Re: MPS: scroll-bars

["Gerd Möllmann" <gerd.moellmann@gmail.com>]

Eli Zaretskii <eliz@gnu.org> writes:

> How to go about that?

Please let's first do the thread stuff. That makes things easier for the
old man here.


>> I assume that the GUI thread you mention is not one the Emacs threads,
>> but something else, so it's not main_thread and not one of the threads
>> made with make-thread.
>
> It isn't a Lisp thread, that's true.  But it's an "Emacs thread" in
> the sense that in the w32 build it is an integral part of Emacs, and
> without it the GUI features and GUI I/O would not work on MS-Windows.

Does it have a struct thread_state associated with it? That's what
igc.c currently knows how to handle.

>
> (You can find the overview of the thread structure of the w32 build in
> a large comment that starts at line 3365 of w32fns.c.)
>
>> Then I think we first of all must make sure that MPS knows about that
>> thread.
>
> Why do we need MPS to know about that thread (or any other non-Lisp
> thread used by Emacs on MS-Windows; there are more)?  is that for MPS
> to scan their C stacks and registers?

9.2. Thread registration

In order to scan a thread’s registers for references (which happens at
each flip), the MPS needs to be able to suspend that thread, and in
order to gain exclusive atomic access to memory in order to scan it, the
MPS needs to be able to suspend all threads that might access that
memory. This means that threads must be registered with the MPS by
calling mps_thread_reg() (and thread roots created; see Thread roots).

A thread must be registered with an arena if:

its control stack and registers form a root (this is enforced by
mps_root_create_thread()); or it reads or writes from a location in an
automatically managed pool in the arena. However, some automatically
managed pool classes may be more liberal than this. See the
documentation for the pool class.