Add feature to only use filament sensor while printing

[sn4k3]

When having a filament sensor, by default they are ON, causing unloading/loading events to trigger even if we don't want to (hand feed or preparation).

[filament_switch_sensor toolhead_runout]
pause_on_runout: true
runout_gcode:
    M117 Runout Detected
    UNLOAD_FILAMENT
insert_gcode:
    M117 Insert Detected
    LOAD_FILAMENT
switch_pin: ^P1.28

We can disable the sensor by default using:

[delayed_gcode DISABLE_FILAMENT_SENSOR]
initial_duration: 1
gcode:
    SET_FILAMENT_SENSOR SENSOR=toolhead_runout ENABLE=0

However, this introduces another problem, we want the sensor ON when printing, but OFF when not printing, as so, this PR allows the user to select a list of sensors to switch ON/OFF on those print events. This will allow user to do any handling of the extruder without the annoyance of removing the filament and it trigger an PAUSE which do HOME, PREHEAT, PARK and UNLOAD or insert the filament in cold just to prepare a future print and it trigger another unrequired sequence of events.

We could use slicer start and end gcode, but that is ugly, don't handle print cancel and make them less sharable. This integrated solution is cleaner and less prompt to error.

Usage:

variable_switch_filament_sensors: ['toolhead_runout'] # example: ('toolhead_runout')

[jschuh]

This can be done quite easily with print status events. You'd run the disable on the ready event and enable on the purge event.

[sn4k3]

This can be done quite easily with print status events. You'd run the disable on the ready event and enable on the purge event.

Worked, tested with:

GCODE_ON_PRINT_STATUS STATUS=ready COMMAND="SET_FILAMENT_SENSOR SENSOR=toolhead_runout ENABLE=0" TYPE=ENTER WHEN=ALWAYS
GCODE_ON_PRINT_STATUS STATUS=purging COMMAND="SET_FILAMENT_SENSOR SENSOR=toolhead_runout ENABLE=1" TYPE=ENTER WHEN=ALWAYS

Thanks! You can close this PR if you wish.

[jschuh]

Yeah, I'm going to close. If I add something specific for runout sensors I'd want to address a broader range of scenarios (e.g. my own runout macro pauses immediately on the first layer, waits for a layer change everywhere else, and debounces the runout events).

[sn4k3]

The filament sensors are poorly handled by klipper and lacking, it only supports them but then all functions must be handed by user macros. We need a more robust way to deal with them (configs and communication)...

Examples:

• LCD and UI integration when runout with some popup actions like: Purge more, Resume and even Toggle Sensor state.
• After a runout, prevent any future runout until user had resume the print (I had experience multiple runouts triggers when playing with the filament insert by hand). In a natural way we expect to happen only once: Runout detected -> fire runout event -> Insert filament -> fire insert event -> Wait for user prompt. (Can be addressed with global variables) however a native solution is best for users.