player: make screenshot commands honor the async flag

And also change input.conf to make all screenshots async. (Except the
every-frame mode, which always uses synchronous mode and ignores the
flag.) By default, the "screenshot" command is still asynchronous,
because scripts etc. might depend on this behavior.

This is only partially async. The code for determining the filename is
still always run synchronously. Only encoding the screenshot and writing
it to disk is asynchronous. We explicitly document the exact behavior as
undefined, so it can be changed any time.

Some of this is a bit messy, because I wanted to avoid duplicating the
message display code between sync and async mode. In async mode, this is
called from a worker thread, which is not safe because showing a message
accesses the thread-unsafe OSD code. So the core has to be locked during
this, which implies accessing the core and all that. So the code has
weird locking calls, and we need to do core destruction in a more
"controlled" manner (thus the outstanding_async field).

(What I'd really want would be the OSD simply showing log messages
instead.)

This is pretty untested, so expect bugs.

Fixes #4250.

1 files changed, 2 insertions, 2 deletions

diff --git a/player/screenshot.h b/player/screenshot.h
index aa5dfac2d0..69f6ac801d 100644
--- a/player/screenshot.h
+++ b/player/screenshot.h
@@ -31,13 +31,13 @@ void screenshot_init(struct MPContext *mpctx);
 //             screenshot slave command (MP_CMD_SCREENSHOT).
 // osd: show status on OSD
 void screenshot_request(struct MPContext *mpctx, int mode, bool each_frame,
-                        bool osd);
+                        bool osd, bool async);
 
 // filename: where to store the screenshot; doesn't try to find an alternate
 //           name if the file already exists
 // mode, osd: same as in screenshot_request()
 void screenshot_to_file(struct MPContext *mpctx, const char *filename, int mode,
-                        bool osd);
+                        bool osd, bool async);
 
 // mode is the same as in screenshot_request()
 struct mp_image *screenshot_get_rgb(struct MPContext *mpctx, int mode);