RNA: use a function to access the nurbs error message

It makes more sense to use a function in this case as this
creates an error message which is not data associated with
the NURBS curve.

release/scripts/startup/bl_ui/properties_data_curve.py

@@ -321,17 +321,16 @@ class DATA_PT_active_spline(CurveButtonsPanelActive, Panel):
 
             layout.prop(act_spline, "use_smooth")
             if act_spline.type == 'NURBS':
-                messages = [act_spline.valid_message_u]
-                if is_surf and act_spline.point_count_v > 1:
-                    messages.append(act_spline.valid_message_v)
-
-                messages = list(filter(None, messages))
-
-                if len(messages) > 0:
-                    layout.separator()
-                    col = layout.column(align=True)
-                    for message in messages:
-                        col.label(text=message, icon='INFO')
+                col = None
+                for direction in range(2):
+                    message = act_spline.valid_message(direction)
+                    if not message:
+                        continue
+                    if col is None:
+                        layout.separator()
+                        col = layout.column(align=True)
+                    col.label(text=message, icon='INFO')
+                del col
 
 
 class DATA_PT_font(CurveButtonsPanelText, Panel):

source/blender/makesrna/intern/rna_curve.c

@@ -562,38 +562,6 @@ static void rna_Curve_offset_set(PointerRNA *ptr, float value)
   cu->offset = 1.0f + value;
 }
 
-static int rna_Nurb_valid_message_u_length(PointerRNA *ptr)
-{
-  char buff[64];
-  Nurb *nu = (Nurb *)ptr->data;
-  BKE_nurb_valid_message(
-      nu->pntsu, nu->orderu, nu->flagu, nu->type, nu->pntsv > 1, "U", buff, sizeof(buff));
-  return strlen(buff);
-}
-
-static void rna_Nurb_valid_message_u(PointerRNA *ptr, char *value)
-{
-  Nurb *nu = (Nurb *)ptr->data;
-  BKE_nurb_valid_message(
-      nu->pntsu, nu->orderu, nu->flagu, nu->type, nu->pntsv > 1, "U", value, 64);
-}
-
-static int rna_Nurb_valid_message_v_length(PointerRNA *ptr)
-{
-  char buff[64];
-  Nurb *nu = (Nurb *)ptr->data;
-  BKE_nurb_valid_message(
-      nu->pntsv, nu->orderv, nu->flagv, nu->type, nu->pntsv > 1, "V", buff, sizeof(buff));
-  return strlen(buff);
-}
-
-static void rna_Nurb_valid_message_v(PointerRNA *ptr, char *value)
-{
-  Nurb *nu = (Nurb *)ptr->data;
-  BKE_nurb_valid_message(
-      nu->pntsv, nu->orderv, nu->flagv, nu->type, nu->pntsv > 1, "V", value, 64);
-}
-
 static int rna_Curve_body_length(PointerRNA *ptr);
 static void rna_Curve_body_get(PointerRNA *ptr, char *value)
 {
@@ -2059,18 +2027,6 @@ static void rna_def_curve_nurb(BlenderRNA *brna)
       prop, "Bezier V", "Make this nurbs surface act like a Bezier spline in the V direction");
   RNA_def_property_update(prop, 0, "rna_Nurb_update_knot_v");
 
-  prop = RNA_def_property(srna, "valid_message_u", PROP_STRING, PROP_NONE);
-  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
-  RNA_def_property_string_funcs(
-      prop, "rna_Nurb_valid_message_u", "rna_Nurb_valid_message_u_length", NULL);
-  RNA_def_property_ui_text(prop, "Valid U", "Validation message for NURBS definition in U");
-
-  prop = RNA_def_property(srna, "valid_message_v", PROP_STRING, PROP_NONE);
-  RNA_def_property_clear_flag(prop, PROP_EDITABLE);
-  RNA_def_property_string_funcs(
-      prop, "rna_Nurb_valid_message_v", "rna_Nurb_valid_message_v_length", NULL);
-  RNA_def_property_ui_text(prop, "Valid V", "Validation message for NURBS definition in V");
-
   prop = RNA_def_property(srna, "use_smooth", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "flag", CU_SMOOTH);
   RNA_def_property_ui_text(prop, "Smooth", "Smooth the normals of the surface or beveled curve");

source/blender/makesrna/intern/rna_curve_api.c

@@ -36,6 +36,39 @@ static float rna_Nurb_calc_length(Nurb *nu, int resolution_u)
   return BKE_nurb_calc_length(nu, resolution_u);
 }
 
+static void rna_Nurb_valid_message(Nurb *nu, int direction, int *result_len, const char **r_result)
+{
+  const bool is_surf = nu->pntsv > 1;
+  const short type = nu->type;
+
+  int pnts;
+  short order, flag;
+  const char *dir;
+  if (direction) {
+    pnts = nu->pntsu;
+    order = nu->orderu;
+    flag = nu->flagu;
+    dir = "U";
+  }
+  else {
+    pnts = nu->pntsv;
+    order = nu->orderv;
+    flag = nu->flagv;
+    dir = "V";
+  }
+
+  char buf[64];
+  if (BKE_nurb_valid_message(pnts, order, flag, type, is_surf, dir, buf, sizeof(buf))) {
+    const int buf_len = strlen(buf);
+    *r_result = BLI_strdupn(buf, buf_len);
+    *result_len = buf_len;
+  }
+  else {
+    *r_result = NULL;
+    *result_len = 0;
+  }
+}
+
 #else
 
 void RNA_api_curve(StructRNA *srna)
@@ -86,6 +119,22 @@ void RNA_api_curve_nurb(StructRNA *srna)
                                 0.0f,
                                 FLT_MAX);
   RNA_def_function_return(func, parm);
+
+  func = RNA_def_function(srna, "valid_message", "rna_Nurb_valid_message");
+  RNA_def_function_ui_description(func, "Return the message");
+  parm = RNA_def_int(
+      func, "direction", 0, 0, 1, "Direction", "The direction where 0-1 maps to U-V", 0, 1);
+  RNA_def_parameter_flags(parm, 0, PARM_REQUIRED);
+  /* return value */
+  parm = RNA_def_string(func,
+                        "result",
+                        "nothing",
+                        64,
+                        "Return value",
+                        "The message or an empty string when there is no error");
+
+  RNA_def_parameter_flags(parm, PROP_DYNAMIC, PARM_OUTPUT);
+  RNA_def_property_clear_flag(parm, PROP_NEVER_NULL);
 }
 
 #endif