So you can certainly declare Ada constants for these.
> Is it intentional or missing from the binding?
We don't in general bind macros, because they are in most cases C-specific (the ones
in glib) or inapplicable to Ada or require an intermediate C file in GtkAda.
These packages are also mostly automatically generated, so it is sometimes complex
to hack on the python script to do the generation.
I have however added those three constants to the development version of GtkAda.