[Gimp-user] Large window size causes lag

[antiart <forums gimpusers com>]

I can confirm this issue. Exactly what I experienced and what I tried.
It doesn't matter if the image is 100x100 or 10000x10000 pixels, only the WINDOW
size makes the cursor slow.
I have a new Lenovo z50-70, which is fairly fast and powerful, fresh install of
Windows 8.1, all updated and with the newest drivers. I tried both, a wacom
Bamboo Pen&Touch and a wacom Intuos 2, both have the lag. I also disabled/tested
those Windows 8 tablet PC settings like hold-pen-to-right-click and the
"flicks". Still lag.
My partner suggested that the issue is related to the GPU, so i tried to force
Gimp to use the Nvidia processor, and then I forced it to the "integrated
processor". There was no difference. I also changed all my graphics settings to
good performance and disabled the "fancy stuff".

Interestingly I just noticed a very similar behavior in myPaint (version
1.1.0+gite06d414). The bigger the window, the more lag. This may be related
(myPaint has an endless canvas, though). However, putting myPaint into
Fullscreen kind of fixed the lagging. Sadly, this does not work for Gimp. There
is still the same lag, no matter if fullscreen or maximized.

And just for the record: None of the other painting application have this issue:
SAI, Krita, Inkscape, ArtRage, Fresh Paint.

> I am using Gimp 2.8.14 (latest version, just installed) with Windows
> 8.1 and a Wacom Intuos tablet. When I maximise, or otherwise enlarge
> the drawing window beyond around 30-40% of my screen size, the tool
> cursor becomes very laggy. When using the paintbrush, for example, the
> painted area, brush outline, and even the little markers on the ruler
> that show the cursor position, lag significantly behind the penstroke.
> With a smaller window, the tools work perfectly. There does not appear
> to be any lag when using the mouse to draw, even for a maximised
> window.
>
> I have increased the tile cache size to no effect, and when looking in
> the task manager it appears that Gimp is only using around 150 Mb or
> so. I have also tried turning the brush outline off (as suggested as
> solutions to similar problems), but this also didn't work and I would
> very much like to keep this switched on. The problem does not appear
> to be affected by canvas size or the amount of the canvas displayed.

-- 
antiart (via www.gimpusers.com/forums)