[LyX/master] Allow compiling with Qt6

[Enrico Forestieri]

On Tue, Mar 16, 2021 at 09:28:03AM +0100, Jean-Marc Lasgouttes wrote:
> Le 16/03/2021 à 07:38, Andreas Nicolai a écrit :
> >   Hi All,
> > 
> > just looked into Qt6 for another project of mine and noticed that there
> > is actually nothing in Qt6 new, that's really needed. Same for Lyx - or
> > is there really any feature of Qt6 necessary?
> > 
> > So, I was wondering - Lyx is being used by a lot of people with not so
> > brand-new notebooks, and hardware, that won't even support upgrading to
> > newer os (talk about the older Macs for example, and quite a few 6
> > +years Linux boxes). Now, Qt6 has a compatibility limit and some of
> > these systems won't be able to run Lyx anylonger.
> 
> Hi Andreas,
> 
> LyX 2.4 will still support Qt 4.8. I trust this is old enough :)

So, I infer that the attached patch is needed.

-- 
Enrico
-------------- next part --------------
diff --git a/configure.ac b/configure.ac
index f258db9adf..17784742c4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -149,7 +149,7 @@ AC_CHECK_HEADERS(magic.h,
 ### setup the qt frontend.
 dnl The code below is not in a macro, because this would cause big
 dnl problems with the AC_REQUIRE contained in QT_DO_IT_ALL.
-QT_DO_IT_ALL([4.5.0])
+QT_DO_IT_ALL([4.8.0])
 AC_SUBST([FRONTENDS_SUBDIRS], [qt])
 FRONTEND_INFO="${FRONTEND_INFO}\
   Qt Frontend:\n\