No-Apply Mechanism for Creating Pipelines

The Problem

When creating visualization pipelines in ParaView, the GUI forces the user to hit "Apply" at every stage in the pipeline before another pipeline stage can be added. Thus to create a simple pipeline such as Reader -> Cut, the user has to create the Reader (or open the data file), then hit Apply, then create the Cut filter and hit Apply again. There are a few problems with this approach:

• The intermediate results are rendered. Even if the sphere had no interest in the output of the reader, he has to wait to see the generated rendering. This is not a huge problem since for really large datasets (based on the settings), this generally leads to rendering only a wireframe.
• The pipeline is not truly demand driven i.e. the reader, since it has no clue what pipelines may be connected, generally ends up reading the full dataset during the first Apply. Even if the Cut filter has means to tell what bounds it's interested in, that information is not available during the first Apply and hence the reader simply has to read everything.

The goal of this proposal is make it possible for the user to build pipelines without having to hit "Apply" or cause execution on the intermediate filters while creating the pipeline.