Re: [Gimp-user] Image doesn't move smoothly

[Steve Kinney <admin pilobilus net>]

On 04/20/2018 08:08 PM, Richard wrote:
> If you have the ability to record your steps on video then that could be more helpful than static 
> screenshots and verbal explanations.  But as a quick experiment, I can confirm that moving layers can 
> result in slow redraw times, potentially creating general visual mess (but the move operation otherwise 
> executes normally and the visual artifacts do clean themselves up afterwards).
>
>
> If you had a case where the "lag" between moving a layer and the window updating got continually worse the 
> more you kept moving the layer, that would be indicative of a cascading event.  Fortunately, that doesn't 
> seem to be the case here....
>
>
> Some caveats I noticed:
>
> - The size of the image canvas, layer in question, and current zoom level seem to have no impact on redraw 
> times; only the actual size of the image window whose area is being redrawn.
>
> - Visual artifacts are most noticeable when moving the object upwards.
>
> - Using the Pan function (Spacebar) always results in smooth movement as it is not actually making changes 
> to the image, just scrolling its position within the image window.
>
>
> I do notice that during the move operation all visual redraws originate from the upper-left of the moved 
> object.  Not necessarily a bad choice, but could the redraw perhaps originate from the cursor's current 
> location within the image window, redrawing outwards?  After all, when you're clicking and dragging 
> something, the area around the cursor is generally what your vision is focused on....

Now this starts to sound like an actual bug in the program.  What
version of the GIMP, on what operating system & operating system
version, is doing this?  Is there a difference when the image is set to
RGB, indexed or grayscale?

The problem Brombur describes and Richard at least partially confirms
may be a 'known issue' or it may need a bug report filed.