diff --git a/gtk/gtkaccessiblepropertyset.c b/gtk/gtkaccessiblepropertyset.c
new file mode 100644
index 0000000000..9a703fe6a9
--- /dev/null
+++ b/gtk/gtkaccessiblepropertyset.c
@@ -0,0 +1,221 @@
+/* gtkaccessiblepropertyset.c: Accessible properties
+ *
+ * Copyright 2020 GNOME Foundation
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see .
+ */
+
+#include "config.h"
+
+#include "gtkaccessiblepropertysetprivate.h"
+
+#include "gtkbitmaskprivate.h"
+#include "gtkenums.h"
+
+/* Keep in sync with GtkAccessibleProperty in gtkenums.h */
+#define LAST_PROPERTY GTK_ACCESSIBLE_PROPERTY_VALUE_TEXT
+
+struct _GtkAccessiblePropertySet
+{
+ GtkBitmask *property_set;
+
+ GtkAccessibleValue **property_values;
+};
+
+static GtkAccessiblePropertySet *
+gtk_accessible_property_set_init (GtkAccessiblePropertySet *self)
+{
+ self->property_set = _gtk_bitmask_new ();
+ self->property_values = g_new (GtkAccessibleValue *, LAST_PROPERTY);
+
+ /* Initialize all property values, so we can always get the full set */
+ for (int i = 0; i < LAST_PROPERTY; i++)
+ self->property_values[i] = gtk_accessible_value_get_default_for_property (i);
+
+ return self;
+}
+
+GtkAccessiblePropertySet *
+gtk_accessible_property_set_new (void)
+{
+ GtkAccessiblePropertySet *set = g_rc_box_new0 (GtkAccessiblePropertySet);
+
+ return gtk_accessible_property_set_init (set);
+}
+
+GtkAccessiblePropertySet *
+gtk_accessible_property_set_ref (GtkAccessiblePropertySet *self)
+{
+ g_return_val_if_fail (self != NULL, NULL);
+
+ return g_rc_box_acquire (self);
+}
+
+static void
+gtk_accessible_property_set_free (gpointer data)
+{
+ GtkAccessiblePropertySet *self = data;
+
+ for (int i = 0; i < LAST_PROPERTY; i++)
+ {
+ if (self->property_values[i] != NULL)
+ gtk_accessible_value_unref (self->property_values[i]);
+ }
+
+ g_free (self->property_values);
+
+ _gtk_bitmask_free (self->property_set);
+}
+
+void
+gtk_accessible_property_set_unref (GtkAccessiblePropertySet *self)
+{
+ g_rc_box_release_full (self, gtk_accessible_property_set_free);
+}
+
+void
+gtk_accessible_property_set_add (GtkAccessiblePropertySet *self,
+ GtkAccessibleProperty property,
+ GtkAccessibleValue *value)
+{
+ g_return_if_fail (property >= GTK_ACCESSIBLE_PROPERTY_ACTIVE_DESCENDANT &&
+ property <= GTK_ACCESSIBLE_PROPERTY_VALUE_TEXT);
+
+ if (gtk_accessible_property_set_contains (self, property))
+ gtk_accessible_value_unref (self->property_values[property]);
+ else
+ self->property_set = _gtk_bitmask_set (self->property_set, property, TRUE);
+
+ self->property_values[property] = gtk_accessible_value_ref (value);
+}
+
+void
+gtk_accessible_property_set_remove (GtkAccessiblePropertySet *self,
+ GtkAccessibleProperty property)
+{
+ g_return_if_fail (property >= GTK_ACCESSIBLE_PROPERTY_ACTIVE_DESCENDANT &&
+ property <= GTK_ACCESSIBLE_PROPERTY_VALUE_TEXT);
+
+ if (gtk_accessible_property_set_contains (self, property))
+ {
+ g_clear_pointer (&(self->property_values[property]), gtk_accessible_value_unref);
+ self->property_set = _gtk_bitmask_set (self->property_set, property, FALSE);
+ }
+}
+
+gboolean
+gtk_accessible_property_set_contains (GtkAccessiblePropertySet *self,
+ GtkAccessibleProperty property)
+{
+ g_return_val_if_fail (property >= GTK_ACCESSIBLE_PROPERTY_ACTIVE_DESCENDANT &&
+ property <= GTK_ACCESSIBLE_PROPERTY_VALUE_TEXT,
+ FALSE);
+
+ return _gtk_bitmask_get (self->property_set, property);
+}
+
+GtkAccessibleValue *
+gtk_accessible_property_set_get_value (GtkAccessiblePropertySet *self,
+ GtkAccessibleProperty property)
+{
+ g_return_val_if_fail (property >= GTK_ACCESSIBLE_PROPERTY_ACTIVE_DESCENDANT &&
+ property <= GTK_ACCESSIBLE_PROPERTY_VALUE_TEXT,
+ NULL);
+
+ return self->property_values[property];
+}
+
+static const char *property_names[] = {
+ [GTK_ACCESSIBLE_PROPERTY_ACTIVE_DESCENDANT] = "active-descendant",
+ [GTK_ACCESSIBLE_PROPERTY_CONTROLS] = "controls",
+ [GTK_ACCESSIBLE_PROPERTY_DESCRIBED_BY] = "described-by",
+ [GTK_ACCESSIBLE_PROPERTY_FLOW_TO] = "flow-to",
+ [GTK_ACCESSIBLE_PROPERTY_HAS_POPUP] = "has-popup",
+ [GTK_ACCESSIBLE_PROPERTY_LABEL] = "label",
+ [GTK_ACCESSIBLE_PROPERTY_LABELLED_BY] = "labelled-by",
+ [GTK_ACCESSIBLE_PROPERTY_LEVEL] = "level",
+ [GTK_ACCESSIBLE_PROPERTY_MULTI_LINE] = "multiline",
+ [GTK_ACCESSIBLE_PROPERTY_MULTI_SELECTABLE] = "multi-selectable",
+ [GTK_ACCESSIBLE_PROPERTY_ORIENTATION] = "orientation",
+ [GTK_ACCESSIBLE_PROPERTY_OWNS] = "owns",
+ [GTK_ACCESSIBLE_PROPERTY_POS_IN_SET] = "pos-in-set",
+ [GTK_ACCESSIBLE_PROPERTY_READ_ONLY] = "read-only",
+ [GTK_ACCESSIBLE_PROPERTY_RELEVANT] = "relevant",
+ [GTK_ACCESSIBLE_PROPERTY_REQUIRED] = "required",
+ [GTK_ACCESSIBLE_PROPERTY_SET_SIZE] = "set-size",
+ [GTK_ACCESSIBLE_PROPERTY_SORT] = "sort",
+ [GTK_ACCESSIBLE_PROPERTY_VALUE_MAX] = "value-max",
+ [GTK_ACCESSIBLE_PROPERTY_VALUE_MIN] = "value-min",
+ [GTK_ACCESSIBLE_PROPERTY_VALUE_NOW] = "value-now",
+ [GTK_ACCESSIBLE_PROPERTY_VALUE_TEXT] = "value-text",
+};
+
+/*< private >
+ * gtk_accessible_property_set_print:
+ * @self: a #GtkAccessiblePropertySet
+ * @only_set: %TRUE if only the set properties should be printed
+ * @buffer: a #GString
+ *
+ * Prints the contents of the #GtkAccessiblePropertySet into @buffer.
+ */
+void
+gtk_accessible_property_set_print (GtkAccessiblePropertySet *self,
+ gboolean only_set,
+ GString *buffer)
+{
+ if (only_set && _gtk_bitmask_is_empty (self->property_set))
+ {
+ g_string_append (buffer, "{}");
+ return;
+ }
+
+ g_string_append (buffer, "{\n");
+
+ for (int i = 0; i < G_N_ELEMENTS (property_names); i++)
+ {
+ if (only_set && !_gtk_bitmask_get (self->property_set, i))
+ continue;
+
+ g_string_append (buffer, " ");
+ g_string_append (buffer, property_names[i]);
+ g_string_append (buffer, ": ");
+
+ gtk_accessible_value_print (self->property_values[i], buffer);
+
+ g_string_append (buffer, ",\n");
+ }
+
+ g_string_append (buffer, "}");
+}
+
+/*< private >
+ * gtk_accessible_property_set_to_string:
+ * @self: a #GtkAccessiblePropertySet
+ *
+ * Prints the contents of a #GtkAccessiblePropertySet into a string.
+ *
+ * Returns: (transfer full): a newly allocated string with the contents
+ * of the #GtkAccessiblePropertySet
+ */
+char *
+gtk_accessible_property_set_to_string (GtkAccessiblePropertySet *self)
+{
+ GString *buf = g_string_new (NULL);
+
+ gtk_accessible_property_set_print (self, TRUE, buf);
+
+ return g_string_free (buf, FALSE);
+}
diff --git a/gtk/gtkaccessiblepropertysetprivate.h b/gtk/gtkaccessiblepropertysetprivate.h
new file mode 100644
index 0000000000..a6874379c4
--- /dev/null
+++ b/gtk/gtkaccessiblepropertysetprivate.h
@@ -0,0 +1,49 @@
+/* gtkaccessiblepropertysetprivate.h: Accessible property set
+ *
+ * Copyright 2020 GNOME Foundation
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see .
+ */
+
+#pragma once
+
+#include "gtkaccessibleprivate.h"
+#include "gtkaccessiblevalueprivate.h"
+
+G_BEGIN_DECLS
+
+typedef struct _GtkAccessiblePropertySet GtkAccessiblePropertySet;
+
+GtkAccessiblePropertySet * gtk_accessible_property_set_new (void);
+GtkAccessiblePropertySet * gtk_accessible_property_set_ref (GtkAccessiblePropertySet *self);
+void gtk_accessible_property_set_unref (GtkAccessiblePropertySet *self);
+
+void gtk_accessible_property_set_add (GtkAccessiblePropertySet *self,
+ GtkAccessibleProperty property,
+ GtkAccessibleValue *value);
+void gtk_accessible_property_set_remove (GtkAccessiblePropertySet *self,
+ GtkAccessibleProperty property);
+gboolean gtk_accessible_property_set_contains (GtkAccessiblePropertySet *self,
+ GtkAccessibleProperty property);
+GtkAccessibleValue * gtk_accessible_property_set_get_value (GtkAccessiblePropertySet *self,
+ GtkAccessibleProperty property);
+
+void gtk_accessible_property_set_print (GtkAccessiblePropertySet *self,
+ gboolean only_set,
+ GString *string);
+char * gtk_accessible_property_set_to_string (GtkAccessiblePropertySet *self);
+
+G_END_DECLS
diff --git a/gtk/meson.build b/gtk/meson.build
index eb0bd421e6..6f7db5d18f 100644
--- a/gtk/meson.build
+++ b/gtk/meson.build
@@ -16,6 +16,7 @@ gtk_private_sources = files([
'fnmatch.c',
'tools/gdkpixbufutils.c',
'gsettings-mapping.c',
+ 'gtkaccessiblepropertyset.c',
'gtkaccessiblestateset.c',
'gtkaccessiblevalue.c',
'gtkaccessiblevaluestatic.c',