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<canvas id="canvas"></canvas>
<div id="hud"></div>
<script src="/assets/javascripts/util.js"></script>
<script src="/assets/javascripts/vendor/bower_components/hidpi-canvas/dist/hidpi-canvas.js"></script>
<script src="/assets/javascripts/vendor/tube.js"></script>
<script src="/assets/javascripts/rectangles/util/constants.js"></script>
<script src="/assets/javascripts/rectangles/util/mouse.js"></script>
<script src="/assets/javascripts/rectangles/models/vec2.js"></script>
<script src="/assets/javascripts/rectangles/models/rect.js"></script>
<script src="/assets/javascripts/vendor/canvasutilities.js"></script>
<script>
var w = canvas.width = 600
var h = canvas.height = 400
var ctx = canvas.getContext('2d')
var vec_a = new Rect( 100, 120, 50, 100 )
var vec_b = new Rect( 20, 200, 120, 120 )
var vecs = [ vec_a, vec_b ]
var points = [ vec_a.x, vec_a.y, vec_b.x, vec_b.y ]
var r = 4
var vec_c = new Rect()
vec_c.x = vec_a.x
vec_c.y = vec_b.x
var intersect = new vec2 ()
var dragging = false, dragging_a, dragging_b
var delta = new vec2( 0, 0 )
var mymouse = new mouse({
el: canvas,
down: function(e, cursor){
points.some(function(p){
if (-cursor.x.a > p.a - r && -cursor.x.a < p.a + r &&
cursor.y.a > p.b - r && cursor.y.a < p.b + r) {
dragging_a = p.a
dragging_b = p.b
dragging = p
return true
}
})
},
drag: function(e, cursor){
if (! dragging) return
delta = cursor.delta()
delta.a = - delta.a
dragging.a = dragging_a + delta.a
dragging.b = dragging_b + delta.b
},
up: function(e, cursor, new_cursor){
delta.zero()
dragging.dragging = false
dragging = false
},
})
function draw () {
ctx.fillStyle = "#fff"
ctx.fillRect(0,0,w,h)
ctx.fillStyle = "#bbb"
points.forEach(drawPoint)
drawLine(vec_a.x, vec_a.y, "#f00")
drawLine(vec_b.x, vec_b.y, "#00f")
drawLine(vec_a.x, vec_b.x, "#080")
var t = perp(vec_c, vec_b) / ( perp(vec_a, vec_b) || 0.0000001 )
intersect.a = vec_a.x.a + ( vec_a.y.a - vec_a.x.a ) * t
intersect.b = vec_a.x.b + ( vec_a.y.b - vec_a.x.b ) * t
var collinear = is_collinear( intersect, vec_b )
var long_enough_to_intersect = 0 <= t && t <= 1
var msg
if (long_enough_to_intersect && collinear) {
ctx.fillStyle = "#f00"
msg = "through"
}
else if (collinear) {
ctx.fillStyle = "#0f0"
msg = "to"
}
else {
ctx.fillStyle = "#000"
msg = "off"
}
hud.innerHTML = [intersect.exactString(), vec_b.exactString(), msg].join("<br>")
drawPoint(intersect)
}
function drawLine (pa, pb, color) {
ctx.fillStyle = color
ctx.strokeStyle = color
var x1 = pa.a
var y1 = pa.b
var x2 = pb.a
var y2 = pb.b
drawArrow(ctx, x1, y1, x2, y2)
}
function drawPoint (p) {
var x = p.a - r
var y = p.b - r
ctx.fillRect(x, y, r*2, r*2)
}
function perp (va, vb) {
return (va.y.a - va.x.a) * (vb.y.b - vb.x.b) - (va.y.b - va.x.b) * (vb.y.a - vb.x.a)
}
function is_collinear (p, vec) {
var on_x, on_y
var pa = round(p.a), pb = round(p.b)
if (vec.x.a < vec.y.a) {
on_x = vec.x.a <= pa && pa <= vec.y.a
}
else {
on_x = vec.x.a >= pa && pa >= vec.y.a
}
if (vec.x.b < vec.y.b) {
on_y = vec.x.b <= pb && pb <= vec.y.b
}
else {
on_y = vec.x.b >= pb && pb >= vec.y.b
}
return !! (on_x && on_y)
}
function animate(){
requestAnimationFrame(animate)
draw()
}
animate()
</script>
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