Start working on mouse highlight of mode- and header-lines.

 xdisp.c (rows_from_pos_range, mouse_face_from_buffer_pos)
 (note_mode_line_or_margin_highlight): Fix comments.

2 files changed, 27 insertions, 24 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 3a1e0810d41..0f7d39e4d8a 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2010-10-16  Eli Zaretskii  <eliz@gnu.org>
+
+        * xdisp.c (rows_from_pos_range, mouse_face_from_buffer_pos)
+        (note_mode_line_or_margin_highlight): Fix comments.
+
 2010-10-09  Eli Zaretskii  <eliz@gnu.org>
 
         Finished work on mouse_face_from_buffer_pos for bidi-reordered
diff --git a/src/xdisp.c b/src/xdisp.c
index 9f39046b1f5..4a7cc275c47 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -23926,7 +23926,7 @@ rows_from_pos_range (struct window *w,
              glyphs it displays has a charpos from the range
              [START_CHARPOS..END_CHARPOS).
 
-             This is not obvious because bidi reordering could have
+             This is not obvious because bidi reordering could make
              buffer positions of a row be 1,2,3,102,101,100, and if we
              want to highlight characters in [50..60), we don't want
              this row, even though [50..60) does intersect [1..103),
@@ -24031,17 +24031,12 @@ mouse_face_from_buffer_pos (Lisp_Object window,
   xassert (NILP (before_string) || STRINGP (before_string));
   xassert (NILP (after_string) || STRINGP (after_string));
 
-  /* FIXME: Sometimes the caller gets "wise" and gives us the window
-     start position instead of the real start of the mouse face
-     property.  This completely messes up the logic of finding the
-     beg_row and end_row.  */
-
   /* Find the rows corresponding to START_CHARPOS and END_CHARPOS.  */
   rows_from_pos_range (w, start_charpos, end_charpos, &r1, &r2);
   if (r1 == NULL)
     r1 = MATRIX_ROW (w->current_matrix, XFASTINT (w->window_end_vpos));
   /* If the before-string or display-string contains newlines,
-     row_containing_pos skips to its last row.  Move back.  */
+     rows_from_pos_range skips to its last row.  Move back.  */
   if (!NILP (before_string) || !NILP (display_string))
     {
       struct glyph_row *prev;
@@ -24614,7 +24609,7 @@ note_mode_line_or_margin_highlight (Lisp_Object window, int x, int y,
              ? MATRIX_MODE_LINE_ROW (w->current_matrix)
              : MATRIX_HEADER_LINE_ROW (w->current_matrix));
 
-      /* Find glyph */
+      /* Find the glyph under the mouse pointer.  */
       if (row->mode_line_p && row->enabled_p)
         {
           glyph = row_start_glyph = row->glyphs[TEXT_AREA];
@@ -24733,14 +24728,15 @@ note_mode_line_or_margin_highlight (Lisp_Object window, int x, int y,
           if (NILP (e))
             e = make_number (SCHARS (string));
 
-          /* Calculate the position(glyph position: GPOS) of GLYPH in
-             displayed string. GPOS is different from CHARPOS.
+          /* Calculate the glyph position GPOS of GLYPH in the
+             displayed string.
 
-             CHARPOS is the position of glyph in internal string
-             object. A mode line string format has structures which
-             is converted to a flatten by emacs lisp interpreter.
-             The internal string is an element of the structures.
-             The displayed string is the flatten string. */
+             Note: GPOS is different from CHARPOS.  CHARPOS is the
+             position of GLYPH in the internal string object.  A mode
+             line string format has structures which are converted to
+             a flattened string by the Emacs Lisp interpreter.  The
+             internal string is an element of those structures.  The
+             displayed string is the flattened string.  */
           gpos = 0;
           if (glyph > row_start_glyph)
             {
@@ -24754,11 +24750,10 @@ note_mode_line_or_margin_highlight (Lisp_Object window, int x, int y,
                 }
             }
 
-          /* Calculate the lenght(glyph sequence length: GSEQ_LENGTH) of
-             displayed string holding GLYPH.
-
-             GSEQ_LENGTH is different from SCHARS (STRING).
-             SCHARS (STRING) returns the length of the internal string. */
+          /* Calculate the glyph sequence length GSEQ_LENGTH of the
+             displayed string to which GLYPH belongs.  Note:
+             GSEQ_LENGTH is different from SCHARS (STRING), because
+             the latter returns the length of the internal string.  */
           for (tmp_glyph = glyph, gseq_length = gpos;
                tmp_glyph->charpos < XINT (e);
                tmp_glyph++, gseq_length++)
@@ -24771,14 +24766,14 @@ note_mode_line_or_margin_highlight (Lisp_Object window, int x, int y,
           for (tmp_glyph = glyph - gpos; tmp_glyph != glyph; tmp_glyph++)
             total_pixel_width += tmp_glyph->pixel_width;
 
-          /* Pre calculation of re-rendering position */
-          hpos = (x - gpos);
+          /* Pre calculation of re-rendering position.  */
+          hpos = x - gpos;
           vpos = (area == ON_MODE_LINE
                   ? (w->current_matrix)->nrows - 1
                   : 0);
 
           /* If the re-rendering position is included in the last
-             re-rendering area, we should do nothing. */
+             re-rendering area, we should do nothing.  */
           if ( EQ (window, dpyinfo->mouse_face_window)
                && dpyinfo->mouse_face_beg_col <= hpos
                && hpos < dpyinfo->mouse_face_end_col
@@ -25137,7 +25132,10 @@ note_mouse_highlight (struct frame *f, int x, int y)
                      previous-single-property-change and
                      next-single-property-change, because
                      rows_from_pos_range needs the real start and end
-                     positions to DTRT in this case.  */
+                     positions to DTRT in this case.  That's because
+                     the first row visible in a window does not
+                     necessarily display the character whose position
+                     is the smallest.  */
                   Lisp_Object lim1 =
                     NILP (XBUFFER (buffer)->bidi_display_reordering)
                     ? Fmarker_position (w->start)