bug#25542: 25.1; Restoring the frame from fullscreen to maximized

[martin rudalics]

>> I just tried this on a Cygwin-w32 build from the master branch.  I put the 
taskbar on the left, started emacs, maximized it, attached gdb, put breakpoints at 
each of the ShowWindow lines, and ran through Dani's recipe for producing the bug.  
The breakpoints were never hit.
>
> I just tried again, but this time with a breakpoint at w32fullscreen_hook so 
that I could follow the flow.  Here are the relevant excerpts from the gdb session:

Thank you very much for checking.

> Breakpoint 2 at 0x10069507a: file ../../master/src/w32term.c, line 6441.
> (gdb) r -Q
> Starting program: /home/kbrown/src/emacs/x86_64-w32/src/emacs -Q
>
> [...]
>
> [Press F11]
>
> Thread 1 "emacs" hit Breakpoint 2, w32fullscreen_hook (f=0x8001f7c88)
>      at ../../master/src/w32term.c:6441
[...]
> 6464          FRAME_PREV_FSMODE (f) = f->want_fullscreen;
> (gdb) p f->want_fullscreen
> $1 = FULLSCREEN_BOTH

While this is the expected value ...

> [...]
>
> (gdb) c
> Continuing.
>
> [Press F11 again]
>
> Thread 1 "emacs" hit Breakpoint 2, w32fullscreen_hook (f=0x8001f7c88)
>      at ../../master/src/w32term.c:6441
[...]
> 6451          if (FRAME_PREV_FSMODE (f) == FULLSCREEN_NONE)
> (gdb) p f->want_fullscreen
> $2 = FULLSCREEN_NONE

... the value I would have expected here is FULLSCREEN_MAXIMIZED.
Something must have got broken before.  Can you please

(1) Verify that the

      f->want_fullscreen &= ~FULLSCREEN_WAIT;

    does not interfere in any respect.  That is, does f->want_fullscreen
    have the same value FULLSCREEN_NONE before anding it with
    FULLSCREEN_WAIT?

(2) Does 'toggle-frame-fullscreen' the second time when you type F11
    correctly call

   (set-frame-parameter frame 'fullscreen fullscreen-restore)

   with 'fullscreen-restore' equal to 'maximized' at all?

(3) Verify that calling w32fullscreen_hook with the taskbar on the
    bottom does hit the breakpoints and subsequently maximize the frame
    as expected.

Thanks again, martin