adf88 wrote:Don't worry about existing NewGRFs and move on.
I don't think adding any of these options would affect old NewGRFs in any way. By "patching NML", I was referring to language, not to source code of older NewGRFs. It should be "patching NMLC"/"patching NML compiler". My bad.
adf88 wrote:You should probably define a new airport property - "flags".
I think this is like my option 1, but it would allow further flags in future without breaking anything. It still has a problem of unknown property and need to patch NMLC to allow it add this property to NewGRF. Maybe treat "Unknown property" when loading NewGRF as a warning and not as fatal error in vanilla would help.
adf88 wrote:I think that NewGRF creators should be able to add as many seaplane airports as they want, not just override existing ones.
Option 1 allows new airports. The property in NML is called "override" but it effectively clones the airport and the properties are set for the clone.
Anyway, so far I have implemented option 1 in my patch.
All seaplane airports no matter how big are in tab "Seaplne airports" in GUI. (May change in future).
For airplanes I have added new property PROP_AIRCRAFT_LAND_SURFACE which is flags for which surfaces the aircraft can land on (ALS_SOLID, ALS_WATER). If no landing surface is set, then ALS_SOLID is added to aircraft for backwards compatibility. This allows for creation of seaplanes, amphibious planes even water landing and amphibios helicopters.