Avoid redisplay problems with too wide wrap-prefix

* src/xdisp.c (display_line): Avoid looping in redisplay when
wrap-prefix is set to a too-wide stretch of whitespace.
(Bug#30432)

(cherry picked from commit 2a1fe08307402d6217d073f8ab7737750d253dd4)

1 files changed, 16 insertions, 1 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 6ca115087c3..2142d771e2d 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -21957,9 +21957,24 @@ display_line (struct it *it, int cursor_vpos)
           break;
         }
 
+      /* Detect overly-wide wrap-prefixes made of (space ...) display
+         properties.  When such a wrap prefix reaches past the right
+         margin of the window, we need to avoid the call to
+         set_iterator_to_next below, so that it->line_wrap is left at
+         its TRUNCATE value wisely set by handle_line_prefix.
+         Otherwise, set_iterator_to_next will pop the iterator stack,
+         restore it->line_wrap, and redisplay might infloop.  */
+      bool overwide_wrap_prefix =
+        CONSP (it->object) && EQ (XCAR (it->object), Qspace)
+        && it->sp > 0 && it->method == GET_FROM_STRETCH
+        && it->current_x >= it->last_visible_x
+        && it->continuation_lines_width > 0
+        && it->line_wrap == TRUNCATE && it->stack[0].line_wrap != TRUNCATE;
+
       /* Proceed with next display element.  Note that this skips
          over lines invisible because of selective display.  */
-      set_iterator_to_next (it, true);
+      if (!overwide_wrap_prefix)
+        set_iterator_to_next (it, true);
 
       /* If we truncate lines, we are done when the last displayed
          glyphs reach past the right margin of the window.  */