2 files changed, 17 insertions, 4 deletions
diff --git a/src/plugins/platforms/xcb/qxcbscreen.cpp b/src/plugins/platforms/xcb/qxcbscreen.cpp
index 6c30d392349..2a538c9b6ea 100644
--- a/src/plugins/platforms/xcb/qxcbscreen.cpp
+++ b/src/plugins/platforms/xcb/qxcbscreen.cpp
@@ -679,10 +679,11 @@ void QXcbScreen::setMonitor(xcb_randr_monitor_info_t *monitorInfo, xcb_timestamp
         m_sizeMillimeters = virtualDesktop()->physicalSize();
 
     m_outputName = getName(monitorInfo);
-    if (connection()->primaryScreenNumber() == virtualDesktop()->number() && monitorInfo->primary)
-        m_primary = true;
-    else
-        m_primary = false;
+    m_primary = false;
+    if (connection()->primaryScreenNumber() == virtualDesktop()->number()) {
+        if (monitorInfo->primary || isPrimaryInXScreen())
+            m_primary = true;
+    }
 
     updateColorSpaceAndEdid();
 }
@@ -699,6 +700,17 @@ QString QXcbScreen::defaultName()
     return name;
 }
 
+bool QXcbScreen::isPrimaryInXScreen()
+{
+    auto primary = Q_XCB_REPLY(xcb_randr_get_output_primary, connection()->xcb_connection(), root());
+    if (!primary)
+        qWarning("failed to get the primary output of the screen");
+
+    const bool isPrimary = primary ? (m_monitor ? m_outputs.contains(primary->output) : m_output == primary->output) : false;
+
+    return isPrimary;
+}
+
 QXcbScreen::~QXcbScreen()
 {
 }
diff --git a/src/plugins/platforms/xcb/qxcbscreen.h b/src/plugins/platforms/xcb/qxcbscreen.h
index 5a844f944a0..49165d3ba40 100644
--- a/src/plugins/platforms/xcb/qxcbscreen.h
+++ b/src/plugins/platforms/xcb/qxcbscreen.h
@@ -163,6 +163,7 @@ public:
     void setCrtc(xcb_randr_crtc_t crtc) { m_crtc = crtc; }
     void setMonitor(xcb_randr_monitor_info_t *monitorInfo, xcb_timestamp_t timestamp = XCB_NONE);
     QString defaultName();
+    bool isPrimaryInXScreen();
 
     void windowShown(QXcbWindow *window);
     QString windowManagerName() const { return m_virtualDesktop->windowManagerName(); }