command: change af/vf property behavior wrt. filter creation failures

The behavior is slightly different in a messy way. The change is in line
with the option-to-property bridge removal mentioned some commits ago
and thus is deemed necessary.

DOCS/interface-changes.rst

@@ -47,6 +47,10 @@ Interface changes
       property now is unavailable if no VO exists (or the VO did not return a
       display FPS), instead of returning the option value in this case. The
       property will keep existing, but writing to it is deprecated.
+    - the vf/af properties now do not reject the set value anymore, even if
+      filter chain initialization fails. Instead, the vf/af options are always
+      set to the user's value, even if it does not reflect the "runtime" vf/af
+      chain.
  --- mpv 0.30.0 ---
     - add `--d3d11-output-format` to enable explicit selection of a D3D11
       swap chain format.

DOCS/man/input.rst

@@ -2708,12 +2708,13 @@ caveats with some properties (due to historical reasons):
 
 ``vf``, ``af``
     If you set the properties during playback, and the filter chain fails to
-    reinitialize, the new value will be rejected. Setting the option or
-    setting the property outside of playback will always succeed/fail in the
-    same way. Also, there are no ``vf-add`` etc. properties, but you can use
-    the ``vf``/``af`` group of commands to achieve the same.
+    reinitialize, the option will be set, but the runtime filter chain does not
+    change. On the other hand, the next video to be played will fail, because
+    the initial filter chain cannot be created.
 
-    Option changes at runtime are affected by this as well.
+    This behavior changed in mpv 0.31.0. Before this, the new value was rejected
+    *iff* video (for ``vf``) or audio (for ``af``) was active. If playback was
+    not active, the behavior was the same as the current behavior.
 
 ``edition``
     While a file is loaded, the property will always return the effective
@@ -2726,7 +2727,8 @@ caveats with some properties (due to historical reasons):
     uses, you should use the ``loadlist`` command instead.
 
 ``window-scale``
-    Might verify the set value when setting while a window is created.
+    Returns the current window values if a window exists, and the option value
+    otherwise.
 
 ``profile``, ``include``
     These are write-only, and will perform actions as they are written to,

player/command.c

@@ -2989,17 +2989,12 @@ static char *print_obj_osd_list(struct m_obj_settings *list)
 static int property_filter(struct m_property *prop, int action, void *arg,
                            MPContext *mpctx, enum stream_type mt)
 {
-    switch (action) {
-    case M_PROPERTY_PRINT: {
+    if (action == M_PROPERTY_PRINT) {
         struct m_config_option *opt = m_config_get_co(mpctx->mconfig,
                                                       bstr0(prop->name));
         *(char **)arg = print_obj_osd_list(*(struct m_obj_settings **)opt->data);
         return M_PROPERTY_OK;
     }
-    case M_PROPERTY_SET:
-        return set_filters(mpctx, mt, *(struct m_obj_settings **)arg) >= 0
-            ? M_PROPERTY_OK : M_PROPERTY_ERROR;
-    }
     return mp_property_generic_option(mpctx, prop, action, arg);
 }
 
@@ -6314,6 +6309,12 @@ void mp_option_change_callback(void *ctx, struct m_config_option *co, int flags)
 
     if (opt_ptr == &opts->record_file)
         open_recorder(mpctx, false);
+
+    if (opt_ptr == &opts->vf_settings)
+        set_filters(mpctx, STREAM_VIDEO, opts->vf_settings);
+
+    if (opt_ptr == &opts->af_settings)
+        set_filters(mpctx, STREAM_AUDIO, opts->af_settings);
 }
 
 void mp_notify_property(struct MPContext *mpctx, const char *property)