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REALbasic for Dummies
by Erick Tejkowski

Learning REALbasic through Applications
by Clayton E., Crooks II

REALbasic for Macintosh
by Michael Swaine

REALbasic Cross-Platform Application Development
by Mark S. Choate

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Build the Interface

This week's interface is really simple to create: one PushButton, one Canvas, and one Slider. When you add them to a window, leave their default names as is. (i.e. PushButton1, Canvas1, and Slider1).

• PushButton1 - Caption = "Plot"
• Canvas1 - width=500; height=400
• Slider1 - minimum=1; maximum=10

Arrange the interface any way you want. An example might look like this:

Source Code

Before you get started with the code for this project, you'll need to make a number of properties. Open the Code Editor for Window1 and add the following properties using Edit-New Property:

• f as double
• r as double
• rad as double
• t as double
• x as integer
• y as integer

The code this week is adapted from an existing Chipmunk BASIC project available here. Double-click PushButton1 and add the following code to its Action event:

  rad = 3.14159271180
  r = 180
  t = 90
  f = 0
  
  canvas1.graphics.foreColor=rgb(0,0,0)
  canvas1.graphics.fillrect 0,0,500,400
  
  while r > 1
    x = sin(t*rad*2)*r
    y = cos(t*rad*3)*r
    plot
    t = t+slider1.value110
    r = r*0.99991
  wend

Next, create a new method named Plot by choosing Edit-New Method. To this method, add the following code:

  
  x=x+250
  y=y+200
  
  if f=0 then
    canvas1.graphics.pixel(x,y)=rgb(255,255,0)
  else
    canvas1.graphics.foreColor=rgb(255,255,0)
    canvas1.graphics.DrawLine x,y,x-250,y-200
  end if

Conclusion

That's it for this week. Select Debug->Run to test your work. Try playing around with the various numbers in the source code to see what results you can produce. With a few more lines of code, you could save this picture for use as a nifty desktop image or for some other task. If you don't feel like creating the project by hand, you can download the finished project. See you next week!