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engines/ultima/ultima4/core/observable.h

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef ULTIMA4_CORE_OBSERVABLE_H
+#define ULTIMA4_CORE_OBSERVABLE_H
+
+#include "ultima/ultima4/core/observer.h"
+#include "ultima/shared/std/containers.h"
+
+namespace Ultima {
+namespace Ultima4 {
+
+/**
+ * Classes can report updates to a list of decoupled Observers by
+ * extending this class.
+ *
+ * The O class parameter should be a pointer to the class of the
+ * observable itself, so it can be passed in a typesafe manner to the
+ * observers update method.
+ *
+ * The A class can be any additional information to pass to observers.
+ * Observables that don't need to pass an argument when they update
+ * observers should use the default "NoArg" class for the second
+ * template parameter and pass nullptr to notifyObservers.
+ */
+template <class O, class A = NoArg *>
+class Observable {
+public:
+	Observable() : _changed(false) {}
+
+	void addObserver(Observer<O, A> *o) {
+		typename Std::vector< Observer<O, A> *>::iterator i;
+		i = Common::find(_observers.begin(), _observers.end(), o);
+		if (i == _observers.end())
+			_observers.push_back(o);
+	}
+
+	int countObservers() const {
+		return _observers.size();
+	}
+
+	void deleteObserver(Observer<O, A> *o) {
+		typename Std::vector< Observer<O, A> *>::iterator i;
+		i = Common::find(_observers.begin(), _observers.end(), o);
+		if (i != _observers.end())
+			_observers.erase(i);
+	}
+
+	void deleteObservers() {
+		_observers.clear();
+	}
+
+	bool hasChanged() const {
+		return _changed;
+	}
+
+	void notifyObservers(A arg) {
+		if (!_changed)
+			return;
+
+		// vector iterators are invalidated if erase is called, so a copy
+		// is used to prevent problems if the observer removes itself (or
+		// otherwise changes the observer list)
+		typename Std::vector< Observer<O, A> *> tmp = _observers;
+
+		clearChanged();
+
+		for (auto *observer : tmp) {
+			observer->update(static_cast<O>(this), arg);
+		}
+	}
+
+protected:
+	void clearChanged() {
+		_changed = false;
+	}
+	void setChanged() {
+		_changed = true;
+	}
+
+private:
+	bool _changed;
+	Std::vector< Observer<O, A> *> _observers;
+};
+
+} // End of namespace Ultima4
+} // End of namespace Ultima
+
+#endif