mupdf cursor down key behavior on NetBSD vs Linux

[Mayuresh <mayuresh%acm.org@localhost>]

Setup 1:

    Void Linux: mupdf-1.24.9_1
    mupdf running locally on a laptop

Setup 2:

    NetBSD 10.1 amd64: mupdf-1.24.10nb3, tigervnc-1.14.0.1.20.13nb3
    Void Linux: tigervnc-1.15.0_1
    mupdf running on NetBSD, accessed over tigervnc from Void Linux

Scenario: viewing a PDF in mupdf with zoom and pan setting such that the
margins on left and right are somewhat cropped (to enlarge the font),

We have reached the bottom of a page.

Now pressing cursor down key:

On Setup 1: it switches to the start of the next page, retaining the zoom
and pan setting. 

PageDown key retains the zoom and pan, but jumps to the end of the next
page.

This is the expected behavior.

On Setup 2: both cursor down and PageDown keys behave the same jumping to
the bottom of the next page. 

Given the minor difference in the mupdf version, this may have to do with
either the OS or tigervnc, rather than mupdf.

Any suggestions?

-- 
Mayuresh