commands: don't use dummy option declaration for properties

The property-to-option bridge (when properties change values normally
set by the command line parser) uses M_PROPERTY_GET_TYPE to get the
exact option type. In these cases, the entry in mp_properties[] is
unused, except for the name field and the property callback. Instead,
mp_property_generic_option() implements M_PROPERTY_GET_TYPE and returns
the m_option as defined in cfg-mplayer.h. However, if a property is
unavailable, mp_property_generic_option() is never actually called, and
M_PROPERTY_GET_TYPE will return the dummy option entry.

We could make sure that the dummy option entry equals the option entry
defined in cfg-mplayer.h. But this would duplicate all information.

Add a dummy option type m_option_type_dummy, which is used by entries
using the property-to-option bridge. Make M_PROPERTY_GET_TYPE fail if
this type is encountered.

This dummy should never be used, as it isn

command.c

@@ -1329,14 +1329,14 @@ static int mp_property_tv_color(m_option_t *prop, int action, void *arg,
 
 // Use option-to-property-bridge. (The property and option have the same names.)
 #define M_OPTION_PROPERTY(name) \
-    {(name), mp_property_generic_option, &m_option_type_choice, 0, 0, 0, (name)}
+    {(name), mp_property_generic_option, &m_option_type_dummy, 0, 0, 0, (name)}
 
 // OPTION_PROPERTY(), but with a custom property handler. The custom handler
 // must let unknown operations fall back to mp_property_generic_option().
 #define M_OPTION_PROPERTY_CUSTOM(name, handler) \
-    {(name), (handler), &m_option_type_choice, 0, 0, 0, (name)}
+    {(name), (handler), &m_option_type_dummy, 0, 0, 0, (name)}
 #define M_OPTION_PROPERTY_CUSTOM_(name, handler, ...) \
-    {(name), (handler), &m_option_type_choice, 0, 0, 0, (name), __VA_ARGS__}
+    {(name), (handler), &m_option_type_dummy, 0, 0, 0, (name), __VA_ARGS__}
 
 /// All properties available in MPlayer.
 /** \ingroup Properties

m_property.c

@@ -35,6 +35,10 @@
 #include "mp_msg.h"
 #include "mpcommon.h"
 
+const struct m_option_type m_option_type_dummy = {
+    .name = "Unknown",
+};
+
 static int do_action(const m_option_t *prop_list, const char *name,
                      int action, void *arg, void *ctx)
 {
@@ -59,7 +63,9 @@ static int do_action(const m_option_t *prop_list, const char *name,
         return M_PROPERTY_UNKNOWN;
     int (*control)(const m_option_t*, int, void*, void*) = prop->p;
     int r = control(prop, action, arg, ctx);
-    if (action == M_PROPERTY_GET_TYPE && r < 0) {
+    if (action == M_PROPERTY_GET_TYPE && r < 0 &&
+        prop->type != &m_option_type_dummy)
+    {
         *(struct m_option *)arg = *prop;
         return M_PROPERTY_OK;
     }

m_property.h

@@ -23,6 +23,8 @@
 
 struct m_option;
 
+extern const struct m_option_type m_option_type_dummy;
+
 enum mp_property_action {
     // Get the property type. This defines the fundamental data type read from
     // or written to the property.