gui: single instance mode.

3rd/SingleApplication-3.5.2/singleapplication.h

@@ -0,0 +1,186 @@
+// Copyright (c) Itay Grudev 2015 - 2023
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// Permission is not granted to use this software or any of the associated files
+// as sample data for the purposes of building machine learning models.
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+#ifndef SINGLE_APPLICATION_H
+#define SINGLE_APPLICATION_H
+
+#include <QtCore/QtGlobal>
+#include <QtNetwork/QLocalSocket>
+
+#ifndef QAPPLICATION_CLASS
+  #define QAPPLICATION_CLASS QCoreApplication
+#endif
+
+#include QT_STRINGIFY(QAPPLICATION_CLASS)
+
+class SingleApplicationPrivate;
+
+/**
+ * @brief Handles multiple instances of the same
+ * Application
+ * @see QCoreApplication
+ */
+class SingleApplication : public QAPPLICATION_CLASS
+{
+    Q_OBJECT
+
+    using app_t = QAPPLICATION_CLASS;
+
+public:
+    /**
+     * @brief Mode of operation of `SingleApplication`.
+     * Whether the block should be user-wide or system-wide and whether the
+     * primary instance should be notified when a secondary instance had been
+     * started.
+     * @note Operating system can restrict the shared memory blocks to the same
+     * user, in which case the User/System modes will have no effect and the
+     * block will be user wide.
+     */
+    enum Mode {
+        /** The `SingleApplication` block should apply user wide
+         * (this adds user specific data to the key used for the shared memory and server name)
+         * */
+        User = 1 << 0,
+        /**
+         * The `SingleApplication` block applies system-wide.
+         */
+        System = 1 << 1,
+        /**
+         * Whether to trigger `instanceStarted()` even whenever secondary instances are started
+         */
+        SecondaryNotification = 1 << 2,
+        /**
+         * Excludes the application version from the server name (and memory block) hash
+         */
+        ExcludeAppVersion = 1 << 3,
+        /**
+         * Excludes the application path from the server name (and memory block) hash
+         */
+        ExcludeAppPath = 1 << 4
+    };
+    Q_DECLARE_FLAGS(Options, Mode)
+
+    /**
+     * @brief Intitializes a `SingleApplication` instance with argc command line
+     * arguments in argv
+     * @arg argc - Number of arguments in argv
+     * @arg argv - Supplied command line arguments
+     * @arg allowSecondary - Whether to start the instance as secondary
+     * if there is already a primary instance.
+     * @arg mode - Whether for the `SingleApplication` block to be applied
+     * User wide or System wide.
+     * @arg timeout - Timeout to wait in milliseconds.
+     * @note argc and argv may be changed as Qt removes arguments that it
+     * recognizes
+     * @note `Mode::SecondaryNotification` only works if set on both the primary
+     * instance and the secondary instance.
+     * @note The timeout is just a hint for the maximum time of blocking
+     * operations. It does not guarantee that the `SingleApplication`
+     * initialisation will be completed in given time, though is a good hint.
+     * Usually 4*timeout would be the worst case (fail) scenario.
+     * @see See the corresponding `QAPPLICATION_CLASS` constructor for reference
+     */
+    explicit SingleApplication( int &argc, char *argv[], bool allowSecondary = false, Options options = Mode::User, int timeout = 1000, const QString &userData = {} );
+    ~SingleApplication() override;
+
+    /**
+     * @brief Checks if the instance is primary instance
+     * @returns `true` if the instance is primary
+     */
+    bool isPrimary() const;
+
+    /**
+     * @brief Checks if the instance is a secondary instance
+     * @returns `true` if the instance is secondary
+     */
+    bool isSecondary() const;
+
+    /**
+     * @brief Returns a unique identifier for the current instance
+     * @returns instance id
+     */
+    quint32 instanceId() const;
+
+    /**
+     * @brief Returns the process ID (PID) of the primary instance
+     * @returns pid
+     */
+    qint64 primaryPid() const;
+
+    /**
+     * @brief Returns the username of the user running the primary instance
+     * @returns user name
+     */
+    QString primaryUser() const;
+
+    /**
+     * @brief Returns the username of the current user
+     * @returns user name
+     */
+    QString currentUser() const;
+
+    /**
+     * @brief Mode of operation of sendMessage.
+     */
+    enum SendMode {
+        NonBlocking,  /** Do not wait for the primary instance termination and return immediately */
+        BlockUntilPrimaryExit,  /** Wait until the primary instance is terminated */
+    };
+
+    /**
+     * @brief Sends a message to the primary instance
+     * @param message data to send
+     * @param timeout timeout for connecting
+     * @param sendMode - Mode of operation
+     * @returns `true` on success
+     * @note sendMessage() will return false if invoked from the primary instance
+     */
+    bool sendMessage( const QByteArray &message, int timeout = 100, SendMode sendMode = NonBlocking );
+
+    /**
+     * @brief Get the set user data.
+     * @returns user data
+     */
+    QStringList userData() const;
+
+Q_SIGNALS:
+    /**
+     * @brief Triggered whenever a new instance had been started,
+     * except for secondary instances if the `Mode::SecondaryNotification` flag is not specified
+     */
+    void instanceStarted();
+
+    /**
+     * @brief Triggered whenever there is a message received from a secondary instance
+     */
+    void receivedMessage( quint32 instanceId, QByteArray message );
+
+private:
+    SingleApplicationPrivate *d_ptr;
+    Q_DECLARE_PRIVATE(SingleApplication)
+    void abortSafely();
+};
+
+Q_DECLARE_OPERATORS_FOR_FLAGS(SingleApplication::Options)
+
+#endif // SINGLE_APPLICATION_H