Install GladeVCP on Raspberry Pi 4

By default the "ID" field in the "General" tab was empty,

Seems that the behavior in the "new" glade versions has changed. I will add that to the documentation.

but after I entered the text "window1" in this field the error stays the same unfortunately.

You have to name the GtkWindow "window1" not your HAL_LED. Pay attention what you have selected in the left panel:

 

Hi HansU,
I am sorry for my late reply (I didn't have a lot of time unfortunately lately to play around with my RPi) but I tried this and it did indeed solve my issue. I am now able to build a nice and functioning GUI, something I was looking forward to for a long time.
Thank you!

If you already have glade installed, download the corresponding version from Linuxcnc -dev. Then in Glade in preferences add Extra catalog & Templste path , look for the Linuxcnc-dev gladevcp folder which is located in the path /lib/python/.   

Recently I happened to do a fresh install LinuxCNC, today I wanted to build a GUI but Glade suddenly looks very different... The version is 3.38.2, it seems that by default it is not possible anymore to use HAL widgets. Perhaps the above post from COFHAL relates to this?

I am not sure what is meant by "If you already have glade installed, download the corresponding version from Linuxcnc -dev.", maybe could someone tell something about that?