Duration bounding box moves with refresh

[joe-elliott]

Everytime I refresh the app the duration bounding box slowly moves to the left:

This behavior makes sense b/c if the user drew an arbitrary box then it should move along with data. However, it's also confusing. Currently we always have a bounding box drawn by default when investigating duration. So the following steps result in a slowly moving box across the screen:

1) Click duration 2) See bounding box that creates the concept of "slow" traces for the list, structural and comparison tabs 3) Add filters, do things, and eventually refresh to get the latest data 4) The box mysteriously moves backward off the screen

I like the idea of always showing the box since it defines the behavior of all the duration tabs, but I'm wondering if we just want a threshold you can drag up and down instead of the ability to draw a free form box. It seems like the behavior of the app would be more easily understood.

Here is the screen after writing this issue up. Presumably it would eventually move off the visible area entirely:

[joe-elliott]

Similarly the following steps create a confusing experience.

1) Range is set to last 15 minutes 2) Click duration, do other things 3) Set range to last 1 hour

You can imagine other scenarios where the user is changing duration/time range and this would get weird. The most straightforward choice seems to be to change this to a horizontal threshold bar you can drag up and down to set the "slow traces" threshold.