zooming in using the Z spin box extremely jerky, Windows 10, trunk

[Alvin Penner]

- Windows 10, Inkscape 0.92+devel 15536
- load the attached file zoomtest.svg, which will be at a zoom level of 100%
- now click on the '+' sign in the Z spinbox in order to zoom in.
- click repeatedly and note that every single click will cause the entire page to move to the bottom left and then to move back to the original location. The final result is more or less as expected, but the intermediate refresh at the bottom left location is very disorienting, and unexpected.
- now click on the '-' sign repeatedly and note that the page first moves to the top right before resuming its expected position
- during this entire process, it appears as though the left hand border of the page is behaving as expected, while the right hand border is showing all the unexpected behavior, meaning that the page size appears to be changing during the intermediate refresh.

[su_v (suv-lp)]

On Windows 10:
- not reproduced with 0.91, 0.92.0, 0.92.1
  (7z from inkscape.org, GTK2)
- reproduced with lp:inkscape r15113
  from http://download.tuxfamily.org/inkscape/win64/
- reproduced with lp:inkscape r15540
  (local build, current devlibs64 with GTK+ 3.19.6)
- not reproduced with lp:inkscape r15536
  from http://download.tuxfamily.org/inkscape/win64/
  (MSYS2 build from Eduard Braun with GTK+ 3.22.8)

On Ubuntu 14.04.5 LTS:
- not reproduced with Inkscape 0.92.0, 0.92.1
  (local builds, GTK+ 2.24.23
- not reproduced with lp:inkscape r15540
  (local build with GTK+ 3.10.8)

On OS X 10.7.5:
- not reproduced with 0.91, 0.92.1 GTK2
- not reproduced with 0.92.x GTK3 (3.18.9, 3.20.5)

[Alvin Penner (apenner)]

I can no longer reproduce this on Windows 10,
Inkscape 1.0alpha (9cedb1b, 2019-02-08)