client API: expose the internal clock

May or may not be useful in some ways.

We require a context parameter for this just to be sure, even if the
internal implementation currently doesn't.

That's one less mpv internal function for the Lua wrapper.

libmpv/client.h

@@ -350,6 +350,18 @@ void mpv_suspend(mpv_handle *ctx);
  */
 void mpv_resume(mpv_handle *ctx);
 
+/**
+ * Return the internal time in microseconds. This has an arbitrary start offset,
+ * but will never wrap or go backwards (note: the latter is probably a lie in
+ * the current implementation, it can go backwards on system clock changes).
+ *
+ * Note that this is always the real time, and doesn't necessarily have to do
+ * with playback time. For example, playback could go faster or slower due to
+ * playback speed, or due to playback being paused. Use the "time-pos" property
+ * instead to get the playback status.
+ */
+int64_t mpv_get_time_us(mpv_handle *ctx);
+
 /**
  * Data format for options and properties. The API functions to get/set
  * properties and options support multiple formats, and this enum describes

player/client.c

@@ -24,6 +24,7 @@
 #include "options/m_option.h"
 #include "options/m_property.h"
 #include "osdep/threads.h"
+#include "osdep/timer.h"
 
 #include "command.h"
 #include "core.h"
@@ -992,3 +993,8 @@ void mpv_free(void *data)
 {
     talloc_free(data);
 }
+
+int64_t mpv_get_time_us(mpv_handle *ctx)
+{
+    return mp_time_us();
+}

player/lua.c

@@ -722,7 +722,8 @@ static int script_get_mouse_pos(lua_State *L)
 
 static int script_get_time(lua_State *L)
 {
-    lua_pushnumber(L, mp_time_sec());
+    struct script_ctx *ctx = get_ctx(L);
+    lua_pushnumber(L, mpv_get_time_us(ctx->client) / (double)(1000 * 1000));
     return 1;
 }