mesa: add support cursor support for relative path shader includes

This will allow us to continue searching the current path for
relative shader includes.

From the ARB_shading_language_include spec:

   "If it is quoted with double quotes in a previously included
   string, then the first search point will be the tree location
   where the previously included string had been found."

Reviewed-by: Witold Baryluk <witold.baryluk@gmail.com>

src/compiler/glsl/glcpp/glcpp-parse.y

@@ -36,6 +36,12 @@ const char *
 _mesa_lookup_shader_include(struct gl_context *ctx, char *path,
                             bool error_check);
 
+size_t
+_mesa_get_shader_include_cursor(struct gl_shared_state *shared);
+
+void
+_mesa_set_shader_include_cursor(struct gl_shared_state *shared, size_t cursor);
+
 static void
 yyerror(YYLTYPE *locp, glcpp_parser_t *parser, const char *error);
 
@@ -344,10 +350,14 @@ control_line_success:
 		}
 	}
 |	HASH_TOKEN INCLUDE NEWLINE {
+		size_t include_cursor = _mesa_get_shader_include_cursor(parser->gl_ctx->Shared);
+
 		/* Remove leading and trailing "" or <> */
 		char *start = strchr($2, '"');
-		if (!start)
+		if (!start) {
+			_mesa_set_shader_include_cursor(parser->gl_ctx->Shared, 0);
 			start = strchr($2, '<');
+		}
 		char *path = strndup(start + 1, strlen(start + 1) - 1);
 
 		const char *shader =
@@ -410,6 +420,8 @@ control_line_success:
 			glcpp_lex_destroy(tmp_parser->scanner);
 			_mesa_hash_table_destroy(tmp_parser->defines, NULL);
 		}
+
+		_mesa_set_shader_include_cursor(parser->gl_ctx->Shared, include_cursor);
 	}
 |	HASH_TOKEN IF pp_tokens NEWLINE {
 		/* Be careful to only evaluate the 'if' expression if

src/compiler/glsl/glcpp/pp_standalone_scaffolding.c

@@ -39,3 +39,19 @@ _mesa_lookup_shader_include(struct gl_context *ctx, char *path,
 
    return NULL;
 }
+
+size_t
+_mesa_get_shader_include_cursor(struct gl_shared_state *shared)
+{
+   (void) shared;
+
+   return 0;
+}
+
+void
+_mesa_set_shader_include_cursor(struct gl_shared_state *shared,
+                                 size_t cursor)
+{
+   (void) shared;
+   (void) cursor;
+}

src/compiler/glsl/glcpp/pp_standalone_scaffolding.h

@@ -37,4 +37,11 @@ const char *
 _mesa_lookup_shader_include(struct gl_context *ctx, char *path,
                             bool error_check);
 
+size_t
+_mesa_get_shader_include_cursor(struct gl_shared_state *shared);
+
+void
+_mesa_set_shader_include_cursor(struct gl_shared_state *shared,
+                                size_t cursor);
+
 #endif /* PP_STANDALONE_SCAFFOLDING_H */