[Smtk-developers] Harmonizing ParaView and SMTK Views

[David Thompson]

Hi all,

I've been examining the issues involved with integrating SMTK views into ModelBuilder (and thus ParaView). Overall, PV views and SMTK views are not incompatible, but do have some different assumptions.

* PV views expect most data to live on the server, while SMTK's current views (the attribute view and its specialized child that presents operator attributes) live on the client.
* SMTK's Qt extension expects to manage a single attribute-view widget per qtUIManager. It's unclear to me whether creating multiple qtUIManagers attached to the same attribute system would accomplish.
* We could add a new SMTK view type for PV render windows, but that could make maintaining ModelBuilder more complicated because changes to PV's render view might then require SMTK changes.

I have a prototype showing some progress (screenshot attached; branch on gitlab.kitware.com/dcthomp/{smtk,cmb}.git, named attribute-view in both repos). What these branches do is
1. enable multiple views by not overwriting qtCMBMainWindow.ui's central widget.
2. add a new PV behavior that exposes PV's empty-view type-selector without also adding point/cell-selection buttons to the render view (which we don't want by default because CMB is in block-selection mode by default).
3. create a new subclass of ParaView's pqView named pqAttributeView (pqSMTKView would be more accurate); a server-side view object (an instance of vtkSMTKAttributeView) associated with the proxy; and a dummy, XML-only representation for this view. Unlike other views in PV, this view does not track the active dataset; instead it is passed a qtUIManager (more on this below) whose top-level SMTK-view it displays on the client.
4. configure pqAttributeView to emit a signal when it is initialized; ModelBuilder connects this signal to SimBuilder so that when a new template is loaded every existing pqAttributeView is informed of the new qtUIManager.

The branch does *not* 

1. incorporate all of John and Haocheng's multi-view work (yet).
2. disable the dockable "Attribute" panel.

The issues that need to be resolved are:

1. A qtUIManager instance (such as the one created by SimBuilder when loading an attribute) can have only a single QWidget view, but ParaView allows multiple views of the same type. So, right now if you create 2 SMTK attribute views, all but the most-recently-created one will be a blank QWidget.

2. The signal connecting SimBuilder to pqAttributeView instances assumes that new pqAttributeViews should always display the currently-loaded simulation -- but another use case would be to display the active model's operator view, or more generally to allow views of multiple attribute systems at a time. Yet another use case would be to allow views to focus on a particular attribute in an attribute system (e.g., a material view, a BC view, an IC view, a solver-parameter view). In this latter use-case, there would not be a single, top-level view in an attribute file, which goes against the current convention.

3. Either we need to expand SMTK's ViewInfo objects to allow a view to be a render-view of model-entities or change the PV behavior mentioned above to be more explicit about what types of PV views we allow.

4. There's still not a clear path for items in a pqAttributeView's attribute to employ server-side PV widgets. The difficulty is that PV uses a dock-panel (the property inspector) to enable/disable widgets, which are only shown for the active pipeline object. However, in ModelBuilder, items in pqAttributeView which might be associated to 3D widgets would display those widgets in a different PV view (the render view). If we change visibility of a 3-D widget in the attribute view, which render-view would that affect?

	David

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