1 files changed, 168 insertions, 0 deletions
diff --git a/geom.lua b/geom.lua
new file mode 100644
index 0000000..891e98d
--- /dev/null
+++ b/geom.lua
@@ -0,0 +1,168 @@
+geom = {}
+
+function geom.on_shape(x,y, drawing, shape)
+  if shape.mode == 'freehand' then
+    return geom.on_freehand(x,y, drawing, shape)
+  elseif shape.mode == 'line' then
+    return geom.on_line(x,y, drawing, shape)
+  elseif shape.mode == 'manhattan' then
+    local p1 = drawing.points[shape.p1]
+    local p2 = drawing.points[shape.p2]
+    if p1.x == p2.x then
+      if x ~= p1.x then return false end
+      local y1,y2 = p1.y, p2.y
+      if y1 > y2 then
+        y1,y2 = y2,y1
+      end
+      return y >= y1-2 and y <= y2+2
+    elseif p1.y == p2.y then
+      if y ~= p1.y then return false end
+      local x1,x2 = p1.x, p2.x
+      if x1 > x2 then
+        x1,x2 = x2,x1
+      end
+      return x >= x1-2 and x <= x2+2
+    end
+  elseif shape.mode == 'polygon' or shape.mode == 'rectangle' or shape.mode == 'square' then
+    return geom.on_polygon(x,y, drawing, shape)
+  elseif shape.mode == 'circle' then
+    local center = drawing.points[shape.center]
+    local dist = geom.dist(center.x,center.y, x,y)
+    return dist > shape.radius*0.95 and dist < shape.radius*1.05
+  elseif shape.mode == 'arc' then
+    local center = drawing.points[shape.center]
+    local dist = geom.dist(center.x,center.y, x,y)
+    if dist < shape.radius*0.95 or dist > shape.radius*1.05 then
+      return false
+    end
+    return geom.angle_between(center.x,center.y, x,y, shape.start_angle,shape.end_angle)
+  elseif shape.mode == 'deleted' then
+  else
+    print(shape.mode)
+    assert(false)
+  end
+end
+
+function geom.on_freehand(x,y, drawing, shape)
+  local prev
+  for _,p in ipairs(shape.points) do
+    if prev then
+      if geom.on_line(x,y, drawing, {p1=prev, p2=p}) then
+        return true
+      end
+    end
+    prev = p
+  end
+  return false
+end
+
+function geom.on_line(x,y, drawing, shape)
+  local p1,p2
+  if type(shape.p1) == 'number' then
+    p1 = drawing.points[shape.p1]
+    p2 = drawing.points[shape.p2]
+  else
+    p1 = shape.p1
+    p2 = shape.p2
+  end
+  if p1.x == p2.x then
+    if math.abs(p1.x-x) > 2 then
+      return false
+    end
+    local y1,y2 = p1.y,p2.y
+    if y1 > y2 then
+      y1,y2 = y2,y1
+    end
+    return y >= y1-2 and y <= y2+2
+  end
+  -- has the right slope and intercept
+  local m = (p2.y - p1.y) / (p2.x - p1.x)
+  local yp = p1.y + m*(x-p1.x)
+  if yp < y-2 or yp > y+2 then
+    return false
+  end
+  -- between endpoints
+  local k = (x-p1.x) / (p2.x-p1.x)
+  return k > -0.005 and k < 1.005
+end
+
+function geom.on_polygon(x,y, drawing, shape)
+  local prev
+  for _,p in ipairs(shape.vertices) do
+    if prev then
+      if geom.on_line(x,y, drawing, {p1=prev, p2=p}) then
+        return true
+      end
+    end
+    prev = p
+  end
+  return geom.on_line(x,y, drawing, {p1=shape.vertices[1], p2=shape.vertices[#shape.vertices]})
+end
+
+-- are (x3,y3) and (x4,y4) on the same side of the line between (x1,y1) and (x2,y2)
+function geom.same_side(x1,y1, x2,y2, x3,y3, x4,y4)
+  if x1 == x2 then
+    return math.sign(x3-x1) == math.sign(x4-x1)
+  end
+  if y1 == y2 then
+    return math.sign(y3-y1) == math.sign(y4-y1)
+  end
+  local m = (y2-y1)/(x2-x1)
+  return math.sign(m*(x3-x1) + y1-y3) == math.sign(m*(x4-x1) + y1-y4)
+end
+
+function math.sign(x)
+  if x > 0 then
+    return 1
+  elseif x == 0 then
+    return 0
+  elseif x < 0 then
+    return -1
+  end
+end
+
+function geom.angle_with_hint(x1, y1, x2, y2, hint)
+  local result = geom.angle(x1,y1, x2,y2)
+  if hint then
+    -- Smooth the discontinuity where angle goes from positive to negative.
+    -- The hint is a memory of which way we drew it last time.
+    while result > hint+math.pi/10 do
+      result = result-math.pi*2
+    end
+    while result < hint-math.pi/10 do
+      result = result+math.pi*2
+    end
+  end
+  return result
+end
+
+-- result is from -π/2 to 3π/2, approximately adding math.atan2 from Lua 5.3
+-- (LÖVE is Lua 5.1)
+function geom.angle(x1,y1, x2,y2)
+  local result = math.atan((y2-y1)/(x2-x1))
+  if x2 < x1 then
+    result = result+math.pi
+  end
+  return result
+end
+
+-- is the line between x,y and cx,cy at an angle between s and e?
+function geom.angle_between(ox,oy, x,y, s,e)
+  local angle = geom.angle(ox,oy, x,y)
+  if s > e then
+    s,e = e,s
+  end
+  -- I'm not sure this is right or ideal..
+  angle = angle-math.pi*2
+  if s <= angle and angle <= e then
+    return true
+  end
+  angle = angle+math.pi*2
+  if s <= angle and angle <= e then
+    return true
+  end
+  angle = angle+math.pi*2
+  return s <= angle and angle <= e
+end
+
+function geom.dist(x1,y1, x2,y2) return ((x2-x1)^2+(y2-y1)^2)^0.5 end