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-- monkey patches for zoetrope Sprite
-- displace on a specific axis
function Sprite:displaceDir(other, dir, hint)
if not self.solid or self == other or not other.solid then return end
if STRICT then assert(other:instanceOf(Sprite), 'asked to displace a non-sprite') end
if other.sprites then
-- handle groups
for _, spr in pairs(other.sprites) do
self:displace(spr, dir)
end
else
-- handle sprites
local dim = util.dim(dir)
local negMove = (other[dir] - self[dir]) + other[dim]
local posMove = (self[dir] + self[dim]) - other[dir]
if hint then
if hint < 0 then
chg = - negMove
elseif hint > 0 then
chg = posMove
else
error('hint should be 1, -1, or nil')
end
else
if negMove < posMove then
chg = - negMove
else
chg = posMove
end
end
end
other[dir] = other[dir] + chg
end
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