Hook Suggestion for vtkProcessObject

[John Biddiscombe]

Dear vtk people,

When a DataObject or Filter calls Update(), a sequence of Update() calls
can propagate backwards through a chain of filters.....

If these filters are 'connected' to a series of GUI 'widgets' holding
parameters, it would be lovely to have an extra hook similar to
StartMethod,EndMethod and ProgressMethod called during a check on Update()
- CheckUpdateMethod - this would give the GUI a chance to write any
modified values into the ProcessObject and set 'Modified' just before the
Update function is executed and thus guarantee that vtk-filters are
synchronized to their GUI counterparts.

This would be a very useful addition - however it might be tedious adding a
call to CheckUpdate - because Update is defined in subclasses of
ProcessObject and each (eg source) implements its own Update routine.

We (RCRU at RAL) have constructed a series of GUI holders for wrapping
filters (and generating wrappers semi-automatically) and connecting them
via drag and drop (very similar to the principia mathematica demo out
there) and it would make them bullet proof if a CheckUpdateMethod was
available. I can make a demo exe available if anyone is curious...

John B



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