[util] Add tristate config option type

src/util/config/config.cpp

@@ -193,6 +193,24 @@ namespace dxvk {
     result = sign * intval;
     return true;
   }
+  
+  
+  bool Config::parseOptionValue(
+    const std::string&  value,
+          Tristate&     result) {
+    if (value == "True") {
+      result = Tristate::True;
+      return true;
+    } else if (value == "False") {
+      result = Tristate::False;
+      return true;
+    } else if (value == "Auto") {
+      result = Tristate::Auto;
+      return true;
+    } else {
+      return false;
+    }
+  }
 
 
   Config Config::getAppConfig(const std::string& appName) {

src/util/config/config.h

@@ -5,6 +5,18 @@
 
 namespace dxvk {
 
+  /**
+   * \brief Tri-state
+   * 
+   * Used to conditionally override
+   * booleans if desired.
+   */
+  enum class Tristate : int32_t {
+    Auto  = -1,
+    False =  0,
+    True  =  1,
+  };
+
   /**
    * \brief Config option set
    * 
@@ -108,7 +120,26 @@ namespace dxvk {
     static bool parseOptionValue(
       const std::string&  value,
             int32_t&      result);
+    
+    static bool parseOptionValue(
+      const std::string&  value,
+            Tristate&     result);
 
   };
 
+
+  /**
+   * \brief Applies tristate option
+   * 
+   * Overrides the given value if \c state is
+   * \c True or \c False, and leaves it intact
+   * otherwise.
+   * \param [out] option The value to override
+   * \param [in] state Tristate to apply
+   */
+  inline void applyTristate(bool& option, Tristate state) {
+    option &= state != Tristate::False;
+    option |= state == Tristate::True;
+  }
+
 }