Allow word wrap together with whitespace-mode (bug #11341)

 src/xdisp.c (IT_DISPLAYING_WHITESPACE): In addition to the loaded
 display element, check also the underlying string or buffer
 character.

2 files changed, 19 insertions, 5 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 8b23806e57f..df0e6135498 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,9 @@
 2012-04-26  Eli Zaretskii  <eliz@gnu.org>
 
+        * xdisp.c (IT_DISPLAYING_WHITESPACE): In addition to the loaded
+        display element, check also the underlying string or buffer
+        character.  (Bug#11341)
+
         * w32menu.c: Include w32heap.h.
         (add_menu_item): If the call to AppendMenuW (via
         unicode_append_menu) fails, disable Unicode menus only if we are
diff --git a/src/xdisp.c b/src/xdisp.c
index 3cbd4b172f4..f2700bd6d25 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -383,11 +383,21 @@ static Lisp_Object Qline_height;
 #define IT_OVERFLOW_NEWLINE_INTO_FRINGE(it) 0
 #endif /* HAVE_WINDOW_SYSTEM */
 
-/* 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'))))         \
 
 /* Name of the face used to highlight trailing whitespace.  */