Delaying control repaint. Is it possible?

[Benton]

Hi there,

Using a foreach, I want to iterate (make visible) all the tabpages of a
tabcontrol, in order to activate the databinding of the controls in each
tabpage.

Is there a way to delay/disable the repainting until the iteration is done,
so the user doesn't see the tabpages switching? Something like:

-Disable control repaint in the form
-Iterate the tabpages
-Enable control repaint (and then the last tabpage activated is shown
instantly)

Regards,

-Benton
Using VS 2005 Beta 2

 

[Guest]

Is there a way to delay/disable the repainting until the iteration is done,

so the user doesn't see the tabpages switching? Something like:

-Disable control repaint in the form
-Iterate the tabpages
-Enable control repaint (and then the last tabpage activated is shown
instantly)

I struggled with a similar problem and came to the solution described below.
My setting is a rich text box (rtb) with many updates for highlighting, and
I wanted to avoid flicker associated with each update.

The idea is to handle the Invalidated event for the rtb. You may need to
handle it for just the tab control or, or maybe for each page, or maybe each
control - I dont know. In the Invalidated event, I call the win32 api
ValidateRect to make windows think it does not need to paint the control.
You need something like this:

Friend Declare Function ValidateRect Lib "user32" ( _
ByVal hWnd As Integer, _
ByVal lpRect As Integer) _
As Integer

and this:

ValidateRect(MyControl.Handle.ToInt32, 0)

where MyControl is a control (rtb in my case, something else in yours).

To put all this together, I have two boolean variables associated with the
rtb, a frozen flag and a dirty flag. When I want to inhibit painting, I set
frozen to true and dirty to false. In the Invalidated event, I do nothing if
not frozen, otherwise I call ValidateRect and set the dirty flag to true. To
resume painting, I set frozen to false, and if dirty, I Invalidate the rtb.

There may be a better way, but all other stabs I tried either failed or had
some side effect (eg a different kind of flicker).