Extending the 'Adding a button into the header bar' section

[MadameMalady]

I have some tips / information based on trial and error that I think could help extend this section a little bit.

Firstly, in this part, you say:

'If you were adding a new action icon it would go in /usr/share/icons/hicolor/scalable/actions'

However, this is only good if you're using default icons, and is no good if you have a theme set that's not hicolor.

A better way (to the best of my knowledge) to explain using symbolic icons would be that it will look for an svg matching the
specified svg name, in the currently set theme, so if you have for example a custon svg you want for a button, and your theme is Yaru, you would copy your svg to /usr/share/icons/Yaru/scalable/actions, than reference its name.

You can also replace a button other than a header bar one with an image with set_icon_name.
Adwaita has 'Adw.ButtonContent for adding an icon next to a label, which may also be worth looking into adding if interested.
I hope this was helpful.

[Taiko2k]

I find the topic of icons in GTK confusing, I'm not sure what the right way of doing it is.

Though,

However, this is only good if you're using default icons, and is no good if you have a theme set that's not hicolor.

A better way (to the best of my knowledge) to explain using symbolic icons would be that it will look for an svg matching the specified svg name, in the currently set theme, so if you have for example a custon svg you want for a button, and your theme is Yaru, you would copy your svg to /usr/share/icons/Yaru/scalable/actions, than reference its name.

Of course, you wouldn't put your app icon in a theme folder, because it wouldn't show if the user had a different theme selected. All themes inherit hicolor so it should work there. GTK should resolve the name without needing to specify file type too.

I don't think this is what most applications do though. I'm not sure what the generally accepted way of doing it is.