source/blender/blenkernel/BKE_blender_version.h

@@ -27,7 +27,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 11
+#define BLENDER_FILE_SUBVERSION 12
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and show a warning if the file

source/blender/blenkernel/intern/curve.cc

@@ -400,6 +400,11 @@ void BKE_curve_init(Curve *cu, const short curve_type)
     BLI_strncpy(cu->str, "Text", 12);
     cu->len = cu->len_char32 = cu->pos = 4;
     cu->strinfo = (CharInfo *)MEM_calloc_arrayN(12, sizeof(CharInfo), "strinfo new");
+    /* Initialize CharInfo mat_nr to 1, since index starts at 1, unlike mesh or nurbs. */
+    CharInfo *info = cu->strinfo;
+    for (int i = cu->len_char32 - 1; i >= 0; i--, info++) {
+      info->mat_nr = 1;
+    }
     cu->totbox = cu->actbox = 1;
     cu->tb = (TextBox *)MEM_calloc_arrayN(MAXTEXTBOX, sizeof(TextBox), "textbox");
     cu->tb[0].w = cu->tb[0].h = 0.0;
@@ -5322,7 +5327,8 @@ void BKE_curve_material_index_remove(Curve *cu, int index)
   if (curvetype == OB_FONT) {
     CharInfo *info = cu->strinfo;
     for (int i = cu->len_char32 - 1; i >= 0; i--, info++) {
-      if (info->mat_nr && info->mat_nr >= index) {
+      /* CharInfo mat_nr starts at 1, unlike mesh & nurbs. */
+      if (info->mat_nr && info->mat_nr > index) {
         info->mat_nr--;
       }
     }
@@ -5342,8 +5348,9 @@ bool BKE_curve_material_index_used(const Curve *cu, int index)
 
   if (curvetype == OB_FONT) {
     const CharInfo *info = cu->strinfo;
+    /* CharInfo mat_nr starts at 1, unlike mesh & nurbs. */
     for (int i = cu->len_char32 - 1; i >= 0; i--, info++) {
-      if (info->mat_nr == index) {
+      if (info->mat_nr == index + 1) {
         return true;
       }
     }
@@ -5366,7 +5373,8 @@ void BKE_curve_material_index_clear(Curve *cu)
   if (curvetype == OB_FONT) {
     CharInfo *info = cu->strinfo;
     for (int i = cu->len_char32 - 1; i >= 0; i--, info++) {
-      info->mat_nr = 0;
+      /* CharInfo mat_nr starts at 1, unlike mesh & nurbs. */
+      info->mat_nr = 1;
     }
   }
   else {
@@ -5387,7 +5395,8 @@ bool BKE_curve_material_index_validate(Curve *cu)
     int i;
     for (i = cu->len_char32 - 1; i >= 0; i--, info++) {
       if (info->mat_nr > max_idx) {
-        info->mat_nr = 0;
+        /* CharInfo mat_nr starts at 1, unlike mesh & nurbs. */
+        info->mat_nr = 1;
         is_valid = false;
       }
     }

source/blender/blenkernel/intern/vfont.cc

@@ -1684,8 +1684,9 @@ static bool vfont_to_curve(Object *ob,
        * time that code is called without an object. */
       if (ob != nullptr && (info->mat_nr > (ob->totcol))) {
         // CLOG_ERROR(
-        //     &LOG, "Illegal material index (%d) in text object, setting to 0", info->mat_nr);
-        info->mat_nr = 0;
+        //     &LOG, "Illegal material index (%d) in text object, setting to 1", info->mat_nr);
+        /* CharInfo mat_nr starts at 1, unlike mesh & nurbs. */
+        info->mat_nr = 1;
       }
       /* We don't want to see any character for '\n'. */
       if (cha != '\n') {

source/blender/blenloader/intern/versioning_400.cc

@@ -13,6 +13,7 @@
 #include "CLG_log.h"
 
 #include "DNA_brush_types.h"
+#include "DNA_curve_types.h"
 #include "DNA_light_types.h"
 #include "DNA_lightprobe_types.h"
 #include "DNA_modifier_types.h"
@@ -28,6 +29,7 @@
 #include "BLI_set.hh"
 #include "BLI_string_ref.hh"
 
+#include "BKE_curve.h"
 #include "BKE_grease_pencil.hh"
 #include "BKE_idprop.hh"
 #include "BKE_main.h"
@@ -363,6 +365,21 @@ void blo_do_versions_400(FileData *fd, Library * /*lib*/, Main *bmain)
     version_vertex_weight_edit_preserve_threshold_exclusivity(bmain);
   }
 
+  if (!MAIN_VERSION_FILE_ATLEAST(bmain, 400, 12)) {
+    LISTBASE_FOREACH (Curve *, curve, &bmain->curves) {
+      const int curvetype = BKE_curve_type_get(curve);
+      if (curvetype == OB_FONT) {
+        CharInfo *info = curve->strinfo;
+        for (int i = curve->len_char32 - 1; i >= 0; i--, info++) {
+          if (info->mat_nr == 0) {
+            /** CharInfo mat_nr starts at 1, unlike mesh & nurbs. */
+            info->mat_nr = 1;
+          }
+        }
+      }
+    }
+  }
+
   /**
    * Versioning code until next subversion bump goes here.
    *