[news.eclipse.platform.swt] Re: Canvas vs Composite Question....

["Emil Crumhorn" <emil.crumhorn@xxxxxxxxx>]

In your use case I would use a Composite to put all your Label and Text 
widgets in and then create a Canvas that does the border drawing via 
painting (You could use a Composite too really, however, Canvas would be the 
appropriate widget to subclass for drawing as you stated, and the Canvas API 
states as well). As a Canvas is a subclass of Composite it can do all the 
stuff a Composite can do, thus, you can put your original Composite 
containing all your Labels/Text widgets onto the Canvas and draw your border 
around it.

(By the way, I assume a Group-style border is not what you wanted, otherwise 
you could just use a Group widget as your parent composite and get a border 
around them.)

Hope that helps,
Regards,
Emil

"Kris Lyon" <kris.lyon@xxxxxxxxxx> wrote in message 
news:4647486a00282874b880689dc134fbf2$1@xxxxxxxxxxxxxxxxxx
> I'm just starting out doing some custom control development and I'm 
> running into what I hope is a simple problem.  From what I've read, I'm 
> fairly certain that I understand the situations where you should subclass 
> Composite vs Canvas.
>
>
> For example:
> I would like to make a composite control made up of existing swt widgets, 
> say a few labels and text boxes, however I'd like to surround them with a 
> custom border.
>
> If I subclass Canvas, im not sure how have the widgets display themselves 
> on the canvas.
>
> If I subclass Composite (which I believe is the right way to go) I can 
> either have the controls draw themselves, OR draw the border.  It seems 
> that if I set the layout on the Control the widgets that have been added 
> to the custom control will display, but the paintListener (which draws my 
> border on the composite) doesn't fire.  If no layout is set on the 
> control, the widgets don't display, but the paintListener fires and the 
> border is displayed fine.
>
> I'm working from memory here, so I apologize in advance for any obvious 
> programming errors...
>
> Any help would be appreciated...
>
>  -k
>
>
>
>
> public class MyWidget extends Composite {
>
>  public MyWidget( Composite parent, int style ){
>    super( parent, style );
>
>    Label first = new Label( this, SWT.NONE );
>    first.setText("One");
>    Label second = new Label( this, SWT.NONE );
>    second.setText("Two");
>    // If this line is commented out my paintControl method will be called 
> and
>    // I see only my custom rectangular border.
>    //
>    // If left un-commented, I see my widgets (labels) but no border.
>    setLayout( new FillLayout(SWT.VERTICAL) );
>    addPaintListener( new PaintListener() {
>       public void paintControl( PaintEvent e ){
>          MyWidget.this.paintControl(e);
>       }
>    });
>  }
>
>
>  public void paintControl( PaintEvent e ){
>     GC gc = e.gc;  // Draw my custom border surrounding both labels 
> here... }
>
>
> }
>