[vtkusers] Design Gripes

[Ken Martin]

I'll address only one issue here since the others have been beat on in
the past. The void (*)(void *) stuff is all old style code left in for
backwards compatibility. I would gladly yank it out but... then a
bunch of people would (with good reason) scream that their code no
longer works. The new style is to use the command observer design
pattern which is implemented in vtkCommand.h. It supports callbacks
with state etc. The examples in VTK/Exmaples/Tutorial/Step2 all show
callbacks using the new observer style. The VTK 4.0 user guide also
only discusses the new style of observer not the old style void (*)
...  Unfortunately leaving the old style code in for backwards
compatibility can be confusing and misleading to new users. In an
ideal world someone should modify the comments above the old style
code to indicate that it is no longer the preferred way to do this.

Thanks
Ken


> Vector3D class. Also, it would be really nice if call back functions
> were function objects that can maintain state. programming
> with function
> pointers like void (*)(void*) and associated argument
> delete functions
> seems clunky at best. I know there are constraints related to the
> underlying graphics libraries. but this still could be
> implemented with
> no more than an additional indirect function call overhead.
> would that
> be so bad for performance? etc..
>
> I found the book helpful in getting to know the mindset of the
> designers. any plans to provide an updated edition for
> vtk4? Are there
> any other design documents that cover vtk4?
>
> best,
>
>
> --
> Murad Nayal M.D. Ph.D.
> Department of Biochemistry and Molecular Biophysics
> College of Physicians and Surgeons of Columbia University
> 630 West 168th Street. New York, NY 10032
> Tel: 212-305-6884	Fax: 212-305-6926
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