COMMON: Add OSDMessageQueue singleton

This class can be used to get messages to display on the OSD from
any thread. Those messages are then passed to the backend in the
graphic thread.

1 files changed, 70 insertions, 0 deletions

diff --git a/common/osd_message_queue.h b/common/osd_message_queue.h
new file mode 100644
index 0000000000..9348497b28
--- /dev/null
+++ b/common/osd_message_queue.h
@@ -0,0 +1,70 @@
+/* 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 2
+ * 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#ifndef COMMON_OSD_MESSAGE_QUEUE_H
+#define COMMON_OSD_MESSAGE_QUEUE_H
+
+#include "common/events.h"
+#include "common/singleton.h"
+#include "common/str.h"
+#include "common/queue.h"
+#include "common/mutex.h"
+
+namespace Common {
+
+/**
+ * Queue OSD messages from any thread to be displayed by the graphic thread.
+ */
+class OSDMessageQueue : public Singleton<OSDMessageQueue>, public EventSource {
+public:
+	OSDMessageQueue();
+	~OSDMessageQueue();
+	
+	enum {
+		kMinimumDelay = 1000 /** < Minimum delay between two OSD messages (in milliseconds) */
+	};
+
+	/**
+	 * Add a message to the OSD message queue.
+	 */
+	void addMessage(const char *msg);
+	
+	/**
+	 * Common::EventSource interface
+	 *
+	 * The OSDMessageQueue registers itself as an event source even if it does not
+	 * actually produce events as a mean to be polled periodically by the GUI or
+	 * engine code.
+	 *
+	 * The periodical polling is used to update the OSD messages.
+	 */
+	virtual bool pollEvent(Common::Event &event) override;
+
+private:
+	Mutex _mutex;
+	Queue<String> _messages;
+	uint32 _lastUpdate;
+};
+
+} // End of namespace Common
+
+#endif