We were using the count of the registered families as the way to determine if the font database had been populated yet. As a result we needed to invalidate the font database every time an application font was added to an empty database, as once the application font was added, the font database was no longer empty, and we would end up failing to populate any of the system/platform fonts. We now have a dedicated flag for tracking whether the font database has been populated, and we track whether an application font has been populated by looking at its properties list, avoiding a second round of populating when the full initialization happens. This also opens up the possibility of the platform font database populating (lazily or fully) fonts up front, for example as part of resolving theme fonts. The Windows font database had to be taught to invalidate itself at the right moment, instead of assuming doing so during populate was okey. Change-Id: I80c893df755d8d35fb8a84dd7a83c6756a8f24a2 Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>