From 2e409596cf4f6dbcb5849fbd9994249badd9be1e Mon Sep 17 00:00:00 2001
From: Leon Henrik Plickat <leonhenrik.plickat@stud.uni-goettingen.de>
Date: Fri, 29 Dec 2023 11:38:26 +0100
Subject: [PATCH] check if layout-demand-handler exists every time it is called

---
 riverguile.c | 33 ++++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/riverguile.c b/riverguile.c
index 0871188..2081e05 100644
--- a/riverguile.c
+++ b/riverguile.c
@@ -56,12 +56,33 @@ static bool scm2uint(uint32_t *x, SCM s)
 	return true;
 }
 
+/**
+ * Try to find a variable named 'name' and returns it, otherwise #f is returned.
+ */
+static SCM scm_c_get_variable (const char *name)
+{
+	return scm_module_variable(
+		scm_current_module(),
+		scm_string_to_symbol(
+			scm_from_utf8_string(name)
+		)
+	);
+}
+
 static void *call_layout_demand_handler (void *data)
 {
 	struct Layout_demand_parameters *params = (struct Layout_demand_parameters *)data;
 
+	SCM layout_demand_handler = scm_c_get_variable("layout-demand-handler");
+	if ( scm_is_false(layout_demand_handler) == 1 )
+	{
+		ret = EXIT_FAILURE;
+		loop = false;
+		return (void *)"ERROR: layout-demand-handler no longer exists.\n";
+	}
+
 	SCM call_result = scm_call_3(
-		scm_variable_ref(scm_c_lookup("layout-demand-handler")),
+		scm_variable_ref(layout_demand_handler),
 		scm_from_uint32(params->view_count),
 		scm_from_uint32(params->width),
 		scm_from_uint32(params->height)
@@ -320,14 +341,8 @@ static void *load_script (void *data)
 	scm_primitive_load_path(scm_from_utf8_string(path));
 
 	/* Check if the handler has been defined. */
-	SCM variable = scm_module_variable(
-		scm_current_module(),
-		scm_string_to_symbol(
-			scm_from_utf8_string("layout-demand-handler")
-		)
-	);
-
-	if ( scm_is_false(variable) == 1 )
+	SCM layout_demand_handler = scm_c_get_variable("layout-demand-handler");
+	if ( scm_is_false(layout_demand_handler) == 1 )
 	{
 		ret = EXIT_FAILURE;
 		loop = false;