Hi. I just built gnuplot from the repository today (2016/9/2), and it looks like any "with lines" splot draws nothing when using the x11 terminal. Only this terminal is affected. Let me know if more information is needed to reproduce, but this is 100% reliable here.
Thanks!
The most recent change to the x11 terminal (gnuplot_x11) was support for fillcolor in textboxes. Hard to see how that could affect anything but the color of textboxes.
Before that was a change to how frequently the cursor is refreshed.
And before that nothing since Feb 2015.
No changes to the inboard driver (x11.trm) since 2015.
So any X11-specific problem is totally unexplained.
Thanks for the note. I just investigated a bit, and I can observe this problem as far back as the 4.6 release. So something happened to my X server, and it's not a gnuplot problem. Sorry for the noise.