This was always a legacy thing. Remove it by applying an orgy of
mp_get_config_group() calls, and sometimes m_config_cache_alloc() or
mp_read_option_raw().
win32 changes untested.
Until now, they could be aborted only by ending playback, and calling
mpv_abort_async_command didn't do anything.
This requires furthering the mess how playback abort is done. The main
reason why mp_cancel exists at all is to avoid that a "frozen" demuxer
(blocked on network I/O or whatever) cannot freeze the core. The core
should always get its way. Previously, there was a single mp_cancel
handle, that could be signaled, and all demuxers would unfreeze. With
external files, we might want to abort loading of a certain external
file, which automatically means they need a separate mp_cancel. So give
every demuxer its own mp_cancel, and "slave" it to whatever parent
mp_cancel handles aborting.
Since the mpv demuxer API conflates creating the demuxer and reading the
file headers, mp_cancel strictly need to be created before the demuxer
is created (or we couldn't abort loading). Although we give every
demuxer its own mp_cancel (as "enforced" by cancel_and_free_demuxer),
it's still rather messy to create/destroy it along with the demuxer.
This flag is used only by the command parser. Its value overlapped with
some of the existing m_option flags, but only flags that did not matter
for the command parser (i.e. the flag bits used had mostly private uses
in each component). It's still a bit unclean and dangerous to use an
essentially random value, so reuse M_OPT_OPTIONAL_PARAM for it.
Since M_OPT_OPTIONAL_PARAM has a slightly longer name than
MP_CMD_OPT_ARG, I'm going to keep the old name.
Before this change, only 1 command or so had named arguments. There is
no reason why other commands can't have them, except that it's a bit of
work to add them.
Commands with variable number of arguments are inherently incompatible
to named arguments, such as the "run" command. They still have dummy
names, but obviously you can't assign multiple values to a single named
argument (unless the argument has an array type, which would be
something different). For now, disallow using named argument APIs with
these commands. This might change later.
2 commands are adjusted to not need a separate default value by changing
flag constants. (The numeric values are C only and can't be set by
users.)
Make the command syntax in the manpage more consistent. Now none of the
allowed choice/flag names are in the command header, and all arguments
are shown with their proper name and quoted with <...>.
Some places in the manpage and the client.h doxygen are updated to
reflect that most commands support named arguments. In addition, try to
improve the documentation of the syntax and need for escaping etc. as
well.
(Or actually most uses of the word "argument" should be "parameter".)
I wanted to put all commands through mpv_command_node_async() instead of
mpv_command_node(). Using synchronous commands over a synchronous
transport doesn't make sense anyway.
This would have used the request_id field in IPC requests as reply ID
for the async commands. But the latter need to be [u]int64, while the
former can be any type. To avoid that we need an extra lookup table for
mapping reply IDs to request_id values, we now require that request_id
fields are integers.
Since this would be an incompatible change, just deprecate non-integers
for now, and plan the change for a later time.
The only effective difference is that the former explicitly checks
whether the JSON value type is string, and errors out if not. The rest
is exactly the same (mpv_set_property_string is mpv_set_property with
MPV_FORMAT_STRING).
It seems silly to keep this, so just remove it.
Many asynchronous commands are potentially long running operations, such
as loading something from network or running a foreign process.
Obviously it shouldn't just be possible for them to freeze the player if
they don't terminate as expected. Also, there will be situations where
you want to explicitly stop some of those operations explicitly. So add
an infrastructure for this.
Commands have to support this explicitly. The next commit uses this to
actually add support to a command.
This supports named arguments. It benefits from the infrastructure of
async commands.
The plan is to reimplement Lua's utils.subprocess() on top of it.
Named arguments should make it easier to have long time compatibility,
even if command arguments get added or removed. They're also much nicer
for commands with a large number of arguments, especially if many
arguments are optional.
As of this commit, this can not be used, because there is no command yet
which supports them. See the following commit.
This enables two types of command behavior:
1. Plain async behavior, like "loadfile" not completing until the file
is fully loaded.
2. Running parts of the command on worker threads, e.g. for I/O, such as
"sub-add" doing network accesses on a thread while the core
continues.
Both have no implementation yet, and most new code is actually inactive.
The plan is to implement a number of useful cases in the following
commits.
The most tricky part is handling internal keybindings (input.conf) and
the multi-command feature (concatenating commands with ";"). It requires
a bunch of roundabout code to make it do the expected thing in
combination with async commands.
There is the question how commands should be handled that come in at a
higher rate than what can be handled by the core. Currently, it will
simply queue up input.conf commands as long as memory lasts. The client
API is limited by the size of the reply queue per client. For commands
which require a worker thread, the thread pool is limited to 30 threads,
and then will queue up work in memory. The number is completely
arbitrary.
This gets rid of run_command() and its big switch statement, which was
an idiotically big function of almost 1000 lines.
The switch is replaced with a callback per command, and each command is
now implemented in its own function. Command IDs are not needed anymore,
so the mp_command_type enum disappears.
There should be no functional changes, but since this refactors 64
commands, regressions are possible.
The handler() parameter is void*, because in theory the input code is
supposed to be independent of the player core code. For example, you
should be able to reuse the command parser code for some other part of
mpv. In practice, the variable containing command list is defined in the
player core anyway, so you could say this doesn't work. But I'm still
trying to hold onto this idea, so I went with void*.
The plan is to remove the command ID enum. This will happen by replacing
the big switch statement in command.c with dispatching to per-command
callbacks. As preparation, remove uses of the command IDs outside of the
actual dispatching mechanism.
Also remove some instances of checking cmd->def for NULL. We now require
this always to be set.
These are old MPlayer commands that were redundant since 2007 or so. In
2013, mpv explicitly deprecated them (actually removed them, but left
this wrapper, which translated them to modern commands). The list was
not extended since 2013, and mpv always warned on the terminal when a
legacy command was used. So it's time to remove it.
As it turns out, there are multiple libmpv users who saw a need to
use the hook API. The API is kind of shitty and was never meant to be
actually public (it was mostly a hack for the ytdl script).
Introduce a proper API and deprecate the old one. The old one will
probably continue to work for a few releases, but will be removed
eventually.
There are some slight changes to the old API, but if a user followed
the manual properly, it won't break.
Mostly untested. Appears to work with ytdl_hook.
Requested. See manpage additions.
The main reason why this goes through the trouble to keep the
action/operation parameter separate is so that we don't expose some
option parser implementation details to the command (although that is a
relatively weak reason), and also to make it more different from the
"set" command, which can't support this type of option as it goes
through the property layer.
Fixes#5435.
It was actually already implemented as ta_dup_ptrtype(), but that seems
like a clunky name. Also we still use the talloc_ names throughout the
source, and I'd rather use an old name instead of a mixing inconsistent
naming conventions.
Replace the static array with dynamic memory allocation. This also
requires some code to honor mp_cmd.nargs more strictly. Generally
allocates more stuff.
Fixes#5375 (although we could also just raise the static limit).
I've decided that MP_TRACE means “noisy spam per frame”, whereas
MP_DBG just means “more verbose debugging messages than MSGL_V”.
Basically, MSGL_DBG shouldn't create spam per frame like it currently
does, and MSGL_V should make sense to the end-user and provide mostly
additional informational output.
MP_DBG is basically what I want to make the new default for --log-file,
so the cut-off point for MP_DBG is if we probably want to know if for
debugging purposes but the user most likely doesn't care about on the
terminal.
Also, the debug callbacks for libass and ffmpeg got bumped in their
verbosity levels slightly, because being external components they're a
bit less relevant to mpv debugging, and a bit too over-eager in what
they consider to be relevant information.
I exclusively used the "try it on my machine and remove messages from
MSGL_* until it does what I want it to" approach of refactoring, so
YMMV.
This was marked GPL, because the implementation in command.c (which is
shared with the subtitle code) was marked as GPL. This has been changed,
so this is unnecessary. The original commands for external audio tracks
have been added to mpv by someone who agreed with the relicensing.
There has been no new developments or agreements, but I was uncertain
about the copyright status of them. Thus this part of code was marked as
being potentially GPL, and was not built in LGPL mode. Now I've taken a
close look again, and decided that these can be relicensed using the
existing relicensing agreements.
OSD level 3 was introduced in commit 8d190244, with the author being
unreachable. As I decided in commit 6ddd95fd, OSD level 3 itself can
be kept, but the "osd" command had to go, and the "rendering" of OSD
level 3 (the HAVE_GPL code in osd.c) was uncertain. But the code for
this was rewritten: instead of duplicating the time/percent formatting
code, it was changed to use common code, and some weird extra logic was
removed. The code inside of the "if" is exactly the same as the code
that formats the OSD status line (covered by LGPL relicensing).
The current commands for adding/removing sub/audio tracks more or less
originated from commit 2f376d1b39, with the author being unreachable.
But the original code was very different, mostly due to MPlayer's
incredibly messy handling of subtitles in general. Nothing of this
remains in the current code. Even the command declarations were
rewritten. The commands (as seen from the user side) are rather similar
in naming and semantics, but we don't consider this copyrightable. So it
doesn't look like anything copyrightable is left.
The add/cycle commands were more or less based on step_property,
introduced in commit 7a71da01d6, with the patch author disagreeing with
the LGPL relicensing. But all code original to the patch has been
replaced in later mpv changes, and the original code was mostly copied
from MP_CMD_SET_PROPERTY anyway. The underlying property interface was
completely changed, the error handling was redone, and all of this is
very similar to the changes that were done on SET_PROPERTY. The command
declarations are completely different in the first place, because the
semantic change from step to add/cycle. The commit also seems to have
been co-authored by reimar to some degree. He also had the idea to
change the original patch from making the command modify a specific
property to making it generic.
(The error message line, especially with its %g formatting, might
contain some level of originality, so change that just to be sure.
This commit Copies and adapts the error message for SET_PROPERTY.)
Although I'm a bit on the fence with all the above things, it really
doesn't look like there's anything substantial that would cause issues.
I thus claim that there is no problem with changing the license to LGPL
for the above things. It's probably still slightly below the standard
that was usually applied in the code relicensing in mpv, but probably
still far above to the usual in open source relicensing (and above
commercial standards as well, if you look what certain tech giants do).
See "Copyright" file for caveats.
This changes the remaining "almost LGPL" files to LGPL, because we think
that the conditions the author set for these was finally fulfilled.
Mouse wheel bindings have always been a cause of user confusion.
Previously, on Wayland and macOS, precise touchpads would generate AXIS
keycodes and notched mouse wheels would generate mouse button keycodes.
On Windows, both types of device would generate AXIS keycodes and on
X11, both types of device would generate mouse button keycodes. This
made it pretty difficult for users to modify their mouse-wheel bindings,
since it differed between platforms and in some cases, between devices.
To make it more confusing, the keycodes used on Windows were changed in
18a45a42d5 without a deprecation period or adequate communication to
users.
This change aims to make mouse wheel binds less confusing. Both the
mouse button and AXIS keycodes are now deprecated aliases of the new
WHEEL keycodes. This will technically break input configs on Wayland and
macOS that assign different commands to precise and non-precise scroll
events, but this is probably uncommon (if anyone does it at all) and I
think it's a fair tradeoff for finally fixing mouse wheel-related
confusion on other platforms.
mpv's mouse button numbering is based on X11 button numbering, which
allows for an arbitrary number of buttons and includes mouse wheel input
as buttons 3-6. This button numbering was used throughout the codebase
and exposed in input.conf, and it was difficult to remember which
physical button each number actually referred to and which referred to
the scroll wheel.
In practice, PC mice only have between two and five buttons and one or
two scroll wheel axes, which are more or less in the same location and
have more or less the same function. This allows us to use names to
refer to the buttons instead of numbers, which makes input.conf syntax a
lot easier to remember. It also makes the syntax robust to changes in
mpv's underlying numbering. The old MOUSE_BTNx names are still
understood as deprecated aliases of the named buttons.
This changes both the input.conf syntax and the MP_MOUSE_BTNx symbols in
the codebase, since I think both would benefit from using names over
numbers, especially since some platforms don't use X11 button numbering
and handle different mouse buttons in different windowing system events.
This also makes the names shorter, since otherwise they would be pretty
long, and it removes the high-numbered MOUSE_BTNx_DBL names, since they
weren't used.
Names are the same as used in Qt:
https://doc.qt.io/qt-5/qt.html#MouseButton-enum
This was attempted before in fc9695e63b, but it was reverted in
1b7ce759b1 because it caused conflicts with other software watching
the same keys (See #2041.) It seems like some PCs ship with OEM software
that watches the volume keys without consuming key events and this
causes them to be handled twice, once by mpv and once by the other
software.
In order to prevent conflicts like this, use the WM_APPCOMMAND message
to handle media keys. Returning TRUE from the WM_APPCOMMAND handler
should indicate to the operating system that we consumed the key event
and it should not be propogated to the shell. Also, we now only listen
for keys that are directly related to multimedia playback (eg. the
APPCOMMAND_MEDIA_* keys.) Keys like APPCOMMAND_VOLUME_* are ignored, so
they can be handled by the shell, or by other mixer software.
While this is perfectly OK on Unix, it causes annoying valgrind
warnings, and might be otherwise confusing to others.
On Windows, the runtime can actually abort the process if this is
called.
push.c part taken from a patch by Pedro Pombeiro.
In a bunch of cases, we emulate highly platform specific APIs on a
higher level across all OSes, such as IPC, terminal, subprocess
handling, and more. We have source files for each OS, and they implement
all the same mpv internal API.
Selecting which source file to use on an OS can be tricky, because there
is partially overlapping and emulated APIs (consider Cygwin on Windows).
Add a pick_first_matching_dep() function to make this slightly easier
and more structured.
Also add dummy backends in some cases, to deal with APIs not being
available.
Clarify the Windows dependency identifiers, as these are the most
confusing.
It was extended by "seru" in 8d190244. This person could not be reached
(or does not reply), and it's in the way of LGPL relicensing. Deprecate
it, and mark the (probably) affected parts of the code with HAVE_GPL. To
be fair, even though the osd.c parts were refactored from the original
code, there's probably no copyright by seru on it. But for now play it
save. The mere existence of a 3rd OSD level is certainly not
copyrightable, so you still can set osd-level to 3 - just that it does
nothing.
cehoyos adds the step_property command in 7a71da01d, and it could be
argued that copyright of this still applies to the later add/cycle
commands (a668ae0ff9). While I'm not sure if this is really the case,
stay conservative for now and mark these commands as GPL-only. Mark the
command.c code too, although that is not being relicensed yet.
I'm leaving the MP_CMD_* enum items, as they are obviously different.
In commit 116ca0c768, "veal" (essentially an anonymous author) adds an
"osd_show_property_text" command (well, the commit message says "based
on" that person's code, so it's not clear how much is from him or from
albeu, who agreed to LGPL). This was later merged again with the
"osd_show_text" command, and then all original code was removed in
commit 58cc0f637f, so I claim that no copyright applies anymore. (Though
technically the input.conf addition still might be copyrighted, so I'm
just dropping it to get rid of the thought.)
"kiriuja" added 2f376d1b39 (sub_load etc.) and be54f4813 (switch_audio).
The latter is gone. I would argue that the former is fully rewritten
with commits b7052b431c and 0f155921b0. But like in the step_property
case, I will be overly conservative for now, and mark them as GPL-only,
as this is potentially shaky and should be thought through first. (Not
bothering with the command define/enum in the header, as it will be
unused in LGPL mode anyway.)
keycodes.c/h can be GPL, except for commit 2b1f95dcc2, which is a
patch by someone who wasn't asked yet. Before doing something radical, I
will wait for a reply.
This adds check_property_scalable, which returns true if the property is
backed by a floating-point number. When the add or cycle commands
operate on these properties, they can benefit from the fractional scale
value in cmd->scale. When the property is not backed by a floating-point
number, cmd->scale_units is used instead, so for axis events, the
property is only incrmented when the user scrolls one full unit.
This solution isn't perfect, because in some cases integer-backed
properties could benefit from accurate scrolling. For example, if an
axis is bound to "cycle audio 5", the cycle command could be made to
change the audio track by one when the user scrolls 1/5th of a unit,
though this behaviour would require more changes to the options system.
This adds some logic for pre-processing MP_AXIS_* events before the
corresponding input command is generated.
Firstly, the events are filtered. A lot of touchpad drivers and
operating systems don't seem to filter axis events, which makes it
difficult to use the verical axis (MP_AXIS_UP/MP_AXIS_DOWN) without
accidentally triggering commands bound to the horizontal axis
(MP_AXIS_LEFT/MP_AXIS_RIGHT) and vice-versa. To fix this, a small
deadzone is used. When one axis breaks out of the deadzone, events on
the other axis are ignored until the user stops scrolling (determined by
a timer.)
Secondly, the scale_units value is determined, which is the integer
number of "units" the user has scrolled, as opposed to scale, which is
the fractional number of units. It's determed by accumulating the
fractional scale values. If an axis is bound to a "non-scalable" command
that doesn't understand fractional units, interpret_key() will queue
that many commands, each with scale = 1.0.
Scalable commands (seek, cycle and add) understand the cmd->scale
parameter and will "scale" their action accordingly, for example, a seek
with scale = 0.5 will only seek half the specified amount and a seek
with scale = 2.0 will seek twice as much.
Mark these commands so in the next commit, input.c will be able to
synthesize input with cmd->scale = 1 for non-scalable commands.
Obviously, this has no effect on commands which do not support this
explicitly. A later commit will enable this for screenshots.
Also add some wording on mpv_command_async(), which has nothing to do
with this. Having a more elegant, unified behavior would be nice. But
the API function was not created for this - it's merely for running
commands _synchronously_ on the core, but without blocking the client
API caller (if the API user consistently uses only async functions).
for a reason i can just assume some key events can vanish from the
event chain and mpv seems unresponsive.
after quite some testing i could confirm that the events are present at
the first entry point of the event chain, the sendEvent method of the
Application, and that they vanish at a point afterwards. now we use
that entry point to grab keyDown and keyUp events. we also stop
propagating those key events to prevent the no key input' error sound.
if we ever need the key events somewhere down the event chain we need
to start propagating them again. though this is not necessary currently.
As preparation for file prefetching, we basically have to get rid of
using mpctx->playback_abort for the main demuxer (i.e. the thing that
can be prefetched). It can't be changed on a running demuxer, and always
using the same cancel handle would either mean aborting playback would
also abort prefetching, or that playback can't be aborted anymore.
Make this more flexible with some refactoring.
Thi is a quite shitty solution if you ask me, but YOLO.
As threatened by the API changes document.
This commit also removes or stubs equivalent calls in IPC and Lua
scripting.
The stubs are left to maintain ABI compatibility. The semantics of the
API functions have been close enough to doing nothing that this probably
won't even break existing API users. Probably.
The intention is to give libmpv users as much flexibility to load
scripts as using mpv from CLI, but without restricting libmpv users from
having to decide everything on creation time, or having to go through
hacks like recreating the libmpv context to update state.
Instead of using input_ctx for waiting, use the dispatch queue directly.
One big change is that the dispatch queue will just process commands
that come in (e.g. from client API) without returning. This should
reduce unnecessary playloop excutions (which is good since the playloop
got a bit fat from rechecking a lot of conditions every iteration).
Since this doesn't force a new playloop iteration on every access, this
has to be enforced manually in some cases.
Normal input (via terminal or VO window) still wakes up the playloop
every time, though that's not too important. It makes testing this
harder, though. If there are missing wakeup calls, it will be noticed
only when using the client API in some form.
At this point we could probably use a normal lock instead of the
dispatch queue stuff.
They're useless, and I have no idea what they're actually supposed to do
(wrt. pending input processing changes).
Also remove their implicit uses from the IPC handlers.
This workaround prevented that libmpv users could accidentally crash
when the SIGPIPE signal was triggered by FFmpeg's OpenSSL/GnuTLS usage.
But it also modifies the global signal handler state, so remove it now
that this workaround is not required anymore.
With the recent vo_opengl changes it doesn't do anything anymore.
I don't think a deprecation period is necessary, because the command
was always marked as experimental.
Old-style commands using _ as separator (e.g. show_progress) were still
used in some places, including documentation and configuration files.
This commit updates all such instances to the new style (show-progress)
so that commands are easier to find in the manual.
For clang, it's enough to just put (void) around usages we are
intentionally ignoring the result of.
Since GCC does not seem to want to respect this decision, we are forced
to disable the warning globally.
E.g. "mouse 100 100 1 double" did not actually process the double-click,
because double-click emulation is on by default. So the user would have
to send two successive clicks instead. This is probably not expected, so
disable this weird logic for artificial input.
Fixes#2899.
The default security descriptor for named pipes in Windows allows the
pipe to be opened for read access by the Everyone group and Anonymous
account, as well as low-integrity processes (like web browser renderer
processes.) This does not allow commands to be ran, but it does allow
events to be received.
I don't think any sensitive data is exposed by events, but that may not
always be the case and Lua plugins might change this, since they can
broadcast their own events with script-message. To be safe, this commit
sets a custom security descriptor on the named pipe which only allows
access from processes running under the same user account with an
integrity level greater than or equal to the one used by mpv.
This implements the JSON IPC protocol with named pipes, which are
probably the closest Windows equivalent to Unix domain sockets in terms
of functionality. Like with Unix sockets, this will allow mpv to listen
for IPC connections and handle multiple IPC clients at once. A few cross
platform libraries and frameworks (Qt, node.js) use named pipes for IPC
on Windows and Unix sockets on Linux and Unix, so hopefully this will
ease the creation of portable JSON IPC clients.
Unlike the Unix implementation, this doesn't share code with
--input-file, meaning --input-file on Windows won't understand JSON
commands (yet.) Sharing code and removing the separate implementation in
pipe-win32.c is definitely a possible future improvement.
Drag&drop mechanisms typically support multiple types for the drop data.
Move most of the logic which types are accepted and preferred to
event.c, where the data is also interpreted.
(Maybe sorting the types by assigning scores is over-engineered, since
they're already sorted by preference, but it's actually not much more
code.)
Not very interesting/meaningful yet, but preparation for the next
commit.
This covers source files which were added in mplayer2 and mpv times
only, and where all code is covered by LGPL relicensing agreements.
There are probably more files to which this applies, but I'm being
conservative here.
A file named ao_sdl.c exists in MPlayer too, but the mpv one is a
complete rewrite, and was added some time after the original ao_sdl.c
was removed. The same applies to vo_sdl.c, for which the SDL2 API is
radically different in addition (MPlayer supports SDL 1.2 only).
common.c contains only code written by me. But common.h is a strange
case: although it originally was named mp_common.h and exists in MPlayer
too, by now it contains only definitions written by uau and me. The
exceptions are the CONTROL_ defines - thus not changing the license of
common.h yet.
codec_tags.c contained once large tables generated from MPlayer's
codecs.conf, but all of these tables were removed.
From demux_playlist.c I'm removing a code fragment from someone who was
not asked; this probably could be done later (see commit 15dccc37).
misc.c is a bit complicated to reason about (it was split off mplayer.c
and thus contains random functions out of this file), but actually all
functions have been added post-MPlayer. Except get_relative_time(),
which was written by uau, but looks similar to 3 different versions of
something similar in each of the Unix/win32/OSX timer source files. I'm
not sure what that means in regards to copyright, so I've just moved it
into another still-GPL source file for now.
screenshot.c once had some minor parts of MPlayer's vf_screenshot.c, but
they're all gone.
The demuxer infrastructure was originally single-threaded. To make it
suitable for multithreading (specifically, demuxing and decoding on
separate threads), some sort of tripple-buffering was introduced. There
are separate "struct demuxer" allocations. The demuxer thread sets the
state on d_thread. If anything changes, the state is copied to d_buffer
(the copy is protected by a lock), and the decoder thread is notified.
Then the decoder thread copies the state from d_buffer to d_user (again
while holding a lock). This avoids the need for locking in the
demuxer/decoder code itself (only demux.c needs an internal, "invisible"
lock.)
Remove the streams/num_streams fields from this tripple-buffering
schema. Move them to the internal struct, and protect them with the
internal lock. Use accessors for read access outside of demux.c.
Other than replacing all field accesses with accessors, this separates
allocating and adding sh_streams. This is needed to avoid race
conditions. Before this change, this was awkwardly handled by first
initializing the sh_stream, and then sending a stream change event. Now
the stream is allocated, then initialized, and then declared as
immutable and added (at which point it becomes visible to the decoder
thread immediately).
This change is useful for PR #2626. And eventually, we should probably
get entirely of the tripple buffering, and this makes a nice first step.
The "script-binding" command is used by the Lua scripting wrapper to
register key bindings on the fly. It's also the only way to get fine-
grained information about key events (such as separate key up/down
events). This information is sent via a "key-binding" message when the
state of a key changes.
Extend it to send name of the mapped key itself. Previously, it was
assumed that the user just uses an unique identifier for the binding's
name, so it wasn't needed. With this change, a user can map exactly the
same command to multiple keys, which is useful especially with the next
commit.
Part of #2612.
libwaio was added due to the complete inability to cancel synchronous
I/O cleanly using the public Windows API in Windows XP. Even calling
TerminateThread on the thread performing I/O was a bad solution, because
the TerminateThread function in XP would leak the thread's stack.
In Vista and up, however, this is no longer a problem. CancelIoEx can
cancel synchronous I/O running on other threads, allowing the thread to
exit cleanly, so replace libwaio usage with native Vista API functions.
It should be noted that this change also removes the hack added in
8a27025 for preventing a deadlock that only seemed to happen in Windows
XP. KB2009703 says that Vista and up are not affected by this, due to a
change in the implementation of GetFileType, so the hack should not be
needed anymore.
There was a complaint that the naming is inaccurate. That's probably
right. Just use the official name instead, which is a bit clunky, but
surely correct.
