Use real LXQt theme name for comparison

Previously, the value of the "theme" key was used, which may differ in letter cases from the current theme name.

Also, the themes list is sorted alphabetically. Previously, the user themes came first.

This PR requires and depends on lxqt/liblxqt#309.

lxqt-config-appearance/lxqtthemeconfig.cpp

@@ -93,6 +93,7 @@ LXQtThemeConfig::LXQtThemeConfig(LXQt::Settings *settings, QWidget *parent) :
         item->setData(0, Qt::UserRole, theme.name());
         ui->lxqtThemeList->addTopLevelItem(item);
     }
+    ui->lxqtThemeList->sortItems(0, Qt::AscendingOrder);
 
     initControls();
 
@@ -109,11 +110,13 @@ LXQtThemeConfig::~LXQtThemeConfig()
 
 void LXQtThemeConfig::initControls()
 {
-    QString currentTheme = mSettings->value(QStringLiteral("theme")).toString();
+    LXQt::LXQtTheme currentTheme{mSettings->value(QStringLiteral("theme")).toString()};
 
     QTreeWidgetItemIterator it(ui->lxqtThemeList);
     while (*it) {
-        if ((*it)->data(0, Qt::UserRole).toString() == currentTheme)
+        // use the theme name for comparison because the value of the "theme" key
+        // may differ in letter cases from it
+        if ((*it)->data(0, Qt::UserRole).toString() == currentTheme.name())
         {
             ui->lxqtThemeList->setCurrentItem((*it));
             break;
@@ -131,10 +134,10 @@ void LXQtThemeConfig::applyLxqtTheme()
         return;
 
     LXQt::LXQtTheme currentTheme{mSettings->value(QStringLiteral("theme")).toString()};
-    QVariant themeName = item->data(0, Qt::UserRole);
-    if(mSettings->value(QStringLiteral("theme")) != themeName)
+    QString themeName = item->data(0, Qt::UserRole).toString();
+    if(currentTheme.name() != themeName)
         mSettings->setValue(QStringLiteral("theme"), themeName);
-    LXQt::LXQtTheme theme(themeName.toString());
+    LXQt::LXQtTheme theme(themeName);
     if(theme.isValid()) {
         QString wallpaper = theme.desktopBackground();
         if(!wallpaper.isEmpty() && (ui->wallpaperOverride->isChecked() || !isWallpaperChanged(currentTheme.desktopBackground()))) {