Here’s an even fancier version:
%%WGT0{"w":[{"name":"canvas","type":"canvas","size":[100,100],"pos":[206,121],"locked":1,"animated":1,"volatile":1,"script":"on view do\n p:colors.black,colors.red\n i:me.copy[]\n me.clear[]\n me.paste[i (-1,0)]\n me.pattern:p[pointer.held]\n dy:(pointer.pos-pointer.prev)[1]\n c:(1,0.5)*me.lsize\n me.line[c c+(0,dy)]\nend","pattern":47,"brush":1,"scale":1}],"d":{}}
It only draws the Y component of the delta, but it draws in red when the pointer is held and black otherwise, and it slowly scrolls old values off to the left instead of clearing each frame, so you can get a sense of whether the black spikes are smaller than the red spikes.
I do see that in Native Decker (also on Linux), but I don’t see it in Web Decker. In Native Decker, I see about the same difference regardless of whether it’s in a tiny window or full-screen, so I don’t think some scaling factor is being applied the wrong number of times.