Text selection does not work as expected

[Scott Kostyshak]

On Sat, Jul 04, 2020 at 07:50:18PM +0200, Yu Jin wrote:
> Am Sa., 4. Juli 2020 um 17:16 Uhr schrieb Scott Kostyshak <skostysh at lyx.org
> >:
> 
> >
> > Thanks for looking into this, Eugene. Just to make sure I understand,
> > you think this is a Qt bug, right? I don't know anything about this
> >
> 
> It looks like a Qt bug indeed, I have reported it on Qt bugtracker.

Great, thanks for doing that. I suggest to put the URL to the Qt bug
report when you commit.

> But to
> clarify, the bug occurs only on touchpads (not on Windows 10 in general).
> I have tested an older LyX version on my notebook, 2.3.1 (with Qt 5.10.1)
> -> no bug. The newer LyX versions, which come with Qt 5.12.5 and also my
> latest betainstaller, where I used Qt 5.15.0, do have that bug, therefore
> it seems like a Qt bug.
> 
> 
> > stuff, so hopefully a different LyX developer takes a look. Don't spend
> > time making a new patch based on my comments (wait for another LyX dev
> > first), but if you do get a +1 to commit, it would be nice to mark
> > exactly what parts of the code are in there because of a workaround for
> > a Qt bug, and how to test that the bug is no longer relevant (e.g., "to
> > test if this workaround is still needed, try to select a word by
> > double-clicking in LyX on Windows 10. For more information, see the
> > following ML thread...").
> >
> > Taking a step back, what changed that triggered this bug? I'm guessing
> > that it is because we compiled LyX 2.3.5 with a newer Qt version. Is that
> > correct? Is it worth compiling 2.3.4 on your machine to double-check that
> > you *can* reproduce the bug (since using a newer Qt version)? What Qt
> > version was 2.3.4 compiled with? I personally would support putting the
> > added lines in preprocessor guards but I don't know how other LyX
> > developers feel about that. Here is the flavor of preprocessor checking
> > that I think is easiest:
> >
> 
> I have compiled master with Qt 5.15.0 on my machine, resulting in the bug
> occuring. Compiling master with Qt 5.9.9 (I could not download 5.10.1, to
> match what is used in the LyX version I have tried above, for some reason)
> didn't produce the bug.

Thanks for those checks.

> > #if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
> >        // code here...
> > #endif
> 
> 
> I see and understand now that workarounds for Qt bugs are not easy to
> handle. Also I can't predict when or if the bug will be fixed in Qt. So
> what is attached is what I can provide for now, maybe other developers have
> more experience or better ideas?

So something like the following could work (but I haven't tested):

#if (QT_VERSION > QT_VERSION_CHECK(5, 9, 9))
       // we do not see the bug with 5.9.9 and do see it with 5.15.0
       // Qt bug report: <URL>
       ...
#endif

> Btw do we have some kind of tracker for
> this kind of issues?

I think in trac we have (or at least had) a keyword "qtbug". But we were
never too careful about using it.

If no one else responds within a couple of days, if you make a patch
with the Qt version guards, I think I would feel comfortable taking a
closer look and would likely give a +1.

Thanks,

Scott
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 488 bytes
Desc: not available
URL: <http://lists.lyx.org/pipermail/lyx-devel/attachments/20200704/dfca2c7d/attachment.asc>