Re: recent change to nsterm.m: four pixels where the Dock is hidden

[Anders Lindgren <andlind@gmail.com>]

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Hi!

The change to make `toggle-frame-maximized' cover the entire screen (when
the dock was hidden) was done much earlier, in 2015-10-23 (see link to
commit below), after a discussion that started in bug 21415 (see link). At
the time, everybody involved in the discussion thought that it was a good
idea for Emacs to cover the full height of the screen, when the dock was
hidden.

When the pretest was released, a user reported that the code didn't work
properly when the dock was visible. Effectively, the dock would cover parts
of Emacs. The commit you referred to is a fix for that problem.

When investigating how an application could check if the dock was hidden,
it turned out that there is no standard API for this, but the normal way
this is checked is to compare the result of [screen frame] (i.e. the size
of a display) with [screen visibleFrame] (i.e. the size, excluding the
parts occupied by the OS). The OS reserves four pixels at the edge where a
hidden dock resides, my code use six as a break-off value in case this is
changed in future OS versions.

I don't consider this a big change -- the fact that the change is 50 lines
is that I prefer a style where each logical step is isolated, well
documented, and there is a natural place for trace output. In this case I
decided to represent the margins using a new struct, and place the margin
calculation into two functions `ns_screen_margins' and
`ns_screen_margins_ignoring_hidden_dock'. Of course, I could easily have
written the code in a very condensed manner, inlining all calculations, but
that wouldn't have been maintainable.

This is the original change:


http://git.savannah.gnu.org/cgit/emacs.git/commit/?h=emacs-25&id=ba24d35a3e82cdeba4be5bd794f7f48bbfa5498e

Discussion:

    http://debbugs.gnu.org/cgi/bugreport.cgi?bug=21415

    -- Anders Lindgren

On Fri, Mar 25, 2016 at 3:59 AM, David Reitter <david.reitter@gmail.com>
wrote:

> Anders,
>
> I appreciate your work on the NS/OSX port.
> Reviewing a recent change, I can’t help but wonder:  Do we really need 50
> lines of a hack to counteract design decisions made at the system level?
>
> If [NSScreen visibleFrame] tells us not to occupy certain space on the
> screen - four pixels where the Dock is hidden - then that’s a standard that
> all applications should adhere to.  It’s probably done for a reason (such
> as being able to un-hide the Dock and to grab the lower horizontal edge of
> the window for resizing).
>
> ns_screen_margins_ignoring_hidden_dock is, excuse my bluntness, ugly as it
> hardcodes some numbers that can change any time with a new OS version. It’s
> a burden for future maintenance.
>
> If this is what #22988 really was about, then it’s not a bug and we
> shouldn’t mess with it.  Also not in 25.1.
>
> If I’m wrong, please excuse me.  Could you explain if there is some deeper
> reasoning that I’m missing?
>
> Thanks,
> David
>
>
> > Author: Anders Lindgren <andlind@gmail.com>
> > Date:   Tue Mar 22 20:18:33 2016 +0100
> >
> >     Make `toggle-frame-maximized' respect the dock on OS X (bug#22988).
> >
> >     * src/nsterm.m (ns_screen_margins): New function.
> >     (ns_screen_margins_ignoring_hidden_dock): New function.
> >     (ns_menu_bar_height): Reimplement in terms of `ns_screen_margins'.
> >     ([EmacsWindow zoom:]): Take all screen margins (except those
> >     originating from a hidden dock) into account.
> >
>

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