renderer: fix shader dump line numbering

- reset line number at GLSL shader start
- use custom line number for the GLSL header to avoid line number duplicates
- use custom line number for the deform vertex header
- reset line count on `#line 0`

Author: illwieckz

src/engine/renderer/gl_shader.cpp

@@ -496,10 +496,14 @@ static void AddConst( std::string& str, const std::string& name, float v1, float
 
 static std::string GenVersionDeclaration( const std::vector<addedExtension_t> &addedExtensions ) {
 	// Declare version.
-	std::string str = Str::Format( "#version %d %s\n\n",
+	std::string str = Str::Format( "#version %d %s\n",
 		glConfig.shadingLanguageVersion,
 		glConfig.shadingLanguageVersion >= 150 ? ( glConfig.glCoreProfile ? "core" : "compatibility" ) : "" );
 
+	str += "#line 1000000000\n";
+
+	str += "\n";
+
 	// Add supported GLSL extensions.
 	for ( const auto& addedExtension : addedExtensions ) {
 		addExtension( str, addedExtension.available, addedExtension.minGlslVersion, addedExtension.name );
@@ -858,7 +862,10 @@ std::string GLShaderManager::GetDeformShaderName( const int index ) {
 std::string GLShaderManager::BuildDeformShaderText( const std::string& steps ) {
 	std::string shaderText;
 
-	shaderText = steps + "\n";
+	shaderText = "\n" + steps + "\n";
+
+	shaderText += "#line 2000000000\n";
+
 	shaderText += GetShaderText( "deformVertexes_vp.glsl" );
 
 	return shaderText;
@@ -1214,6 +1221,13 @@ std::string GLShaderManager::ProcessInserts( const std::string& shaderText ) con
 
 	while ( std::getline( shaderTextStream, line, '\n' ) ) {
 		++lineCount;
+
+		/* The deform vertex header is prepended to the mainText and is part
+		of the shaderText, so we should reset line numbering after it. */
+		if ( line == "#line 0" ) {
+			lineCount = 0;
+		}
+
 		const std::string::size_type position = line.find( "#insert" );
 		if ( position == std::string::npos || line.find_first_not_of( " \t" ) != position ) {
 			out += line + "\n";
@@ -1344,7 +1358,9 @@ void GLShaderManager::InitShader( GLShader* shader ) {
 		if ( shaderType.enabled ) {
 			Com_sprintf( filename, sizeof( filename ), "%s%s.glsl", shaderType.path.c_str(), shaderType.postfix );
 
-			shaderType.mainText = GetShaderText( filename );
+			/* The deform vertex header is prepended to the mainText,
+			so we should reset line numbering after it. */
+			shaderType.mainText = "#line 0\n" + GetShaderText( filename );
 		}
 	}