opengl: Use glxgallium Mesa when VirtualGL is not appropriate

pkgs/opengl/default.nix

@@ -3,7 +3,9 @@
 # Add a setup hook to the mesa_noglu package that automatically adds
 # a libvglfaker.so dependency to executables that depend on libGL.so.
 
-{ super, lib, buildEnv, makeSetupHook, file, bash, xorg }:
+{ super, stdenv, buildEnv, substituteAll, bash
+, autoreconfHook, pkgconfig, python2
+, xorg, llvmPackages, expat, mesa_glxgallium, mesa_noglu, libglvnd }:
 
 let
   autoVirtualGLHook =
@@ -15,28 +17,105 @@ let
 
       libGL = super.libGL;
       libGLU = super.libGLU.override { inherit libGL; };
-      libGLU_combined = (buildEnv {
+      libGLU_combined = buildEnv {
         name = "libGLU-combined";
         paths = [ libGL libGLU ];
         extraOutputsToInstall = [ "dev" ];
-      });
+      };
 
       virtualglLib = (super.virtualglLib.override { inherit libGLU_combined fltk; });
       fltk = super.fltk.override { inherit libGLU_combined freeglut; };
       freeglut = super.freeglut.override { inherit libGL libGLU; };
     in
-      makeSetupHook {
-        name = "insert-virtualgl";
-        deps = [ file virtualglLib ];
-        substitutions = { inherit virtualglLib bash; inherit (xorg) libXext; };
-      } ./insert-virtualgl.sh;
+      substituteAll {
+        src = ./insert-virtualgl.sh;
+        bash = "${bash}/bin/bash";
+        virtualglLib = "${virtualglLib}/lib/libvglfaker.so";
+      };
 
 in {
-  libGL = super.libGL.overrideAttrs ( attrs: {
-    # Done as a non-standard build command, so have to add it in this way
 
-    buildCommand = attrs.buildCommand + ''
-      echo '${autoVirtualGLHook}' >> $dev/nix-support/propagated-build-inputs
+  # Mesa build for glxgallium software rendering (works with all X11 forwarding)
+
+  mesa_glxgallium = stdenv.mkDerivation rec {
+    version = super.mesa_noglu.version;
+    name = "mesa-glxgallium-${version}";
+    src = super.mesa_noglu.src;
+
+    outputs = [ "out" "dev" ];
+
+    configureFlags = [
+      "--with-gallium-drivers=swrast"
+      "--with-platforms=x11"           # surfaceless would make sense, but egl requires dri
+      "--disable-dri"
+      "--enable-glx=gallium-xlib"      # gallium-xlib requires no dri
+      "--enable-gallium-osmesa"
+      "--enable-llvm"
+      "--disable-egl"                  # egl requries dri for some reason
+      "--disable-gbm"                  # gbm requires dri for some reason
+      "--enable-llvm-shared-libs"
+      "--disable-opencl"
+    ];
+
+    nativeBuildInputs = [
+      autoreconfHook pkgconfig
+      python2
+    ];
+    propagatedBuildInputs = [ ];
+    buildInputs = [
+      llvmPackages.llvm
+      xorg.xorgproto xorg.libX11 xorg.libXext xorg.libxcb
+      expat
+    ];
+
+    enableParallelBuilding = true;
+
+    meta = with stdenv.lib; {
+      description = "An open source implementation of OpenGL";
+      homepage = https://www.mesa3d.org/;
+      license = licenses.mit; # X11 variant, in most files
+      platforms = platforms.linux;
+    };
+  };
+
+
+  # Duplicate mesa_noglu.stub with mesa_glxgallium stuffed in as the libGL source
+
+  libGL = stdenv.mkDerivation {
+    name = "libGL-${libglvnd.version}";
+    outputs = [ "out" "dev" ];
+
+    nativeBuildInputs = [ xorg.lndir ];
+
+    # Use stub libraries from mesa_glxgallium and libglvnd and headers from lib_noglu
+    buildCommand = ''
+      mkdir -p $out/lib
+      lndir -silent ${mesa_glxgallium.out}/lib $out/lib
+      lndir -silent ${libglvnd.out}/lib $out/lib
+
+      mkdir -p $dev/{,lib/pkgconfig,nix-support}
+      echo "$out" > $dev/nix-support/propagated-build-inputs
+      echo ${autoVirtualGLHook} >> $dev/nix-support/propagated-build-inputs
+      ln -s ${mesa_noglu.dev}/include $dev/include
+
+      genPkgConfig() {
+        local location="$1"
+        local name="$2"
+        local lib="$3"
+
+        cat <<EOF >$dev/lib/pkgconfig/$name.pc
+      Name: $name
+      Description: $lib library
+      Version: ${mesa_noglu.version}
+      Libs: -L$location/lib -l$lib
+      Cflags: -I${mesa_noglu.dev}/include
+      EOF
+      }
+
+      genPkgConfig ${mesa_glxgallium.out} gl GL
+      genPkgConfig ${libglvnd.out} egl EGL
+      genPkgConfig ${libglvnd.out} glesv1_cm GLESv1_CM
+      genPkgConfig ${libglvnd.out} glesv2 GLESv2
     '';
-    } );
+  };
 }