Add the possibility of adding custom widgets to the LVGL structure

[numo68]

Describe the problem you have/What new integration you would like

A few years ago I have designed a crude and incomplete GUI for my own purposes, this was never ready and polished enough to try to contribute it. Now I am seeing the LVGL that seems really great (thanks, @clydebarrow !) and will be most probably the reason to throw away my code as soon as it gets the chart widget (#2869) and perhaps some small stuff like #2914.

The problem is that there will always be tasks not fitting any existing widget 100%. It would be great to be able to just inherit some general widget, write a class, a drawing method and a few lines of python in the usual ESPHome way and integrate it to the LVGL widget structure. I did not find it in the documentation and the code is a bit cryptic, which is to be expected when interfacing a bunch of plain C functions.

Is this possible and only needs to be documented, or is there some enabler code needed in the ESPHome, or is it something that the library and/or the ESPHome are not meant to support?

Please describe your use case for this integration and alternatives you've tried:

Accessing the low-level LVGL drawing functions from custom_components.

Additional context

[nagyrobi]

You're likely interested in canvas, which is not yet supported in ESPHome.