mouse_controlled_rectangle.py

from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.GLU import *
import math
window = 0                                              # glut window number

# initial position of the rectangle
rect_x = 0
rect_y = 200

# constants
RECT_WIDTH = 50
RECT_HEIGHT = 50
RECT_DELAY = 20
width, height = 400, 400                                # width and height of the window
dx = 0                                                  # direction to x
dy = 0                                                  # direction to y
mouse_y = 0                                             # position of mouse cursor to x
mouse_x = 0                                             # position of mouse cursor to y
s = 0                                                   # path 
v = 3                                                   # speed of movement of the ball

# window size
def draw_rect(x, y, width, height):
    glBegin(GL_QUADS)                                   # start drawing a rectangle
    glVertex2f(x, y)                                    # bottom left point
    glVertex2f(x + width, y)                            # bottom right point
    glVertex2f(x + width, y + height)                   # top right point
    glVertex2f(x, y + height)                           # top left point
    glEnd() 

def refresh2d(width, height):
    glViewport(0, 0, width, height)
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    glOrtho(0.0, width, 0.0, height, 0.0, 1.0)
    glMatrixMode (GL_MODELVIEW)
    glLoadIdentity()

def draw():                                             # ondraw is called all the time
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)  # clear the screen
    glLoadIdentity()                                    # reset position

    # ToDo draw rectangle
    refresh2d(width, height)
    glColor3f(0.0, 0.0, 2.0)
    draw_rect(rect_x, rect_y, RECT_WIDTH, RECT_HEIGHT)
    glutSwapBuffers()                                   # important for double buffering


def mouseControl( mx, my):

    global rect_x, rect_y, dx, dy, s, mouse_x, mouse_y

    my_new = height - my 
    mouse_x = mx
    mouse_y = my_new

    dif_x = mx - rect_x                                 # differnce between position of mouse cursor and rectangle to x
    dif_y = my_new - rect_y                             # differnce between position of mouse cursor and rectangle to y

    s = math.sqrt(dif_x ** 2 + dif_y ** 2)
    k = v / s
    dx = k * dif_x
    dy = k * dif_y


def movement(value):

    global rect_x, rect_y, mouse_x, mouse_y

    rect_x += dx
    rect_y += dy

    dif_x_new = mouse_x - rect_x                            # new differnce between position of mouse cursor and rectangle to x while rectangle is going
    dif_y_new = mouse_y - rect_y                            # new differnce between position of mouse cursor and rectangle to y while rectangle is going
    step_s = math.sqrt( dif_x_new ** 2 +  dif_y_new ** 2)   # path changed all the time when rectangle approaches to mouse cursor

# stop move when rectangle is on the cursor position
    if int(step_s) <= v:
        rect_x = mouse_x
        rect_y = mouse_y

    glutTimerFunc(RECT_DELAY, movement, 0)



glutInit()                                                 # initialize glut
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_ALPHA | GLUT_DEPTH)
glutInitWindowSize(width, height)                          # set window size
glutInitWindowPosition(0, 0)                               # set window position
window = glutCreateWindow("Approaching rectangle")         # create window with title
glutDisplayFunc(draw)                                      # set draw function callback
glutIdleFunc(draw)                                         # draw all the time
glutPassiveMotionFunc(mouseControl)
glutTimerFunc(RECT_DELAY, movement, 0)
glutMainLoop()