✨ Add support for explicit API layers

fixes #29
refs #28

Author: fredemmott

src/APILayer.hpp

@@ -23,10 +23,14 @@ struct APILayer {
   enum class Value {
     Enabled,
     Disabled,
+    NotInstalled,
     Win32_NotDWORD,
   };
+  enum class Kind {
+    Explicit,
+    Implicit,
+  };
 
-  APILayer() = delete;
   APILayer(
     const APILayerStore* source,
     const std::filesystem::path& manifestPath,
@@ -35,15 +39,31 @@ struct APILayer {
       mManifestPath(manifestPath),
       mValue(value) {}
 
+  static APILayer MakeAbsentExplicit(const std::string_view name) {
+    APILayer ret {nullptr, {}, Value::NotInstalled};
+    ret.mReferencedName = name;
+    return ret;
+  }
+
+  Kind GetKind() const noexcept;
+
   const APILayerStore* mSource {nullptr};
   std::filesystem::path mManifestPath;
   Value mValue;
 
+  /// Only set for explicit API layers that are referenced but not
+  /// present
+  std::string mReferencedName;
+
+  [[nodiscard]]
   constexpr bool IsEnabled() const noexcept {
     return mValue == Value::Enabled;
   };
 
   bool operator==(const APILayer&) const noexcept = default;
+
+ private:
+  APILayer() = default;
 };
 
 struct Extension {

src/APILayerDetails.cpp

@@ -7,6 +7,7 @@
 #include <fstream>
 
 #include "APILayer.hpp"
+#include "APILayerStore.hpp"
 #include "Platform.hpp"
 
 namespace FredEmmott::OpenXRLayers {
@@ -31,6 +32,16 @@ static void SetStringOrNumber(
   }
 }
 
+APILayer::Kind APILayer::GetKind() const noexcept {
+  if (!mSource) {
+    /// If we didn't find it in the registry or manifest locations,
+    /// it can't be implicit.
+    return Kind::Explicit;
+  }
+
+  return mSource->GetKind();
+}
+
 APILayerDetails::APILayerDetails(const std::filesystem::path& jsonPath) {
   if (!std::filesystem::exists(jsonPath)) {
     mState = State::NoJsonFile;

src/APILayerStore.hpp

@@ -13,6 +13,8 @@ class APILayerStore {
  public:
   virtual ~APILayerStore() = default;
 
+  virtual APILayer::Kind GetKind() const noexcept = 0;
+
   // e.g. "Win64-HKLM"
   virtual std::string GetDisplayName() const noexcept = 0;
   virtual std::vector<APILayer> GetAPILayers() const noexcept = 0;

src/linters/DisabledByEnvironmentLinter.cpp

@@ -17,6 +17,10 @@ class DisabledByEnvironmentLinter final : public Linter {
         continue;
       }
 
+      if (layer.GetKind() != APILayer::Kind::Implicit) {
+        continue;
+      }
+
       const auto& enableEnv = details.mEnableEnvironment;
       if ((!enableEnv.empty()) && !std::getenv(enableEnv.c_str())) {
         errors.push_back(

src/linters/SkippedByLoaderLinter.cpp

@@ -32,6 +32,10 @@ class SkippedByLoaderLinter final : public Linter {
         continue;
       }
 
+      if (layer.GetKind() != APILayer::Kind::Implicit) {
+        continue;
+      }
+
       if (!layer.mSource->IsForCurrentArchitecture()) {
         continue;
       }

src/windows/WindowsAPILayerStore.cpp

@@ -20,15 +20,19 @@
 
 namespace FredEmmott::OpenXRLayers {
 
-static constexpr auto SubKey {
+static constexpr auto ImplicitSubKey {
   L"SOFTWARE\\Khronos\\OpenXR\\1\\ApiLayers\\Implicit"};
+static constexpr auto ExplicitSubKey {
+  L"SOFTWARE\\Khronos\\OpenXR\\1\\ApiLayers\\Explicit"};
 
 WindowsAPILayerStore::WindowsAPILayerStore(
   std::string_view displayName,
+  APILayer::Kind kind,
   RegistryBitness bitness,
   HKEY rootKey,
   REGSAM desiredAccess)
   : mDisplayName(displayName),
+    mLayerKind(kind),
     mRegistryBitness(bitness),
     mRootKey(rootKey) {
   REGSAM samFlags {desiredAccess};
@@ -43,7 +47,7 @@ WindowsAPILayerStore::WindowsAPILayerStore(
   if (
     RegCreateKeyExW(
       rootKey,
-      SubKey,
+      (kind == APILayer::Kind::Implicit) ? ImplicitSubKey : ExplicitSubKey,
       0,
       nullptr,
       REG_OPTION_NON_VOLATILE,
@@ -59,11 +63,15 @@ WindowsAPILayerStore::WindowsAPILayerStore(
     return;
   }
   mEvent.reset(CreateEvent(nullptr, false, false, nullptr));
-  this->Poll();
+  this->WindowsAPILayerStore::Poll();
 }
 
 WindowsAPILayerStore::~WindowsAPILayerStore() = default;
 
+APILayer::Kind WindowsAPILayerStore::GetKind() const noexcept {
+  return mLayerKind;
+}
+
 std::string WindowsAPILayerStore::GetDisplayName() const noexcept {
   return mDisplayName;
 }
@@ -139,20 +147,23 @@ class ReadOnlyWindowsAPILayerStore final : public WindowsAPILayerStore {
  public:
   ReadOnlyWindowsAPILayerStore(
     std::string_view displayName,
+    APILayer::Kind kind,
     RegistryBitness bitness,
     HKEY rootKey)
-    : WindowsAPILayerStore(displayName, bitness, rootKey, KEY_READ) {}
+    : WindowsAPILayerStore(displayName, kind, bitness, rootKey, KEY_READ) {}
 };
 
 class ReadWriteWindowsAPILayerStore final : public WindowsAPILayerStore,
                                             public ReadWriteAPILayerStore {
  public:
   ReadWriteWindowsAPILayerStore(
     std::string_view displayName,
+    APILayer::Kind kind,
     RegistryBitness bitness,
     HKEY rootKey)
     : WindowsAPILayerStore(
         displayName,
+        kind,
         bitness,
         rootKey,
         KEY_READ | KEY_WRITE) {}
@@ -220,19 +231,32 @@ class ReadWriteWindowsAPILayerStore final : public WindowsAPILayerStore,
 template <class TInterface, class TConcrete>
 std::span<const TInterface*> GetStaticStores() noexcept {
   using RB = WindowsAPILayerStore::RegistryBitness;
+  using enum APILayer::Kind;
   static const TConcrete sHKLM64 {
-    "Win64-HKLM", RB::Wow64_64, HKEY_LOCAL_MACHINE};
+    "Win64-HKLM", Implicit, RB::Wow64_64, HKEY_LOCAL_MACHINE};
   static const TConcrete sHKCU64 {
-    "Win64-HKCU", RB::Wow64_64, HKEY_CURRENT_USER};
+    "Win64-HKCU", Implicit, RB::Wow64_64, HKEY_CURRENT_USER};
   static const TConcrete sHKLM32 {
-    "Win32-HKLM", RB::Wow64_32, HKEY_LOCAL_MACHINE};
+    "Win32-HKLM", Implicit, RB::Wow64_32, HKEY_LOCAL_MACHINE};
   static const TConcrete sHKCU32 {
-    "Win32-HKCU", RB::Wow64_32, HKEY_CURRENT_USER};
+    "Win32-HKCU", Implicit, RB::Wow64_32, HKEY_CURRENT_USER};
+  static const TConcrete sExplicitHKLM64 {
+    "Explicit Win64-HKLM", Explicit, RB::Wow64_64, HKEY_LOCAL_MACHINE};
+  static const TConcrete sExplicitHKCU64 {
+    "Explicit Win64-HKCU", Explicit, RB::Wow64_64, HKEY_CURRENT_USER};
+  static const TConcrete sExplicitHKLM32 {
+    "Explicit Win32-HKLM", Explicit, RB::Wow64_32, HKEY_LOCAL_MACHINE};
+  static const TConcrete sExplicitHKCU32 {
+    "Explicit Win32-HKCU", Explicit, RB::Wow64_32, HKEY_CURRENT_USER};
   static const TInterface* sStores[] {
     &sHKLM64,
     &sHKCU64,
     &sHKLM32,
     &sHKCU32,
+    &sExplicitHKLM64,
+    &sExplicitHKCU64,
+    &sExplicitHKLM32,
+    &sExplicitHKCU32,
   };
   return sStores;
 }

src/windows/WindowsAPILayerStore.hpp

@@ -21,6 +21,8 @@ class WindowsAPILayerStore : public virtual APILayerStore {
   WindowsAPILayerStore() = delete;
   ~WindowsAPILayerStore() override;
 
+  APILayer::Kind GetKind() const noexcept override;
+
   std::string GetDisplayName() const noexcept override;
 
   std::vector<APILayer> GetAPILayers() const noexcept override;
@@ -42,6 +44,7 @@ class WindowsAPILayerStore : public virtual APILayerStore {
  protected:
   WindowsAPILayerStore(
     std::string_view displayName,
+    APILayer::Kind layerKind,
     RegistryBitness bitness,
     HKEY rootKey,
     REGSAM desiredAccess);
@@ -51,6 +54,7 @@ class WindowsAPILayerStore : public virtual APILayerStore {
 
  private:
   const std::string mDisplayName;
+  const APILayer::Kind mLayerKind;
   const RegistryBitness mRegistryBitness;
   const HKEY mRootKey;
 };