mods that hopefully work for a TechAge-based pack

mods/techage_modpack/player_physics_design_pattern.md

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+# Player Physics Access Control
+
+To be able to control the access to player physics (like speed, gravity) and privs (like fast, fly)
+a common design pattern is used for the following mod-pack mods:
+
+- autobahn (fast, speed)
+- towercrane (fly, speed)
+- ta4_jetpack (gravity, speed)
+- ta4_paraglider
+- stamina (resets the gravity/speed cyclically)
+- 3d_armor (changes physics based on APi calls)
+
+All of these mods try to change the player physics, which is a common resource and should only be changed by one mod.
+
+This access control design pattern takes care that only one mod at a time is able to change physics or privs.
+
+```lua
+local function change_player_physics(player)
+	local physics = player:get_physics_override()
+	local meta = player:get_meta()
+	
+	-- Check access conflicts with other mods
+	if meta:get_int("player_physics_locked") == 0 then
+		meta:set_int("player_physics_locked", 1)
+
+        -- store old values, here speed and gravity
+		meta:set_int("mymod_normal_player_speed", physics.speed)
+		meta:set_int("mymod_normal_player_gravity", physics.gravity)
+
+		-- do whatever is needed
+        
+        player:set_physics_override(physics)
+        meta:set_int("mymod_is_active", 1)
+	end
+end
+
+local function restore_player_physics(player)
+	local physics = player:get_physics_override()
+	local meta = player:get_meta()
+	
+    if meta:get_int("mymod_is_active") == 1 then
+        meta:set_int("mymod_is_active", 0)
+
+        -- restore old values (speed and gravity)
+        physics.speed = meta:get_int("mymod_normal_player_speed")
+        physics.gravity = meta:get_int("mymod_normal_player_gravity")
+		player:set_physics_override(physics)
+    end
+	meta:set_int("player_physics_locked", 0)
+end
+
+
+
+minetest.register_on_joinplayer(function(player)
+	restore_player_physics(player)
+end)
+
+minetest.register_on_respawnplayer(function(player)
+	restore_player_physics(player)
+end)
+
+-- optional
+minetest.register_on_leaveplayer(function(player)
+	restore_player_physics(player)
+end)
+
+-- optional
+minetest.register_on_dieplayer(function(player)
+	restore_player_physics(player)
+end)
+```
+