bug#23689: Daemon-mode on Windows - "w32-initialized" is set too early

[Paul Moore <p.f.moore@gmail.com>]

On 4 June 2016 at 11:58, Eli Zaretskii <eliz@gnu.org> wrote:
> Frankly, I'm not sure what is the situation for which you want to
> test.  Can you describe the original problem in more detail?

Sure. The issue arises with Spacemacs. I'll give the basic idea (as
well as I understand it, I'm not an expert by any means) but the
actual code is at
https://github.com/syl20bnr/spacemacs/blob/master/core/core-display-init.el#L28

When spacemacs starts up, it wants to set the fonts as configured by
the user. To do so, it checks that the user-selected font exists using
find-font (there's new code in the develop branch that allows the user
to set a list of fonts, and picks the first on the list that actually
exists on the system). But in daemon mode, find-font doesn't return a
useful value until the display system is initialised, so there's a
macro:

(defmacro spacemacs|do-after-display-system-init (&rest body)
  "If the display-system is initialized, run `BODY', otherwise,
add it to a queue of actions to perform after the first graphical frame is
created."
  `(let ((init (cond ((boundp 'ns-initialized) 'ns-initialized)
                     ((boundp 'w32-initialized) 'w32-initialized)
                     ((boundp 'x-initialized) 'x-initialized)
                     (t 't))))           ; fallback to normal loading behavior
     (if (symbol-value init)
         (progn
           ,@body)
       (push (lambda () ,@body) spacemacs--after-display-system-init-list))))

The actions on spacemacs--after-display-system-init-list are executed
when the first GUI frame is displayed, via advice on
server-create-window-system-frame.

This process works fine on non-Windows systems, I guess because
ns-initialized and x-initialized are false during daemon startup. But
on Windows it fails and from my testing this appears to be because
w32-initialized is true at this point (unlike the other two). As a
result, the font selection code gets run immediately - specifically
*before* the point when find-font will give a correct answer.

To demonstrate, create a .emacs.d/init.el containing

(progn
    (message "%S" w32-initialized)
    (message "%S" (find-font (font-spec :name "Courier New")))
    (message "%S" w32-initialized))

Set HOME to the directory containing .emacs.d and run emacs --daemon.
The result is

t
nil
t

Do the same on Unix (I used Ubuntu) using x-initialized (and a font
that exists on the Unix system in place of Courier New) and you get

nil
nil
nil

Do the same using emacs (no --daemon) and look in the *Messages*
buffer, and you see

t
<a font object>
t

in both cases.

Hopefully, that clarifies a little.
Paul