func UpdateImgPositions(sz size.Event, u *uistate.UIState) {
// must copy u.WindowSize instead of creating a pointer to it
oldWindowSize := coords.MakeVec(u.WindowSize.X, u.WindowSize.Y)
updateWindowSize(sz, u)
if windowExists(oldWindowSize) && windowExists(u.WindowSize) {
u.Padding = scaleVar(u.Padding, oldWindowSize, u.WindowSize)
AdjustImgs(oldWindowSize, u)
}
}