[fltk] FLTK 1.3 is still needed as 1.4 is not fully backwards compatible

[CendioOssman]

Description / Steps to reproduce the issue

1. Install FLTK from MSYS
2. Download TigerVNC source
3. Build TigerVNC

Expected behavior

TigerVNC builds

Actual behavior

TigerVNC fails to build (and if it would build, it would not behave correctly).

Verification

• I have verified that my MSYS2 is up-to-date before submitting the report (see https://www.msys2.org/docs/updating/)

Windows Version

10.0.20348

MINGW environments affected

• MINGW64
• MINGW32
• UCRT64
• CLANG64
• CLANGARM64

Are you willing to submit a PR?

No response

[CendioOssman]

Related, FLTK 1.3.10 was released at the same time as FLTK 1.4.0 and contains new functionality that TigerVNC wants. So it would be nice to get that new version packaged in to MSYS.

[CendioOssman]

As a temporary workaround, we've put this in place: TigerVNC/tigervnc@f06e574

[lazka]

According to upstream (https://www.fltk.org/roadmap.php) "...FLTK 1.3 is no longer in active development...FLTK 1.3.10 (released on Nov 16, 2024) is presumably the final release of branch 1.3.".

We could add back a 1.3 version if really needed. How large are the incompatibilities? All our reverse deps built just fine with it.

[Biswa96]

There would be file conflict if both fltk 1.3 and 1.4 is installed. I think the underlying issue should be fixed in tigervnc.

[CendioOssman]

We could add back a 1.3 version if really needed. How large are the incompatibilities? All our reverse deps built just fine with it.

We have not dug in to it. TigerVNC is a very advanced user of FLTK, and FLTK 1.4 has been in development for many years. So there are likely many things that need to be adjusted. As an example, we've got a report that the rendering pipeline is not compatible any more (linked above).

To make things more complicated, we will likely need to support FLTK 1.3 for some time, as I would not assume 1.4 will be available in older Linux distributions.

In short, FLTK 1.4 support in TigerVNC is not something anyone will have time to look at anytime soon.

As a comparison, macOS homebrew now packages both 1.4 and 1.3: https://formulae.brew.sh/formula/fltk@1.3

I'm fairly sure this kind of overlap was also done for some time when 1.3 was released, which also wasn't fully backwards compatible with the previous version of FLTK.

[lazka]

ok, thanks. Fedora is also thinking about it: https://bugzilla.redhat.com/show_bug.cgi?id=2253781

[lazka]

There would be file conflict if both fltk 1.3 and 1.4 is installed. I think the underlying issue should be fixed in tigervnc.

There are two way to go about it:

• just conflict and restrict what can be installed
• split 1.3 into a runtime and a dev package, and only the dev package conflicts with fltk 1.4

[CendioOssman]

Conflicts are likely fine for us for the foreseeable future. We usually statically link stuff for distribution, so FLTK 1.3 just needs to be installed when building.