From 272154f2602ac55700c15cf38f84c44a67fb11b0 Mon Sep 17 00:00:00 2001
From: Atemu <atemu.main@gmail.com>
Date: Sun, 14 May 2023 18:17:29 +0200
Subject: [PATCH 1/2] mangohud: add bitness suffix to layer name

The VK loader finds the 32-bit layer first and does not attempt to load the
64-bit layer afterwards; likely because it shares the same name. Simply giving
them different names fixes the issue; both layers are tried and the correct one
succeeds.

A similar patter is employed by obs-vkcapture which continued working after
https://github.com/NixOS/nixpkgs/pull/228870.

Fixes https://github.com/NixOS/nixpkgs/issues/230978
---
 pkgs/tools/graphics/mangohud/default.nix | 26 ++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/pkgs/tools/graphics/mangohud/default.nix b/pkgs/tools/graphics/mangohud/default.nix
index 5b6e5e8e76de..7903155af40d 100644
--- a/pkgs/tools/graphics/mangohud/default.nix
+++ b/pkgs/tools/graphics/mangohud/default.nix
@@ -194,16 +194,26 @@ stdenv.mkDerivation (finalAttrs: {
     ''}
   '';
 
-  postFixup = ''
+  postFixup = let
+    archMap = {
+      "x86_64-linux" = "x86_64";
+      "i686-linux" = "x86";
+    };
+    layerPlatform = archMap."${stdenv.hostPlatform.system}" or null;
+    # We need to give the different layers separate names or else the loader
+    # might try the 32-bit one first, fail and not attempt to load the 64-bit
+    # layer under the same name.
+  in lib.optionalString (layerPlatform != null) ''
+    substituteInPlace $out/share/vulkan/implicit_layer.d/MangoHud.${layerPlatform}.json \
+      --replace "VK_LAYER_MANGOHUD_overlay" "VK_LAYER_MANGOHUD_overlay_${toString stdenv.hostPlatform.parsed.cpu.bits}"
+  '' + ''
     # Add OpenGL driver path to RUNPATH to support NVIDIA cards
     addOpenGLRunpath "$out/lib/mangohud/libMangoHud.so"
-    ${lib.optionalString gamescopeSupport ''
-      addOpenGLRunpath "$out/bin/mangoapp"
-    ''}
-    ${lib.optionalString finalAttrs.doCheck ''
-      # libcmocka.so is only used for tests
-      rm "$out/lib/libcmocka.so"
-    ''}
+  '' + lib.optionalString gamescopeSupport ''
+    addOpenGLRunpath "$out/bin/mangoapp"
+  '' + lib.optionalString finalAttrs.doCheck ''
+    # libcmocka.so is only used for tests
+    rm "$out/lib/libcmocka.so"
   '';
 
   passthru.updateScript = nix-update-script { };

From 7eacc7f5492f39286696e57fa99bb2becf711bd5 Mon Sep 17 00:00:00 2001
From: Atemu <atemu.main@gmail.com>
Date: Sun, 14 May 2023 18:28:30 +0200
Subject: [PATCH 2/2] mangohud: make lower bitness support configurable

This allows the user to disable 32-bit support for closure size reasons or in
order to mitigate loader issues like
https://github.com/NixOS/nixpkgs/issues/230978.

The name is weird because it can't start with a digit :/
---
 pkgs/tools/graphics/mangohud/default.nix | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/pkgs/tools/graphics/mangohud/default.nix b/pkgs/tools/graphics/mangohud/default.nix
index 7903155af40d..877123951448 100644
--- a/pkgs/tools/graphics/mangohud/default.nix
+++ b/pkgs/tools/graphics/mangohud/default.nix
@@ -30,6 +30,7 @@
 , glfw
 , xorg
 , gamescopeSupport ? true # build mangoapp and mangohudctl
+, lowerBitnessSupport ? stdenv.hostPlatform.is64bit # Support 32 bit on 64bit
 , nix-update-script
 }:
 
@@ -128,7 +129,7 @@ stdenv.mkDerivation (finalAttrs: {
     substituteInPlace bin/mangohud.in \
       --subst-var-by libraryPath ${lib.makeSearchPath "lib/mangohud" ([
         (placeholder "out")
-      ] ++ lib.optionals (stdenv.hostPlatform.system == "x86_64-linux") [
+      ] ++ lib.optionals lowerBitnessSupport [
         mangohud32
       ])} \
       --subst-var-by dataDir ${placeholder "out"}/share
@@ -184,7 +185,7 @@ stdenv.mkDerivation (finalAttrs: {
 
   # Support 32bit Vulkan applications by linking in 32bit Vulkan layers
   # This is needed for the same reason the 32bit preload workaround is needed.
-  postInstall = lib.optionalString (stdenv.hostPlatform.system == "x86_64-linux") ''
+  postInstall = lib.optionalString lowerBitnessSupport ''
     ln -s ${mangohud32}/share/vulkan/implicit_layer.d/MangoHud.x86.json \
       "$out/share/vulkan/implicit_layer.d"