This reverts commit 3ee0efbd19. It works
in the main branch, it works in separate branches when starting
workflows manually, but it doesn't work when a CI run is started with a
merge request.
This was a regression following the move to the edition 2021.
The CallbackUserData was not capture in the lamda, its member were moved.
So the destructor was called right after it was set.
We must make sure we capture the whole CallbackUserData, so put the callback
inside of it. This also reduce a bit of code duplication at the same time.
Test the callback invokation with statefull lambda
We want to be able to put existing functionality behind a feature flag while keeping
the semver compatibility.
This is only possible if that new feature flag is enabled by default, but this is not
working if the users have done `default-features = false` in their Cargo.toml.
So we add new `compat-x-y-z` feature that is mandatory to have and which is
enforced with a `compile_error!`
Now, users that whishes to not have the default features must enable it explicitly.
Say we want only x11 but not qt and wayland, the user will do
```toml
sixtyfps = { version = "0.2", default-features = false, features = ["x11", "compat-0-2-0"] }
```
Now, imagine that in the version 0.2.3, we put the SVG support behind a feature flag.
we will do this in out Cargo.toml:
```toml
[features]
default = ["compat-0-2-0", "x11", "wayland"]
compat-0-2-0 = ["compat-0-2-3", "svg"]
compat-0-2-3 = []
svg = [...]
...
```
That way, the svg feature will be enabled by default for all the users who used previous version
of SixtyFPS, and people that want to disable "svg" can just change from compat-0-2-0 to
compat-0-2-3 in their Cargo.toml
git can create Cargo.toml.orig if there was a conflict. That file might then prevent
the compilation as it contains merge conflict and this crate cannot parse it.
So only use the .orig if the Cargo.toml file don't contains docs comments
