patch 9.0.1664: divide by zero when scrolling with 'smoothscroll' set
Problem: Divide by zero when scrolling with 'smoothscroll' set.
Solution: Avoid using a negative width. (closes #12540, closes #12528)
diff --git a/src/testdir/dumps/Test_smoothscroll_zero_bot.dump b/src/testdir/dumps/Test_smoothscroll_zero_bot.dump
new file mode 100644
index 0000000..179b95c
--- /dev/null
+++ b/src/testdir/dumps/Test_smoothscroll_zero_bot.dump
@@ -0,0 +1,19 @@
+| +0#af5f00255#ffffff0||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+|@+0#4040ff13&||+1#0000000&| +0&&@9
+>@+0#4040ff13&||+1#0000000&| +0&&@9
+|<+3&&| |<+1&&|a|m|e|]| |[|+|]|
+| +0&&@11
diff --git a/src/testdir/test_scroll_opt.vim b/src/testdir/test_scroll_opt.vim
index 4604166..279e547 100644
--- a/src/testdir/test_scroll_opt.vim
+++ b/src/testdir/test_scroll_opt.vim
@@ -833,4 +833,28 @@
call StopVimInTerminal(buf)
endfunc
+" this was dividing by zero bug in scroll_cursor_bot
+func Test_smoothscroll_zero_width_scroll_cursor_bot()
+ CheckScreendump
+
+ let lines =<< trim END
+ silent normal yy
+ silent normal 19p
+ winsize 0 19
+ vsplit
+ vertical resize 0
+ set foldcolumn=1
+ set number
+ set smoothscroll
+ silent normal 20G
+ END
+ call writefile(lines, 'XSmoothScrollZeroBot', 'D')
+ let buf = RunVimInTerminal('-u NONE -S XSmoothScrollZeroBot', #{rows: 19, wait_for_ruler: 0})
+ call TermWait(buf, 1000)
+
+ call VerifyScreenDump(buf, 'Test_smoothscroll_zero_bot', {})
+
+ call StopVimInTerminal(buf)
+endfunc
+
" vim: shiftwidth=2 sts=2 expandtab