Fix #115183: Show errors only shows errors when channels have been expanded

When enabling the "Only Show Errors" option in the Dope Sheet/Graph Editor,
it might not show anything even though there are FCurves with errors.
The issue is that the flag `FCURVE_DISABLED` is set by the drawing code,
which means the channels have to be visible first.
This creates a workflow issue where you want to filter down to only the
curves with problems, but you need to find them first...

This PR fixes the issue by validating all FCurves whenever the option
is enabled.

Pull Request: https://projects.blender.org/blender/blender/pulls/116815

source/blender/makesrna/intern/rna_action.cc

@@ -23,6 +23,7 @@
 #include "RNA_access.hh"
 #include "RNA_define.hh"
 #include "RNA_enum_types.hh"
+#include "RNA_path.hh"
 
 #include "rna_internal.h"
 
@@ -37,6 +38,7 @@
 #  include "DEG_depsgraph.hh"
 
 #  include "ANIM_action.hh"
+#  include "ED_anim_api.hh"
 
 #  include "WM_api.hh"
 
@@ -348,6 +350,44 @@ bool rna_Action_actedit_assign_poll(PointerRNA *ptr, PointerRNA value)
   return 0;
 }
 
+/* All FCurves need to be validated when the "show_only_errors" button is enabled. */
+static void rna_Action_show_errors_update(bContext *C, PointerRNA * /*ptr*/)
+{
+  bAnimContext ac;
+
+  /* Get editor data. */
+  if (ANIM_animdata_get_context(C, &ac) == 0) {
+    return;
+  }
+
+  if (!(ac.ads->filterflag & ADS_FILTER_ONLY_ERRORS)) {
+    return;
+  }
+
+  /* Need to take off the flag before filtering, else the filter code would skip the FCurves, which
+   * have not yet been validated. */
+  ac.ads->filterflag &= ~ADS_FILTER_ONLY_ERRORS;
+  ListBase anim_data = {nullptr, nullptr};
+  const eAnimFilter_Flags filter = ANIMFILTER_DATA_VISIBLE | ANIMFILTER_FCURVESONLY;
+  ANIM_animdata_filter(&ac, &anim_data, filter, ac.data, eAnimCont_Types(ac.datatype));
+
+  LISTBASE_FOREACH (bAnimListElem *, ale, &anim_data) {
+    FCurve *fcu = (FCurve *)ale->key_data;
+    PointerRNA ptr;
+    PropertyRNA *prop;
+    PointerRNA id_ptr = RNA_id_pointer_create(ale->id);
+    if (RNA_path_resolve_property(&id_ptr, fcu->rna_path, &ptr, &prop)) {
+      fcu->flag &= ~FCURVE_DISABLED;
+    }
+    else {
+      fcu->flag |= FCURVE_DISABLED;
+    }
+  }
+
+  ANIM_animdata_freelist(&anim_data);
+  ac.ads->filterflag |= ADS_FILTER_ONLY_ERRORS;
+}
+
 static char *rna_DopeSheet_path(const PointerRNA * /*ptr*/)
 {
   return BLI_strdup("dopesheet");
@@ -420,7 +460,9 @@ static void rna_def_dopesheet(BlenderRNA *brna)
                            "Only Show Errors",
                            "Only include F-Curves and drivers that are disabled or have errors");
   RNA_def_property_ui_icon(prop, ICON_ERROR, 0);
-  RNA_def_property_update(prop, NC_ANIMATION | ND_ANIMCHAN | NA_EDITED, nullptr);
+  RNA_def_property_flag(prop, PROP_CONTEXT_UPDATE);
+  RNA_def_property_update(
+      prop, NC_ANIMATION | ND_ANIMCHAN | NA_EDITED, "rna_Action_show_errors_update");
 
   /* Object Collection Filtering Settings */
   prop = RNA_def_property(srna, "filter_collection", PROP_POINTER, PROP_NONE);