From dbb7c6e5b8c7c6281ec82071c2eaa838e8a1122c Mon Sep 17 00:00:00 2001
From: Syres916 <46537884+Syres916@users.noreply.github.com>
Date: Thu, 11 Jul 2024 23:50:26 +0100
Subject: [PATCH] [Gui] Preferences - fix the theme combobox index lookup...

...when the user has FreeCAD-themes (and no doubt other theme addons) installed.
---
 .../PreferencePages/DlgSettingsGeneral.cpp    | 28 ++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/src/Gui/PreferencePages/DlgSettingsGeneral.cpp b/src/Gui/PreferencePages/DlgSettingsGeneral.cpp
index 9030ecd9e2..4980894b63 100644
--- a/src/Gui/PreferencePages/DlgSettingsGeneral.cpp
+++ b/src/Gui/PreferencePages/DlgSettingsGeneral.cpp
@@ -425,18 +425,44 @@ void DlgSettingsGeneral::loadThemes()
 {
     ui->themesCombobox->clear();
 
-    ParameterGrp::handle hGrp = App::GetApplication().GetParameterGroupByPath("User parameter:BaseApp/Preferences/MainWindow");
+    ParameterGrp::handle hGrp = App::GetApplication().GetParameterGroupByPath(
+        "User parameter:BaseApp/Preferences/MainWindow");
 
     QString currentTheme = QString::fromLatin1(hGrp->GetASCII("Theme", "").c_str());
 
     Application::Instance->prefPackManager()->rescan();
     auto packs = Application::Instance->prefPackManager()->preferencePacks();
+    QString currentStyleSheet = QString::fromLatin1(hGrp->GetASCII("StyleSheet", "").c_str());
+    QFileInfo fi(currentStyleSheet);
+    currentStyleSheet = fi.baseName();
+    QString themeClassic = QString::fromStdString("classic");  // handle the upcoming name change
+    QString similarTheme;
+    QString packName;
     for (const auto& pack : packs) {
         if (pack.second.metadata().type() == "Theme") {
+            packName = QString::fromStdString(pack.first);
+            if (packName.contains(themeClassic, Qt::CaseInsensitive)) {
+                themeClassic = QString::fromStdString(pack.first);
+            }
+            if (packName.contains(currentStyleSheet, Qt::CaseInsensitive)) {
+                similarTheme = QString::fromStdString(pack.first);
+            }
             ui->themesCombobox->addItem(QString::fromStdString(pack.first));
         }
     }
 
+    if (currentTheme.isEmpty()) {
+        if (!currentStyleSheet.isEmpty()
+            && !similarTheme.isEmpty()) {  // a user upgrading from 0.21 or earlier
+            hGrp->SetASCII("Theme", similarTheme.toStdString());
+            currentTheme = QString::fromLatin1(hGrp->GetASCII("Theme", "").c_str());
+        }
+        else {  // a brand new user
+            hGrp->SetASCII("Theme", themeClassic.toStdString());
+            currentTheme = QString::fromLatin1(hGrp->GetASCII("Theme", "").c_str());
+        }
+    }
+
     int index = ui->themesCombobox->findText(currentTheme);
     if (index >= 0 && index < ui->themesCombobox->count()) {
         ui->themesCombobox->setCurrentIndex(index);