GDI+ (onpaint override) and autoscroll

[BKQc]

I'm trying to develop an application that draws a bar graph on a panel. Depending on the graph resolution, the graph have to be larger that the viewport so what I did is create usercontrol within my project, define the usercontrol autoscroll to true and then add a panel in it on which I draw my bar graph. For the paint event, I overriden the onpaint sub of the usercontrol in which I get a ref to the graphics of the inenr panel (my drawing plane).

Up to there, everything works as expected. The problem occurs if I try to scroll the scroll bar: the onpaint sub doesn't get called. I looked at a sample from MS (

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dndotnet/html/designsurface.asp)

and tried to find what was the difference between this application and mine (since they support autoscroll and that it works fine) and I found nothing except maybe the fact that they don't use an inner panel.

So now, 3 questions:
1- Is it better to override the onpaint sub or use the paint event (and why)?
2- How can I directly paint on the usercontrol and still get the autoscroll to show scrollbars (since it won't know to what extent I'm drawing)?
3- Why isn't the sub called on scrolls?

Thank you!

 

[ThatRickGuy]

1) I use OnPaint to handle items that need to change for the paint event. I use Paint to do the actual painting functionality.
2)Can you go with your original solution, catch the autoscroll event and call your UserControl.Refresh method? .Refresh should raise a paint event
3)No idea.

-Rick

VB.Net Forum forum796 forum855 ASP.NET Forum
I believe in killer coding ninja monkeys.

 

[BKQc]

There's no event for autoscroll...
What do you mean by "handle items that need to change for the paint event"?

 

[ThatRickGuy]

Never mind, I was having one of those brain dead friday morning moments.

-Rick

VB.Net Forum forum796 forum855 ASP.NET Forum
I believe in killer coding ninja monkeys.