1 files changed, 75 insertions, 0 deletions
diff --git a/src/plugins/platforms/wasm/qwasmwindowstack.h b/src/plugins/platforms/wasm/qwasmwindowstack.h
new file mode 100644
index 0000000000..c75001157a
--- /dev/null
+++ b/src/plugins/platforms/wasm/qwasmwindowstack.h
@@ -0,0 +1,75 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
+
+#ifndef QWASMWINDOWSTACK_H
+#define QWASMWINDOWSTACK_H
+
+#include <qglobal.h>
+#include <QtCore/qlist.h>
+
+#include <vector>
+
+QT_BEGIN_NAMESPACE
+
+class QWasmWindow;
+
+// Maintains a z-order hierarchy for a set of windows. The first added window is always treated as
+// the 'root', which always stays at the bottom. Other windows are 'regular', which means they are
+// subject to z-order changes via |raise| and |lower|/
+// If the root is ever removed, all of the current and future windows in the stack are treated as
+// regular.
+// Access to the top element is facilitated by |topWindow|.
+// Changes to the top element are signaled via the |topWindowChangedCallback| supplied at
+// construction.
+class Q_AUTOTEST_EXPORT QWasmWindowStack
+{
+public:
+    using WindowOrderChangedCallbackType = std::function<void()>;
+
+    using StorageType = QList<QWasmWindow *>;
+
+    using iterator = StorageType::reverse_iterator;
+    using const_iterator = StorageType::const_reverse_iterator;
+    using const_reverse_iterator = StorageType::const_iterator;
+
+    enum class PositionPreference {
+        StayOnBottom,
+        Regular,
+        StayOnTop,
+    };
+
+    explicit QWasmWindowStack(WindowOrderChangedCallbackType topWindowChangedCallback);
+    ~QWasmWindowStack();
+
+    void pushWindow(QWasmWindow *window, PositionPreference position);
+    void removeWindow(QWasmWindow *window);
+    void raise(QWasmWindow *window);
+    void lower(QWasmWindow *window);
+    void windowPositionPreferenceChanged(QWasmWindow *window, PositionPreference position);
+
+    // Iterates top-to-bottom
+    iterator begin();
+    iterator end();
+    const_iterator begin() const;
+    const_iterator end() const;
+
+    // Iterates bottom-to-top
+    const_reverse_iterator rbegin() const;
+    const_reverse_iterator rend() const;
+
+    bool empty() const;
+    size_t size() const;
+    QWasmWindow *topWindow() const;
+
+private:
+    PositionPreference getWindowPositionPreference(StorageType::iterator windowIt) const;
+
+    WindowOrderChangedCallbackType m_windowOrderChangedCallback;
+    QList<QWasmWindow *> m_windowStack;
+    StorageType::iterator m_regularWindowsBegin;
+    StorageType::iterator m_alwaysOnTopWindowsBegin;
+};
+
+QT_END_NAMESPACE
+
+#endif // QWASMWINDOWSTACK_H