Add KSharedConfig::openStateConfig for storing state information

Summary:
A common complaint is that our apps store 'state' information such as recent files or window sizes in their configuration files, making it ugly to store them in version control systems.

Therefore we should not store such information in XDG_CONFIG_DIR but instead use XDG_DATA_DIR for this.

This patch adds a utility method that creates a KSharedConfig backed by a file in such a suitable location.

For e.g. dolphin the file .local/share/dolphin/dolphinstaterc would be created.

See T12246 for some context

Reviewers: #frameworks, dfaure

Reviewed By: dfaure

Subscribers: kde-frameworks-devel

Tags: #frameworks

Differential Revision: https://phabricator.kde.org/D26440

src/core/ksharedconfig.cpp

@@ -121,6 +121,17 @@ KSharedConfigPtr KSharedConfig::openConfig(const QString &_fileName,
     return ptr;
 }
 
+KSharedConfig::Ptr KSharedConfig::openStateConfig(const QString &_fileName)
+{
+    QString fileName(_fileName);
+
+    if (fileName.isEmpty()) {
+        fileName = QCoreApplication::applicationName() + QLatin1String("staterc");
+    }
+
+    return openConfig(fileName, SimpleConfig, QStandardPaths::AppDataLocation);
+}
+
 KSharedConfig::KSharedConfig(const QString &fileName,
                              OpenFlags flags,
                              QStandardPaths::StandardLocation resType)

src/core/ksharedconfig.h

@@ -75,6 +75,28 @@ public:
                                          OpenFlags mode = FullConfig,
                                          QStandardPaths::StandardLocation type = QStandardPaths::GenericConfigLocation);
 
+    /**
+     * Creates a KSharedConfig object to manipulate a configuration file suitable
+     * for storing state information. Use this for storing information that is
+     * changing frequently and should not be saved by configuration backup
+     * utilities.
+     *
+     * If an absolute path is specified for @p fileName, that file will be used
+     * as the store for the configuration settings. If a non-absolute path
+     * is provided, the file will be looked for in the standard data directory
+     * (QStandardPaths::AppDataLocation). If no path is provided, a default
+     * configuration file will be used based on the name of the main
+     * application component.
+     *
+     * @param fileName the configuration file to open. If empty, it will be determined
+     *                 automatically from the application name + "staterc"
+     *
+     * @since 5.67
+     *
+     * @sa KConfig
+     */
+    static KSharedConfig::Ptr openStateConfig(const QString &fileName = QString());
+
     ~KSharedConfig() override;
 
 private: