Slang seperation

README.md

@@ -101,6 +101,8 @@ cmake --preset vs2022-x64-debug `
   -DDECKLINK_SDK_ROOT="D:/SDKs/Blackmagic DeckLink SDK 16.0"
 ```
 
+At runtime, Slang compilation follows the same root order: `SLANG_ROOT`, `THIRD_PARTY_ROOT`, repo `video-io-3rdParty/`, then repo or packaged `3rdParty/`. The packaged layout uses `3rdParty/slang/bin/slangc.exe`; development bundles can use `slang-2026.8-windows-x86_64/bin/slangc.exe`.
+
 ## Build
 
 Configure and build the native app:

docs/FORKING_RENDER_CADENCE_BASE.md

@@ -66,7 +66,7 @@ Do not move DeckLink, NDI, file I/O, shader compilation, or control handling int
 Before cutting a long-lived fork, fix or decide these items:
 
 - Keep `runtimeShaderId` empty in checked-in config unless this repo intentionally wants a default startup shader again.
-- Align remaining runtime third-party discovery with CMake. Font atlas generation now checks `MSDF_ATLAS_GEN_ROOT`, `THIRD_PARTY_ROOT`, `3rdParty`, and `video-io-3rdParty`; shader compiler lookup still needs the same treatment for Slang.
+- Keep runtime third-party discovery aligned with CMake. Font atlas generation and Slang compilation now both check explicit tool roots, `THIRD_PARTY_ROOT`, the private `video-io-3rdParty` bundle, and legacy or packaged `3rdParty` layouts.
 - Make `config/runtime-host.json` portable. Current checked-in defaults include a local NDI source name and DeckLink output.
 - Decide whether the fork keeps the Slang shader package contract. If not, retire or clearly isolate `shaders/SHADER_CONTRACT.md`, shader package UI, and shader manifest tests.
 - Mark older docs that reference `apps/LoopThroughWithOpenGLCompositing` as historical, or update them to point at the current `src/` implementation.
@@ -75,13 +75,13 @@ Before cutting a long-lived fork, fix or decide these items:
 
 ## Verification Snapshot
 
-Last checked locally on 2026-05-30 after the font-builder lookup fix:
+Last checked locally on 2026-05-30 after the Slang lookup alignment:
 
-- Worktree was clean before documentation changes.
 - UI production build passed with `npm.cmd run build`.
-- Native debug build passed with `cmake --build --preset build-debug --parallel`.
-- Native tests passed 24 of 24 with `ctest --test-dir build\vs2022-x64-debug -C Debug --output-on-failure`.
+- Native debug build passed for `RenderCadenceCompositor`, `ShaderSlangValidationTests`, and `ShaderCompilerLookupTests`.
+- Native tests passed 26 of 26 with `ctest --test-dir build\vs2022-x64-debug -C Debug --output-on-failure`.
 - `FontAtlasBuilderTests` now passes with `msdf-atlas-gen.exe` supplied by the private `video-io-3rdParty/msdf-atlas-gen` bundle.
+- `ShaderCompilerLookupTests` covers `SLANG_ROOT`, `THIRD_PARTY_ROOT`, repo `video-io-3rdParty`, legacy `3rdParty`, and packaged `3rdParty/slang` Slang layouts.
 
 The generated Visual Studio `RUN_TESTS` target did not build missing test executables by itself during the first local run; building the debug preset first produced the test binaries.
 

src/README.md

@@ -368,6 +368,8 @@ On startup the app first tries to restore `runtime/runtime_state.json`. Valid sa
 
 The render thread keeps drawing the simple motion renderer while Slang compiles. It does not choose packages, launch Slang, or track build lifecycle. Once a completed shader artifact is published, the render-thread-owned runtime scene queues changed layers to a shared-context GL prepare worker. That worker compiles/links runtime shader programs off the cadence thread. The render thread only swaps in an already-prepared GL program at a frame boundary. If either the Slang build or GL preparation fails, the app keeps rendering the current renderer or simple motion fallback.
 
+The Slang compiler lookup matches the CMake third-party layout: `SLANG_ROOT` first, then `THIRD_PARTY_ROOT`, then repo `video-io-3rdParty/`, then repo or packaged `3rdParty/`. Packaged builds use `3rdParty/slang/bin/slangc.exe`; development bundles can use `slang-2026.8-windows-x86_64/bin/slangc.exe`.
+
 `POST /api/reload` rescans `shaders/`, re-reads manifests, refreshes supported shader metadata, reconciles active layer parameters against changed definitions, and queues recompilation for every catalog-valid layer in the active stack. It does not compile every package in the shader library; packages are compiled when they are part of the active stack.
 
 Current runtime shader support is deliberately limited to stateless full-frame packages:

src/shader/ShaderCompiler.cpp

@@ -3,8 +3,9 @@
 
 #include "NativeHandles.h"
 
-#include <fstream>
 #include <cctype>
+#include <cstdlib>
+#include <fstream>
 #include <regex>
 #include <sstream>
 #include <vector>
@@ -150,6 +151,90 @@ std::string BuildHistorySwitchCases(const std::string& samplerPrefix, unsigned h
 		source << "\tcase " << index << ": return " << samplerPrefix << index << ".Sample(tc);\n";
 	return source.str();
 }
+
+bool UseExecutableIfPresent(const std::filesystem::path& candidate, std::filesystem::path& compilerPath)
+{
+	if (!std::filesystem::exists(candidate) || std::filesystem::is_directory(candidate))
+		return false;
+
+	compilerPath = candidate;
+	return true;
+}
+
+bool UseSlangRootIfPresent(const std::filesystem::path& root, std::filesystem::path& compilerPath)
+{
+	if (root.empty())
+		return false;
+
+	if (UseExecutableIfPresent(root, compilerPath))
+		return true;
+
+	if (UseExecutableIfPresent(root / "slangc.exe", compilerPath))
+		return true;
+
+	return UseExecutableIfPresent(root / "bin" / "slangc.exe", compilerPath);
+}
+
+std::filesystem::path EnvironmentPath(const char* variableName)
+{
+#if defined(_MSC_VER)
+	char* value = nullptr;
+	std::size_t size = 0;
+	if (_dupenv_s(&value, &size, variableName) != 0 || value == nullptr)
+		return std::filesystem::path();
+	std::string text(value);
+	std::free(value);
+	if (text.empty())
+		return std::filesystem::path();
+	return std::filesystem::path(text);
+#else
+	const char* value = std::getenv(variableName);
+	if (value == nullptr || *value == '\0')
+		return std::filesystem::path();
+	return std::filesystem::path(value);
+#endif
+}
+
+bool UseEnvironmentSlangRoot(const char* variableName, std::filesystem::path& compilerPath)
+{
+	return UseSlangRootIfPresent(EnvironmentPath(variableName), compilerPath);
+}
+
+bool UseThirdPartyRootIfPresent(const std::filesystem::path& thirdPartyRoot, std::filesystem::path& compilerPath)
+{
+	if (thirdPartyRoot.empty())
+		return false;
+
+	const std::vector<std::filesystem::path> preferredRoots = {
+		thirdPartyRoot / "slang-2026.8-windows-x86_64",
+		thirdPartyRoot / "slang",
+		thirdPartyRoot
+	};
+	for (const std::filesystem::path& root : preferredRoots)
+	{
+		if (UseSlangRootIfPresent(root, compilerPath))
+			return true;
+	}
+
+	std::error_code directoryError;
+	if (!std::filesystem::exists(thirdPartyRoot, directoryError) || !std::filesystem::is_directory(thirdPartyRoot, directoryError))
+		return false;
+
+	for (const auto& entry : std::filesystem::directory_iterator(thirdPartyRoot, directoryError))
+	{
+		if (directoryError)
+			break;
+
+		std::error_code entryError;
+		if (!entry.is_directory(entryError))
+			continue;
+
+		if (UseSlangRootIfPresent(entry.path(), compilerPath))
+			return true;
+	}
+
+	return false;
+}
 }
 
 ShaderCompiler::ShaderCompiler(
@@ -218,38 +303,25 @@ bool ShaderCompiler::BuildWrapperSlangSource(const ShaderPackage& shaderPackage,
 
 bool ShaderCompiler::FindSlangCompiler(std::filesystem::path& compilerPath, std::string& error) const
 {
-	char slangRootBuffer[MAX_PATH] = {};
-	const DWORD slangRootLength = GetEnvironmentVariableA("SLANG_ROOT", slangRootBuffer, static_cast<DWORD>(sizeof(slangRootBuffer)));
-	if (slangRootLength > 0 && slangRootLength < sizeof(slangRootBuffer))
+	return FindSlangCompilerPath(mRepoRoot, compilerPath, error);
+}
+
+bool ShaderCompiler::FindSlangCompilerPath(const std::filesystem::path& repoRoot, std::filesystem::path& compilerPath, std::string& error)
 {
-		std::filesystem::path candidate = std::filesystem::path(slangRootBuffer) / "bin" / "slangc.exe";
-		if (std::filesystem::exists(candidate))
-		{
-			compilerPath = candidate;
+	if (UseEnvironmentSlangRoot("SLANG_ROOT", compilerPath))
 		return true;
-		}
-	}
 
-	std::filesystem::path thirdPartyRoot = mRepoRoot / "3rdParty";
-	if (!std::filesystem::exists(thirdPartyRoot))
-	{
-		error = "3rdParty directory was not found under the repository root.";
-		return false;
-	}
-
-	for (const auto& entry : std::filesystem::directory_iterator(thirdPartyRoot))
-	{
-		if (!entry.is_directory())
-			continue;
-		std::filesystem::path candidate = entry.path() / "bin" / "slangc.exe";
-		if (std::filesystem::exists(candidate))
-		{
-			compilerPath = candidate;
+	const std::filesystem::path thirdPartyRoot = EnvironmentPath("THIRD_PARTY_ROOT");
+	if (UseThirdPartyRootIfPresent(thirdPartyRoot, compilerPath))
 		return true;
-		}
-	}
 
-	error = "Could not find slangc.exe under 3rdParty.";
+	if (UseThirdPartyRootIfPresent(repoRoot / "video-io-3rdParty", compilerPath))
+		return true;
+
+	if (UseThirdPartyRootIfPresent(repoRoot / "3rdParty", compilerPath))
+		return true;
+
+	error = "Could not find slangc.exe. Set SLANG_ROOT, set THIRD_PARTY_ROOT to a bundle containing slang-2026.8-windows-x86_64, or place Slang under video-io-3rdParty or 3rdParty.";
 	return false;
 }
 

src/shader/ShaderCompiler.h

@@ -15,6 +15,8 @@ public:
 		const std::filesystem::path& patchedGlslPath,
 		unsigned maxTemporalHistoryFrames);
 
+	static bool FindSlangCompilerPath(const std::filesystem::path& repoRoot, std::filesystem::path& compilerPath, std::string& error);
+
 	bool BuildPassFragmentShaderSource(const ShaderPackage& shaderPackage, const ShaderPassDefinition& pass, std::string& fragmentShaderSource, std::string& error) const;
 
 private:

tests/CMakeLists.txt

@@ -137,6 +137,11 @@ add_video_shader_test(ShaderSlangValidationTests
 	"${TEST_DIR}/ShaderSlangValidationTests.cpp"
 )
 
+add_video_shader_test(ShaderCompilerLookupTests
+	"${SRC_DIR}/shader/ShaderCompiler.cpp"
+	"${TEST_DIR}/ShaderCompilerLookupTests.cpp"
+)
+
 add_video_shader_test(Std140BufferTests
 	"${TEST_DIR}/Std140BufferTests.cpp"
 )
@@ -169,5 +174,5 @@ set_tests_properties(RenderCadenceCompositorLoggerTests PROPERTIES
 )
 
 set_tests_properties(ShaderSlangValidationTests PROPERTIES
-	ENVIRONMENT "SLANG_ROOT=${SLANG_ROOT}"
+	ENVIRONMENT "SLANG_ROOT=${SLANG_ROOT};THIRD_PARTY_ROOT=${THIRD_PARTY_ROOT}"
 )

tests/ShaderCompilerLookupTests.cpp

@@ -0,0 +1,203 @@
+#include "ShaderCompiler.h"
+
+#include <cstdlib>
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+#include <string>
+
+namespace
+{
+int gFailures = 0;
+
+void Expect(bool condition, const std::string& message)
+{
+	if (condition)
+		return;
+
+	++gFailures;
+	std::cerr << "FAIL: " << message << "\n";
+}
+
+std::filesystem::path MakeTestRoot(const std::string& name)
+{
+	const std::filesystem::path root =
+		std::filesystem::temp_directory_path() /
+		("shader-compiler-lookup-" + name + "-" + std::to_string(std::filesystem::file_time_type::clock::now().time_since_epoch().count()));
+	std::filesystem::create_directories(root);
+	return root;
+}
+
+void WriteFakeSlangCompiler(const std::filesystem::path& path)
+{
+	std::filesystem::create_directories(path.parent_path());
+	std::ofstream output(path, std::ios::binary);
+	output << "not a real compiler";
+}
+
+std::string ReadEnvironmentVariable(const char* name)
+{
+#if defined(_MSC_VER)
+	char* value = nullptr;
+	std::size_t size = 0;
+	if (_dupenv_s(&value, &size, name) != 0 || value == nullptr)
+		return std::string();
+	std::string text(value);
+	std::free(value);
+	return text;
+#else
+	const char* value = std::getenv(name);
+	return value ? std::string(value) : std::string();
+#endif
+}
+
+void WriteEnvironmentVariable(const char* name, const std::string& value)
+{
+#if defined(_MSC_VER)
+	_putenv_s(name, value.c_str());
+#else
+	if (value.empty())
+		unsetenv(name);
+	else
+		setenv(name, value.c_str(), 1);
+#endif
+}
+
+class ScopedEnvironmentVariable
+{
+public:
+	ScopedEnvironmentVariable(const char* name, const std::string& value) :
+		mName(name),
+		mOriginal(ReadEnvironmentVariable(name))
+	{
+		WriteEnvironmentVariable(name, value);
+	}
+
+	~ScopedEnvironmentVariable()
+	{
+		WriteEnvironmentVariable(mName.c_str(), mOriginal);
+	}
+
+	ScopedEnvironmentVariable(const ScopedEnvironmentVariable&) = delete;
+	ScopedEnvironmentVariable& operator=(const ScopedEnvironmentVariable&) = delete;
+
+private:
+	std::string mName;
+	std::string mOriginal;
+};
+
+bool SamePath(const std::filesystem::path& left, const std::filesystem::path& right)
+{
+	std::error_code leftError;
+	std::error_code rightError;
+	return std::filesystem::weakly_canonical(left, leftError) == std::filesystem::weakly_canonical(right, rightError);
+}
+
+void TestSlangRootWinsOverThirdPartyRoot()
+{
+	const std::filesystem::path root = MakeTestRoot("slang-root");
+	const std::filesystem::path expected = root / "env-slang" / "bin" / "slangc.exe";
+	const std::filesystem::path thirdPartyCompiler = root / "third-party" / "slang-2026.8-windows-x86_64" / "bin" / "slangc.exe";
+	WriteFakeSlangCompiler(expected);
+	WriteFakeSlangCompiler(thirdPartyCompiler);
+
+	ScopedEnvironmentVariable slangRoot("SLANG_ROOT", (root / "env-slang").string());
+	ScopedEnvironmentVariable thirdPartyRoot("THIRD_PARTY_ROOT", (root / "third-party").string());
+
+	std::filesystem::path actual;
+	std::string error;
+	Expect(ShaderCompiler::FindSlangCompilerPath(root, actual, error), "SLANG_ROOT compiler is found");
+	Expect(SamePath(actual, expected), "SLANG_ROOT has priority over THIRD_PARTY_ROOT");
+
+	std::filesystem::remove_all(root);
+}
+
+void TestThirdPartyRootUsesCMakeBundleLayout()
+{
+	const std::filesystem::path root = MakeTestRoot("third-party-root");
+	const std::filesystem::path thirdPartyRootPath = root / "video-io-3rdParty";
+	const std::filesystem::path expected = thirdPartyRootPath / "slang-2026.8-windows-x86_64" / "bin" / "slangc.exe";
+	WriteFakeSlangCompiler(expected);
+
+	ScopedEnvironmentVariable slangRoot("SLANG_ROOT", "");
+	ScopedEnvironmentVariable thirdPartyRoot("THIRD_PARTY_ROOT", thirdPartyRootPath.string());
+
+	std::filesystem::path actual;
+	std::string error;
+	Expect(ShaderCompiler::FindSlangCompilerPath(root, actual, error), "THIRD_PARTY_ROOT compiler is found");
+	Expect(SamePath(actual, expected), "THIRD_PARTY_ROOT matches CMake's Slang bundle layout");
+
+	std::filesystem::remove_all(root);
+}
+
+void TestRepoVideoIoBundleWinsOverLegacyRepoBundle()
+{
+	const std::filesystem::path root = MakeTestRoot("repo-video-io");
+	const std::filesystem::path expected = root / "video-io-3rdParty" / "slang-2026.8-windows-x86_64" / "bin" / "slangc.exe";
+	const std::filesystem::path legacy = root / "3rdParty" / "slang-2026.8-windows-x86_64" / "bin" / "slangc.exe";
+	WriteFakeSlangCompiler(expected);
+	WriteFakeSlangCompiler(legacy);
+
+	ScopedEnvironmentVariable slangRoot("SLANG_ROOT", "");
+	ScopedEnvironmentVariable thirdPartyRoot("THIRD_PARTY_ROOT", "");
+
+	std::filesystem::path actual;
+	std::string error;
+	Expect(ShaderCompiler::FindSlangCompilerPath(root, actual, error), "repo video-io-3rdParty compiler is found");
+	Expect(SamePath(actual, expected), "repo video-io-3rdParty has priority over repo 3rdParty");
+
+	std::filesystem::remove_all(root);
+}
+
+void TestPackagedSlangFolderIsAccepted()
+{
+	const std::filesystem::path root = MakeTestRoot("packaged");
+	const std::filesystem::path expected = root / "3rdParty" / "slang" / "bin" / "slangc.exe";
+	WriteFakeSlangCompiler(expected);
+
+	ScopedEnvironmentVariable slangRoot("SLANG_ROOT", "");
+	ScopedEnvironmentVariable thirdPartyRoot("THIRD_PARTY_ROOT", "");
+
+	std::filesystem::path actual;
+	std::string error;
+	Expect(ShaderCompiler::FindSlangCompilerPath(root, actual, error), "packaged 3rdParty/slang compiler is found");
+	Expect(SamePath(actual, expected), "packaged Slang install layout is accepted");
+
+	std::filesystem::remove_all(root);
+}
+
+void TestLegacyThirdPartyScanStillAcceptsVersionedFolders()
+{
+	const std::filesystem::path root = MakeTestRoot("legacy-scan");
+	const std::filesystem::path expected = root / "3rdParty" / "slang-custom-build" / "bin" / "slangc.exe";
+	WriteFakeSlangCompiler(expected);
+
+	ScopedEnvironmentVariable slangRoot("SLANG_ROOT", "");
+	ScopedEnvironmentVariable thirdPartyRoot("THIRD_PARTY_ROOT", "");
+
+	std::filesystem::path actual;
+	std::string error;
+	Expect(ShaderCompiler::FindSlangCompilerPath(root, actual, error), "legacy 3rdParty scan finds versioned Slang folders");
+	Expect(SamePath(actual, expected), "legacy scan returns the discovered compiler path");
+
+	std::filesystem::remove_all(root);
+}
+}
+
+int main()
+{
+	TestSlangRootWinsOverThirdPartyRoot();
+	TestThirdPartyRootUsesCMakeBundleLayout();
+	TestRepoVideoIoBundleWinsOverLegacyRepoBundle();
+	TestPackagedSlangFolderIsAccepted();
+	TestLegacyThirdPartyScanStillAcceptsVersionedFolders();
+
+	if (gFailures != 0)
+	{
+		std::cerr << gFailures << " ShaderCompiler lookup test failure(s).\n";
+		return 1;
+	}
+
+	std::cout << "ShaderCompiler lookup tests passed.\n";
+	return 0;
+}