4 files changed, 16 insertions, 23 deletions
diff --git a/src/plugins/platforms/xcb/qxcbnativeinterface.cpp b/src/plugins/platforms/xcb/qxcbnativeinterface.cpp
index 7d950f8dee..14f5cd0747 100644
--- a/src/plugins/platforms/xcb/qxcbnativeinterface.cpp
+++ b/src/plugins/platforms/xcb/qxcbnativeinterface.cpp
@@ -191,16 +191,6 @@ bool QXcbNativeInterface::systrayVisualHasAlphaChannel() {
     }
 }
 
-void QXcbNativeInterface::clearRegion(const QWindow *qwindow, const QRect& rect)
-{
-    if (const QPlatformWindow *platformWindow = qwindow->handle()) {
-        const QXcbWindow *qxwindow = static_cast<const QXcbWindow *>(platformWindow);
-        xcb_connection_t *xcb_conn = qxwindow->xcb_connection();
-
-        xcb_clear_area(xcb_conn, false, qxwindow->xcb_window(), rect.x(), rect.y(), rect.width(), rect.height());
-    }
-}
-
 void QXcbNativeInterface::setParentRelativeBackPixmap(const QWindow *qwindow)
 {
     if (const QPlatformWindow *platformWindow = qwindow->handle()) {
diff --git a/src/plugins/platforms/xcb/qxcbnativeinterface.h b/src/plugins/platforms/xcb/qxcbnativeinterface.h
index 742984ae36..388d774853 100644
--- a/src/plugins/platforms/xcb/qxcbnativeinterface.h
+++ b/src/plugins/platforms/xcb/qxcbnativeinterface.h
@@ -104,7 +104,6 @@ public:
 
     Q_INVOKABLE void beep();
     Q_INVOKABLE bool systemTrayAvailable(const QScreen *screen) const;
-    Q_INVOKABLE void clearRegion(const QWindow *qwindow, const QRect& rect);
     Q_INVOKABLE void setParentRelativeBackPixmap(const QWindow *window);
     Q_INVOKABLE bool systrayVisualHasAlphaChannel();
     Q_INVOKABLE bool requestSystemTrayWindowDock(const QWindow *window);
diff --git a/src/plugins/platforms/xcb/qxcbwindow.cpp b/src/plugins/platforms/xcb/qxcbwindow.cpp
index 9298e874b8..34289fb90e 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.cpp
+++ b/src/plugins/platforms/xcb/qxcbwindow.cpp
@@ -2307,6 +2307,11 @@ void QXcbWindow::handleXEmbedMessage(const xcb_client_message_event_t *event)
     case XEMBED_EMBEDDED_NOTIFY:
         Q_XCB_CALL(xcb_map_window(xcb_connection(), m_window));
         xcbScreen()->windowShown(this);
+        // Without Qt::WA_TranslucentBackground, we use a ParentRelative BackPixmap.
+        // Clear the whole tray icon window to its background color as early as possible
+        // so that we can get a clean result from grabWindow() later.
+        Q_XCB_CALL(xcb_clear_area(xcb_connection(), false, m_window, 0, 0, geometry().width(), geometry().height()));
+        xcb_flush(xcb_connection());
         break;
     case XEMBED_FOCUS_IN:
         Qt::FocusReason reason;
diff --git a/src/widgets/util/qsystemtrayicon_x11.cpp b/src/widgets/util/qsystemtrayicon_x11.cpp
index 070ab367f7..2b153d53d9 100644
--- a/src/widgets/util/qsystemtrayicon_x11.cpp
+++ b/src/widgets/util/qsystemtrayicon_x11.cpp
@@ -88,6 +88,7 @@ private:
     bool addToTray();
 
     QSystemTrayIcon *q;
+    QPixmap background;
 };
 
 QSystemTrayIconSys::QSystemTrayIconSys(QSystemTrayIcon *qIn)
@@ -151,6 +152,8 @@ bool QSystemTrayIconSys::addToTray()
         qWarning("requestSystemTrayWindowDock failed.");
         return false;
     }
+    if (!background.isNull())
+        background = QPixmap();
     show();
     return true;
 }
@@ -230,18 +233,14 @@ void QSystemTrayIconSys::paintEvent(QPaintEvent *)
         painter.setCompositionMode(QPainter::CompositionMode_Source);
         painter.fillRect(rect, Qt::transparent);
     } else {
-        // Without Qt::WA_TranslucentBackground, we use a ParentRelative BackPixmap and jump through
-        // some hops to draw this background below our icon. This clears the whole tray icon to its
-        // background color and thus causes flickering (you can see that the icon is being
-        // repainted). However, we can't really do much about this.
-        QMetaObject::invokeMethod(QGuiApplication::platformNativeInterface(),
-                                    "clearRegion", Qt::DirectConnection,
-                                    Q_ARG(const QWindow *, windowHandle()),
-                                    Q_ARG(const QRect&, rect)
-                                 );
-        painter.drawPixmap(QPoint(0, 0),
-                        QGuiApplication::primaryScreen()->grabWindow(winId(),
-                                0, 0, rect.size().width(), rect.size().height()));
+        // clearRegion() was called on XEMBED_EMBEDDED_NOTIFY, so we hope that got done by now.
+        // Grab the tray background pixmap, before rendering the icon for the first time.
+        if (background.isNull()) {
+            background = QGuiApplication::primaryScreen()->grabWindow(winId(),
+                                0, 0, rect.size().width(), rect.size().height());
+        }
+        // Then paint over the icon area with the background before compositing the icon on top.
+        painter.drawPixmap(QPoint(0, 0), background);
     }
     painter.setCompositionMode(QPainter::CompositionMode_SourceOver);
     q->icon().paint(&painter, rect);