command: add touch-pos property

This adds touch-pos property, which contains the information of all
current touch points. The property has sub properties:

touch-pos/count: the number of current touch points
touch-pos/N/x,y: the position of touch point N
touch-pos/N/id: unique identifier of the touch point

DOCS/interface-changes/touch-pos.txt

@@ -0,0 +1 @@
+add `touch-pos` property

DOCS/man/input.rst

@@ -2800,7 +2800,7 @@ Property list
     not being opened yet or not being supported by the VO.
 
 ``mouse-pos``
-    Read-only - last known mouse position, normalizd to OSD dimensions.
+    Read-only - last known mouse position, normalized to OSD dimensions.
 
     Has the following sub-properties (which can be read as ``MPV_FORMAT_NODE``
     or Lua table with ``mp.get_property_native``):
@@ -2813,6 +2813,35 @@ Property list
         coordinates should be ignored when this value is false, because the
         video backends update them only when the pointer hovers the window.
 
+``touch-pos``
+    Read-only - last known touch point positions, normalized to OSD dimensions.
+
+    This has a number of sub-properties. Replace ``N`` with the 0-based touch
+    point index. Whenever a new finger touches the screen, a new touch point is
+    added to the list of touch points with the smallest unused ``N`` available.
+
+    ``touch-pos/count``
+        Number of active touch points.
+
+    ``touch-pos/N/x``, ``touch-pos/N/y``
+        Position of the Nth touch point.
+
+    ``touch-pos/N/id``
+        Unique identifier of the touch point. This can be used to identify
+        individual touch points when their indexes change.
+
+    When querying the property with the client API using ``MPV_FORMAT_NODE``,
+    or with Lua ``mp.get_property_native``, this will return a mpv_node with
+    the following contents:
+
+    ::
+
+        MPV_FORMAT_NODE_ARRAY
+            MPV_FORMAT_NODE_MAP (for each touch point)
+                "x"        MPV_FORMAT_INT64
+                "y"        MPV_FORMAT_INT64
+                "id"       MPV_FORMAT_INT64
+
 ``sub-ass-extradata``
     The current ASS subtitle track's extradata. There is no formatting done.
     The extradata is returned as a string as-is. This property is not

player/command.c

@@ -2897,6 +2897,32 @@ static int mp_property_mouse_pos(void *ctx, struct m_property *prop,
     return M_PROPERTY_NOT_IMPLEMENTED;
 }
 
+static int get_touch_pos(int item, int action, void *arg, void *ctx)
+{
+    const int **pos = (const int **)ctx;
+    struct m_sub_property props[] = {
+        {"x", SUB_PROP_INT(pos[0][item])},
+        {"y", SUB_PROP_INT(pos[1][item])},
+        {"id", SUB_PROP_INT(pos[2][item])},
+        {0}
+    };
+
+    int r = m_property_read_sub(props, action, arg);
+    return r;
+}
+
+#define MAX_TOUCH_POINTS 10
+static int mp_property_touch_pos(void *ctx, struct m_property *prop,
+                                 int action, void *arg)
+{
+    MPContext *mpctx = ctx;
+    int xs[MAX_TOUCH_POINTS], ys[MAX_TOUCH_POINTS], ids[MAX_TOUCH_POINTS];
+    int count = mp_input_get_touch_pos(mpctx->input, MAX_TOUCH_POINTS, xs, ys, ids);
+    const int *pos[3] = {xs, ys, ids};
+    return m_property_read_list(action, arg, MPMIN(MAX_TOUCH_POINTS, count),
+                                get_touch_pos, (void *)pos);
+}
+
 /// Video fps (RO)
 static int mp_property_fps(void *ctx, struct m_property *prop,
                            int action, void *arg)
@@ -4045,6 +4071,7 @@ static const struct m_property mp_properties_base[] = {
     {"osd-ass-cc", mp_property_osd_ass},
 
     {"mouse-pos", mp_property_mouse_pos},
+    {"touch-pos", mp_property_touch_pos},
 
     // Subs
     {"sid", property_switch_track, .priv = (void *)(const int[]){0, STREAM_SUB}},
@@ -4182,7 +4209,7 @@ static const char *const *const mp_event_property_change[] = {
     E(MP_EVENT_CHANGE_PLAYLIST, "playlist", "playlist-pos", "playlist-pos-1",
       "playlist-count", "playlist/count", "playlist-current-pos",
       "playlist-playing-pos"),
-    E(MP_EVENT_INPUT_PROCESSED, "mouse-pos"),
+    E(MP_EVENT_INPUT_PROCESSED, "mouse-pos", "touch-pos"),
     E(MP_EVENT_CORE_IDLE, "core-idle", "eof-reached"),
 };
 #undef E