typing: Union type for 'any kind of display-like object'

[jepler]

During PyCon sprints, a participant raised the issue of needing to type an argument as 'any kind of displayio display'. It would be nice if the core (or maybe circuitpython-typing?) had a Union type that included all these types, for libraries to refer to.

[tekktrik]

circuitpython_typing could add a typing.Protocol for displays (or multiple kinds) if we want to duck type it. Can you link to an example of where it would be used to know what methods/attributes are required?

[jepler]

I didn't take note of which repo the author was working on. However, adafruit_bitmapsaver looks like one such:

def save_pixels(                                                                
    file_or_filename: Union[str, BufferedWriter],                               
    pixel_source: Union[Display, Bitmap] = None,                                
    palette: Optional[Palette] = None,                                          
) -> None:                                                                      

[tekktrik]

Assigning to myself so I don't forget about this!

[dhalbert]

Moving this to https://github.com/adafruit/Adafruit_CircuitPython_Typing

Related to:

• Add typing shorthand for display-related types circuitpython#10109

@jepler could the helpers you introduced in adafruit/circuitpython#10109 be defined in circuitpython_typing? Would they still be defined both places?

[jepler]

I don't know whether its needed in both places. I think having it in the core might suffice?

[tekktrik]

@FoamyGuy looking through old notifications - was this solved by #48?

[tekktrik]

It wasn't duck typing via a protocol, but it was an "any display" type.

[FoamyGuy]

@tekktrik I do think it's resolved by #48.

I hadn't seen this discussion before I added it to circuitpython_typing. I do think having it in both places is good because I don't think the RTD build process uses circuitpython-stubs so it will not "see" the instance from the core while it is building and will raise an error I believe.