LVGL & Headless Mode

[ellisgl]

Looks like screen.h won't define GetFrameBuffer() when in headless mode, so LVGL won't build. If you use a RPi 4 and only want to use some sort of SPI / I2C display, then it's a no go, unless you modify the header file.

[rsta2]

You shouldn't define SCREEN_HEADLESS for that purpose and simply not include the class CScreenDevice in your project. Circle Step48 is not prepared for LVGL use with SPI / I2C displays. This will change with the next release and is already implemented on the develop branch. Unfortunately the docs have not been updated yet, but here are some notes on this.