Fix cursor display (bug#23993)

[gnu-emacs] / src / xdisp.c

diff --git a/src/xdisp.c b/src/xdisp.c
index d05eca169c33294bd9f14a1b100e48ad9f114194..efd5f54fa39f57a6b4c0d9cb32bfa2029c52998f 100644 (file)
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -1321,6 +1321,11 @@ pos_visible_p (struct window *w, ptrdiff_t charpos, int *x, int *y,
   if (CHARPOS (top) > ZV)
     SET_TEXT_POS (top, BEGV, BEGV_BYTE);
 
+  /* If the top of the window is after CHARPOS, the latter is surely
+     not visible.  */
+  if (charpos >= 0 && CHARPOS (top) > charpos)
+    return visible_p;
+
   /* Compute exact mode line heights.  */
   if (WINDOW_WANTS_MODELINE_P (w))
     w->mode_line_height
@@ -2232,7 +2237,7 @@ get_phys_cursor_geometry (struct window *w, struct glyph_row *row,
   ascent = row->ascent;
   if (row->ascent < glyph->ascent)
     {
-      y =- glyph->ascent - row->ascent;
+      y -= glyph->ascent - row->ascent;
       ascent = glyph->ascent;
     }
 
@@ -15512,12 +15517,14 @@ try_scrolling (Lisp_Object window, bool just_this_one_p,
 
    The new window start will be computed, based on W's width, starting
    from the start of the continued line.  It is the start of the
-   screen line with the minimum distance from the old start W->start.  */
+   screen line with the minimum distance from the old start W->start,
+   which is still before point (otherwise point will definitely not
+   be visible in the window).  */
 
 static bool
 compute_window_start_on_continuation_line (struct window *w)
 {
-  struct text_pos pos, start_pos;
+  struct text_pos pos, start_pos, pos_before_pt;
   bool window_start_changed_p = false;
 
   SET_TEXT_POS_FROM_MARKER (start_pos, w->start);
@@ -15545,10 +15552,14 @@ compute_window_start_on_continuation_line (struct window *w)
       reseat_at_previous_visible_line_start (&it);
 
       /* If the line start is "too far" away from the window start,
-         say it takes too much time to compute a new window start.  */
-      if (CHARPOS (start_pos) - IT_CHARPOS (it)
-         /* PXW: Do we need upper bounds here?  */
-         < WINDOW_TOTAL_LINES (w) * WINDOW_TOTAL_COLS (w))
+         say it takes too much time to compute a new window start.
+         Also, give up if the line start is after point, as in that
+         case point will not be visible with any window start we
+         compute.  */
+      if (IT_CHARPOS (it) <= PT
+         || (CHARPOS (start_pos) - IT_CHARPOS (it)
+             /* PXW: Do we need upper bounds here?  */
+             < WINDOW_TOTAL_LINES (w) * WINDOW_TOTAL_COLS (w)))
        {
          int min_distance, distance;
 
@@ -15558,12 +15569,14 @@ compute_window_start_on_continuation_line (struct window *w)
             decreased, the new window start will be < the old start.
             So, we're looking for the display line start with the
             minimum distance from the old window start.  */
-         pos = it.current.pos;
+         pos_before_pt = pos = it.current.pos;
          min_distance = INFINITY;
          while ((distance = eabs (CHARPOS (start_pos) - IT_CHARPOS (it))),
                 distance < min_distance)
            {
              min_distance = distance;
+             if (CHARPOS (pos) <= PT)
+               pos_before_pt = pos;
              pos = it.current.pos;
              if (it.line_wrap == WORD_WRAP)
                {
@@ -15586,6 +15599,13 @@ compute_window_start_on_continuation_line (struct window *w)
                move_it_by_lines (&it, 1);
            }
 
+         /* It makes very little sense to make the new window start
+            after point, as point won't be visible.  If that's what
+            the loop above finds, fall back on the candidate before
+            or at point that is closest to the old window start.  */
+         if (CHARPOS (pos) > PT)
+           pos = pos_before_pt;
+
          /* Set the window start there.  */
          SET_MARKER_FROM_TEXT_POS (w->start, pos);
          window_start_changed_p = true;
@@ -27349,8 +27369,8 @@ x_produce_glyphs (struct it *it)
 
          eassume (0 < glyph_len); /* See Bug#8512.  */
          do
-           c = COMPOSITION_GLYPH (cmp, --glyph_len);
-         while (c == '\t' && 0 < glyph_len);
+           c = COMPOSITION_GLYPH (cmp, glyph_len - 1);
+         while (c == '\t' && 0 < --glyph_len);
 
          bool right_padded = glyph_len < cmp->glyph_len;
          for (i = 0; i < glyph_len; i++)