fix: adds the mod alpha_workaround

This fixes some issues with the texture alpha property
that requires quite some changes in order to be properly fixed
in all sort of mods we currently have.

This gives us almost the same behavior of the previous API.

mods/alpha_workaround/.gitignore

@@ -0,0 +1,41 @@
+# Compiled Lua sources
+luac.out
+
+# luarocks build files
+*.src.rock
+*.zip
+*.tar.gz
+
+# Object files
+*.o
+*.os
+*.ko
+*.obj
+*.elf
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Libraries
+*.lib
+*.a
+*.la
+*.lo
+*.def
+*.exp
+
+# Shared objects (inc. Windows DLLs)
+*.dll
+*.so
+*.so.*
+*.dylib
+
+# Executables
+*.exe
+*.out
+*.app
+*.i*86
+*.x86_64
+*.hex
+

mods/alpha_workaround/README.md

@@ -0,0 +1,3 @@
+# `use_texture_alpha` workaround
+
+This mod converts boolean `use_texture_alpha` values to string on the server, allowing MT5.9+ clients to join.

mods/alpha_workaround/init.lua

@@ -0,0 +1,67 @@
+-- alpha_workaround/init.lua
+-- Fix rendering issues on client 5.9 caused by boolean values of use_texture_alpha
+--[[
+  Copyright (C) 2024  1F616EMO
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU Affero General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU Affero General Public License for more details.
+
+  You should have received a copy of the GNU Affero General Public License
+  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+]]
+
+if not minetest.features.use_texture_alpha_string_modes then
+    error("[alpha_workaround] This version of Minetest Engine does not support string mode alpha.")
+end
+
+-- According to https://github.com/minetest/minetest/pull/10819
+local value_map   = {}
+
+value_map.normal  = { "clip", "opaque" }
+value_map.other   = { "blend", "clip" }
+value_map.nodebox = { "blend", "opaque" }
+value_map.mesh    = value_map.nodebox
+
+local defaults    = {
+    normal        = "opaque",
+    other         = "clip",
+    nodebox       = "clip", -- Adopting old client value
+    mesh          = "clip",
+    liquid        = "opaque",
+    flowingliquid = "opaque"
+}
+
+minetest.register_on_mods_loaded(function()
+    for name, def in pairs(minetest.registered_nodes) do
+        local alpha_type = type(def.use_texture_alpha)
+        if alpha_type ~= "string" then
+            local drawtype = def.drawtype or "normal"
+            local alpha
+
+            if alpha_type == "boolean" then
+                alpha = (value_map[drawtype] or value_map.other)[def.use_texture_alpha and 1 or 2]
+                minetest.log("warning", "[alpha_workaround] Node " .. name .. " is using boolean use_texture_alpha, " ..
+                    "assuming use_texture_alpha = " .. alpha)
+            elseif (drawtype == "liquid" or drawtype == "flowingliquid") and def.alpha then
+                alpha = def.alpha == 255 and "opaque" or "blend"
+                minetest.log("warning", "[alpha_workaround] Node " .. name .. " is using the alpha field, " ..
+                    "assuming use_texture_alpha = " .. alpha)
+            else
+                -- DAMN, we cannot detect texture transparency
+                -- So we apply defaults no matter what
+                alpha = defaults[drawtype] or defaults.other
+            end
+
+            minetest.override_item(name, {
+                use_texture_alpha = alpha
+            })
+        end
+    end
+end)

mods/alpha_workaround/mod.conf

@@ -0,0 +1,7 @@
+name = alpha_workaround
+title = use_texture_alpha workaround
+description = Fix boolean use_texture_alpha on MT5.9+
+min_minetest_version = 5.4
+author = Emojiminetest
+release = 23246
+

world.mt

@@ -20,6 +20,7 @@ load_mod_3d_armor_ui = true
 load_mod_abriglass = true
 load_mod_accountmgr = true
 load_mod_airutils = true
+load_mod_alpha_workaround = true
 load_mod_animalia = true
 load_mod_anvil = true
 load_mod_areas = true