findSpawnPos: Add setting for max height above water level

Increase default from 6 to 16 to help with mgv7 and mgfractal
Large-scale or alternative mapgens can result in a lowland spawn point not
being found, causing a spawn at (0, 0, 0) possibly buried underground
The max height is now settable to allow correct player spawn
in any mapgen or when using custom noise parameters

builtin/settingtypes.txt

@@ -693,6 +693,12 @@ enable_pvp (Player versus Player) bool true
 #    If this is set, players will always (re)spawn at the given position.
 static_spawnpoint (Static spawnpoint) string
 
+#    Maximum distance above water level for player spawn.
+#    Larger values result in spawn points closer to (x = 0, z = 0).
+#    Smaller values may result in a suitable spawn point not being found,
+#    resulting in a spawn at (0, 0, 0) possibly buried underground.
+vertical_spawn_range (Vertical spawn range) int 16
+
 #    If enabled, new players cannot join with an empty password.
 disallow_empty_password (Disallow empty passwords) bool false
 

minetest.conf.example

@@ -829,6 +829,13 @@
 #    type: string
 # static_spawnpoint = 
 
+#    Maximum distance above water level for player spawn.
+#    Larger values result in spawn points closer to (x = 0, z = 0).
+#    Smaller values may result in a suitable spawn point not being found,
+#    resulting in a spawn at (0, 0, 0) possibly buried underground.
+#    type: int
+# vertical_spawn_range = 16
+
 #    If enabled, new players cannot join with an empty password.
 #    type: bool
 # disallow_empty_password = false

src/defaultsettings.cpp

@@ -245,6 +245,7 @@ void set_default_settings(Settings *settings)
 	settings->setDefault("default_privs", "interact, shout");
 	settings->setDefault("player_transfer_distance", "0");
 	settings->setDefault("enable_pvp", "true");
+	settings->setDefault("vertical_spawn_range", "16");
 	settings->setDefault("disallow_empty_password", "false");
 	settings->setDefault("disable_anticheat", "false");
 	settings->setDefault("enable_rollback_recording", "false");

src/server.cpp

@@ -3269,7 +3269,7 @@ v3f Server::findSpawnPos()
 	}
 
 	s16 water_level = map.getWaterLevel();
-
+	s16 vertical_spawn_range = g_settings->getS16("vertical_spawn_range");
 	bool is_good = false;
 
 	// Try to find a good place a few times
@@ -3282,9 +3282,9 @@ v3f Server::findSpawnPos()
 
 		// Get ground height at point
 		s16 groundheight = map.findGroundLevel(nodepos2d);
-		if (groundheight <= water_level) // Don't go underwater
+		// Don't go underwater or to high places
-			continue;
+		if (groundheight <= water_level ||
-		if (groundheight > water_level + 6) // Don't go to high places
+				groundheight > water_level + vertical_spawn_range)
 			continue;
 
 		v3s16 nodepos(nodepos2d.X, groundheight, nodepos2d.Y);