A long time ago - in a place far, far away (sorry, couldn't resist), I remember seeing a cool little program on the Apple 2c that taught kids programming by having them move a little turtle around a screen. This was based on the Logo programming language. Someone mentioned it on a thread yesterday in CF-TALK, and me being the crazy person I am I decided - what the heck - let me try to recreate this in ColdFusion.
So with that - I present CF_LOGO. This is a custom tag that lets you create a canvas and then issue commands for the turtle (or pen) to draw. For example:
<cf_logo>
forward 100
right 90
forward 60
right 90
forward 90
right 90
forward 50
left 90
forward 99
home
forward 100
</cf_logo>
This tells the turtle/pen to move, turn, move, etc. The home command simply returns the turtle to the center of the canvas. This creates the following image:
The language supports many operations, but my tag supports the following commands:
| forward/fd X | Move the pen forward X pixels. |
| right x | Turn to the right X degrees. Currently X is ignored and all turns are 90 degrees. |
| left x | Turn to the left X degrees. Currently X is ignored and all turns are 90 degrees. |
| clearscreen/cs | Clears the screen. |
| home | Moves the pen to the center of the canvas. |
| penup/pu | Lifts the pen. Any future drawing operations won't be displayed. |
| pendown/pd | Lowers the pen. Any future drawing operations will be displayed. |
The custom tag allows you to specify a height and width, a background and pen color, and you can even tell it to return the image as a CFImage object:
<cf_logo variable="test">
forward 100
right 90
forward 60
right 90
forward 90
</cf_logo>
<cfset imageScaleToFit(test,100,100)>
<cfimage action="writetobrowser" source="#test#">
Finally, I've set up a demo that lets you issue commands one at a time, to basically draw a picture online:
http://www.coldfusionjedi.com/demos/logo/test3.cfm
You can download the test files, the demo, and the custom tag below.
And yes - this is a complete and utter waste of time. That's what made it fun.