[Mono-winforms-list] System.Windows.Forms.Form:PaintEventHandler is called only when you increase the form

[Kornél Pál]

Hi,

This is the expected behavior of Win32 so this is MS SWF behavior as well
and it is of course the expected behavior of MWF.

Windows only stores the bitmap you see on the screen. When a part of a
window becomes visible either because you uncovered it by moving another one
or increased its size you have to paint that area but only that area that
saves memory and speeds up drawing as well.

As Jackson pointed out if you want to redraw the entire form you have to
change default behavior. Note that there is a protected Control.ResizeRedraw
property (Form is a Control). The easiest way to get the behavior you want
is to add

this.ResizeRedraw = true;

to the constructor of the form.

By using the line

e.Graphics.Clear(Color.FromKnownColor((KnownColor)((i = (i + 1) % 167) +
1)));

in the Paint event of the form you will see how a window is drawn. Note that
you will have to have a field named i in the form class.

Kornél

----- Original Message -----
From: "Jackson Harper" <jackson at ximian.com>
To: "Alexander Reiter" <r.alex at utanet.at>
Cc: <mono-winforms-list at lists.ximian.com>
Sent: Tuesday, November 01, 2005 9:23 PM
Subject: Re: [Mono-winforms-list]
System.Windows.Forms.Form:PaintEventHandler is called only when you increase
the form


> On Tue, 2005-11-01 at 21:13 +0100, Alexander Reiter wrote:
>> hi all,
>>
>>    I've a problem with the System.Windows.Forms.Form Paint Event. I am
>> calling the paint event with the following
>>    line: this.Paint += new PaintEventHandler(Draw_Graphics); the
>> Draw_Graphics part is simple drawing some
>>    curves and lines to the Form.
>>    My problem is now, that as soon as I start to resize the form the
>> Paint event is only called when I increase the
>>    form size. When I decrease the size nothing is happening.
>
> I believe that is the intended behavoir. Have you tested on windows?
> You can do a SetStyle (ControlStyles.ResizeRedraw, true) or you can
> subscribe to the SizeChanged event and do drawing there.
>
> Cheers,
> Jackson
>
>
>>    I just started to get deeper into C# and mono + forms, so any hint
>> where I can start to search ?
>>
>> br
>> alex
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