buttons: Debounce gcode_button and filament_switch_sensor (#6848)

Add `debounce_delay` config option which sets the debounce time, defaults to 0

Signed-off-by: Gareth Farrington <gareth@waves.ky>

klippy/extras/buttons.py

@@ -244,6 +244,33 @@ class HalfStepRotaryEncoder(BaseRotaryEncoder):
          BaseRotaryEncoder.R_START | BaseRotaryEncoder.R_DIR_CCW),
     )
 
+class DebounceButton:
+    def __init__(self, config, button_action):
+        self.printer = config.get_printer()
+        self.reactor = self.printer.get_reactor()
+        self.button_action = button_action
+        self.debounce_delay = config.getfloat('debounce_delay', 0., minval=0.)
+        self.logical_state = None
+        self.physical_state = None
+        self.latest_eventtime = None
+    def button_handler(self, eventtime, state):
+        self.physical_state = state
+        self.latest_eventtime = eventtime
+        # if there would be no state transition, ignore the event:
+        if self.logical_state == self.physical_state:
+            return
+        trigger_time = eventtime + self.debounce_delay
+        self.reactor.register_callback(self._debounce_event, trigger_time)
+    def _debounce_event(self, eventtime):
+        # if there would be no state transition, ignore the event:
+        if self.logical_state == self.physical_state:
+            return
+        # if there were more recent events, they supersede this one:
+        if (eventtime - self.debounce_delay) < self.latest_eventtime:
+            return
+        # enact state transition and trigger action
+        self.logical_state = self.physical_state
+        self.button_action(self.latest_eventtime, self.logical_state)
 
 ######################################################################
 # Button registration code
@@ -261,6 +288,14 @@ class PrinterButtons:
             self.adc_buttons[pin] = adc_buttons = MCU_ADC_buttons(
                 self.printer, pin, pullup)
         adc_buttons.setup_button(min_val, max_val, callback)
+    def register_debounce_button(self, pin, callback, config):
+        debounce = DebounceButton(config, callback)
+        return self.register_buttons([pin], debounce.button_handler)
+    def register_debounce_adc_button(self, pin, min_val, max_val, pullup
+                                     , callback, config):
+        debounce = DebounceButton(config, callback)
+        return self.register_adc_button(pin, min_val. min_val, max_val, pullup
+                                        , debounce.button_handler)
     def register_adc_button_push(self, pin, min_val, max_val, pullup, callback):
         def helper(eventtime, state, callback=callback):
             if state: