Add pause button to live view

[bilbofroggins]

*Issue number of the reported bug or feature request: #404 *

Describe your changes
P key to pause, and when paused, U key to unpause.
Couldn't see anything built in to rich live that will automatically do this, so I just split the TUI class into a layout class (TUI) and a data class (TUIData) so that we can snapshot the data when the user pauses and show the snapshot while continuing to write to the live version of data in the background (in update_snapshot)

Previously used to put the whole _snapshot (Iterable[AllocationRecord]) within the TUI class and then extract what we cared about in the render stage (get_body) but there's a bunch of extra stuff in there it seems like is not needed. Instead, extracting the data we need in update_snapshot and then get_body can just pull from TUIData.

Testing performed
Tested an application that has a couple threads - made sure you can still arrow through them.
Sorting still works and carries over paused/unpaused states.
Ran pytest locally.

Closes: #418

[pablogsal]

I have not reviewed the code yet, but I noticed that when running memray run --live -m test test_asyncio and pausing, hitting U or P to unpause doesn't continue the process and the table does not keep updating for me.

[pablogsal]

Update: seems that it only updates when I keep pressing U

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: +0.13 🎉

Comparison is base (3ca2337) 84.85% compared to head (37bc373) 84.99%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #418      +/-   ##
==========================================
+ Coverage   84.85%   84.99%   +0.13%     
==========================================
  Files          29       29              
  Lines        3631     3631              
==========================================
+ Hits         3081     3086       +5     
+ Misses        550      545       -5     

Flag	Coverage Δ
cpp	84.99% <ø> (+0.13%)	⬆️

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see 3 files with indirect coverage changes

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[bilbofroggins]

Update: seems that it only updates when I keep pressing U

Oh interesting, I'm not seeing that on my side but I just put in a flag to prevent data from being copied a bunch while holding the keys down - and pushed that up. Possibly related?

[pablogsal]

Update: seems that it only updates when I keep pressing U

Oh interesting, I'm not seeing that on my side but I just put in a flag to prevent data from being copied a bunch while holding the keys down - and pushed that up. Possibly related?

Unfortunately still happens on my end after the latest commit Hummm, I think my terminal was busted or something because after retrying it works as expected! Sorry for the confusion @bilbofroggins

[pablogsal]

Thanks a lot @bilbofroggins this looks fantastic. Very good job! 🚀

Can you maybe add a small test that checks the pause() and unpause() functions simulating an update in the middle?

[bilbofroggins]

Thanks a lot @bilbofroggins this looks fantastic. Very good job! 🚀

Can you maybe add a small test that checks the pause() and unpause() functions simulating an update in the middle?

👍 Added

[pablogsal]

Will make another pass tomorrow! Thanks for the ping

[pablogsal]

LGTM! Excellent work @bilbofroggins ✨

Thanks a lot for contributing to memray :)