Re: Control Painting

The Paint event will send you a Graphics object - you should use that to
paint your figure rather than create a new one

Also public void DrawFigure should only invalidate the canvas.

This will cause a Paint event to fire, and it's in there that you should
use the passed in Graphics object to paint to.



> -----Original Message-----
> From: Discussion forum for developers using Windows Forms to build
apps
> and controls [mailto:[email protected]] On Behalf Of
> Peter Osucha
> Sent: 22 May 2007 22:16
> To: [email protected]
> Subject: [DOTNET-WINFORMS] Control Painting
> 
> One more for you gentlemen (and ladies)...
> 
> 
> 
> I have a class that accepts a 'canvas' in its constructor (a reference
> which is held in the class with the variable '_canvas').  The canvas
is
> any control that has a Graphics object that can be drawn to (normally,
> I
> use a System.Windows.Forms.Panel object that is placed on a form).
> 
> 
> 
> The main method in this class is called 'DrawFigure' and it is
intended
> to do all the drawing of the 'Figure' the class is working with.
> 
> 
> 
> I have added several event handlers to the class - probably most
> importantly is a handler for the _canvas.Paint event.  And this is
> where
> I lose a bit of understanding.
> 
> 
> 
> In the event handler I have hooked to _canvas.Paint, I call the
> 'DrawFigure'method - I don't do anything else.
> 
> 
> 
> The 'DrawFigure' method looks like...
> 
> 
> 
>         public void DrawFigure()
> 
>         {
> 
> 
> 
>             _canvas.SuspendLayout ( );
> 
> 
> 
>             Graphics g = Graphics.FromHwnd ( _canvas.Handle );
> 
> 
> 
>             g.Clear ( _canvas.BackColor);
> 
>             g.TextRenderingHint =
> System.Drawing.Text.TextRenderingHint.AntiAlias;
> 
>             g.TextContrast = 12;
> 
> 
> 
> // blah, blah, blah code to draw what I want...
> 
> 
> 
>             _canvas.ResumeLayout ( );
> 
> 
> 
>             // Always dispose fo the Graphics object.
> 
>             g.Dispose ( );
> 
>         }
> 
> 
> 
> Now to my question...  I want to use another control for the canvas
> (FWIW, it's a Infragistics.UltraGroupBox - not that that should
> necessarily matter).  However, I must be doing something screwy with
> the
> painting since my drawing doesn't show up on this new 'canvas' until I
> click on a part of it (and then only part of drawing shows).
> 
> 
> 
> I don't understand the event chain that is going on and what and when
I
> should probably be painting.  Any suggestions about where to look get
> my
> class drawing correctly on this new 'canvas'?
> 
> 
> 
> Peter
> 
> 
> 
> 
>