Previously I had created a node system for levels which is a database of level themes and connections between them. After the introduction of "static" or special room types in some levels I had to re-think stairs creation in their actual form as objects in the level. This far the generation process found some empty floor and there you had it.
What I needed was some kind of way to tell stairs creation about static places for stairs. For that purpose it was easy to set up a list of "clues" for stairs. It's a coordinate set during the creation process and then retrieved when creating stairs. There could have been many ways to do this, but I chose this way, because you browse through node connections which then can be matched with the clue.
At first it returned a wrong location. It was a bit of a mystery, but finally I realized the location was not set correctly, because the room interior was created later than stairs clue was pushed into the list. Some of the interior was terrain generation (with Blueprint class) which I then moved to the routine which is creating the actual shape and terrain of the room.
Now it works and I can set up special locations for stairs. Of course, it's not yet done. Even random generation needs better "clues" where stairs should be created.
As this example is showing. The sign of stairs is created next to door. It should be quite easy to prevent this by removing that place from possible creation locations. The same also need to be done for walls, because doors also could be created into poor place, next to something that's in the room against the wall.