From 841159b26fa13e260e3f76b85749fe98f437de29 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Buckwalter?= <bjorn@buckwalter.se>
Date: Thu, 27 Apr 2023 08:29:43 +0200
Subject: [PATCH] Fix undo of multiline insertion.

Problem fixed: Insert a newline at cj>1. Undo (^Z). The undo operation
removes cj-1 characters following the point of the insertion.
---
 buffer.lua | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/buffer.lua b/buffer.lua
index ac41e2d..3fe5b74 100644
--- a/buffer.lua
+++ b/buffer.lua
@@ -334,7 +334,11 @@ function buffer.op_undo(b, sl)
 	if sl.op == "del" then
 		return b:bufins(sl, true)
 	elseif sl.op == "ins" then
-		return b:bufdel(sl.ci+#sl-1, sl.cj+ulen(sl[#sl]), true)
+		if #sl == 1 then -- Insertion was limited to part of a single line
+			return b:bufdel(sl.ci+#sl-1, sl.cj+ulen(sl[#sl]), true)
+		else -- Insertion spanned multiple lines
+			return b:bufdel(sl.ci+#sl-1, ulen(sl[#sl]), true)
+		end
 	else
 		return nil, "unknown op"
 	end