That's pretty cool, Ádám! I reckon that mode of interpolation is a bit too harsh for xy pad use, though - touch two places and it'll draw a direct line between them, which is a bit radical for some uses.
Yeah, it needs some improvement. The original idea was that, since pictslider is probably using qelems to trigger it's output, when you click-and-move the mouse inside the object, you won't get a continuous output. My approach works basically to overcome this problem. Probably a timer+gate combo or something similar should be inserted to turn off the 'direct line interpolation' effect.