Use QGnomePlatform as default platform theme on GNOME

Resolves: bz#2174905

qt6-qtbase.spec

@@ -71,6 +71,7 @@ Source10: macros.qt6-qtbase
 # downside: binaries produced with these differently-versioned symbols are no longer
 # compatible with qt-project.org's Qt binary releases.
 Patch1: qtbase-tell-truth-about-private-api.patch
+Patch2: qtbase-use-qgnomeplatform-as-default-platform-theme-on-gnome.patch
 
 # upstreamable patches
 # namespace QT_VERSION_CHECK to workaround major/minor being pre-defined (#1396755)
@@ -843,6 +844,10 @@ make check -k ||:
 
 
 %changelog
+* Sun Mar 05 2023 Jan grulich <jgrulich@redhat.com> - 6.4.2-5
+- Use QGnomePlatform as default platform theme on GNOME
+  Resolves: bz#2174905
+
 * Wed Feb 08 2023 Jan Grulich <jgrulich@redhat.com> - 6.4.2-4
 - Fix possible DOS involving the Qt SQL ODBC driver plugin
   CVE-2023-24607

qtbase-use-qgnomeplatform-as-default-platform-theme-on-gnome.patch

@@ -0,0 +1,12 @@
+diff --git a/src/gui/platform/unix/qgenericunixthemes.cpp b/src/gui/platform/unix/qgenericunixthemes.cpp
+index 1efd759b..d0129f73 100644
+--- a/src/gui/platform/unix/qgenericunixthemes.cpp
++++ b/src/gui/platform/unix/qgenericunixthemes.cpp
+@@ -977,6 +977,7 @@ QStringList QGenericUnixTheme::themeNames()
+                 result.push_back(QLatin1StringView(QKdeTheme::name));
+ #endif
+             } else if (gtkBasedEnvironments.contains(desktopName)) {
++                result.push_back(QStringLiteral("qgnomeplatform"));
+                 // prefer the GTK3 theme implementation with native dialogs etc.
+                 result.push_back(QStringLiteral("gtk3"));
+                 // fallback to the generic Gnome theme if loading the GTK3 theme fails