[sdl2] Make dbus dependency optional.

[dsvensson]

Instead of having dbus as a mandatory dependency, make it optional, but enabled by the default features to keep behavior for people who just depend on sdl2 without disabling default features. Trims about 85% off the build time if disabled.

Fixes #40632

[dsvensson]

@microsoft-github-policy-service agree

[dsvensson]

@FrankXie05 Not sure what's up with the failed Windows builds given that they have nothing to do with dbus.

[FrankXie05]

@dsvensson Thanks for PR, please see https://github.com/microsoft/vcpkg-docs/blob/main/vcpkg/contributing/maintainer-guide.md#versioning

[dsvensson]

@FrankXie05 That did the trick, thanks!

[dg0yt]

The choice of the dbus feature must also be handled in the portfile.cmake, or you end up with installation order and system libs surprises.

[dsvensson]

@dg0yt Could you explain how, I'm not sure I follow.

[dg0yt]

ATM this PR just make it optional to have the dbus port installed by vcpkg before the sdl2 port.
But what is needed is to ensure that sdl2 never uses dbus unless the feature is selected (explicitly or implicitly). When I run:

vcpkg install dbus
vcpkg install sdl2[core]

sdl2 must not use dbus. (Similar for system-provided dbus.)

If there is a CMake option to control this goal, you can use that option. If there is find_package, you could use CMAKE_DISABLE_FIND_PACKAGE_<pkg>. Worst case, you must patch.

[dsvensson]

Doesn't the same apply to x11, Wayland etc. If you happen to not have the system headers installed they are silently disabled even if requested?

[dsvensson]

@dg0yt https://github.com/libsdl-org/SDL/blob/SDL2/CMakeLists.txt#L1593-L1601

root@765c033c3c6c:/vcpkg/buildtrees/sdl2# grep -i dbus *
config-x64-linux-dbg-CMakeCache.txt.log:SDL_DBUS:BOOL=OFF

using:

FROM debian:unstable

RUN apt-get update && apt-get -qq install --no-install-recommends build-essential git cmake ninja-build autoconf libtool python3 python3-jinja2 curl zip unzip tar ca-certificates libltdl-dev pkg-config

RUN <<EOF cat >> vcpkg.json
{
  "\$schema": "https://raw.githubusercontent.com/microsoft/vcpkg-tool/main/docs/vcpkg.schema.json",
  "name": "ezquake",
  "version": "1.0.0",
  "dependencies": [
    { "name": "dbus", "default-features": false },
    { "name": "sdl2", "default-features": false }
  ]
}
EOF

#RUN git clone https://github.com/microsoft/vcpkg
RUN git clone https://github.com/dsvensson/vcpkg && (cd vcpkg; git reset --hard origin/patch-1)
RUN VCPKG_DISABLE_METRICS=1 vcpkg/bootstrap-vcpkg.sh && vcpkg/vcpkg install

....and removing the dbus line and passing "features": ["dbus"] to sdl2 corectly enables it.

[dsvensson]

@FrankXie05 @dg0yt Anything else that stands out?

[dsvensson]

@dg0yt Could this be the final version? Or there's more CI torture left 😂

[dg0yt]

LGTM but somebody else must approve.
Thanks @dsvensson.

[dsvensson]

@FrankXie05 what do you think, ready?

[FrankXie05]

@dsvensson Thanks for this PR， and @dg0yt thanks for review. :)

[dsvensson]

@FrankXie05 Now that it's marked as reviewed, approved etc, what phases are left until it's merged? Just trying to get an understanding of the PR workflow in this project as I have some other ports that I carry some changes for so just want to align my expectations.

[vicroms]

@dsvensson after PR has been marked info:reviewed a member of the Microsoft/vcpkg team gives a final review and clicks the merge button.