Only load valid themes, fallback to "Light" theme otherwise (#3285)

* Only load valid themes, fallback to "light" otherwise

* Refactor PR3285 a bit

* fix

Co-authored-by: Nathan Marley <nathan.marley@gmail.com>

Author: 2 people

src/qt/dash.qrc

@@ -54,10 +54,12 @@
         <file alias="network_disabled">res/icons/network_disabled.png</file>
     </qresource>
     <qresource prefix="/css">
-        <file alias="dark">res/css/dark.css</file>
-        <file alias="light">res/css/light.css</file>
         <file alias="scrollbars">res/css/scrollbars.css</file>
-        <file alias="trad">res/css/trad.css</file>
+    </qresource>
+    <qresource prefix="/themes">
+        <file alias="Dark">res/css/dark.css</file>
+        <file alias="Light">res/css/light.css</file>
+        <file alias="Traditional">res/css/trad.css</file>
     </qresource>
     <qresource prefix="/images">
         <file alias="arrow_down">res/images/arrow_down.png</file>

src/qt/guiutil.cpp

@@ -922,25 +922,23 @@ void migrateQtSettings()
 // Open CSS when configured
 QString loadStyleSheet()
 {
-    QString styleSheet;
     QSettings settings;
-    QString cssName;
     QString theme = settings.value("theme", "").toString();
 
-    if(!theme.isEmpty()){
-        cssName = QString(":/css/") + theme;
-    }
-    else {
-        cssName = QString(":/css/light");
-        settings.setValue("theme", "light");
+    QDir themes(":themes");
+    // Make sure settings are pointing to an existent theme
+    // Set "Light" theme by default if settings are missing or incorrect
+    if (theme.isEmpty() || !themes.exists(theme)) {
+        theme = "Light";
+        settings.setValue("theme", theme);
     }
 
-    QFile qFile(cssName);
+    QFile qFile(":themes/" + theme);
     if (qFile.open(QFile::ReadOnly)) {
-        styleSheet = QLatin1String(qFile.readAll());
+        return QLatin1String(qFile.readAll());
     }
 
-    return styleSheet;
+    return QString();
 }
 
 void setClipboard(const QString& str)

src/qt/optionsdialog.cpp

@@ -91,9 +91,10 @@ OptionsDialog::OptionsDialog(QWidget *parent, bool enableWallet) :
     }
 
     /* Theme selector */
-    ui->theme->addItem(QString("Dark"), QVariant("dark"));
-    ui->theme->addItem(QString("Light"), QVariant("light"));
-    ui->theme->addItem(QString("Traditional"), QVariant("trad"));
+    QDir themes(":themes");
+    for (const QString &entry : themes.entryList()) {
+        ui->theme->addItem(entry, QVariant(entry));
+    }
 
     /* Language selector */
     QDir translations(":translations");