#167 scrolling to selected annotations causes problems

[Philip Ogren]

The selection and temporary selection of annotations can cause the scrollbar to jump around. This can be disorienting and slow down annotation for a variety of reasons. One use case is for that of annotating coreference chains that may span an entire document (i.e. - the chained references for a single chain may exist throughout the document). In order to add a noun phrase to a coreference chain, you must first select the coreference chain and then add the noun phrase as a slot value. This is problematic if you select a chain whose first reference is near the beginning of the document and the noun phrase you want to add is near the end because the scrollbar will jump to the top of the page when you select the coreference annotation and then you must navigate back to the location of the noun phrase. A similar problem happens when an annotation is temporarily selected in the course of finding an annotation. When you mouse over a selection in the context menu the annotation will be temporarily displayed and the scrollbar may move anywhere. If you abandon the context menu (or the annotation picker dialog) the scrollbar will stay wherever it happen to leave off from temporary selections. This may be *very* disorienting and undesirable.

There are two things that can fix these problems:
1) Provide 4 scrolling options for the selection of an annotation
- ensure visibility of the first slot that appears in the text or the span of the annotation itself, whichever comes first.
- ensure visibility of the last slot that appears in the text or the span of the annotation itself, whichever comes last.
- do not scroll when a new annotation is selected
2) Ensure that the original location of the scrollbar is reset after temporary selection of an annotation. When you are done mousing over annotations the scrollbar should snap back to where it previously was.