WM: return the string length from operator name conversion

- In some cases it avoids using strlen on the result.
- Use ATTR_NONNULL for all arguments.
- Remove NULL pointer check for WM_operator_bl_idname src argument.
- Rename from/to to src/dst.

source/blender/makesrna/intern/rna_wm.c

@@ -1157,9 +1157,7 @@ static int rna_wmKeyMapItem_idname_length(PointerRNA *ptr)
 {
   wmKeyMapItem *kmi = ptr->data;
   char pyname[OP_MAX_TYPENAME];
-
-  WM_operator_py_idname(pyname, kmi->idname);
-  return strlen(pyname);
+  return WM_operator_py_idname(pyname, kmi->idname);
 }
 
 static void rna_wmKeyMapItem_idname_set(PointerRNA *ptr, const char *value)

source/blender/windowmanager/WM_api.h

@@ -895,12 +895,14 @@ char *WM_prop_pystring_assign(struct bContext *C,
                               int index);
 /**
  * Convert: `some.op` -> `SOME_OT_op` or leave as-is.
+ * \return the length of `dst`.
  */
-void WM_operator_bl_idname(char *to, const char *from);
+size_t WM_operator_bl_idname(char *dst, const char *src) ATTR_NONNULL(1, 2);
 /**
  * Convert: `SOME_OT_op` -> `some.op` or leave as-is.
+ * \return the length of `dst`.
  */
-void WM_operator_py_idname(char *to, const char *from);
+size_t WM_operator_py_idname(char *dst, const char *src) ATTR_NONNULL(1, 2);
 /**
  * Sanity check to ensure #WM_operator_bl_idname won't fail.
  * \returns true when there are no problems with \a idname, otherwise report an error.

source/blender/windowmanager/intern/wm_operators.c

@@ -106,47 +106,38 @@
 /** \name Operator API
  * \{ */
 
-void WM_operator_py_idname(char *to, const char *from)
+size_t WM_operator_py_idname(char *dst, const char *src)
 {
-  const char *sep = strstr(from, "_OT_");
+  const char *sep = strstr(src, "_OT_");
   if (sep) {
-    int ofs = (sep - from);
+    int ofs = (sep - src);
 
     /* NOTE: we use ascii `tolower` instead of system `tolower`, because the
      * latter depends on the locale, and can lead to `idname` mismatch. */
-    memcpy(to, from, sizeof(char) * ofs);
-    BLI_str_tolower_ascii(to, ofs);
+    memcpy(dst, src, sizeof(char) * ofs);
+    BLI_str_tolower_ascii(dst, ofs);
 
-    to[ofs] = '.';
-    BLI_strncpy(to + (ofs + 1), sep + 4, OP_MAX_TYPENAME - (ofs + 1));
-  }
-  else {
-    /* should not happen but support just in case */
-    BLI_strncpy(to, from, OP_MAX_TYPENAME);
+    dst[ofs] = '.';
+    return BLI_strncpy_rlen(dst + (ofs + 1), sep + 4, OP_MAX_TYPENAME - (ofs + 1)) + (ofs + 1);
   }
+  /* Should not happen but support just in case. */
+  return BLI_strncpy_rlen(dst, src, OP_MAX_TYPENAME);
 }
 
-void WM_operator_bl_idname(char *to, const char *from)
+size_t WM_operator_bl_idname(char *dst, const char *src)
 {
-  if (from) {
-    const char *sep = strchr(from, '.');
-
-    int from_len;
-    if (sep && (from_len = strlen(from)) < OP_MAX_TYPENAME - 3) {
-      const int ofs = (sep - from);
-      memcpy(to, from, sizeof(char) * ofs);
-      BLI_str_toupper_ascii(to, ofs);
-      memcpy(to + ofs, "_OT_", 4);
-      memcpy(to + (ofs + 4), sep + 1, (from_len - ofs));
-    }
-    else {
-      /* should not happen but support just in case */
-      BLI_strncpy(to, from, OP_MAX_TYPENAME);
-    }
-  }
-  else {
-    to[0] = 0;
+  const char *sep = strchr(src, '.');
+  int from_len;
+  if (sep && (from_len = strlen(src)) < OP_MAX_TYPENAME - 3) {
+    const int ofs = (sep - src);
+    memcpy(dst, src, sizeof(char) * ofs);
+    BLI_str_toupper_ascii(dst, ofs);
+    memcpy(dst + ofs, "_OT_", 4);
+    memcpy(dst + (ofs + 4), sep + 1, (from_len - ofs));
+    return (from_len - ofs) - 1;
   }
+  /* Should not happen but support just in case. */
+  return BLI_strncpy_rlen(dst, src, OP_MAX_TYPENAME);
 }
 
 bool WM_operator_py_idname_ok_or_report(ReportList *reports,