Thanks for the suggestion Mike.
Cheers, solly
On Fri, 27 May 2005, Mike Tammerman wrote:
1. Retrieve all items from the canvas with QCanvas.allItems() method,
then make a set with the points of the item. Call it A.
2. Make a full set with all the points in the canvas. Call it B.
3. Get the difference. (B - A)
If your items are as simple as rectangels, it would be trivial.
Mike
On 5/27/05, Solly Brown <[EMAIL PROTECTED]> wrote:
I've got a qcanvas with a number of canvasitems moving about on it. I need
to efficiently identify which areas of the canvas are empty (ie. don't
have any objects on them).
The simplest implementation is to lay down a grid of qpoints on the
canvas, and then just check whether there are collisions with each point
-- if there are no collisions then that particular point area is empty.
The problem with this is that it's really slow... a 40x40 grid has 1600
points and looping through all of them and calling 'collisions' on each
one makes my display slow to a crawl.
Can anyone suggest an efficient way of identifying which points on a grid
are clear (don't have collisions above them)?
Thanks for your help....!
Solly
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