[feat]: migrate to slang from glsl

2 files changed, 139 insertions, 0 deletions

diff --git a/Tools/compile-shaders.sh b/Tools/compile-shaders.sh
new file mode 100755
index 0000000..ea1aa15
--- /dev/null
+++ b/Tools/compile-shaders.sh
@@ -0,0 +1,110 @@
+#!/usr/bin/env bash
+#
+# Compiles every Assets/Shaders/*.slang to all backend targets, into
+# Assets/Shaders/generated/ (gitignored):
+#
+#   OpenGL : <name>.glsl        - combined "#type" GLSL 4.10 (Slang -> SPIR-V ->
+#                                 SPIRV-Cross), macOS-4.1-core valid, loaded by
+#                                 OpenGLShader.
+#   Vulkan : <name>.<entry>.spv - SPIR-V per entry point.
+#   Metal  : <name>.metal       - MSL, whole module.
+#
+# Entry points are auto-discovered from Slang [shader("stage")] attributes.
+# Override tool paths with SLANGC / SPIRV_CROSS.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+SLANGC="${SLANGC:-$ROOT/Tools/slang/bin/slangc}"
+SPIRV_CROSS="${SPIRV_CROSS:-$(command -v spirv-cross || echo spirv-cross)}"
+SRC="$ROOT/Assets/Shaders"
+OUT="$SRC/generated"
+
+[ -x "$SLANGC" ] || { echo "compile-shaders: slangc not found at $SLANGC (run Tools/fetch-slang.sh)"; exit 1; }
+command -v "$SPIRV_CROSS" >/dev/null 2>&1 || { echo "compile-shaders: spirv-cross not found (brew install spirv-cross)"; exit 1; }
+
+mkdir -p "$OUT"
+shopt -s nullglob
+shaders=("$SRC"/*.slang)
+[ ${#shaders[@]} -gt 0 ] || { echo "compile-shaders: no .slang files in $SRC yet"; exit 0; }
+
+# Prints "stage entryName" for each [shader("stage")] entry point in a file.
+entry_points() {
+  awk '
+    /\[shader\(/ { if (match($0, /"[a-zA-Z]+"/)) { stage = substr($0, RSTART+1, RLENGTH-2); want = 1 } next }
+    want && $0 ~ /^[ \t]*\[/ { next }              # skip further attributes
+    want && /\(/ {
+      sig = $0; sub(/\(.*/, "", sig)
+      n = split(sig, t, /[ \t*&]+/); name = t[n]
+      if (name != "") print stage, name
+      want = 0
+    }
+  ' "$1"
+}
+
+fail=0
+for f in "${shaders[@]}"; do
+  name="$(basename "$f" .slang)"
+  echo "== $name.slang =="
+
+  # Metal: whole module.
+  if "$SLANGC" "$f" -target metal -o "$OUT/$name.metal" 2>"$OUT/.err"; then
+    echo "   metal  -> $name.metal"
+  else echo "   metal  FAILED:"; sed 's/^/     /' "$OUT/.err"; fail=1; fi
+
+  # OpenGL + Vulkan: per entry point. Shaders that declare a ConstantBuffer keep
+  # real UBO blocks (the Engine binds them by name); the rest have Slang's
+  # $Globals flattened to loose uniforms so per-draw glUniform* calls still work.
+  if grep -q 'ConstantBuffer<' "$f"; then ubo=1; else ubo=0; fi
+  combined="$OUT/$name.glsl"; : > "$combined"
+  while read -r stage entry; do
+    [ -z "${stage:-}" ] && continue
+    spv="$OUT/$name.$entry.spv"
+
+    if ! "$SLANGC" "$f" -target spirv -entry "$entry" -stage "$stage" -o "$spv" 2>"$OUT/.err"; then
+      echo "   spirv  FAILED ($entry):"; sed 's/^/     /' "$OUT/.err"; fail=1; continue
+    fi
+    echo "   spirv  -> $name.$entry.spv ($stage)"
+
+    # SPIR-V -> classic GLSL 4.10 (combined samplers, no binding layouts).
+    xcopts="--version 410 --no-es --no-420pack-extension"
+    [ "$ubo" = 0 ] && xcopts="$xcopts --glsl-emit-ubo-as-plain-uniforms"
+
+    if "$SPIRV_CROSS" $xcopts "$spv" --output "$OUT/.stage.glsl" 2>"$OUT/.err"; then
+      if [ "$ubo" = 1 ]; then
+        # Real UBOs: strip SPIRV-Cross's "_std140" block-name suffix so the block
+        # names match glGetUniformBlockIndex("Camera") etc. in the Engine.
+        perl -i -pe 's/_std140//g' "$OUT/.stage.glsl"
+      else
+        # Flatten "struct S {..}; uniform S inst;" into loose "uniform TYPE NAME;"
+        # and strip the "inst." prefix, so uniforms keep their original names and
+        # the existing C++ SetMat4("u_X") / SetFloat("u_Y") calls work unchanged.
+        perl -0777 -i -pe '
+          while (/struct\s+(\w+)\s*\{(.*?)\}\s*;\s*uniform\s+\1\s+(\w+)\s*;/s) {
+            my ($s,$body,$inst)=($1,$2,$3); my @u;
+            while ($body =~ /([A-Za-z_]\w*)\s+([A-Za-z_]\w*(?:\[\d+\])?)\s*;/g) { push @u,"uniform $1 $2;"; }
+            my $loose=join("\n",@u);
+            s/struct\s+\Q$s\E\s*\{.*?\}\s*;\s*uniform\s+\Q$s\E\s+\Q$inst\E\s*;/$loose/s;
+            s/\b\Q$inst\E\.//g;
+          }
+        ' "$OUT/.stage.glsl"
+      fi
+      # SPIRV-Cross names inter-stage varyings per stage and relies on explicit
+      # locations, but macOS's GL linker matches varyings by NAME. Rename each
+      # varying to a location-canonical name (_v<loc>) so stages agree: rename
+      # `out` in vertex stages and `in` in fragment stages (never attributes).
+      case "$stage" in vertex) vdir=out ;; fragment) vdir=in ;; *) vdir="" ;; esac
+      if [ -n "$vdir" ]; then
+        DIR="$vdir" perl -0777 -i -pe '
+          my $d=$ENV{DIR}; my %m;
+          while (/layout\(location = (\d+)\)\s+\Q$d\E\s+\w+\s+(\w+)\s*;/g) { $m{$2}="_v$1"; }
+          for my $n (keys %m) { s/\b\Q$n\E\b/$m{$n}/g; }
+        ' "$OUT/.stage.glsl"
+      fi
+      { echo "#type $stage"; cat "$OUT/.stage.glsl"; echo; } >> "$combined"
+      echo "   glsl   -> $name.glsl (#type $stage)"
+    else echo "   glsl   FAILED ($entry):"; sed 's/^/     /' "$OUT/.err"; fail=1; fi
+  done < <(entry_points "$f")
+done
+
+rm -f "$OUT/.err" "$OUT/.stage.glsl"
+exit $fail
diff --git a/Tools/fetch-slang.sh b/Tools/fetch-slang.sh
new file mode 100755
index 0000000..5ee6de5
--- /dev/null
+++ b/Tools/fetch-slang.sh
@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+#
+# Fetches the Slang shader-compiler toolchain into Tools/slang (gitignored).
+# Slang is the single shader-authoring language for Donut; slangc cross-compiles
+# each Assets/Shaders/*.slang to GLSL (OpenGL), SPIR-V (Vulkan), and MSL (Metal).
+#
+# Re-run to (re)install. Pin the version here so builds are reproducible.
+set -euo pipefail
+
+VERSION="2026.14.1"
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+DEST="$ROOT/Tools/slang"
+
+case "$(uname -s)-$(uname -m)" in
+  Darwin-arm64|Darwin-aarch64) ASSET="macos-aarch64" ;;
+  Darwin-x86_64)               ASSET="macos-x86_64" ;;
+  Linux-x86_64)                ASSET="linux-x86_64" ;;
+  Linux-aarch64|Linux-arm64)   ASSET="linux-aarch64" ;;
+  *) echo "fetch-slang: unsupported platform $(uname -s)-$(uname -m)"; exit 1 ;;
+esac
+
+URL="https://github.com/shader-slang/slang/releases/download/v${VERSION}/slang-${VERSION}-${ASSET}.tar.gz"
+
+echo "fetch-slang: downloading Slang ${VERSION} (${ASSET})..."
+rm -rf "$DEST"
+mkdir -p "$DEST"
+curl -fsSL "$URL" | tar -xz -C "$DEST"
+
+"$DEST/bin/slangc" -v >/dev/null 2>&1 && echo "fetch-slang: installed to $DEST (slangc $("$DEST/bin/slangc" -v))"