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hide object

Dalibor Toth
Ranch Hand

Joined: Jul 16, 2001
Posts: 38
If I draw, say, a circle, how do I make it hidden and, of course, visible again.
Manfred Leonhardt
Ranch Hand

Joined: Jan 09, 2001
Posts: 1492
Hi Dalibor,
You can do it 2 different ways.
1. Draw it with some color (not background) to show. Draw it with background to hide it.
2. Set XOR graphics mode. Draw it with some color will now toggle it from shown to hidden.
Dirk Schreckmann

Joined: Dec 10, 2001
Posts: 7023
There are lots of ways to do what you are asking. Here are a few of them:
You could just draw a new circle on top of the original, this time using the background color.

You could use clearRect(x, y, width, height) to clear a rectangle (draw a filled rectangle of the background color) surrounding the circle.

Note: The cleared rectangle width and height are set to be one pixel wider and taller than one might think is necessary. Play with it to convince yourself that this is necessary.
You could use an image file containing a circle and another blank image file and display the blank image on top of the circle image.

You could use double-buffering techniques to first draw to an offscreen image buffer and then display that image when the time is right. This is especially useful when you need smooth animation effects.

Note: There are cleaner implementations of Double-Buffering, but this one is a beginning.
Hopefully something here helps you.
Good Luck,
-Dirk Schreckmann
[ January 31, 2002: Message edited by: Dirk Schreckmann ]

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Dalibor Toth
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Joined: Jul 16, 2001
Posts: 38
Guys, all I can comment is thank you!
I agree. Here's the link:
subject: hide object