CSC111 Lab 12 2014

--D. Thiebaut (talk) 18:47, 21 April 2014 (EDT)

---

Building a car using the Graphics111 library

• Get a copy of the graphics111.py library
• Save it in your main directory (where you keep you python programs) and save it as graphics111.py
• Create a car using the new classes now available in the graphics111 library. Call it lab12.py.

from graphics111 import *

MAXWIDTH  = 600
MAXHEIGHT = 400

class Car:
    def __init__(self, x, y, w, h, color ):
        self._body = Rectangle( x, y, w, h, color )
        self._w1   = Wheel( x+w//4, y+h, w//4 )
        self._w2   = Wheel( x+3*w//4, y+h, w//4 )
        
    def draw( self, canvas ):
        self._body.draw( canvas )
        self._w1.draw( canvas )
        self._w2.draw( canvas )
        
def main():    
    win = GraphicsWindow(MAXWIDTH, MAXHEIGHT)
    canvas = win.canvas()

    car = Car( 100, 100, 50, 20, (250, 250, 0) )
    car.draw( canvas )

    win.wait()
    win.close()

main()

• Notice how short the program is now that the classes for the wheels and rectangles are in the graphics111 library!

Adding A Menu

• Add a menu at the top left of the window. Don't try to activate it, it won't respond yet...

from graphics111 import *

MAXWIDTH  = 600
MAXHEIGHT = 400
class Car:
    def __init__(self, x, y, w, h, color ):
        self._body = Rectangle( x, y, w, h, color )
        self._w1   = Wheel( x+w//4, y+h, w//4 )
        self._w2   = Wheel( x+3*w//4, y+h, w//4 )
        
    def draw( self, canvas ):
        self._body.draw( canvas )
        self._w1.draw( canvas )
        self._w2.draw( canvas )
        

def main():
    win = GraphicsWindow(MAXWIDTH, MAXHEIGHT)
    canvas = win.canvas()

    menu = Menu()
    menu.draw( canvas )
    
    car = Car( 100, 100, 50, 20, (250, 250, 0) )
    car.draw( canvas )

    win.wait()
    win.close()

main()

A Bit of Hacking

• Figure out where the menu is located in the graphics111.py program, and change its color to red. All the symbols should show up in red when your modification is over.

Adding a Call-Back Function

• Modify your program and add a call-back function as shown below.
• Run it and click the mouse on the window, several times. Make sure you check the output in the console.

from graphics111 import *

MAXWIDTH  = 600
MAXHEIGHT = 400

class Car:
    def __init__(self, x, y, w, h, color ):
        self._body = Rectangle( x, y, w, h, color )
        self._w1   = Wheel( x+w//4, y+h, w//4 )
        self._w2   = Wheel( x+3*w//4, y+h, w//4 )
        
    def draw( self, canvas ):
        self._body.draw( canvas )
        self._w1.draw( canvas )
        self._w2.draw( canvas )

def mouseEvent( win, canvas, x, y ):
    print( "Caught an event. Received x=%d, y=%d" % (x,y) )
    
def main():
    global menu 

    win = GraphicsWindow(MAXWIDTH, MAXHEIGHT)
    canvas = win.canvas()
    canvas.setCallbackFunction( mouseEvent )    

    menu = Menu()
    menu.draw( canvas )
    
    car = Car( 100, 100, 50, 20, (250, 250, 0) )
    car.draw( canvas )

    win.wait()
    win.close()

main()

Challenge 1: Circles on Mouse-Clicks

• Make your program generate a colored circle where ever the user clicks the mouse.
• Make the program generate red circles on the left side of the canvas, and green circles on the right side of the canvas.

Activating the Menu

Using the menu is now fairly easy. All we have to do is call its main method called buttonClicked( x, y ) which returns the name of the symbol clicked if the user pressed one, or None if the mouse was not clicked on the menu.

def mouseEvent( win, canvas, x, y ):
    global menu 
    button = menu.buttonClicked( x, y )

    if button == "LeftArrow":
        print( "left-arrow clicked!" )
        return
    if button == "RightArrow":
        print( "right-arrow clicked!" )
        return
    if button == "Minus":
        print( "minus clicked!" )
        return
    if button == "Plus":
        print( "plus clicked!" )
        return

• Run your program.
• Click on the menu symbols and observe the printouts in the console. You should be able to detects clicks on the

Menu-Driven Action

• Add a new method to your car that will move its body and its wheels by some distance dx in the horizontal direction, and dy in the vertical direction when called:

class Car:
    def __init__(self, x, y, w, h, color ):
        self._body = Rectangle( x, y, w, h, color )
        self._w1   = Wheel( x+w//4, y+h, w//4 )
        self._w2   = Wheel( x+3*w//4, y+h, w//4 )
        
    def draw( self, canvas ):
        self._body.draw( canvas )
        self._w1.draw( canvas )
        self._w2.draw( canvas )

    # move the car dx pixels to the right if dx is positive, dx pixels to the left if dx is negative.
    # move the car dy pixels down if dy is positive, dy pixels up if dy is negative.
    def move( self, canvas, dx, dy ):
        self._body.move( canvas, dx, dy )
        self._w1.move( canvas, dx, dy )
        self._w2.move( canvas, dx, dy )

• Make the call-back function move the car left or right when the user clicks on the lef- or right-arrow, respectively.

def mouseEvent( win, canvas, x, y ):
    global menu
    global car
    button = menu.buttonClicked( x, y )

    if button == "LeftArrow":
        print( "left-arrow clicked!" )
        return
    if button == "RightArrow":
        print( "right-arrow clicked!" )
        car.move( ... )    # figure out what to pass to this method!
        return
    if button == "Minus":
        print( "minus clicked!" )
        return
    if button == "Plus":
        print( "plus clicked!" )
        return

• make the car global in the main() function, the same way you made the menu global. This way the callback function mouseEvent() will be able to access the car object created in the main() function.