[Emacs-diffs] master 1cbbece: Fix automatic hscrolling of only the current line

[Eli Zaretskii]

branch: master
commit 1cbbecee66617a232d6ed361f842128564599e70
Author: Eli Zaretskii <address@hidden>
Commit: Eli Zaretskii <address@hidden>

    Fix automatic hscrolling of only the current line
    
    * src/xdisp.c (display_line): When hscrolling only the current
    line, increment iterator's first_visible_x and last_visible_x
    values to account for the hscroll.  This propagates the hscroll
    effect on the iterator geometry all the way down to the
    subroutines called by display_line, and avoids scrolling bugs
    under large hscroll values.  (Bug#26994)
---
 src/xdisp.c | 70 ++++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 39 insertions(+), 31 deletions(-)

diff --git a/src/xdisp.c b/src/xdisp.c
index 96bc1a5..c0e821a 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -20671,8 +20671,11 @@ display_line (struct it *it, int cursor_vpos)
   ptrdiff_t min_pos = ZV + 1, max_pos = 0;
   ptrdiff_t min_bpos UNINIT, max_bpos UNINIT;
   bool pending_handle_line_prefix = false;
+  bool hscroll_this_line = (cursor_vpos >= 0 && it->vpos == cursor_vpos
+                           && hscrolling_current_line_p (it->w));
   int first_visible_x = it->first_visible_x;
   int last_visible_x = it->last_visible_x;
+  int x_incr = 0;
 
   /* We always start displaying at hpos zero even if hscrolled.  */
   eassert (it->hpos == 0 && it->current_x == 0);
@@ -20704,25 +20707,23 @@ display_line (struct it *it, int cursor_vpos)
 
   /* If we are going to display the cursor's line, account for the
      hscroll of that line.  */
-  if (cursor_vpos >= 0 && it->vpos == cursor_vpos
-      && hscrolling_current_line_p (it->w))
-    {
-      int x_incr =
-       window_hscroll_limited (it->w, it->f) * FRAME_COLUMN_WIDTH (it->f);
-
-      first_visible_x += x_incr;
-      last_visible_x  += x_incr;
-    }
+  if (hscroll_this_line)
+    x_incr = window_hscroll_limited (it->w, it->f) * FRAME_COLUMN_WIDTH 
(it->f);
 
   /* Move over display elements that are not visible because we are
      hscrolled.  This may stop at an x-position < first_visible_x
      if the first glyph is partially visible or if we hit a line end.  */
-  if (it->current_x < first_visible_x)
+  if (it->current_x < it->first_visible_x + x_incr)
     {
       enum move_it_result move_result;
 
       this_line_min_pos = row->start.pos;
-      move_result = move_it_in_display_line_to (it, ZV, first_visible_x,
+      if (hscroll_this_line)
+       {
+         it->first_visible_x += x_incr;
+         it->last_visible_x  += x_incr;
+       }
+      move_result = move_it_in_display_line_to (it, ZV, it->first_visible_x,
                                                MOVE_TO_POS | MOVE_TO_X);
       /* If we are under a large hscroll, move_it_in_display_line_to
         could hit the end of the line without reaching
@@ -20730,10 +20731,10 @@ display_line (struct it *it, int cursor_vpos)
         especially important on a TTY, where we will call
         extend_face_to_end_of_line, which needs to know how many
         blank glyphs to produce.  */
-      if (it->current_x < first_visible_x
+      if (it->current_x < it->first_visible_x
          && (move_result == MOVE_NEWLINE_OR_CR
              || move_result == MOVE_POS_MATCH_OR_ZV))
-       it->current_x = first_visible_x;
+       it->current_x = it->first_visible_x;
 
       /* Record the smallest positions seen while we moved over
         display elements that are not visible.  This is needed by
@@ -20927,7 +20928,7 @@ display_line (struct it *it, int cursor_vpos)
       if (/* Not a newline.  */
          nglyphs > 0
          /* Glyphs produced fit entirely in the line.  */
-         && it->current_x < last_visible_x)
+         && it->current_x < it->last_visible_x)
        {
          it->hpos += nglyphs;
          row->ascent = max (row->ascent, it->max_ascent);
@@ -20937,13 +20938,13 @@ display_line (struct it *it, int cursor_vpos)
                                  it->max_phys_ascent + it->max_phys_descent);
          row->extra_line_spacing = max (row->extra_line_spacing,
                                         it->max_extra_line_spacing);
-         if (it->current_x - it->pixel_width < first_visible_x
+         if (it->current_x - it->pixel_width < it->first_visible_x
              /* In R2L rows, we arrange in extend_face_to_end_of_line
                 to add a right offset to the line, by a suitable
                 change to the stretch glyph that is the leftmost
                 glyph of the line.  */
              && !row->reversed_p)
-           row->x = x - first_visible_x;
+           row->x = x - it->first_visible_x;
          /* Record the maximum and minimum buffer positions seen so
             far in glyphs that will be displayed by this row.  */
          if (it->bidi_p)
@@ -20968,9 +20969,9 @@ display_line (struct it *it, int cursor_vpos)
              if (/* Lines are continued.  */
                  it->line_wrap != TRUNCATE
                  && (/* Glyph doesn't fit on the line.  */
-                     new_x > last_visible_x
+                     new_x > it->last_visible_x
                      /* Or it fits exactly on a window system frame.  */
-                     || (new_x == last_visible_x
+                     || (new_x == it->last_visible_x
                          && FRAME_WINDOW_P (it->f)
                          && (row->reversed_p
                              ? WINDOW_LEFT_FRINGE_WIDTH (it->w)
@@ -20979,7 +20980,7 @@ display_line (struct it *it, int cursor_vpos)
                  /* End of a continued line.  */
 
                  if (it->hpos == 0
-                     || (new_x == last_visible_x
+                     || (new_x == it->last_visible_x
                          && FRAME_WINDOW_P (it->f)
                          && (row->reversed_p
                              ? WINDOW_LEFT_FRINGE_WIDTH (it->w)
@@ -21122,10 +21123,10 @@ display_line (struct it *it, int cursor_vpos)
                           ? WINDOW_LEFT_FRINGE_WIDTH (it->w)
                           : WINDOW_RIGHT_FRINGE_WIDTH (it->w)) == 0)
                        produce_special_glyphs (it, IT_CONTINUATION);
-                     it->continuation_lines_width += last_visible_x;
+                     it->continuation_lines_width += it->last_visible_x;
                      row->ends_in_middle_of_char_p = true;
                      row->continued_p = true;
-                     glyph->pixel_width = last_visible_x - x;
+                     glyph->pixel_width = it->last_visible_x - x;
                      it->starts_in_middle_of_char_p = true;
                      if (WINDOW_LEFT_MARGIN_WIDTH (it->w) > 0
                          || WINDOW_RIGHT_MARGIN_WIDTH (it->w) > 0)
@@ -21169,7 +21170,7 @@ display_line (struct it *it, int cursor_vpos)
 
                  break;
                }
-             else if (new_x > first_visible_x)
+             else if (new_x > it->first_visible_x)
                {
                  /* Increment number of glyphs actually displayed.  */
                  ++it->hpos;
@@ -21180,14 +21181,14 @@ display_line (struct it *it, int cursor_vpos)
                  if (it->bidi_p)
                    RECORD_MAX_MIN_POS (it);
 
-                 if (x < first_visible_x && !row->reversed_p)
+                 if (x < it->first_visible_x && !row->reversed_p)
                    /* Glyph is partially visible, i.e. row starts at
                       negative X position.  Don't do that in R2L
                       rows, where we arrange to add a right offset to
                       the line in extend_face_to_end_of_line, by a
                       suitable change to the stretch glyph that is
                       the leftmost glyph of the line.  */
-                   row->x = x - first_visible_x;
+                   row->x = x - it->first_visible_x;
                  /* When the last glyph of an R2L row only fits
                     partially on the line, we need to set row->x to a
                     negative offset, so that the leftmost glyph is
@@ -21195,12 +21196,12 @@ display_line (struct it *it, int cursor_vpos)
                     going to produce the truncation glyph, this will
                     be taken care of in produce_special_glyphs.  */
                  if (row->reversed_p
-                     && new_x > last_visible_x
+                     && new_x > it->last_visible_x
                      && !(it->line_wrap == TRUNCATE
                           && WINDOW_LEFT_FRINGE_WIDTH (it->w) == 0))
                    {
                      eassert (FRAME_WINDOW_P (it->f));
-                     row->x = last_visible_x - new_x;
+                     row->x = it->last_visible_x - new_x;
                    }
                }
              else
@@ -21210,7 +21211,7 @@ display_line (struct it *it, int cursor_vpos)
                     move_it_in_display_line at the start of this
                     function, unless the text display area of the
                     window is empty.  */
-                 eassert (first_visible_x <= last_visible_x);
+                 eassert (it->first_visible_x <= it->last_visible_x);
                }
            }
          /* Even if this display element produced no glyphs at all,
@@ -21279,8 +21280,8 @@ display_line (struct it *it, int cursor_vpos)
                    ? WINDOW_LEFT_FRINGE_WIDTH (it->w)
                    : WINDOW_RIGHT_FRINGE_WIDTH (it->w))
                   || it->what == IT_IMAGE))
-             ? (it->current_x >= last_visible_x)
-             : (it->current_x > last_visible_x)))
+             ? (it->current_x >= it->last_visible_x)
+             : (it->current_x > it->last_visible_x)))
        {
          /* Maybe add truncation glyphs.  */
          if (!FRAME_WINDOW_P (it->f)
@@ -21314,7 +21315,7 @@ display_line (struct it *it, int cursor_vpos)
              /* produce_special_glyphs overwrites the last glyph, so
                 we don't want that if we want to keep that last
                 glyph, which means it's an image.  */
-             if (it->current_x > last_visible_x)
+             if (it->current_x > it->last_visible_x)
                {
                  it->current_x = x_before;
                  if (!FRAME_WINDOW_P (it->f))
@@ -21375,7 +21376,7 @@ display_line (struct it *it, int cursor_vpos)
 
   /* If line is not empty and hscrolled, maybe insert truncation glyphs
      at the left window margin.  */
-  if (first_visible_x
+  if (it->first_visible_x
       && IT_CHARPOS (*it) != CHARPOS (row->start.pos))
     {
       if (!FRAME_WINDOW_P (it->f)
@@ -21503,6 +21504,13 @@ display_line (struct it *it, int cursor_vpos)
      row to be used.  */
   it->current_x = it->hpos = 0;
   it->current_y += row->height;
+  /* Restore the first and last visible X if we adjusted them for
+     current-line hscrolling.  */
+  if (hscroll_this_line)
+    {
+      it->first_visible_x = first_visible_x;
+      it->last_visible_x  = last_visible_x;
+    }
   SET_TEXT_POS (it->eol_pos, 0, 0);
   ++it->vpos;
   ++it->glyph_row;