We were doing it all the wrong way, fixing one combo box object at a
time. So this commit basically reverses commits 68a33ab5bd, 6dfca83c2a
and a9a979b2d0 and instead runs the same code in the class code. This
way, all objects based on these base classes will have the fix from
scratch.
These improved various other drop-down lists (I found some of them, and
probably not all) as I fixed all GIMP custom widgets based on
GtkComboBox.
Note that it has to be run after filling the list apparently (I had the
problem especially with GimpIntComboBox if running in the _init() code,
then the list widget showed wrong).
(cherry picked from commit 1d984542e9)
Add private API _gimp_unit_store_sync_units() which emits
"row-inserted" on each unit that didn't exist when the GimpUnitStore
was created, or when sync_units() was called the last time.
In GimpUnitComboBox, call sync_units() each time the combo is popped
up, or a unit is set on the combo.
to allow having unit combos without "pixels". Adapt GimpUnitComboBox
to not assume that the unit is equal to the index in the store and
enable "menu_has_pixels" in GimpSizeEntry again.
