Custom double buffer

26 Nov 2004 1:02 AM

Kuba Florczyk

Hi

I've got some problem doing double buffer.
Here is my problem:
I've got custom control on which i paint some data (chat messages, lets call
it ChatControl), this control is puted on a scrollable panel.
Of course i've set right styles on a ChatControl:

//styles
   this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
   this.SetStyle(ControlStyles.DoubleBuffer, true);
   this.SetStyle(ControlStyles.UserPaint, true);
   this.SetStyle(ControlStyles.ResizeRedraw, true);

Everything is ok,but i've got some performance problems. Chat messages
arrived in every 5 seconds, and i call on ChatControl Refresh(), so my
OnPaint method is called - and thats ok. But control is repainted more times
than on in every 5 second refresh: user used scroll, or something like that.

And now i want to made some additional double buffer, because i want to draw
remembered graphic (thru bitmap), than draw it again - because its neccesery
when i only refresh control. I know i should do something like this:

Bitmap bmp = new Bitmap(this.ClientRectangle.Witdh,
this.ClientRectangle.Height);
Graphics g = Graphics.FromImage(bmp);

and than i should draw on g

but there is a "small" problem - beacuse i know control size after i draw
something (thats depends at chat messages count)! so how i can get a bitmap
from my base graphics or how to create bitmap that will resize automaticly
to my graphic size ? Or .... maybe somebody got any idea?

regards
kuba florczyk

26 Nov 2004 10:22 AM

Bob Powell [MVP]

You should possibly consider manual double buffering. What you're doing is
essentially double buffering and then writing that the the systems
back-buffer so you might as well do it yourself.

Windows Forms Tips and Tricks has an article on double buffering and shows
you how to manage a back-buffer that changes size in response to the
OnSizeChanged method calls.

--
Bob Powell [MVP]
Visual C#, System.Drawing

Find great Windows Forms articles in Windows Forms Tips and Tricks
http://www.bobpowell.net/tipstricks.htm

Answer those GDI+ questions with the GDI+ FAQ
http://www.bobpowell.net/faqmain.htm

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Show quote

"Kuba Florczyk" <c***@poczta.onet.pl> wrote in message
news:%23GO1sP10EHA.3504@TK2MSFTNGP12.phx.gbl...
> Hi
>
> I've got some problem doing double buffer.
> Here is my problem:
> I've got custom control on which i paint some data (chat messages, lets
call
> it ChatControl), this control is puted on a scrollable panel.
> Of course i've set right styles on a ChatControl:
>
> //styles
>    this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
>    this.SetStyle(ControlStyles.DoubleBuffer, true);
>    this.SetStyle(ControlStyles.UserPaint, true);
>    this.SetStyle(ControlStyles.ResizeRedraw, true);
>
> Everything is ok,but i've got some performance problems. Chat messages
> arrived in every 5 seconds, and i call on ChatControl Refresh(), so my
> OnPaint method is called - and thats ok. But control is repainted more
times
> than on in every 5 second refresh: user used scroll, or something like
that.
>
> And now i want to made some additional double buffer, because i want to
draw
> remembered graphic (thru bitmap), than draw it again - because its
neccesery
> when i only refresh control. I know i should do something like this:
>
> Bitmap bmp = new Bitmap(this.ClientRectangle.Witdh,
> this.ClientRectangle.Height);
> Graphics g = Graphics.FromImage(bmp);
>
> and than i should draw on g
>
> but there is a "small" problem - beacuse i know control size after i draw
> something (thats depends at chat messages count)! so how i can get a
bitmap
> from my base graphics or how to create bitmap that will resize automaticly
> to my graphic size ? Or .... maybe somebody got any idea?
>
> regards
> kuba florczyk
>
>