Sub-activities overlap in the timeline view

[jtrimble2100]

I created an activity with two sub activities, all with the same duration. The sub-activities overlap. See the screen grab.

https://docs.google.com/a/nasa.gov/file/d/0B8yT2AXIcluCYjhicGU4Y3h3YjQ/edit?usp=sharing

[VWoeltjen]

This appears to be a side effect of #42

[VWoeltjen]

Based on this, definitions for activity constraints have been revised

• It is okay for subactivities to overlap temporally (not visually)
• An activity should expand as necessary to fit its subactivities
• Top-level activities should be in separate "blocks" (line-separated sets of rows)
• Overlapping subactivities should be moved down to separate "rows" as necessary to avoid overlapping visually. These rows may be the same as the ones used for deeper sub-activities. There may be some visual ambiguity between peer subactivities and nested subactivities in this case, but this is fine for now
• Decisions should act as if they are linked to whichever two activities immediately preceed or follow them in a row. This includes expanding to fit, pushing, and pulling those activities. There are some "holes" in this strategy, but for now we assume that the user will not create object graphs complicated enough for this to become an issue

Since this will remove most of the "push" style behavior currently associated with sub-activities, the solution to #27 probably needs to be reconsidered. That is, the user will much more often be dragging sub-activities such that they overlap, and waiting until the gesture is complete to reorder the rows is probably not desirable. Since we don't want the activity itself "moving" out from under the user's mouse, maybe other activities on the same row should move out of the way instead?

It is probably advantageous in this context to give each decision (along with only the two (sub-)activities it separates) its own row, such that dragging other objects doesn't alter row assignment mid-drag and create confusion about which two activities a decision separates

[harleigh]

Verified in hackathon 9/16/13