#1349 qt terminal can't zoom into large images

[dima]

I'm observing that when plotting large images and zooming in closely, the qt terminal plots nothing (I just get a gray screen). Attached is a data file that shows this (it's a DEM of an area of Southern California). I'm using a fairly recent gnuplot from the repository (latest commit is 'Allow changing textcolor of the timestamp').

Recipe:

set terminal qt
set cbrange [0:3500]
plot "N34W119.hgt" binary format="%short" endian=big array=(1201,1201) with image

So far so good. I see the image. Now I zoom in

set xrange [200:205]
set yrange [200:205]
replot

Now I see just blank gray space, instead of the zoomed image. This works fine with the x11 terminal. Also this works fine if I don't zoom in quite as closely.

[Ethan Merritt]

I do not know what causes the problem, but a work-around is to add the keyword "failsafe" after the "with image". This tells the program to draw each pixel of the image as an independent rectangle rather than manipulating the whole thing at once.