🚧 WIP: Add HEATER_LOWER_TEMP 50

[3d-gussner]

to lower instead of turining off the hotend temperature during a pause. Thanks for the request #4716 by @alexiri

[github-actions]

All values in bytes. Δ Delta to base

Target	ΔFlash	ΔSRAM	Used Flash	Used SRAM	Free Flash	Free SRAM
MK3S_MULTILANG	10	0	248312	5654	5640	2538
MK3_MULTILANG	10	0	247682	5663	6270	2529

[gudnimg]

I think this new setting should be off by default so that we do not change the default behavior. Users who know what they are doing can then change this setting on their own in my opinion.

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I feel this description could be more detailed. This doesn't really tell me what the setting does, and I would have look at the source code to understand. They way I see it, the comment/description here is basically our documentation.

Suggested description:

Uncomment to change the maximum allowed temperature drop while a print is paused. The default behavior sets the target temperature to 0°C.
Example: HEATER_LOWER_TEMP = 10 and target temperature is 215°C when the print was paused. The target temperature will then be set to 205°C instead of 0°C.

[leptun]

Also agree with off by default. Was a bit confused about the feature until I read the source code for the PR (recall discussion from last meeting). I like the description provided by @gudnimg 👍

[gudnimg]

I think we need some protection here to cover edges cases. This can produce negative values: HEATER_LOWER_TEMP > target_temperature[active_extruder]

What happens if we are coming from a temperature error? ThermalStop() can sometimes pause prints.

[3d-gussner]

Very good point, thanks. Fan check, uvlo and ThermalStop call lcd_pause_print --> LcdCommands::LongPause -> long_pause`

[leptun]

Might want to subtract only if the target temperature is >= HEATER_LOWER_TEMP. Otherwise you might underflow the target temperature in even more scenarios where the target is a small number