Buttons come with an intrinsic min-width but lack a method to alter this
property. Setting the requested size to zero has also no effect on it.
The only way found to work is to hard code the CSS into the button.
The AButton class is designed as full a substitute to ALabel. The
GtkButton attribute 'button_' is initialized with a label. This
label can the be referenced by the subsequent inheritors of AButton
instead of the GtkLabel attribute 'label_' of ALabel.
For convenience a GtkLabel* 'label_' attribute is added to AButton.
If the button cannot be clicked it is disabled, effectively acting
like its label predecessor.
GtkButton seems to catch one-click mouse events regardless of the
flags set on it. Therefore, 'signal_pressed' is connected to a
function creating a fake GdkEventButton* and calling 'handleToggle'
(for details on this possible bug in GTK see:
https://stackoverflow.com/questions/45334911 )
In accordance with other GtkButtons (i.e. the sway/workspace ones)
set_relief(Gtk::RELIEF_NONE) is called on the 'button_' instance.
