HIDInput | device driver that emulates mouse | Keyboard library

...or at least an explanation of why gpiozero when_pressed is not playing nice.

My workaround was to have a private __capture() function, which acts as a wrapper to Clock.schedule_once(self.capture). capture_btn.when_pressed would use this private wrapper callback to avoid calling the problematic code directly, and any other uses of capture() would use the public one as normal since that works fine when not interacting with gpiozero.

In the following code I would prefer for capture() and __capture() to have swapped names since that would fit better with the philosophy of private functions, but unfortunately that's throwing AttributeError: 'RootWidget' object has no attribute '__capture' when I try that and I don't know how to fix that (using _RootWidget__capture isn't helping). The lines commented with ## illustrate my preferred but nonfunctional way.

The __init__() of GPIOButton is being called twice. Once when your build() method is called and self.root = LifterGUI() is executed. This creates the GPIOButton that appears in your GUI via the kv rules. The __init__() method is called again when ok_btn = GPIOButton(btn_gpio_pin = ok_btn_pin) is executed in your LeftSidebar class. This second call creates an instance of GPIOButton that does not appear in your GUI, but it is the one that is referenced in the update() method.

Since you already have setup a reference to the GPIOButton in your kv, you can modify the LeftSidebar class to use that reference: