Add GnomeTheme class

app/src/desktopthemes/gnometheme.cpp

+#include "gnometheme.h"
+
+#include <QStringList>
+#include <QDir>
+#include <QProcess>
+
+GnomeTheme::GnomeTheme(const QString &path, QObject *parent)
+    : QObject(parent), path_(path)
+{
+    themeName_ = QDir(path_).dirName();
+}
+
+bool GnomeTheme::applyAsWallpaper() const
+{
+    return setConfig("org.gnome.desktop.background", "picture-uri", "file://" + path_);
+}
+
+bool GnomeTheme::applyAsIcon() const
+{
+    return setConfig("org.gnome.desktop.interface", "icon-theme", themeName_);
+}
+
+bool GnomeTheme::applyAsCursor() const
+{
+    return setConfig("org.gnome.desktop.interface", "cursor-theme", themeName_);
+}
+
+bool GnomeTheme::applyAsGtk3Theme() const
+{
+    return setConfig("org.gnome.desktop.interface", "gtk-theme", themeName_);
+}
+
+bool GnomeTheme::applyAsGnomeShellTheme() const
+{
+    return setConfig("org.gnome.shell.extensions.user-theme", "name", themeName_);
+}
+
+bool GnomeTheme::setConfig(const QString &schema, const QString &key, const QString &value) const
+{
+    return QProcess::startDetached("gsettings", QStringList() << "set" << schema << key << value);
+}

app/src/desktopthemes/gnometheme.h

+#pragma once
+
+#include <QObject>
+
+class GnomeTheme : public QObject
+{
+    Q_OBJECT
+
+public:
+    explicit GnomeTheme(const QString &path, QObject *parent = nullptr);
+
+    bool applyAsWallpaper() const;
+    bool applyAsIcon() const;
+    bool applyAsCursor() const;
+    bool applyAsGtk3Theme() const;
+    bool applyAsGnomeShellTheme() const;
+
+private:
+    bool setConfig(const QString &schema, const QString &key, const QString &value) const;
+
+    QString path_;
+    QString themeName_;
+};