Re: Plot failure: "Visible pixel grid has a scan line longer than previous scan lines"

[Dima K. <gn...@di...>]

Ethan A Merritt <me...@uw...> writes:

> On Monday, 29 June 2020 19:51:04 PDT Dima Kogan wrote:
>> Alright, I debugged this (rr was invaluable), and I know mostly what's
>> going on. The flow is roughly this:
>>
>> 1. The data is read here:
>>
>>    https://sourceforge.net/p/gnuplot/gnuplot-main/ci/branch-5-4-stable/tree/src/plot3d.c#l1037
>>
>>    At the end of the first line, x is 3999.0000000000005, which is just outside the
>>    xrange [0:3999]. This isn't unexpected due to the "using" expression
>
> But the x coordinates should come out identically the same in the "good" and "bad"
> cases, right?  So how does this explain a different between them?

In the "good" case we're getting lucky in step 5. The corners (which
were out-of-bounds in step 2, and were thus ignored for computing
view_port_z[]) still end up in-bounds in step 5. There's an extra step
that I didn't mention in the previous email:

3.5. We expand the autoranged axis extents to nice, round numbers:

     https://sourceforge.net/p/gnuplot/gnuplot-main/ci/branch-5-4-stable/tree/src/axis.c#l960

This provides some margin so that getting lucky in this way is possible.