helptoc popup J/K navigation flickers and jumps with hlsearch on

[VimWei]

Context

I initially reported this to the Vim issue tracker (vim/vim#21051), but I bisected it down to vim-cool: with vim-cool enabled the problem occurs; after disabling it, everything works as expected. So this is very likely a vim-cool bug, not a Vim bug.

Steps to reproduce

1. Create test.md with hierarchical headers:

   # level 1 a
   ## level 2 b
   ### level 3 c
   ### level 3 d
   ### level 3 e
   ### level 3 f
   

2. set hlsearch, then search /level and press Enter so v:hlsearch is 1.

3. Open the :HelpToc popup.

4. Press J / K to move through the popup entries.

Observed behavior

• Every J/K press makes the popup flicker/redraw.
• When moving across heading depths (e.g. from ## level 2 b down to ### level 3 c), the first J keeps the cursor on ## level 2 b; the second J finally moves to ### level 3 c.
• Continuing to ### level 3 d makes the cursor retreat back up to ## level 2 b.

Expected behavior

J/K should move smoothly through the popup entries regardless of hlsearch state, with no flicker or wrong jumps.

Possible cause

s:StartHL() runs from the CursorMoved autocommand, which also fires in popup windows (the helptoc buffer). It calls winsaveview(), go<byte>, norm! n, and winrestview() inside the popup buffer, which conflicts with the popup's own cursor management — the n search-move inside the popup is likely what causes the wrong jump and the redraw flicker. The popup's cursor position is not properly restored by winrestview().

If vim-cool could skip popup windows (e.g. ignore buffers where buftype is popup, or bail out when inside a popup), the problem would likely disappear.

Environment

• OS: Windows 10
• Vim: gVim 9.2.0907 x64
• vim-cool: latest master