Do not crash when no callback function is provided

gooey/gooey.lua

@@ -67,8 +67,13 @@ function M.mask_text(text, mask)
 end
 
 
+-- no-operation
+-- empty function to use when no component callback function was provided
+local function nop() end
+
+
 function M.button(node_id, action_id, action, fn, refresh_fn)
-	local b = button(node_id, action_id, action, fn, refresh_fn)
+	local b = button(node_id, action_id, action, fn or nop, refresh_fn)
 	if current_group then
 		current_group.components[#current_group.components + 1] = b
 	end
@@ -77,7 +82,7 @@ end
 
 
 function M.checkbox(node_id, action_id, action, fn, refresh_fn)
-	local c = checkbox(node_id, action_id, action, fn, refresh_fn)
+	local c = checkbox(node_id, action_id, action, fn or nop, refresh_fn)
 	if current_group then
 		current_group.components[#current_group.components + 1] = c
 	end
@@ -86,20 +91,20 @@ end
 
 
 function M.radiogroup(group_id, action_id, action, fn)
-	return radio.group(group_id, action_id, action, fn, refresh_fn)
+	return radio.group(group_id, action_id, action, fn or nop, refresh_fn)
 end
 
 
 function M.radio(node_id, group_id, action_id, action, fn, refresh_fn)
-	local r = radio.button(node_id, group_id, action_id, action, fn, refresh_fn)
+	local r = radio.button(node_id, group_id, action_id, action, fn or nop, refresh_fn)
 	if current_group then
 		current_group.components[#current_group.components + 1] = r
 	end
 	return r
 end
 
 function M.static_list(list_id, stencil_id, item_ids, action_id, action, config, fn, refresh_fn)
-	local l = list.static(list_id, stencil_id, item_ids, action_id, action, config, fn, refresh_fn)
+	local l = list.static(list_id, stencil_id, item_ids, action_id, action, config, fn or nop, refresh_fn)
 	if current_group then
 		current_group.components[#current_group.components + 1] = l
 	end
@@ -109,15 +114,15 @@ end
 function M.horizontal_static_list(list_id, stencil_id, item_ids, action_id, action, config, fn, refresh_fn)
 	config = config or {}
 	config.horizontal = true
-	return M.static_list(list_id, stencil_id, item_ids, action_id, action, config, fn, refresh_fn)
+	return M.static_list(list_id, stencil_id, item_ids, action_id, action, config, fn or nop, refresh_fn)
 end
 
 function M.vertical_static_list(list_id, stencil_id, item_ids, action_id, action, config, fn, refresh_fn)
-	return M.static_list(list_id, stencil_id, item_ids, action_id, action, config, fn, refresh_fn)
+	return M.static_list(list_id, stencil_id, item_ids, action_id, action, config, fn or nop, refresh_fn)
 end
 
 function M.dynamic_list(list_id, stencil_id, item_id, data, action_id, action, config, fn, refresh_fn)
-	local l = list.dynamic(list_id, stencil_id, item_id, data, action_id, action, config, fn, refresh_fn)
+	local l = list.dynamic(list_id, stencil_id, item_id, data, action_id, action, config, fn or nop, refresh_fn)
 	if current_group then
 		current_group.components[#current_group.components + 1] = l
 	end
@@ -127,15 +132,15 @@ end
 function M.horizontal_dynamic_list(list_id, stencil_id, item_id, data, action_id, action, config, fn, refresh_fn)
 	config = config or {}
 	config.horizontal = true
-	return M.dynamic_list(list_id, stencil_id, item_id, data, action_id, action, config, fn, refresh_fn)
+	return M.dynamic_list(list_id, stencil_id, item_id, data, action_id, action, config, fn or nop, refresh_fn)
 end
 
 function M.vertical_dynamic_list(list_id, stencil_id, item_id, data, action_id, action, config, fn, refresh_fn)
-	return M.dynamic_list(list_id, stencil_id, item_id, data, action_id, action, config, fn, refresh_fn)
+	return M.dynamic_list(list_id, stencil_id, item_id, data, action_id, action, config, fn or nop, refresh_fn)
 end
 
 function M.vertical_scrollbar(handle_id, bounds_id, action_id, action, config, fn, refresh_fn)
-	local sb = scrollbar.vertical(handle_id, bounds_id, action_id, action, config, fn, refresh_fn)
+	local sb = scrollbar.vertical(handle_id, bounds_id, action_id, action, config, fn or nop, refresh_fn)
 	if current_group then
 		current_group.components[#current_group.components + 1] = sb
 	end