When calling set_selected_index() on ComboBox, allow its on_change
callback to be disabled. Fixes FontEditor window state erroneously
switching to modified when initializing between different slopes
and weights.
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
