Bug 366024

This is a pretty major issue with instant preview since it basically means I cannot do thumbnailing or work in a zoomed out setting both of which are kinda crucial to working at high resolutions.

I have a Yiynova MVP22U+(RH) on digimend V6 configured with evdev on arch linux with KDE; the issue may only affect certain tablet brands, I don't know (I think this didn't happen on my old wacom)

What happens basically is that the first stroke I draw while zoomed out always goes well, but if I start doing another stroke within like a second after the first one ends, I can encounter bugs like the stroke going on a different trajectory or starting in a different spot than my cursor was, and also sometimes the stroke will not show immediately, then when it does show (after I raise my pen) maybe only a part of the stroke was completed. Basically all sorts of mess can happen between strokes in instant preview whilst zoomed out, the issue strangely enough didn't occur when at 100% or closer zoom. The issue becomes worse the further I zoom out and less noticable at a closer zoom (Like 120% seems to work pretty ok)

I'm working at a pretty high resolution (8K) on a 1920x1080 monitor, so the particularly high resolution and how far I need to zoom out (like 13% zoom sometimes) may have a major impact on this.

Reproducible: Always

Steps to Reproduce:
1. Make a new image at 8192x8192 resolution, zoom out to fit screen (assumed:1920x1080) and select a brush, make sure instant preview is enabled.
2. Draw quick successive strokes (I recommend rapid handwriting)
3. Watch everything go wrong! (Only the first letter/stroke looks right! :( )

Actual Results:  
Misaligned and disproportionate and often misshapen strokes

Expected Results:  
Strokes aligned with the cursor/pen and proportional to the distance the pen/cursor actually travelled.

I confirmed that disabling instant preview indeed fixes the problem.