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List:       koffice-devel
Subject:    Re: [Uml-devel] Re: karbon/umbrello
From:       Andrew Sutton <asutton () cs ! kent ! edu>
Date:       2003-05-27 15:00:08
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> > > But how do you want to implement rendering?
> >
> > YourVeryOwnRenderingVisitor v.visit( *morph );

the clean way, yes, but i don't think its going to be very efficient for 
editing applications. for simple generators/exporters this is fine, but for 
karbon, kivio and umbrello, i don't think that's the best choice. there 
should be some kind of kpainter integration.

i think for editing or vector graphic manipluation applications you need a 
higher degree of responsiveness in the painting. changes should be immediate. 
you shouldn't have to re-visit the entire graph just to redraw a single node.

> Mabe I misunderstand something, but if you decouple KCanvasElement from the
> actual renderer, you have to
> make the document classes (KCanvasDocument / VDocument) a more complex
> class hierarchy than I thought.
> My idea was to make KCanvasDocument itself a rather "intelligent" class, at
> least it could handle rendering by calling the appropriate rendering
> methods from its canvas elements. Because the document knows enough about
> its elements, it could handle things like optimized rendering (drawing only
> the parts which are afected from the latest changes.
> I your proposal you seem to have to implement this functionality in
> children of KCanasDocument, i.e. in KarbonDocument, UmbrelloDocument,
> KiioDocument, separately?

these aren't issues we should be worried about right now. my primary concern 
is getting kpainter and opal in line. so i have somewhere to go on my 
umbrello work. i figure if i can have a good object hierarchy for drawing and 
a good rendering surface/api, then the canvas will be easy.

andy
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