Re: MPS: scroll-bars

[Eli Zaretskii <eliz@gnu.org>]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: eller.helmut@gmail.com,  emacs-devel@gnu.org
> Date: Mon, 06 May 2024 17:53:40 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Btw, did we decide what to do with these chains:
> >
> >   struct frame
> >   {
> >   [...]
> >   /* List of scroll bars on this frame.
> >      Actually, we don't specify exactly what is stored here at all; the
> >      scroll bar implementation code can use it to store anything it likes.
> >      This field is marked by the garbage collector.  It is here
> >      instead of in the `device' structure so that the garbage
> >      collector doesn't need to look inside the window-system-dependent
> >      structure.  */
> >   Lisp_Object scroll_bars;
> >   Lisp_Object condemned_scroll_bars;
> >
> > They are doubly-linked lists via the ->next and ->prev fields in the C
> > 'struct scroll_bar', in X as well as w32, see XSCROLL_BAR.  The
> > Lisp_Object's above are the last scroll bar on the frame's windows,
> > and the rest are reachable via the ->next and ->prev pointers.  Do we
> > need to do anything about those ->next and ->prev pointers?
> 
> For NS, and I must always add that I don't know NS at all, the
> condemned_scroll_bars are fine I think. NS sets a flag in an NS
> EmacsScroller object to condemn/redeem it, and doesn't use the frame's
> field, says clangd.
> 
> The scroll_bars field was something strange. It didn't contain struct
> scroll_bars but someting like optimized Lisp_Misc_Ptrs (see
> xmint_pointer in lisp.h) which point to EmacsScrollers.
> 
> In summary, I came for NS to the conclusion that we should be good with
> what we currently have. Famous last words.

Helmut, WDYT about the scroll bars on X (and by extension on w32)?