Add basic test for QWindow foreign windows

Only implemented on macOS and Windows for now.

Change-Id: Ib6330bc7024453d23675c1770367e8da6c4c9a34
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

tests/auto/gui/kernel/qwindow/CMakeLists.txt

@@ -14,6 +14,22 @@ qt_internal_add_test(tst_qwindow
         Qt::GuiPrivate
 )
 
+if(APPLE OR WIN32)
+    qt_internal_add_test(tst_foreignwindow
+        SOURCES
+            tst_foreignwindow.cpp
+        LIBRARIES
+            Qt::CorePrivate
+            Qt::Gui
+            Qt::GuiPrivate
+    )
+
+    if(APPLE)
+        target_compile_options(tst_foreignwindow PRIVATE -x objective-c++)
+        set_property(TARGET tst_foreignwindow PROPERTY PROPERTY MACOSX_BUNDLE TRUE)
+    endif()
+endif()
+
 ## Scopes:
 #####################################################################
 

tests/auto/gui/kernel/qwindow/tst_foreignwindow.cpp

@@ -0,0 +1,121 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+#include <QTest>
+
+#include <QtCore/qloggingcategory.h>
+#include <private/qguiapplication_p.h>
+#include <qpa/qplatformintegration.h>
+
+#if defined(Q_OS_MACOS)
+#  include <AppKit/AppKit.h>
+#elif defined(Q_OS_WIN)
+#  include <winuser.h>
+#endif
+
+Q_LOGGING_CATEGORY(lcTests, "qt.gui.tests")
+
+class NativeWindow
+{
+    Q_DISABLE_COPY(NativeWindow)
+public:
+    NativeWindow();
+    ~NativeWindow();
+
+    operator WId() const { return reinterpret_cast<WId>(m_handle); }
+
+private:
+#if defined(Q_OS_MACOS)
+    NSView *m_handle = nullptr;
+#elif defined(Q_OS_WIN)
+    HWND m_handle = nullptr;
+#endif
+};
+
+#if defined(Q_OS_MACOS)
+
+@interface View : NSView
+@end
+
+@implementation View
+- (instancetype)init
+{
+    if ((self = [super init])) {
+        qCDebug(lcTests) << "Initialized" << self;
+    }
+    return self;
+}
+
+- (void)dealloc
+{
+    qCDebug(lcTests) << "Deallocating" << self;
+    [super dealloc];
+}
+@end
+
+NativeWindow::NativeWindow()
+    : m_handle([View new])
+{
+}
+
+NativeWindow::~NativeWindow()
+{
+    [m_handle release];
+}
+
+#elif defined(Q_OS_WIN)
+
+NativeWindow::NativeWindow()
+{
+    static const LPCWSTR className = []{
+        WNDCLASS wc = {};
+        wc.lpfnWndProc = DefWindowProc;
+        wc.hInstance = GetModuleHandle(nullptr);
+        wc.lpszClassName = L"Native Window";
+        RegisterClass(&wc);
+        return wc.lpszClassName;
+    }();
+    m_handle = CreateWindowEx(0, className, nullptr, WS_POPUP,
+                CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
+                nullptr, nullptr, GetModuleHandle(nullptr), nullptr);
+}
+
+NativeWindow::~NativeWindow()
+{
+    DestroyWindow(m_handle);
+}
+
+#endif
+
+class tst_ForeignWindow: public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void initTestCase()
+    {
+        auto *platformIntegration = QGuiApplicationPrivate::platformIntegration();
+        if (!platformIntegration->hasCapability(QPlatformIntegration::ForeignWindows))
+            QSKIP("This platform does not support foreign windows");
+    }
+
+    void fromWinId();
+};
+
+void tst_ForeignWindow::fromWinId()
+{
+    NativeWindow nativeWindow;
+    QVERIFY(nativeWindow);
+
+    std::unique_ptr<QWindow> foreignWindow(QWindow::fromWinId(nativeWindow));
+    QVERIFY(foreignWindow);
+    QVERIFY(foreignWindow->flags().testFlag(Qt::ForeignWindow));
+    QVERIFY(foreignWindow->handle());
+
+    // fromWinId does not take (exclusive) ownership of the native window,
+    // so deleting the foreign window should not be a problem/cause crashes.
+    foreignWindow.reset();
+}
+
+#include <tst_foreignwindow.moc>
+QTEST_MAIN(tst_ForeignWindow)