Fix errors with hscrolling mini-windows under truncate-lines

* src/xdisp.c (hscroll_window_tree): Disallow hscroll in
mini-windows that display echo-area messages.  (Bug#50096)

diff --git a/src/xdisp.c b/src/xdisp.c
index ada9ed6c22bb02a3071b3d381c2d03a363e3f253..dd2ceda023d87fa3436ef4c12ec889ad72c2e7db 100644 (file)
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -11771,7 +11771,7 @@ display_echo_area (struct window *w)
   /* If there is no message, we must call display_echo_area_1
      nevertheless because it resizes the window.  But we will have to
      reset the echo_area_buffer in question to nil at the end because
-     with_echo_area_buffer will sets it to an empty buffer.  */
+     with_echo_area_buffer will set it to an empty buffer.  */
   bool i = display_last_displayed_message_p;
   /* According to the C99, C11 and C++11 standards, the integral value
      of a "bool" is always 0 or 1, so this array access is safe here,
@@ -14898,7 +14898,15 @@ hscroll_window_tree (Lisp_Object window)
 
       if (WINDOWP (w->contents))
        hscrolled_p |= hscroll_window_tree (w->contents);
-      else if (w->cursor.vpos >= 0)
+      else if (w->cursor.vpos >= 0
+              /* Don't allow hscroll in mini-windows that display
+                 echo-area messages.  This is because desired_matrix
+                 of such windows was prepared while momentarily
+                 switched to an echo-area buffer, which is different
+                 from w->contents, and wew simply cannot hscroll such
+                 windows safely.  */
+              && !(w == XWINDOW (echo_area_window)
+                   && !NILP (echo_area_buffer[0])))
        {
          int h_margin;
          int text_area_width;