Revert "tdf#123011 Detect kde5 desktop in Plasma Wayland session"

kde5 plugin on Wayland still shows too many issues, like e.g.
tdf#123654 and was barely tested, so don't use it by default
in libreoffice-6-2 branch, but prefer gtk3.

This does not affect the X11 case.

This reverts commit 3e447810.

Change-Id: I7f74a6b5f377f65b81cf5ae189e8672bdce82c95
Reviewed-on: https://gerrit.libreoffice.org/73193
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

vcl/unx/generic/desktopdetect/desktopdetector.cxx

@@ -191,13 +191,16 @@ static bool is_kde4_desktop( Display* pDisplay )
     return false;
 }
 
-static bool is_kde5_desktop()
+static bool is_kde5_desktop( Display* pDisplay )
 {
     static const char * pFullVersion = getenv( "KDE_FULL_SESSION" );
     static const char * pSessionVersion = getenv( "KDE_SESSION_VERSION" );
     if ( pFullVersion && pSessionVersion && strcmp(pSessionVersion, "5") == 0)
         return true;
 
+    if ( KDEVersion( pDisplay ) == 5 )
+        return true;
+
     return false;
 }
 
@@ -277,9 +280,6 @@ DESKTOP_DETECTOR_PUBLIC DesktopType get_desktop_environment()
         ret = DESKTOP_LXQT;
     else
     {
-        if ( is_kde5_desktop() )
-            return DESKTOP_KDE5;
-
         // tdf#121275 if we still can't tell, and WAYLAND_DISPLAY
         // is set, default to gtk3
         const char* pWaylandStr = getenv("WAYLAND_DISPLAY");
@@ -328,7 +328,9 @@ DESKTOP_DETECTOR_PUBLIC DesktopType get_desktop_environment()
 
         XErrorHandler pOldHdl = XSetErrorHandler( autodect_error_handler );
 
-        if ( is_kde4_desktop( pDisplay ) )
+        if ( is_kde5_desktop( pDisplay ) )
+            ret = DESKTOP_KDE5;
+        else if ( is_kde4_desktop( pDisplay ) )
             ret = DESKTOP_KDE4;
         else if ( is_gnome_desktop( pDisplay ) )
             ret = DESKTOP_GNOME;