Enforce Offline tile limit when merging sideloaded databases

1 files changed, 9 insertions, 3 deletions

diff --git a/include/mbgl/storage/default_file_source.hpp b/include/mbgl/storage/default_file_source.hpp
index 942749fc00..929fb3d7c3 100644
--- a/include/mbgl/storage/default_file_source.hpp
+++ b/include/mbgl/storage/default_file_source.hpp
@@ -106,12 +106,18 @@ public:
      * executed on the database thread; it is the responsibility of the SDK bindings
      * to re-execute a user-provided callback on the main thread.
      *
+     * The secondary database may need to be upgraded to the latest schema. This is done
+     * in-place and requires write-access to `sideDatabasePath`; it is the
+     * responsibility of the SDK bindings to ensure that this path is writeable.
+     *
      * Only resources and tiles that belong to a region will be copied over. Identical
      * regions will be flattened into a single new region in the main database.
      *
-     * Note that the resulting new regions may not be in a completed status if the
-     * secondary database does not contain all the tiles or resources required by the
-     * region definition.
+     * Invokes the callback with a `MapboxOfflineTileCountExceededException` error if
+     * the merge operation would result in the offline tile count limit being exceeded.
+     *
+     * Merged regions may not be in a completed status if the secondary database
+     * does not contain all the tiles or resources required by the region definition.
      */
     void mergeOfflineRegions(const std::string& sideDatabasePath,
                             std::function<void (expected<OfflineRegions, std::exception_ptr>)>);