local box2d = require'box2d'

Math for 2D rectangles defined as (x, y, w, h) where w > 0 and h > 0.

API

representation forms
box2d.corners(x, y, w, h) -> x1, y1, x2, y2	left,top and right,bottom corners
box2d.rect(x1, y1, x2, y2) -> x, y, w, h	box given left,top and right,bottom corners
normalization
box2d.normalize(x, y, w, h) -> x, y, w, h	return the same box with positive width and height
layouting
box2d.align(w, h, halign, valign, bx, by, bw, bh) -> x, y, w, h	align a box in another box
box2d.vsplit(i, sh, x, y, w, h) -> x, y, w, h	slice a box horizontally at a certain height and return the i’th box2d. if sh is negative, slicing is done from the bottom side.
box2d.hsplit(i, sw, x, y, w, h) -> x, y, w, h	slice a box vertically at a certain width and return the i’th box2d. if sw is negative, slicing is done from the right side.
box2d.nsplit(i, n, direction, x, y, w, h) -> x, y, w, h	slice a box in n equal slices, vertically or horizontally, and return the i’th box2d. direction = ‘v’ or ‘h’
box2d.translate(x0, y0, x, y, w, h) -> x, y, w, h	move a box
box2d.offset(d, x, y, w, h) -> x, y, w, h	offset a box by d, outward if d is positive
box2d.fit(w, h, bw, bh) -> w, h	fit a box into another box preserving aspect ratio. use align() to position the box
hit testing
box2d.hit(x0, y0, x, y, w, h) -> true | false	check if a point (x0, y0) is inside rect (x, y, w, h)
box2d.hit_edges(x0, y0, d, x, y, w, h) -> hit, left, top, right, bottom	hit test for edges and corners
edge snapping
box2d.snap_edges(d, x, y, w, h, rectangles[, opaque]) -> x, y, w, h	snap the sides of a rectangle against a list of rectangles of form {{x=,y=,w=,h=},...}. if opaque = true, the rectangles are considered opaque, in which case they must be sorted front-to-back.
box2d.snap_pos(d, x, y, w, h, rectangles[, opaque]) -> x, y, w, h	snap the position of a rectangle against a list of rectangles.
box2d.snapped_edges(d, x1, y1, w1, h1, x2, y2, w2, h2[, opaque]) -> snapped, left, top, right, bottom	check if two boxes are snapped and on which edges.
overlapping test
box2d.overlapping(x1, y1, w1, h1, x2, y2, w2, h2) -> true | false	check if two boxes overlap.
clipping
box2d.clip(x, y, w, h, x0, y0, w0, h0) -> x1, y1, w1, h1	intersect two normalized boxes
bounding box
box2d.bounding_box(x1, y1, w1, h1, x2, y2, w2, h2) -> x, y, w, h	join two normalized boxes
scrolling
box2d.scroll_to_view(x, y, w, h, pw, ph, sx, sy) -> sx, sy	move a box from (sx, sy) inside (pw, ph) so that it becomes completely visible.

OOP API

Operations never mutate the object, instead they return a new one.

box2d(x, y, w, h) -> box	create a new box object
box.x, box.y, box.w, box.h	box coordinates (for reading and writing)
box:rect() -> x, y, w, h box() -> x, y, w, h	coordinates unpacked
box:corners() -> x1, y1, x2, y2	left,top and right,bottom corners
box:align(halign, valign, parent_box) -> box	align
box:vsplit(i, sh) -> box	split vertically
box:hsplit(i, sw) -> box	split horizontally
box:nsplit(i, n, direction) -> box	split in equal parts
box:translate(x0, y0) -> box	translate
box:offset(d) -> box	offset by d (outward if d is positive)
box:fit(parent_box, halign, valign) -> box	enlarge/shrink-to-fit and align
box:hit(x0, y0) -> true | false	hit test
box:hit_edges(x0, y0, d) -> hit, left, top, right, bottom	hit test for edges
box:snap_edges(d, boxes) -> box	snap the edges to a list of boxes
box:snap_pos(d, boxes) -> box	snap the position
box:overlapping(box) -> true | false	overlapping test
box:clip(box) -> box	clip box to fit inside another box
box:join(box)	make box the bounding box of itself and another box

Last updated: 19 months ago | Edit on GitHub