Raul Santos <raulsntos@gmail.com>
The setting is initially assigned the name of the Godot project,
but it's kept freezed to prevent issues when renaming the Godot
project.
The user can always rename the C# project and solution manually and
change the setting to the new name.
This new version does not support the following type arguments:
- Generic types
- Array of Godot Object (Godot.Object[]) or derived types
The new implementation uses delegate pointers to call the Variant
conversion methods. We do type checking only once in the static
constructor to get the conversion delegates.
Now, we no longer need to do type checking every time, and we no
longer have to box value types.
This is the best implementation I could come up with, as C# generics
don't support anything similar to C++ template specializations.
- Array and Dictionary now store `Variant` instead of `System.Object`.
- Removed generic Array and Dictionary.
They cause too much issues, heavily relying on reflection and
very limited by the lack of a generic specialization.
- Removed support for non-Godot collections.
Support for them also relied heavily on reflection for marshaling.
Support for them will likely be re-introduced in the future, but
it will have to rely on source generators instead of reflection.
- Reduced our use of reflection.
The remaining usages will be moved to source generators soon.
The only usage that I'm not sure yet how to replace is dynamic
invocation of delegates.
Changed the signal declaration signal to:
```
// The following generates a MySignal event
[Signal] public delegate void MySignalEventHandler(int param);
```
Previously, we added source generators for invoking/accessing methods,
properties and fields in scripts. This freed us from the overhead of
reflection. However, the generated code still used our dynamic
marshaling functions, which do runtime type checking and box value
types.
This commit changes the bindings and source generators to include
'static' marshaling. Based on the types known at compile time, now
we generate the appropriate marshaling call for each type.
The editor no longer needs to create temporary instances to get the
default values. The initializer values of the exported properties are
still evaluated at runtime. For example, in the following example,
`GetInitialValue()` will be called when first looks for default values:
```
[Export] int MyValue = GetInitialValue();
```
Exporting fields with a non-supported type now results in a compiler
error rather than a runtime error when the script is used.
This base implementation is still very barebones but it defines the path
for how exporting will work (at least when embedding the .NET runtime).
Many manual steps are still needed, which should be automatized in the
future. For example, in addition to the API assemblies, now you also
need to copy the GodotPlugins assembly to each game project.
We're targeting .NET 5 for now to make development easier while
.NET 6 is not yet released.
TEMPORARY REGRESSIONS
---------------------
Assembly unloading is not implemented yet. As such, many Godot
resources are leaked at exit. This will be re-implemented later
together with assembly hot-reloading.
The main focus here was to remove the majority of code that relied on
Mono's embedding APIs, specially the reflection APIs. The embedding
APIs we still use are the bare minimum we need for things to work.
A lot of code was moved to C#. We no longer deal with any managed
objects (`MonoObject*`, and such) in native code, and all marshaling
is done in C#.
The reason for restructuring the code and move away from embedding APIs
is that once we move to .NET Core, we will be limited by the much more
minimal .NET hosting.
PERFORMANCE REGRESSIONS
-----------------------
Some parts of the code were written with little to no concern about
performance. This includes code that calls into script methods and
accesses script fields, properties and events.
The reason for this is that all of that will be moved to source
generators, so any work prior to that would be a waste of time.
DISABLED FEATURES
-----------------
Some code was removed as it no longer makes sense (or won't make sense
in the future).
Other parts were commented out with `#if 0`s and TODO warnings because
it doesn't make much sense to work on them yet as those parts will
change heavily when we switch to .NET Core but also when we start
introducing source generators.
As such, the following features were disabled temporarily:
- Assembly-reloading (will be done with ALCs in .NET Core).
- Properties/fields exports and script method listing (will be
handled by source generators in the future).
- Exception logging in the editor and stack info for errors.
- Exporting games.
- Building of C# projects. We no longer copy the Godot API assemblies
to the project directory, so MSBuild won't be able to find them. The
idea is to turn them into NuGet packages in the future, which could
also be obtained from local NuGet sources during development.
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.
All iOS devices since the iPhone 5S support ARMv8 (64-bit).
The last iOS version supported on ARMv7 devices is 10.x, which is
too old to run Godot 4.0 projects since the minimum supported
iOS version is 11.0.
This fixes a conflict with the `pressed` signal.
The new name is temporary and only intended to solve the conflict for upcoming
alpha builds. Discussions are still ongoing regarding the BaseButton API and
how to rename and refactor more of its properties, signals and methods to have
a clearer API in 4.0.
Apply suggestions from code review
Merging @akien-mga's suggestion with the matching change to the CS project
Co-authored-by: Rémi Verschelde <rverschelde@gmail.com>
Use `System.Array.Empty<T>` to get an empty array instead of allocating
a new one every time. Since arrays are immutable there is no need to
allocate them every time.
