Rework TemplateString for standard compliance

Creating an std::integer_sequence from a user-defined string literal is
a non-standard gcc extension. This alternative implementation should
conform to C++20.

tools/quake3/q3map2/autopk3.cpp

@@ -107,7 +107,7 @@ static void parseBspFile( const char *bspPath, StrList& outShaders, StrList& out
 		}
 
 		for ( size_t i = 0; i < bspShaders.size(); ++i ){
-			if ( drawsurfSHs[i] && !( bspShaders[i].surfaceFlags & GetRequiredSurfaceParm( "nodraw"_Tstring ).surfaceFlags ) ){ // also sort out nodraw patches
+			if ( drawsurfSHs[i] && !( bspShaders[i].surfaceFlags & GetRequiredSurfaceParm<"nodraw">().surfaceFlags ) ){ // also sort out nodraw patches
 				res2list( pk3Shaders, bspShaders[i].shader );
 			}
 		}

tools/quake3/q3map2/convert_map.cpp

@@ -340,7 +340,7 @@ static void ConvertBrush( FILE *f, int bspBrushNum, const Vector3& origin, bool
 
 	/* find out if brush is detail */
 	int contentFlag = 0;
-	if( !( bspShaders[bspBrushes[bspBrushNum].shaderNum].contentFlags & GetRequiredSurfaceParm( "structural"_Tstring ).contentFlags ) ){ // sort out structural transparent brushes, e.g. hints
+	if( !( bspShaders[bspBrushes[bspBrushNum].shaderNum].contentFlags & GetRequiredSurfaceParm<"structural">().contentFlags ) ){ // sort out structural transparent brushes, e.g. hints
 		for( const auto& leaf : bspLeafs ){
 			if( leaf.cluster >= 0 )
 				for( auto id = bspLeafBrushes.cbegin() + leaf.firstBSPLeafBrush, end = id + leaf.numBSPLeafBrushes; id != end; ++id ){

tools/quake3/q3map2/map.cpp

@@ -496,10 +496,10 @@ static void SetBrushContents( brush_t& b ){
 		else if ( s->compileFlags & C_FOG ){
 			b.contentShader = s->shaderInfo;
 		}
-		else if ( b.contentShader->contentFlags & GetRequiredSurfaceParm( "playerclip"_Tstring ).contentFlags ){
+		else if ( b.contentShader->contentFlags & GetRequiredSurfaceParm<"playerclip">().contentFlags ){
 			continue;
 		}
-		else if ( s->contentFlags & GetRequiredSurfaceParm( "playerclip"_Tstring ).contentFlags ){
+		else if ( s->contentFlags & GetRequiredSurfaceParm<"playerclip">().contentFlags ){
 			b.contentShader = s->shaderInfo;
 		}
 		else if (!( b.contentShader->compileFlags & C_SOLID )){

tools/quake3/q3map2/q3map2.h

@@ -67,6 +67,7 @@
 #include "bitflags.h"
 #include <list>
 #include <forward_list>
+#include <algorithm>
 #include "qmath.h"
 
 #include <cstddef>
@@ -1662,17 +1663,21 @@ void                        TCMod( const tcMod_t& mod, Vector2& st );
 bool                        ApplySurfaceParm( const char *name, int *contentFlags, int *surfaceFlags, int *compileFlags );
 const surfaceParm_t         *GetSurfaceParm( const char *name );
 
-// Encode the string as a type
-template <char... chars>
-using TemplateString = std::integer_sequence<char, chars...>;
-// Create a user defined literal operator
-template <typename T, T... chars>
-constexpr TemplateString<chars...> operator""_Tstring() { return { }; }
+// Encode the string as a structural literal class type
+template <std::size_t N>
+struct TemplateString
+{
+	consteval TemplateString( const char(&string)[N] ) {
+		std::copy_n( string, N, m_data );
+		ENSURE( string[N - 1] == '\0' && "TemplateString must be null-terminated" ); // consteval ensures this is evaluated at compile time, despite not being a static_assert
+	}
+	char m_data[N];
+};
+
 /// \brief returns statically evaluated \c surfaceParm_t for the given name or emits \c Error
-template<char... chars>
-const surfaceParm_t         &GetRequiredSurfaceParm( const TemplateString<chars...> ){
-    static constexpr char str[sizeof...(chars) + 1] = { chars..., '\0' }; // Recover the character data
-	static const surfaceParm_t *const sp = GetSurfaceParm( str );
+template<TemplateString string>
+const surfaceParm_t         &GetRequiredSurfaceParm(){
+	static const surfaceParm_t *const sp = GetSurfaceParm( string.m_data ); // null-termination ensured in constructor
 	ENSURE( sp != nullptr );
     return *sp;
 }

tools/quake3/q3map2/surface_meta.cpp

@@ -383,7 +383,7 @@ static void TriangulatePatchSurface( const entity_t& e, mapDrawSurface_t *ds ){
 	memcpy( dsNew, ds, sizeof( *ds ) );
 
 	/* if the patch is nonsolid, then discard it */
-	if ( !( ds->shaderInfo->compileFlags & C_SOLID ) && !( ds->shaderInfo->contentFlags & GetRequiredSurfaceParm( "playerclip"_Tstring ).contentFlags ) ) {
+	if ( !( ds->shaderInfo->compileFlags & C_SOLID ) && !( ds->shaderInfo->contentFlags & GetRequiredSurfaceParm<"playerclip">().contentFlags ) ) {
 		ClearSurface( ds );
 	}