From irederik m@iii@g oii oib@@et  Sat Apr 20 07:27:28 2019
From: irederik m@iii@g oii oib@@et (irederik m@iii@g oii oib@@et)
Date: Fri, 19 Apr 2019 22:27:28 -0700
Subject: [Rd] src/modules/X11/devX11.c, can we remove "#if BUG" yet
Message-ID: <20190420052728.7tgjr4zxqdddsimm@localhost>

Dear R Devel,

I know that someone put this line in src/modules/X11/devX11.c:2824 for
a reason, because commenting it out causes R to miss an important
ConfigureNotify event in my window manager. The result is that plots
are initially drawn off the window borders, unreadable.

     R_ProcessX11Events((void*) NULL);

Unfortunately for me, this line is commented in the standard release
of R, it has "#if BUG ... #endif" around it.

I guess it is also unfortunate for anyone who uses the same window
manager as I do, namely i3, which I think is pretty popular among Unix
power users these days; not to mention other full-screen window
managers which probably exhibit the same bug in R.

Maybe everyone on the Core team uses twm as their window manager? Or
RStudio on Windows? Which would be sad because then we're not
representing an important user demographic, namely those who prefer
software which is modern and powerful, yet simple to understand and
modify; fully configurable and interoperable and so on.

I first reported this bug 3 years ago. In doing research for my bug
report, I found that the line was commented out by Peter Dalgaard in
2001 with the explanation "X11 segfault fix - I hope".

I don't know what the way forward is. Obviously the Core Team has
reason to say, "look, this isn't very important, it's been broken
since 2001, maybe fixing it will cause the undocumented segfault bug
to reappear, clearly no one here uses your window manager". Do I have
to submit a correctness proof for the proposed change? What do I do?

https://bugs.r-project.org/bugzilla/show_bug.cgi?id=16702

As mentioned in my bug report, I checked using gdb that
ConfigureNotify is indeed being received by the call to
R_ProcessX11Events() when it is uncommented. I haven't experienced any
segfaults.

It's good that Peter left evidence that "R_ProcessX11Events" was being
called 18 years ago from X11DeviceDriver(). If he had deleted the
line, rather than commenting it, then discovering the reason for the
window rendering bug would have been much harder for me.

However, the downside is that now it is not just a matter of inserting
the line where it belongs; I also feel a bit like I have to explain
why it was initially removed. But although I've given it some thought,
I still have no idea.

Somewhat tangentially, I am wondering if there is some way that we
could make the development of R's graphics code proceed at a faster
rate, for example by pulling it out into a separate module, so that
people could offer alternative implementations via CRAN etc., rather
than having R Core be the bottleneck. Would this make sense? Has it
already been done?

Thank you,

Frederick



[Rd] src/modules/X11/devX11.c, can we remove "#if BUG" yet
irederik m@iii@g oii oib@@et