feat: Live mode button widget

[fdrgsp]

Creating a new general purpose two-state (on-off) Live mode QPushButton widget.

It works with new startContinuousSequenceAcquisition and stopSequenceAcquisition events signals added to pymmcore-plus in PR https://github.com/tlambert03/pymmcore-plus/pull/115.

When the button is toggled on, a continuous Sequence Acquisition is started (using a new pymmcore-plus startContinuous Sequence Acquisition method) and a starting signal is emitted. In main_window the signal is connected to the _toggle_live function where the new frames are added to the napari viewer through a QTimer.

When the button is toggled off, the Sequence Acquisition is stopped (using a new pymmcore-plus stop Sequence Acquisition method). The connected 'stop' signal connected to main_window will stop updating the napari viewer and resets the QTimer.

[ianhi]

When toggled on, a signal is emitted (_emitFrameSignal) through a QTimer. In main_window the signal is connected to the update_viewer function.

@tlambert03 @ianhi Do you think it can be a valid solution?

This is a really good start! But I think we can go farther in the decoupling if we can stomach adding a new core signal. I think my ideal would be:

1. core gets the new signals: continuousSequenceAcquisition[Started/Stopped]
2. Live button is only responsible for:
   • stopping and starting the sequence
   • Temporarily pausing the acquisition when the exposure is updated
     (actually this could maybe even be moved onto core)
3. main_window listens to the new signals and starts its own QTimer based on the exposure

This works out if all listeners call getLastImage because that doesn't actually remove anything from the circular buffer.

I think that that's more or less analogous to what your doing with the snap button. This is also y preference because it feels like a cleaner separation of concerns. The live button is just responsible for toggling a single state on core - not managing timers and emitting data. Ideally the only place other components receive data from is the core.

Alternatively, we can push the timer logic into the button as you've done now. But in that case I think we should:

1. make the signal public
2. consider changing the name - in this case it's really more of a live_manager than a button.

[fdrgsp]

some tests are failing because of the new signals not yet added to pymmcore-plus.

[codecov]

Codecov Report

Merging #148 (d7691a1) into main (2384b6d) will increase coverage by 0.54%.
The diff coverage is 85.52%.

@@            Coverage Diff             @@
##             main     #148      +/-   ##
==========================================
+ Coverage   82.68%   83.23%   +0.54%     
==========================================
  Files          27       28       +1     
  Lines        2385     2433      +48     
==========================================
+ Hits         1972     2025      +53     
+ Misses        413      408       -5     

Impacted Files	Coverage Δ
micromanager_gui/main_window.py	77.41% <71.42%> (+4.13%)	⬆️
...romanager_gui/_core_widgets/_live_button_widget.py	86.56% <86.56%> (ø)
micromanager_gui/_gui_objects/_tab_widget.py	93.42% <100.00%> (-0.41%)	⬇️

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[tlambert03]

i think you want this assert (and those on ln 34,35,40,41,45,46) to be outside of the waitSignal context. Though it may work as is it's likely to be just because it happens nearly instantaneously. but if the goal is to make the wait for the signal occur before you make the assertions, then the assertions should be after the context.

[tlambert03]

This looks good to me, couple minor comments on the tests. @ianhi, I think this generally follows the pattern you were also endorsing. Good with this?

[ianhi]

This looks good to me, couple minor comments on the tests. @ianhi, I think this generally follows the pattern you were also endorsing. Good with this?

missed this but yes it does! nice stuff