Turning applications into applets

Many of you have used JyScript to make applications that you now want to turn into applets. Here's an example that shows an easy way to do it.

We earlier made an animation that moved a box across the screen. Here is the code: 

from JyScript import *

x = -1
def draw(p):
    p.beginpage()

    p.center()
    p.scale(50)
    p.box(x, -1, 2, 2)
    p.fill(0, 0, 1)
    p.stroke()

    p.endpage()

def step():
    global x
    x += 0.02
    refresh()

settimer(25, step)

def begin():
    starttimer()
addbutton("Start", begin)

def pause():
    stoptimer()
addbutton("Stop", pause)

def reset():
    global x
    stoptimer()
    x = -1
    refresh()
addbutton("Reset", reset)    

openframe(200, 200, draw)

To make this into an applet, we won't need a frame anymore so remove the openframe command. 

#openframe(200, 200, draw)

Suppose that this code is in BoxAnimation.py. Define an applet file BoxAnimationApplet, where we import BoxAnimation, like this. 

from JyScript import *
from javax.swing import *
import BoxAnimation

class BoxAnimationApplet(JApplet):
    def __init__(self):
        layoutapplet(200, 200, BoxAnimation.draw, self)

Remember that the name of the file must agree with the name of the class so this file should be called BoxAnimationApplet.py. You may test your applet by including the command 

testapplet(BoxAnimationApplet())

When it works well, remove the testapplet command and build a jar file by typing this on the command line. 

jythonc -j boxanimation.jar -c BoxAnimationApplet.py

Finally, construct your HTML tag: 

<applet 
  code=BoxAnimationApplet 
  width=200 
  height=240
  archive=boxanimation.jar>
</applet>

If your application has several panels called, say, left and right, you may put them into the applet with 

        layoutapplet([BoxAnimation.left, BoxAnimation.right], self)