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+// SPDX-License-Identifier: GPL-2.0-or-later
+/**
+ * @file
+ * Action Accel
+ * A simple tracker for accelerator keys associated to an action
+ *
+ * Authors:
+ *   Rafael Siejakowski <rs@rs-math.net>
+ *
+ * Copyright (C) 2022 the Authors.
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+#ifndef ACTION_ACCEL_H_SEEN
+#define ACTION_ACCEL_H_SEEN
+
+#include <gdk/gdk.h>
+#include <glibmm/ustring.h>
+#include <gtkmm.h>
+#include <set>
+#include <sigc++/sigc++.h>
+#include <vector>
+
+namespace Inkscape {
+namespace Util {
+
+/** Gtk::AccelKey but with equality and less-than operators */
+class AcceleratorKey : public Gtk::AccelKey
+{
+public:
+    bool operator==(AcceleratorKey const &other) const
+    {
+        return (get_key() == other.get_key()) && (get_mod() == other.get_mod());
+    }
+
+    bool operator<(AcceleratorKey const &other) const
+    {
+        return (get_key() < other.get_key()) || (get_key() == other.get_key()
+                                                 && get_mod() < other.get_mod());
+    }
+
+    AcceleratorKey(Gtk::AccelKey const &ak) : Gtk::AccelKey{ak} {};
+};
+
+/**
+ * \brief The ActionAccel class stores the keyboard shortcuts for a given action
+ * and automatically keeps track of changes in the keybindings.
+ *
+ * Additionally, a signal is emitted when the keybindings for the action change.
+ *
+ * In order to create an ActionAccel object, one must pass a Glib::ustring containing the
+ * action name to the constructor. The object will automatically observe the
+ * keybindings for that action, so you always get up-to-date keyboard shortcuts.
+ * To check if a given key event triggers one of these keybindings, use `isTriggeredBy()`.
+ *
+ * Typical usage example:
+ * \code{.cpp}
+    auto accel = Inkscape::Util::ActionAccel("doc.undo");
+    GdkEventKey *key = get_from_somewhere();
+    if (accel.isTriggeredBy(key)) {
+        ... // do stuff
+    }
+    accel.connectModified( []() { // This code will run when the user changes
+                                  // the keybindings for this action.
+                                } );
+   \endcode
+ */
+class ActionAccel
+{
+private:
+    sigc::signal<void ()> _we_changed;   ///< Emitted when the keybindings for the action are changed
+    sigc::connection _prefs_changed;  ///< To listen to changes to the keyboard shortcuts
+    Glib::ustring _action;            ///< Name of the action
+    std::set<AcceleratorKey> _accels; ///< Stores the accelerator keys for the action
+
+    /** Queries and updates the stored shortcuts, returning true if they have changed. */
+    bool _query();
+
+    /** Runs when the keyboard shortcut settings have changed */
+    void _onShortcutsModified();
+
+public:
+    /**
+     * @brief Construct an ActionAccel object which will keep track of keybindings for a given action.
+     * @param action_name - the name of the action to hold and observe the keybindings of.
+     */
+    ActionAccel(Glib::ustring action_name);
+
+    ~ActionAccel();
+
+    /**
+     * @brief Returns all keyboard shortcuts for the action.
+     * @return a vector containing a Gtk::AccelKey for each of the keybindings present for the action.
+     */
+    std::vector<Gtk::AccelKey> getKeys() const
+    {
+        return std::vector<Gtk::AccelKey>(_accels.begin(), _accels.end());
+    }
+
+    /**
+     * @brief Connects a void callback which will run whenever the keybindings for the action change.
+     *        At the time when the callback runs, the values stored in the ActionAccel object will have
+     *        already been updated. This means that the new keybindings can be queried by the callback.
+     * @param slot - the sigc::slot representing the callback function.
+     * @return the resulting sigc::connection.
+     */
+    sigc::connection connectModified(sigc::slot<void ()> const &slot) { return _we_changed.connect(slot); }
+
+    /**
+     * @brief Checks whether a given key event triggers this action.
+     * @param key - a pointer to a GdkEventKey struct containing key event data.
+     * @return true if one of the keyboard shortcuts for the action is triggered by the passed event,
+     *         false otherwise.
+     */
+    bool isTriggeredBy(GdkEventKey *key) const;
+};
+
+} // namespace Util
+} // namespace Inkscape
+
+#endif // ACTION_ACCEL_H_SEEN
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :