Support older Qt versions, down to 5.6

[rubdos]

Hi!

I know 5.6 is kinda old (an LTS that has known life from 2016-03-16 until 2019-03-16), but this is still what SailfishOS uses, and will probably be that for a while, until they switch to 5.12 (or hopefully something even more recent).

With the eye on keeping the difference between my qmetaobject-sfos-rs fork and your upstream as small as possible, I'd like to introduce cfg flags on all functionality between 5.6 and 5.most-recent. This should not impact upstream, but should provide me with a way more maintainable set of patches.

I hope this is alright for you folks! If it is, I will start adding the relevant cfg flags to all structs and methods that require them.

TODO:

• Perhaps update the readme for minimum needed Qt version?
• git rebase --autosquash
• Should we annotate the docs of relevant public functions with their respective Qt versions?
• Rebase my fork and test whether it works!

[bundyo]

A bit offtopic - where one can read how to use this fork for SFOS development? I've been waiting a long time for Jolla to upgrade Qt, but this might not happen soon and I have an app to rewrite. :)

[rubdos]

A bit offtopic - where one can read how to use this fork for SFOS development? I've been waiting a long time for Jolla to upgrade Qt, but this might not happen soon and I have an app to rewrite. :)

You happen to be on IRC or Matrix? We can discuss this further on #whisperfish:rubdos.be or freenode #whisperfish if you want. There are more people interested in SFOS+Rust than I imagined before.

I've been using it for Whisperfish, which is nearing beta release. You can read how it's done there, but it's currently extremely ugly (and it doesn't work in the official SDK, so I use some... workarounds). Its ugliness is partially resolved by this PR ;-)

[bundyo]

Unfortunately IRC and Matrix are not among my channels, I'm using almost everything else. :) I'll consider Matrix.

[rubdos]

Unfortunately IRC and Matrix are not among my channels, I'm using almost everything else. :) I'll consider Matrix.

Feel free to send an email, get in contact on the Sailfish forum, or use the fork's issue tracker at https://gitlab.com/rubdos/qmetaobject-sfos-rs/-/issues/, or Twitter, or ... anything really :-)

[rubdos]

8590a14, 0523076, 5b57f5d are related to how simple cpp_build is: it cannot exclude code from compilation merely based on a #[cfg(qt_5_7)] flag; it will instead include everything. That's of course not possible in my case...

[rubdos]

Guarding C++ code with cfg() generated by build.rs is sadly impossible, so I've done it a bit hacky (5419d84). Suggestions welcome. I've squashed the other commits, as these were slight fixups, and addressed most other comments.

[ogoffart]

looks good to me. Could you rebase?

[rubdos]

looks good to me. Could you rebase?

done. I still have some other Sailfish related issues, but I'll do them separate.

[ogoffart]

thanks!

[rubdos]

Seems that my Travis addon points to some other problem, cfr. https://travis-ci.org/github/woboq/qmetaobject-rs/jobs/743931414

diff --git a/qmetaobject/tests/tests.rs b/qmetaobject/tests/tests.rs
index d1a8d9b..8b0acfa 100644
--- a/qmetaobject/tests/tests.rs
+++ b/qmetaobject/tests/tests.rs
@@ -720,6 +720,7 @@ struct MyEnumObject {
     base: qt_base_class!(trait QObject),
 }

+#[cfg(qt_5_7)]
 #[test]
 fn enum_properties() {
     qml_register_enum::<MyEnum>(

should do it.