GraphicsCcontext and bounds - screenshot.gif (0/1) 
Author Message
 GraphicsCcontext and bounds - screenshot.gif (0/1)

Hi All

I need to display some elements in editor window. Elements and their
wrappers are contained in CompositePart. Now, I have tried to display
border around each element, so I modified displyOn: method of wrappers
(I have my own wrapper class and I have to avoid to use

The inciminated method follows: (DocumentElementWrapper is subclass of
DocumentElementWrapper>>displayOn: aGraphicsContext
        | pl |
        super displayOn: aGraphicsContext.

        aGraphicsContext paint: ColorValue red.
        pl := Polyline fromRectangle: self bounds.
        pl displayStrokedOn: aGraphicsContext.

        aGraphicsContext paint: ColorValue blue.
        pl := Polyline fromRectangle: self preferredBounds.
        pl displayStrokedOn: aGraphicsContext.

Result is in attached image.

Can some explain this behavior? And can some give me short
introduction to concept of bounds and preferredBounds? (My own view
based on reading methods and class comment leads in thins broken

Thank a lot
        Petr Bouda

Tue, 01 Feb 2005 15:10:48 GMT  
 GraphicsCcontext and bounds - screenshot.gif (0/1)

>Can some explain this behavior? And can some give me short
>introduction to concept of bounds and preferredBounds? (My own view
>based on reading methods and class comment leads in thins broken

The basic difference between bounds and preferredBounds is that bounds is the
visible bounds of the view, while preferredBounds is the size of the actual
object being displayed. Thus, in a text, image, or list when the size of the
elements being displayed is larger than the box it displays in (i.e. when
scrollbars are in use), then the preferredBounds will be bigger than the bounds.

However, what you are seeing is something more. The only place where bounds or
preferredBounds tend to make any real sense is when you ask the view. The
various wrappers and composites translate these values adding or subtracting or
combining values.

My suggestion, although not having the whole thing in front of me, I'm just
guessing, is to ask the "visual" elements for their bounds, and use those as
your drawing basis.

                                And So It Goes

Samuel S. Shuster [|]
VisualWorks Engineering, GUI Project
Go Smalltalk!

Tue, 01 Feb 2005 23:53:36 GMT  
 [ 2 post ] 

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