vo_opengl_cb: add a function to report vsync time

And also let vo.c know of it.

Currently, this does not help much, but will facilitate future
improvements.

DOCS/client-api-changes.rst

@@ -26,6 +26,7 @@ API changes
 ::
 
  --- mpv 0.9.0 will be released ---
+ 1.16   - add mpv_opengl_cb_report_flip()
  1.15   - mpv_initialize() will now load config files. This requires setting
           the "config" and "config-dir" options. In particular, it will load
           mpv.conf.

DOCS/client_api_examples/qml_direct/main.cpp

@@ -96,6 +96,8 @@ void MpvObject::handleWindowChanged(QQuickWindow *win)
             this, &MpvObject::sync, Qt::DirectConnection);
     connect(win, &QQuickWindow::sceneGraphInvalidated,
             this, &MpvObject::cleanup, Qt::DirectConnection);
+    connect(win, &QQuickWindow::frameSwapped,
+            this, &MpvObject::swapped, Qt::DirectConnection);
     win->setClearBeforeRendering(false);
 }
 
@@ -110,6 +112,11 @@ void MpvObject::sync()
     renderer->size = window()->size() * window()->devicePixelRatio();
 }
 
+void MpvObject::swapped()
+{
+    mpv_opengl_cb_report_flip(mpv_gl, 0);
+}
+
 void MpvObject::cleanup()
 {
     if (renderer) {

DOCS/client_api_examples/qml_direct/main.h

@@ -37,6 +37,7 @@ public:
 public slots:
     void command(const QVariant& params);
     void sync();
+    void swapped();
     void cleanup();
 signals:
     void onUpdate();

libmpv/client.h

@@ -195,7 +195,7 @@ extern "C" {
  * relational operators (<, >, <=, >=).
  */
 #define MPV_MAKE_VERSION(major, minor) (((major) << 16) | (minor) | 0UL)
-#define MPV_CLIENT_API_VERSION MPV_MAKE_VERSION(1, 15)
+#define MPV_CLIENT_API_VERSION MPV_MAKE_VERSION(1, 16)
 
 /**
  * Return the MPV_CLIENT_API_VERSION the mpv source has been compiled with.

libmpv/mpv.def

@@ -23,6 +23,7 @@ mpv_initialize
 mpv_load_config_file
 mpv_observe_property
 mpv_opengl_cb_init_gl
+mpv_opengl_cb_report_flip
 mpv_opengl_cb_render
 mpv_opengl_cb_set_update_callback
 mpv_opengl_cb_uninit_gl

libmpv/opengl_cb.h

@@ -198,6 +198,18 @@ int mpv_opengl_cb_init_gl(mpv_opengl_cb_context *ctx, const char *exts,
  */
 int mpv_opengl_cb_render(mpv_opengl_cb_context *ctx, int fbo, int vp[4]);
 
+/**
+ * Tell the renderer that a frame was flipped at the given time. This is
+ * optional, but can help the player to achieve better timing.
+ *
+ * If this is called while no video or no OpenGL is initialized, it is ignored.
+ *
+ * @param time The mpv time (using mpv_get_time_us()) at which the flip call
+ *             returned. If 0 is passed, mpv_get_time_us() is used instead.
+ * @return error code
+ */
+int mpv_opengl_cb_report_flip(mpv_opengl_cb_context *ctx, int64_t time);
+
 /**
  * Destroy the mpv OpenGL state.
  *

player/client.c

@@ -1709,6 +1709,10 @@ int mpv_opengl_cb_render(mpv_opengl_cb_context *ctx, int fbo, int vp[4])
 {
     return MPV_ERROR_NOT_IMPLEMENTED;
 }
+int mpv_opengl_cb_report_flip(mpv_opengl_cb_context *ctx, int64_t time)
+{
+    return MPV_ERROR_NOT_IMPLEMENTED;
+}
 int mpv_opengl_cb_uninit_gl(mpv_opengl_cb_context *ctx)
 {
     return MPV_ERROR_NOT_IMPLEMENTED;

video/out/vo_opengl_cb.c

@@ -19,6 +19,7 @@
 #include "vo.h"
 #include "video/mp_image.h"
 #include "sub/osd.h"
+#include "osdep/timer.h"
 
 #include "common/global.h"
 #include "player/client.h"
@@ -76,6 +77,7 @@ struct mpv_opengl_cb_context {
     struct m_config *new_opts_cfg;
     bool eq_changed;
     struct mp_csp_equalizer eq;
+    int64_t recent_flip;
 
     // --- All of these can only be accessed from the thread where the host
     //     application's OpenGL context is current - i.e. only while the
@@ -342,6 +344,15 @@ int mpv_opengl_cb_render(struct mpv_opengl_cb_context *ctx, int fbo, int vp[4])
     return left;
 }
 
+int mpv_opengl_cb_report_flip(mpv_opengl_cb_context *ctx, int64_t time)
+{
+    pthread_mutex_lock(&ctx->lock);
+    ctx->recent_flip = time > 0 ? time : mp_time_us();
+    pthread_mutex_unlock(&ctx->lock);
+
+    return 0;
+}
+
 static void draw_image(struct vo *vo, mp_image_t *mpi)
 {
     struct vo_priv *p = vo->priv;
@@ -486,6 +497,16 @@ static int control(struct vo *vo, uint32_t request, void *data)
         *arg = p->ctx ? &p->ctx->hwdec_info : NULL;
         return true;
     }
+    case VOCTRL_GET_RECENT_FLIP_TIME: {
+        int r = VO_FALSE;
+        pthread_mutex_lock(&p->ctx->lock);
+        if (p->ctx->recent_flip) {
+            *(int64_t *)data = p->ctx->recent_flip;
+            r = VO_TRUE;
+        }
+        pthread_mutex_unlock(&p->ctx->lock);
+        return r;
+    }
     }
 
     return VO_NOTIMPL;