vo: use mp_poll wrapper in wait_events when applicable

On linux, several platforms poll for events over a fd. This has ms
accuracy, but mpv's timer is in ns now so lots of precision is lost. We
can use an mp_poll wrapper to use ppoll instead which takes a timespec
directly with nanosecond precision. On systems without ppoll this falls
back to old poll behavior. On wayland, we don't actually use this
because ppoll completely messes up the event loop for some unknown
reason.

meson.build

@@ -424,6 +424,9 @@ if posix and not darwin
                      'osdep/timer-linux.c')
 endif
 
+features += {'ppoll': cc.has_function('ppoll', args: '-D_GNU_SOURCE',
+                                      prefix: '#include <poll.h>')}
+
 cd_devices = {
     'windows': 'D:',
     'cygwin': 'D:',

osdep/poll_wrapper.c

@@ -20,9 +20,20 @@
 #include <sys/select.h>
 #include <stdio.h>
 
+#include "config.h"
 #include "poll_wrapper.h"
+#include "timer.h"
 
 
+int mp_poll(struct pollfd *fds, int nfds, int64_t timeout_ns)
+{
+#if HAVE_PPOLL
+    struct timespec ts = mp_time_ns_to_realtime(timeout_ns);
+    return ppoll(fds, nfds, &ts, NULL);
+#endif
+    return poll(fds, nfds, timeout_ns / 1e6);
+}
+
 // poll shim that supports device files on macOS.
 int polldev(struct pollfd fds[], nfds_t nfds, int timeout)
 {

osdep/poll_wrapper.h

@@ -1,7 +1,12 @@
 #pragma once
 
 #include <poll.h>
+#include <stdint.h>
 
 // Behaves like poll(3) but works for device files on macOS.
 // Only supports POLLIN and POLLOUT.
 int polldev(struct pollfd fds[], nfds_t nfds, int timeout);
+
+// Generic polling wrapper. It will try and use higher resolution
+// polling (ppoll) if available.
+int mp_poll(struct pollfd *fds, int nfds, int64_t timeout_ns);

video/out/drm_common.c

@@ -42,6 +42,7 @@
 #include "common/msg.h"
 #include "options/m_config.h"
 #include "osdep/io.h"
+#include "osdep/poll_wrapper.h"
 #include "osdep/timer.h"
 #include "misc/ctype.h"
 #include "video/out/vo.h"
@@ -283,12 +284,12 @@ static void vt_switcher_destroy(struct vt_switcher *s)
     close(vt_switcher_pipe[1]);
 }
 
-static void vt_switcher_poll(struct vt_switcher *s, int timeout_ms)
+static void vt_switcher_poll(struct vt_switcher *s, int timeout_ns)
 {
     struct pollfd fds[1] = {
         { .events = POLLIN, .fd = vt_switcher_pipe[0] },
     };
-    poll(fds, 1, timeout_ms);
+    mp_poll(fds, 1, timeout_ns);
     if (!fds[0].revents)
         return;
 
@@ -1309,8 +1310,8 @@ void vo_drm_wait_events(struct vo *vo, int64_t until_time_ns)
     struct vo_drm_state *drm = vo->drm;
     if (drm->vt_switcher_active) {
         int64_t wait_ns = until_time_ns - mp_time_ns();
-        int timeout_ms = MPCLAMP((wait_ns + 500000) / 1e6, 0, 10000);
-        vt_switcher_poll(&drm->vt_switcher, timeout_ms);
+        int64_t timeout_ns = MPCLAMP((wait_ns + 500000), 0, 1e7);
+        vt_switcher_poll(&drm->vt_switcher, timeout_ns);
     } else {
         vo_wait_default(vo, until_time_ns);
     }

video/out/x11_common.c

@@ -55,6 +55,7 @@
 #include "vo.h"
 #include "win_state.h"
 #include "osdep/io.h"
+#include "osdep/poll_wrapper.h"
 #include "osdep/timer.h"
 #include "osdep/subprocess.h"
 
@@ -2177,9 +2178,9 @@ void vo_x11_wait_events(struct vo *vo, int64_t until_time_ns)
         { .fd = x11->wakeup_pipe[0], .events = POLLIN },
     };
     int64_t wait_ns = until_time_ns - mp_time_ns();
-    int timeout_ms = MPCLAMP((wait_ns + 999000) / 1e6, 0, 10000);
+    int64_t timeout_ns = MPCLAMP((wait_ns + 999000), 0, 1e7);
 
-    poll(fds, 2, timeout_ms);
+    mp_poll(fds, 2, timeout_ns);
 
     if (fds[1].revents & POLLIN)
         mp_flush_wakeup_pipe(x11->wakeup_pipe[0]);