Re: Line wrap reconsidered

[Yuan Fu <casouri@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 271 bytes --]

The redisplay code now works! Now I need to explore how to apply the text properties. I had a look at category table. IIUC, a category table for all unicode characters would be impractically large and unnecessary. A normal list of ranges would probably work. 

Yuan


[-- Attachment #2: wrap.patch --]
[-- Type: application/octet-stream, Size: 6019 bytes --]

diff --git a/src/xdisp.c b/src/xdisp.c
index 01f272033e..7f04c1bc67 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -427,6 +427,28 @@ #define IT_DISPLAYING_WHITESPACE(it)					\
 	   && (*BYTE_POS_ADDR (IT_BYTEPOS (*it)) == ' '			\
 	       || *BYTE_POS_ADDR (IT_BYTEPOS (*it)) == '\t'))))
 
+/* Return true if the current character allows wrapping before it.   */
+static bool char_can_wrap_before (struct it *it)
+{
+  Lisp_Object charpos = make_fixnum (IT_CHARPOS (*it));
+  Lisp_Object prop = Fget_text_property (charpos, Qcan_wrap, Qnil);
+  if (EQ (Qt, prop) || EQ (Qbefore_only, prop))
+    return true;
+  else
+    return false;
+}
+
+/* Return true if the current character allows wrapping after it.   */
+static bool char_can_wrap_after (struct it *it)
+{
+  Lisp_Object charpos = make_fixnum (IT_CHARPOS (*it));
+  Lisp_Object prop = Fget_text_property (charpos, Qcan_wrap, Qnil);
+  if (EQ (Qt, prop) || EQ (Qafter_only, prop))
+    return true;
+  else
+    return false;
+}
+
 /* If all the conditions needed to print the fill column indicator are
    met, return the (nonnegative) column number, else return a negative
    value.  */
@@ -9098,9 +9120,12 @@ #define IT_RESET_X_ASCENT_DESCENT(IT)			\
 	{
 	  if (it->line_wrap == WORD_WRAP && it->area == TEXT_AREA)
 	    {
-	      if (IT_DISPLAYING_WHITESPACE (it))
+              /* If this character displays a whitespace or the text
+                 property says you can wrap after it, the next one can
+                 wrap.  */
+	      if (IT_DISPLAYING_WHITESPACE (it) || char_can_wrap_after (it))
 		may_wrap = true;
-	      else if (may_wrap)
+	      if (! IT_DISPLAYING_WHITESPACE (it) && may_wrap)
 		{
 		  /* We have reached a glyph that follows one or more
 		     whitespace characters.  If the position is
@@ -9249,9 +9274,13 @@ #define IT_RESET_X_ASCENT_DESCENT(IT)			\
 			      bool can_wrap = true;
 
 			      /* If we are at a whitespace character
-				 that barely fits on this screen line,
-				 but the next character is also
-				 whitespace, we cannot wrap here.  */
+				 (or a character that allows wrapping
+				 after it) that barely fits on this
+				 screen line, but the next character
+				 is also whitespace (or a character
+				 that forbids wrapping before it), we
+				 cannot wrap here.
+                              */
 			      if (it->line_wrap == WORD_WRAP
 				  && wrap_it.sp >= 0
 				  && may_wrap
@@ -9263,7 +9292,8 @@ #define IT_RESET_X_ASCENT_DESCENT(IT)			\
 				  SAVE_IT (tem_it, *it, tem_data);
 				  set_iterator_to_next (it, true);
 				  if (get_next_display_element (it)
-				      && IT_DISPLAYING_WHITESPACE (it))
+				      && (IT_DISPLAYING_WHITESPACE (it)
+                                          || !char_can_wrap_before (it)))
 				    can_wrap = false;
 				  RESTORE_IT (it, &tem_it, tem_data);
 				}
@@ -9342,19 +9372,23 @@ #define IT_RESET_X_ASCENT_DESCENT(IT)			\
 		  else
 		    IT_RESET_X_ASCENT_DESCENT (it);
 
-		  /* If the screen line ends with whitespace, and we
-		     are under word-wrap, don't use wrap_it: it is no
-		     longer relevant, but we won't have an opportunity
-		     to update it, since we are done with this screen
-		     line.  */
+		  /* If the screen line ends with whitespace (or
+		     wrap-able character), and we are under word-wrap,
+		     don't use wrap_it: it is no longer relevant, but
+		     we won't have an opportunity to update it, since
+		     we are done with this screen line.  */
 		  if (may_wrap && IT_OVERFLOW_NEWLINE_INTO_FRINGE (it)
 		      /* If the character after the one which set the
-			 may_wrap flag is also whitespace, we can't
-			 wrap here, since the screen line cannot be
-			 wrapped in the middle of whitespace.
-			 Therefore, wrap_it _is_ relevant in that
+			 may_wrap flag is also whitespace (or is a
+			 character that forbids wrapping before it),
+			 we can't wrap here, since the screen line
+			 cannot be wrapped in the middle of whitespace
+			 (or before a character that forbids wrapping
+			 before it).  Therefore, wrap_it (previously
+			 found wrap-point) _is_ relevant in that
 			 case.  */
-		      && !(moved_forward && IT_DISPLAYING_WHITESPACE (it)))
+		      && !(moved_forward && (IT_DISPLAYING_WHITESPACE (it)
+                                             || !char_can_wrap_before (it))))
 		    {
 		      /* If we've found TO_X, go back there, as we now
 			 know the last word fits on this screen line.  */
@@ -23180,9 +23214,9 @@ #define RECORD_MAX_MIN_POS(IT)					\
 
 	  if (it->line_wrap == WORD_WRAP && it->area == TEXT_AREA)
 	    {
-	      if (IT_DISPLAYING_WHITESPACE (it))
+	      if (IT_DISPLAYING_WHITESPACE (it) || char_can_wrap_after (it))
 		may_wrap = true;
-	      else if (may_wrap)
+	      if (! IT_DISPLAYING_WHITESPACE (it) && may_wrap)
 		{
 		  SAVE_IT (wrap_it, *it, wrap_data);
 		  wrap_x = x;
@@ -23328,7 +23362,8 @@ #define RECORD_MAX_MIN_POS(IT)					\
 				 was a space or tab AND (ii) the
 				 current character is not.  */
 			      && (!may_wrap
-				  || IT_DISPLAYING_WHITESPACE (it)))
+				  || IT_DISPLAYING_WHITESPACE (it)
+                                  || char_can_wrap_after (it)))
 			    goto back_to_wrap;
 
 			  /* Record the maximum and minimum buffer
@@ -23362,7 +23397,8 @@ #define RECORD_MAX_MIN_POS(IT)					\
 					  was a space or tab AND (ii) the
 					  current character is not.  */
 				       && (!may_wrap
-					   || IT_DISPLAYING_WHITESPACE (it)))
+					   || IT_DISPLAYING_WHITESPACE (it)
+                                           || char_can_wrap_after (it)))
 				goto back_to_wrap;
 
 			    }
@@ -34231,6 +34267,9 @@ syms_of_xdisp (void)
   DEFSYM (QCfile, ":file");
   DEFSYM (Qfontified, "fontified");
   DEFSYM (Qfontification_functions, "fontification-functions");
+  DEFSYM (Qcan_wrap, "can-wrap");
+  DEFSYM (Qbefore_only, "before-only");
+  DEFSYM (Qafter_only, "after-only");
 
   /* Name of the symbol which disables Lisp evaluation in 'display'
      properties.  This is used by enriched.el.  */