commands: use "up" and "down" as 2nd argument for cycle command

Allow the values "up" and "down" as step argument for the cycle input
command. Previously, this argument was a float, which specified an
arbitrary step value and direction (similar to the add command).
Instead of "1" and "-1", "up" and "down" is to be used.

Float values are still accepted. That capability might be removed in the
future, as there's probably hardly any actual use for arbitrary step
values.

DOCS/man/en/input.rst

@@ -79,10 +79,10 @@ add <property> [<value>]
     Add the given value to the property. On overflow or underflow, clamp the
     property to the maximum. If <value> is omitted, assume ``1``.
 
-cycle <property> [<value>]
-    Cycle the given property. Negative values cycle the property backwards. On
+cycle <property> [up|down]
+    Cycle the given property. ``up`` and ``down`` set the cycle direction. On
     overflow, set the property back to the minimum, on underflow set it to the
-    maximum. If <value> is omitted, assume ``1``.
+    maximum. If ``up`` or ``down`` is omitted, assume ``up``.
 
 speed_mult <value>
     Multiply the ``speed`` property by the given value.

etc/input.conf

@@ -93,7 +93,7 @@ v cycle sub-visibility
 # stretch SSA/ASS subtitles with anamorphic videos to match historical
 V cycle ass-vsfilter-aspect-compat
 j cycle sub                             # cycle through subtitles
-J cycle sub -1                          # ...backwards
+J cycle sub down                        # ...backwards
 F cycle sub-forced-only
 SHARP cycle audio                       # switch audio streams
 _ cycle video

input/input.c

@@ -100,6 +100,13 @@ struct key_name {
                                            M_CHOICES(c)},                      \
                                   .optional = true, .v.i = def }
 
+static int parse_cycle_dir(const struct m_option *opt, struct bstr name,
+                           struct bstr param, void *dst);
+static const struct m_option_type m_option_type_cycle_dir = {
+    .name = "up|down",
+    .parse = parse_cycle_dir,
+};
+
 static const mp_cmd_t mp_cmds[] = {
   { MP_CMD_IGNORE, "ignore", },
 #ifdef CONFIG_RADIO
@@ -173,7 +180,12 @@ static const mp_cmd_t mp_cmds[] = {
   { MP_CMD_SET, "set", { ARG_STRING,  ARG_STRING } },
   { MP_CMD_GET_PROPERTY, "get_property", { ARG_STRING } },
   { MP_CMD_ADD, "add", { ARG_STRING, OARG_FLOAT(0) } },
-  { MP_CMD_CYCLE, "cycle", { ARG_STRING, OARG_FLOAT(0) } },
+  { MP_CMD_CYCLE, "cycle", {
+      ARG_STRING,
+      { .type = {"", NULL, &m_option_type_cycle_dir},
+        .optional = true,
+        .v.f = 1 },
+  }},
 
   { MP_CMD_SET_MOUSE_POS, "set_mouse_pos", { ARG_INT, ARG_INT } },
 
@@ -730,6 +742,21 @@ int mp_input_add_key_fd(struct input_ctx *ictx, int fd, int select,
     return 1;
 }
 
+static int parse_cycle_dir(const struct m_option *opt, struct bstr name,
+                           struct bstr param, void *dst)
+{
+    float val;
+    if (bstrcmp0(param, "up") == 0) {
+        val = +1;
+    } else if (bstrcmp0(param, "down") == 0) {
+        val = -1;
+    } else {
+        return m_option_type_float.parse(opt, name, param, dst);
+    }
+    *(float *)dst = val;
+    return 1;
+}
+
 static bool read_token(bstr str, bstr *out_rest, bstr *out_token)
 {
     bstr t = bstr_lstrip(str);