From 3b2949940efbe8c05263fce7ebcc390a9f178c01 Mon Sep 17 00:00:00 2001 From: Benno Schulenberg Date: Thu, 22 Apr 2021 19:28:34 +0200 Subject: [PATCH 13/34] editing: prevent the pointer for the top row from becoming dangling When undoing several actions, it is possible for the line at the top of the screen to be removed, leaving 'edittop' pointing to a structure that has been freed. Soon after, 'edittop' is referenced to determine whether the cursor is offscreen... Prevent this invalid reference by stepping 'edittop' one line back in that special case. This changes the normal centering behavior of Undo when the cursor goes offscreen, but... so be it. When a single node is deleted, it is always possible to step one line back, because a buffer contains always at least one line (even though maybe empty), so if the current line could be deleted, there must be one before it (when at the top of the screen). This fixes https://savannah.gnu.org/bugs/?60436. Bug existed since version 2.3.3, commit 60815461, since undoing does not always center the cursor. --- src/nano.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/src/nano.c b/src/nano.c index 913329a5..2b6c416f 100644 --- a/src/nano.c +++ b/src/nano.c @@ -104,6 +104,9 @@ void splice_node(linestruct *afterthis, linestruct *newnode) /* Free the data structures in the given node. */ void delete_node(linestruct *line) { + /* If the first line on the screen gets deleted, step one back. */ + if (line == openfile->edittop) + openfile->edittop = line->prev; #ifdef ENABLE_WRAPPING /* If the spill-over line for hard-wrapping is deleted... */ if (line == openfile->spillage_line) -- 2.29.3