-/* Test if the display element loaded in IT is a space or tab
- character. This is used to determine word wrapping. */
-
-#define IT_DISPLAYING_WHITESPACE(it) \
- (it->what == IT_CHARACTER && (it->c == ' ' || it->c == '\t'))
+/* Test if the display element loaded in IT, or the underlying buffer
+ or string character, is a space or a TAB character. This is used
+ to determine where word wrapping can occur. */
+
+#define IT_DISPLAYING_WHITESPACE(it) \
+ ((it->what == IT_CHARACTER && (it->c == ' ' || it->c == '\t')) \
+ || ((STRINGP (it->string) \
+ && (SREF (it->string, IT_STRING_BYTEPOS (*it)) == ' ' \
+ || SREF (it->string, IT_STRING_BYTEPOS (*it)) == '\t')) \
+ || (it->s \
+ && (it->s[IT_BYTEPOS (*it)] == ' ' \
+ || it->s[IT_BYTEPOS (*it)] == '\t')) \
+ || (IT_BYTEPOS (*it) < ZV_BYTE \
+ && (*BYTE_POS_ADDR (IT_BYTEPOS (*it)) == ' ' \
+ || *BYTE_POS_ADDR (IT_BYTEPOS (*it)) == '\t')))) \