Minor GUI cleanup for Fancy Menu

 1. Tooltips of categories are removed because they were the same as displayed names and only disruptive.
 2. The icon of config center button is corrected (its text was already corrected by @@stefonarch in ed50e7a).
 3. About button is added.

plugin-fancymenu/lxqtfancymenucategoriesmodel.cpp

@@ -53,7 +53,6 @@ QVariant LXQtFancyMenuCategoriesModel::data(const QModelIndex &idx, int role) co
     switch (role)
     {
     case Qt::DisplayRole:
-    case Qt::ToolTipRole:
         return item.menuTitle;
     case Qt::EditRole:
         return item.menuName;

plugin-fancymenu/lxqtfancymenuwindow.cpp

@@ -155,7 +155,7 @@ LXQtFancyMenuWindow::LXQtFancyMenuWindow(QWidget *parent)
     connect(mSearchEdit, &QLineEdit::returnPressed, this, &LXQtFancyMenuWindow::activateCurrentApp);
 
     mSettingsButton = new QToolButton;
-    mSettingsButton->setIcon(XdgIcon::fromTheme(QStringLiteral("preferences-desktop"))); //TODO: preferences-system?
+    mSettingsButton->setIcon(XdgIcon::fromTheme(QStringLiteral("preferences-system")));
     mSettingsButton->setText(tr("LXQt Configuration Center"));
     mSettingsButton->setToolTip(mSettingsButton->text());
     connect(mSettingsButton, &QToolButton::clicked, this, &LXQtFancyMenuWindow::runSystemConfigDialog);
@@ -166,6 +166,12 @@ LXQtFancyMenuWindow::LXQtFancyMenuWindow(QWidget *parent)
     mPowerButton->setToolTip(mPowerButton->text());
     connect(mPowerButton, &QToolButton::clicked, this, &LXQtFancyMenuWindow::runPowerDialog);
 
+    mAboutButton = new QToolButton;
+    mAboutButton->setIcon(XdgIcon::fromTheme(QStringLiteral("lxqt-about")));
+    mAboutButton->setText(tr("About LXQt"));
+    mAboutButton->setToolTip(mAboutButton->text());
+    connect(mAboutButton, &QToolButton::clicked, this, &LXQtFancyMenuWindow::runAboutgDialog);
+
     mAppView = new QListView;
     mAppView->setObjectName(QStringLiteral("AppView"));
     mAppView->setSelectionMode(QListView::SingleSelection);
@@ -207,6 +213,7 @@ LXQtFancyMenuWindow::LXQtFancyMenuWindow(QWidget *parent)
     mMainLayout->addLayout(mViewLayout);
 
     mButtonsLayout = new QHBoxLayout;
+    mButtonsLayout->addWidget(mAboutButton);
     mButtonsLayout->addStretch();
     mButtonsLayout->addWidget(mSettingsButton);
     mButtonsLayout->addWidget(mPowerButton);
@@ -295,6 +302,11 @@ void LXQtFancyMenuWindow::runSystemConfigDialog()
     runCommandHelper(QLatin1String("lxqt-config"));
 }
 
+void LXQtFancyMenuWindow::runAboutgDialog()
+{
+    runCommandHelper(QLatin1String("lxqt-about"));
+}
+
 void LXQtFancyMenuWindow::onAppViewCustomMenu(const QPoint& p)
 {
     QModelIndex idx = mAppView->indexAt(p);
@@ -602,6 +614,7 @@ void LXQtFancyMenuWindow::updateButtonIconSize()
     const QSize iconSize(sz, sz);
     mSettingsButton->setIconSize(iconSize);
     mPowerButton->setIconSize(iconSize);
+    mAboutButton->setIconSize(iconSize);
 }
 
 void LXQtFancyMenuWindow::setSearchEditFocus()

plugin-fancymenu/lxqtfancymenuwindow.h

@@ -109,6 +109,7 @@ private slots:
 
     void runPowerDialog();
     void runSystemConfigDialog();
+    void runAboutgDialog();
 
     void onAppViewCustomMenu(const QPoint &p);
 
@@ -133,6 +134,7 @@ private slots:
 
     QToolButton *mSettingsButton;
     QToolButton *mPowerButton;
+    QToolButton *mAboutButton;
     QLineEdit *mSearchEdit;
     QListView *mAppView;
     QListView *mCategoryView;