Sleeping execution

General
1

Me: Xojo 2021v3, M1 mac mini, MacOS 15.2

My app draws stuff to a canvas: (called from the canvas Paint(g) event)
for i = 0 to 100
g.DrawLine(2i, 5i, 10, 20)
next

This works fine. What happens is that the result of all the drawing appears instantly. I assume this is because the computer is really fast. Maybe some other reason for appearing instantly (buffering?)

What I want to have happen is to pause execution between the drawing the items:
for i = 0 to 100
g.DrawLine(2i, 5i, 10, 20)
SleepCurrentThread(1000)
next

But this seems to get lost. (looping?)

Is there any way to accomplish the goal of seeing items being drawn to a canvas individually, with a short pause between their appearances?

Is there some problem with
self.Show, calling this loop from a dialog box, etc?

2

Are you doing this in a thread? If not, I’m not sure what the SleepCurrentThread will do.

If it’s not in a thread, suggest you put it in one. You won’t be able to put the g.Drawline in the thread through, so your logic will get harder.

3

You should read the series of articles I wrote on animation in Xojo. It’s best to use a timer and draw in steps. There are other ways to accomplish this, but you’re bound to run in to other issues.

Animating Xojo, Part 1
Animating Xojo, Part 2
Animating Xojo, Part 3
Animating Xojo, Part 4

4

you could sub class a canvas, add a property for your iteration.
invalidate (EraseBackground =False) this canvas by a timer
draw a line at paint event with the help of your property (location)
change your property as example Me.Y=Me.Y+1

5

Your text implies to me that you have a wrong concept of a paint event. That is being called whenever it is necessary to refresh a control, so everything it should be used for is to (re)create the looks of the control. Its content will be shown when it is finished but not while drawing. If a paint event takes long to finish, the result will be a bad screen refresh rate but not an animation.

A Canvas’ Graphics object is not an image buffer. Or rather a volatile one which will be cleared when the next screen refresh is started.
With that in mind, Anthony’s series should give you all information necessary for your task.

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