Timer In Canvas - Won't Activate Depending on Invalidate Location

General
1

I have a strange issue.
I’ve subclassed a canvas and I’m trying to emulate a textbox, therefore using a timer to create a blinking cursor.

I have a timer(xojo.core.timer) as a private property of the canvas, the class’s constructor sets it up, adds the handler. Then, a mouse click down event will change the timer’s mode to multiple… should start the timer.

The handler simply flips a boolean value and then calls a method which draws the textbox with or without the cursor to a picture, Then, invalidate is called to Paint the picture.

Sub Handler(myTimer as Xojo.Core.Timer) show = not show DrawTextBox //invalidate end sub

If Invalidate is called from the Handler it works

If Invalidate is called inside DrawTextBox it seems to kill the timer.

Sub DrawTextBox() Buffer = new picture(width, height) dim g as Graphics g = Buffer.Graphics g.Draw... //do stuff if show then //draw cursor... end if invalidate //this here seems to mess up the timer end sub
Strange and Frustrating.

Lastly, I created a dumbed down version to try to reproduce it. Making the same calls and the same code flow. I can’t reproduce the behavior.

Any tips on how else to debug this?

2

Don’t call Invalidate or Refresh from a Paint event or any methods that are called from it (drawing code). You’ll potentially get yourself into an endless loop depending on how aggressively it redraws.

3

Hey Greg, I see what you’re saying, and I think that’s the issue, but my main drawing code is not in the paint event as I buffer to a picture and then paint the picture.

Something in my drawing code is invalidating the canvas.

What else can trigger the paint event?

4

What version of Xojo are you using?
What does your paint event look like?

5

Thanks all for the provocative comments. I found that my Paint Event was calling a redundant method which was calling Invalidate

Problem solved.