PRB: MediaView: Jump to SubTopic Fails

• MediaView version 1.0

SYMPTOMS

When attempting to jump to a subtopic, MediaView may jump to the enclosing topic but will not correctly scroll the media view to the location of the subtopic.

CAUSE

In order to jump to a subtopic, you must acquire a virtual address (VA) for that topic. To get this, you might call vaMVConvertContextString() which will convert a context string to a VA. Then you would pass the VA to fMVSetAddress() which would cause the jump to occur.

The problem is that context strings are not in and of themselves guaranteed to be allocated a new VA. Normally, when this problem occurs it is happening because the subtopic is getting assigned the same VA as either a preceding subtopic or perhaps the topic itself. The end result is that the media view gets scrolled to an unexpected location.

RESOLUTION

To ensure that a new VA is generated for each context string, you must ensure that the context string resides in a new paragraph and that it has some paragraph formatting that is distinct from the previous paragraph.

Paragraph formatting includes: justification, first-line indent, spacing, borders, keep-with-next, and keep-together. In addition, tab stops are also considered part of paragraph formatting (at least for the purpose of determining VAs). Font changes are classified as character formatting and will not affect VA generation.

One simple solution to ensure that a new VA is created for each subtopic is to insert a phantom tab stop for each new subtopic. Just be sure that the tab stop is different from the preceding paragraph.

STATUS

This behavior is by design.

MORE INFORMATION

In MediaView, you can include subtopics within a given topic by arbitrarily inserting a pound-sign (#) footnote to mark the location of the subtopic. Jumps to subtopics should cause a jump to the enclosing topic with the media view scrolled to the point where the subtopic context string was authored.

REFERENCES

MediaView Documentation Player.