EGL fixes, ensure necessary env variables are set to isolate

dependencies from the host

snap/local/launcher

@@ -1,4 +1,5 @@
-#!/bin/sh
+#!/bin/bash
+set -euo pipefail
 
 export XDG_CONFIG_HOME="$SNAP_REAL_HOME/.config"
 export XDG_DATA_HOME="$SNAP_REAL_HOME/.local/share"
@@ -12,6 +13,62 @@ else
   ARCH="$SNAP_ARCH-linux-gnu"
 fi
 
-export LD_LIBRARY_PATH=$SNAP/usr/lib/$ARCH${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}
+# VDPAU_DRIVER_PATH only supports a single path, rely on LD_LIBRARY_PATH instead
+LD_LIBRARY_PATH=${LD_LIBRARY_PATH:+$LD_LIBRARY_PATH:}${SNAP}/usr/lib/${ARCH}:${SNAP}/usr/lib/${ARCH}/vdpau
+LIBGL_DRIVERS_PATH=${LIBGL_DRIVERS_PATH:+$LIBGL_DRIVERS_PATH:}${SNAP}/usr/lib/${ARCH}/dri/
+LIBVA_DRIVERS_PATH=${LIBVA_DRIVERS_PATH:+$LIBVA_DRIVERS_PATH:}${SNAP}/usr/lib/${ARCH}/dri/
+
+__EGL_VENDOR_LIBRARY_DIRS=${__EGL_VENDOR_LIBRARY_DIRS:+$__EGL_VENDOR_LIBRARY_DIRS:}${SNAP}/usr/share/glvnd/egl_vendor.d
+__EGL_EXTERNAL_PLATFORM_CONFIG_DIRS=${__EGL_EXTERNAL_PLATFORM_CONFIG_DIRS:+$__EGL_EXTERNAL_PLATFORM_CONFIG_DIRS:}${SNAP}/usr/share/egl/egl_external_platform.d
+DRIRC_CONFIGDIR=${SNAP}/usr/share/drirc.d
+VK_LAYER_PATH=${VK_LAYER_PATH:+$VK_LAYER_PATH:}${SNAP}/usr/share/vulkan/implicit_layer.d/:${SNAP}/usr/share/vulkan/explicit_layer.d/
+XDG_DATA_DIRS=${XDG_DATA_DIRS:+$XDG_DATA_DIRS:}${SNAP}/usr/share
+XLOCALEDIR="${SNAP}/usr/share/X11/locale"
+
+# These are in the default LD_LIBRARY_PATH, but in case the snap dropped it inadvertently
+if [ -d "/var/lib/snapd/lib/gl" ] && [[ ! ${LD_LIBRARY_PATH} =~ (^|:)/var/lib/snapd/lib/gl(:|$) ]]; then
+  LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/var/lib/snapd/lib/gl
+fi
+
+if [ -d "/var/lib/snapd/lib/gl32" ] && [[ ! ${LD_LIBRARY_PATH} =~ (^|:)/var/lib/snapd/lib/gl32(:|$) ]]; then
+  LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/var/lib/snapd/lib/gl32
+fi
+
+if [ -d "/var/lib/snapd/lib/glvnd/egl_vendor.d" ]; then
+  # This needs to be prepended, as glvnd goes depth-first on these
+  # TODO maybe collect the JSONs into a separate location so their ordering matters,
+  #  and not the dir order
+  __EGL_VENDOR_LIBRARY_DIRS=/var/lib/snapd/lib/glvnd/egl_vendor.d:${__EGL_VENDOR_LIBRARY_DIRS}
+fi
+
+if [ -d "/var/lib/snapd/lib/vulkan/icd.d" ]; then
+  XDG_DATA_DIRS=${XDG_DATA_DIRS}:/var/lib/snapd/lib
+fi
+
+if [ -d "/var/lib/snapd/lib/gl/vdpau" ]; then
+  LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/var/lib/snapd/lib/gl/vdpau
+fi
+
+if [ -d "/var/lib/snapd/lib/gl32/vdpau" ]; then
+  LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/var/lib/snapd/lib/gl32/vdpau
+fi
+
+if [ -d "/var/lib/snapd/lib/gl/gbm" ]; then
+  export GBM_BACKENDS_PATH=/var/lib/snapd/lib/gl/gbm
+fi
+
+export LD_LIBRARY_PATH
+export LIBGL_DRIVERS_PATH
+if [ "${__NV_PRIME_RENDER_OFFLOAD:-}" != 1 ]; then
+  # Prevent picking VA-API (Intel/AMD) over NVIDIA VDPAU
+  # https://download.nvidia.com/XFree86/Linux-x86_64/510.54/README/primerenderoffload.html#configureapplications
+  export LIBVA_DRIVERS_PATH
+fi
+export __EGL_VENDOR_LIBRARY_DIRS
+export __EGL_EXTERNAL_PLATFORM_CONFIG_DIRS
+export DRIRC_CONFIGDIR
+export VK_LAYER_PATH
+export XDG_DATA_DIRS
+export XLOCALEDIR
 
 exec "$@"