Zooming level is broken if XFCE Window Scale is used

Steps to reproduce:

• open ristretto like this: GDK_SCALE=2 ristretto file-to-open.png
• Ask for Normal Size Ctrl 0

Expected at this point:

• Have the picture open pixel-by-pixel as it was

Actually at this point:

• The image will be zoomed in by a factor of 2

If I understand the issue correctly, this is an understandable side-effect of automatic scaling. Yet, it would make sense for ristretto to show the correct zoom level I think. And to make the Ctrl 0 zoom work correctly. I think the GDK_SCALE has to be compensated against (backwards)

Note that just ignoring GDK_SCALE is not a desired course of action, because the fact that UI elements are automatically scaled is great actually!

// Scaling is used for e.g. hi-dpi monitors.