Re: master 3b41141708: Expose the name of an event's input device to Lisp

[Eli Zaretskii <eliz@gnu.org>]

> From: Brian Cully <bjc@spork.org>
> Cc: Lars Ingebrigtsen <larsi@gnus.org>, luangruo@yahoo.com,
>  monnier@iro.umontreal.ca, rms@gnu.org, emacs-devel@gnu.org
> Date: Sat, 09 Apr 2022 13:52:52 -0400
> 
> > I would hope that such an event could be called just 'footpad-b', so
> > that any device capable of such events could be implemented as
> > emitting it, regardless of the device name/type/etc.
> 
> 	I may have missed this earlier in the thread, but where would
> these mappings of device identifier (name, USB VID:PID, whatever) to
> device classes come from? How would that work for devices that can be
> made to look like a *lot* of different input types?

The same way any other input event works: Emacs generates a Lisp form
of each event in low-level C code.

> 	I’ve got a Steam Controller I can set up as a joystick, keyboard
> (HID report and boot protocols), relative and absolute mouse, all at the
> same time, and I can swap its functions on the fly. I’ve got a mouse
> that can send both “pixel” scroll events as well as normal line-based
> ones depending on how it’s configured. I have a programmable keyboard
> that I can make look like any USB device I want.
> 
>      Is Emacs going to be responsible for mapping thousands of device
> identifiers to device classes (which may change at runtime?) I just
> don’t understand what this looks like from a user’s perspective.

When your device behaves like a joystick, it will emit events that
joysticks produce, and Emacs will treat that as a joystick.

If this still doesn't help, my suggestion is to follow the code that
produces existing events in Emacs, for example mouse events.