from Processing import *

window(600, 600)

startX, startY = 0, 0

def doMousePressed(o, e):
    global startX, startY
    startX = mouseX()
    startY = mouseY()

def doMouseDragged(o, e):
    fill(0, 0, 255, 64)
    stroke(0, 0, 255)
    endX = mouseX()
    endY = mouseY()
    minX = min(startX, endX)
    maxX = max(startX, endX)
    minY = min(startY, endY)
    maxY = max(startY, endY)
    w = maxX - minX
    h = maxY - minY
    background(255)
    rect(minX, minY, w, h)
    #print(minX, minY, w, h)

def doMouseReleased(o, e):
    background(255)

onMousePressed += doMousePressed
onMouseDragged += doMouseDragged
onMouseReleased += doMouseReleased

background(255)