By opening a pdf (or a ps) file with the --watch option and selecting 'Fit
width to window' in the view menu, gv incrementally zooms in the view every
time the pdf file is regenerated.

The reproduction can be made by doing:

1. gv --watch test.pdf

2. Select 'Fit width to window' in the menu

3. latex test.tex && dvips test.dvi && ps2pdf test.ps

Then repeat step 3. several times and gv will zoom in for each reload. This
seems to happen with the combination of --watch option and 'Fit width to
window'.