patch 8.0.0732: when updating a buffer modeless selection is lost commit https://github.com/vim/vim/commit/80dd3f9d41ce2ff6ab3544cdb266627bbdfc34a6 Author: Bram Moolenaar <Bram@vim.org> Date: Wed Jul 19 12:51:52 2017 +0200 patch 8.0.0732: when updating a buffer modeless selection is lost Problem: When updating a buffer for a callback the modeless selection is lost. Solution: Do not insert or delete screen lines when redrawing for a callback and there is a modeless selection.

Test for writing and reading a file of over 100 Kbyte

1 line: "This is the start"
3001 lines: "This is the leader"
1 line: "This is the middle"
3001 lines: "This is the trailer"
1 line: "This is the end"

STARTTEST
:%d
aThis is the start
This is the leader
This is the middle
This is the trailer
This is the endkY3000p2GY3000p
:w! Xtest
:%d
:e! Xtest
:.w! test.out
3003G:.w >>test.out
6005G:.w >>test.out
:qa!
ENDTEST