Just one quick addon:
my code with the speedfactor does indeed move the (stretched) imagebox correctly.
The red bit is the end of the imagebox in a wider window:
Its children, the images, are the problem in this setup, since they are set to fit. So I thought I’d adjust the speedfactor of the imagebox depending on the width of a resized window to make it move slower and so have the last image rest at the end.
I just needed to point this out for my sake and show you that I am not a total
when it comes to coding.