Add more info about QX11Info alternatives

Pick-to: 6.4 6.2
Fixes: QTBUG-103856
Task-number: QTBUG-103715
Change-Id: If66172bc4c7840a1c267c5d0d3ed4b49fee42af5
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

5 files changed, 100 insertions, 0 deletions

diff --git a/doc/src/snippets/porting-qx11info/main.cpp b/doc/src/snippets/porting-qx11info/main.cpp
new file mode 100644
index 000000000..2de11ac0c
--- /dev/null
+++ b/doc/src/snippets/porting-qx11info/main.cpp
@@ -0,0 +1,16 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "testwindow.h"
+
+#include <QtGui/QGuiApplication>
+
+int main(int argc, char **argv)
+{
+    QGuiApplication app(argc, argv);
+
+    TestWindow win;
+    win.show();
+
+    return app.exec();
+}
diff --git a/doc/src/snippets/porting-qx11info/porting-qx11info.pro b/doc/src/snippets/porting-qx11info/porting-qx11info.pro
new file mode 100644
index 000000000..adaf9f5ac
--- /dev/null
+++ b/doc/src/snippets/porting-qx11info/porting-qx11info.pro
@@ -0,0 +1,9 @@
+lessThan(QT_MAJOR_VERSION, 6) {
+   QT += x11extras
+}
+
+LIBS += -lxcb -lX11
+
+HEADERS  = testwindow.h
+SOURCES += testwindow.cpp \
+    main.cpp
diff --git a/doc/src/snippets/porting-qx11info/testwindow.cpp b/doc/src/snippets/porting-qx11info/testwindow.cpp
new file mode 100644
index 000000000..d46c75e0e
--- /dev/null
+++ b/doc/src/snippets/porting-qx11info/testwindow.cpp
@@ -0,0 +1,55 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "testwindow.h"
+
+//! [0]
+#include <QtGui/QGuiApplication>
+//! [0]
+#include <QDebug>
+
+#if defined(Q_OS_UNIX)
+#if QT_VERSION < 0x060000
+#include <QtX11Extras/QX11Info>
+#endif
+#endif
+
+#include <X11/Xlib.h>
+#include <xcb/xcb.h>
+
+TestWindow::TestWindow(QWindow *parent)
+    : QWindow(parent)
+{
+
+#if QT_VERSION < 0x060000
+    Display *display = QX11Info::display();
+    xcb_connection_t *connection = QX11Info::connection();
+    bool isPlatformX11 = QX11Info::isPlatformX11();
+#else
+//! [1]
+    Display *display = nullptr;
+    xcb_connection_t *connection = nullptr;
+    bool isPlatformX11 = false;
+    if (auto *x11Application = qGuiApp->nativeInterface<QNativeInterface::QX11Application>()) {
+        display = x11Application->display();
+        connection = x11Application->connection();
+        isPlatformX11 = true;
+    }
+    // or
+    // isPlatformX11 = qGuiApp->nativeInterface<QNativeInterface::QX11Application>();
+//! [1]
+#endif
+
+    qDebug() << "Display *display=" << display;
+    if (display)
+        qDebug() << "XConnectionNumber=" << XConnectionNumber(display);
+
+    qDebug() << "xcb_connection_t *xcbConnection=" << connection;
+    if (connection) {
+        const xcb_setup_t *xcbSetup = xcb_get_setup(connection);
+        if (xcbSetup)
+            qDebug() << "protocol_major_version=" << xcbSetup->protocol_major_version << ", protocol_minor_version=" << xcbSetup->protocol_minor_version;
+    }
+
+    qDebug() << "isPlatformX11=" << isPlatformX11;
+}
diff --git a/doc/src/snippets/porting-qx11info/testwindow.h b/doc/src/snippets/porting-qx11info/testwindow.h
new file mode 100644
index 000000000..7110c5d91
--- /dev/null
+++ b/doc/src/snippets/porting-qx11info/testwindow.h
@@ -0,0 +1,16 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef TESTWINDOW_H
+#define TESTWINDOW_H
+
+#include <QtGui/QWindow>
+
+class TestWindow : public QWindow
+{
+    Q_OBJECT
+public:
+    explicit TestWindow(QWindow *parent = nullptr);
+};
+
+#endif // TESTWINDOW_H
diff --git a/doc/src/snippets/snippets.pro b/doc/src/snippets/snippets.pro
index 08f21c8d3..ee7f4bd5c 100644
--- a/doc/src/snippets/snippets.pro
+++ b/doc/src/snippets/snippets.pro
@@ -90,3 +90,7 @@ SUBDIRS         = brush \
 #                  whatsthis \
                   widget-mask \
                   xml
+
+qtConfig(xcb) {
+    SUBDIRS += porting-qx11info
+}