Update detection of $DESKTOP_SESSION

I don't know how widespread this use is, but apparently sddm seems to
set DESKTOP_SESSION to be the .desktop file that it used to launch the
session (minus the .desktop extension). In that case, we should read the
DesktopName entry from the file to get the actual desktop type.

And since the desktop detection from QGenericUnixServices should
suffice, we don't need to repeat the same code in QGenericUnixThemes.

Change-Id: I0e1a09998253489388abfffd14b5eeefbd7fe740
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>

2 files changed, 29 insertions, 7 deletions

diff --git a/src/platformsupport/services/genericunix/qgenericunixservices.cpp b/src/platformsupport/services/genericunix/qgenericunixservices.cpp
index dee983264d..cdb5d33859 100644
--- a/src/platformsupport/services/genericunix/qgenericunixservices.cpp
+++ b/src/platformsupport/services/genericunix/qgenericunixservices.cpp
@@ -40,12 +40,14 @@
 #include "qgenericunixservices_p.h"
 #include <QtGui/private/qtguiglobal_p.h>
 
-#include <QtCore/QStandardPaths>
+#include <QtCore/QDebug>
+#include <QtCore/QFile>
 #if QT_CONFIG(process)
 # include <QtCore/QProcess>
 #endif
+#include <QtCore/QSettings>
+#include <QtCore/QStandardPaths>
 #include <QtCore/QUrl>
-#include <QtCore/QDebug>
 
 #include <stdlib.h>
 
@@ -68,11 +70,29 @@ static inline QByteArray detectDesktopEnvironment()
         return QByteArrayLiteral("GNOME");
 
     // Fallback to checking $DESKTOP_SESSION (unreliable)
-    const QByteArray desktopSession = qgetenv("DESKTOP_SESSION");
+    QByteArray desktopSession = qgetenv("DESKTOP_SESSION");
+
+    // This can be a path in /usr/share/xsessions
+    int slash = desktopSession.lastIndexOf('/');
+    if (slash != -1) {
+#ifndef QT_NO_SETTINGS
+        QSettings desktopFile(QFile::decodeName(desktopSession + ".desktop"), QSettings::IniFormat);
+        desktopFile.beginGroup(QStringLiteral("Desktop Entry"));
+        QByteArray desktopName = desktopFile.value(QStringLiteral("DesktopNames")).toByteArray();
+        if (!desktopName.isEmpty())
+            return desktopName;
+#endif
+
+        // try decoding just the basename
+        desktopSession = desktopSession.mid(slash + 1);
+    }
+
     if (desktopSession == "gnome")
         return QByteArrayLiteral("GNOME");
-    if (desktopSession == "xfce")
+    else if (desktopSession == "xfce")
         return QByteArrayLiteral("XFCE");
+    else if (desktopSession == "kde")
+        return QByteArrayLiteral("KDE");
 
     return QByteArrayLiteral("UNKNOWN");
 }
diff --git a/src/platformsupport/themes/genericunix/qgenericunixthemes.cpp b/src/platformsupport/themes/genericunix/qgenericunixthemes.cpp
index e9116223bd..8dfae2ca0b 100644
--- a/src/platformsupport/themes/genericunix/qgenericunixthemes.cpp
+++ b/src/platformsupport/themes/genericunix/qgenericunixthemes.cpp
@@ -824,11 +824,13 @@ QStringList QGenericUnixTheme::themeNames()
                 result.push_back(QStringLiteral("gtk3"));
                 // fallback to the generic Gnome theme if loading the GTK3 theme fails
                 result.push_back(QLatin1String(QGnomeTheme::name));
+            } else {
+                // unknown, but lowercase the name (our standard practice) and
+                // remove any "x-" prefix
+                QString s = QString::fromLatin1(desktopName.toLower());
+                result.push_back(s.startsWith(QLatin1String("x-")) ? s.mid(2) : s);
             }
         }
-        const QString session = QString::fromLocal8Bit(qgetenv("DESKTOP_SESSION"));
-        if (!session.isEmpty() && session != QLatin1String("default") && !result.contains(session))
-            result.push_back(session);
     } // desktopSettingsAware
     result.append(QLatin1String(QGenericUnixTheme::name));
     return result;