4 files changed, 55 insertions, 0 deletions

diff --git a/src/plugins/platforms/wasm/qwasmcompositor.cpp b/src/plugins/platforms/wasm/qwasmcompositor.cpp
index 8ba67040a5..8af49c5fc3 100644
--- a/src/plugins/platforms/wasm/qwasmcompositor.cpp
+++ b/src/plugins/platforms/wasm/qwasmcompositor.cpp
@@ -168,6 +168,11 @@ void QWasmCompositor::setEnabled(bool enabled)
     m_isEnabled = enabled;
 }
 
+void QWasmCompositor::startResize(Qt::Edges edges)
+{
+    m_windowManipulation.startResize(edges);
+}
+
 void QWasmCompositor::addWindow(QWasmWindow *window)
 {
     m_windowVisibility.insert(window, false);
@@ -788,6 +793,11 @@ void QWasmCompositor::WindowManipulation::onPointerDown(
 void QWasmCompositor::WindowManipulation::onPointerMove(
     const PointerEvent& event)
 {
+    m_systemDragInitData = {
+        .lastMouseMovePoint = m_screen->clipPoint(event.point),
+        .lastMousePointerId = event.pointerId,
+    };
+
     if (operation() == Operation::None || event.pointerId != m_state->pointerId)
         return;
 
@@ -822,6 +832,34 @@ void QWasmCompositor::WindowManipulation::onPointerUp(const PointerEvent& event)
     m_state.reset();
 }
 
+void QWasmCompositor::WindowManipulation::startResize(Qt::Edges edges)
+{
+    Q_ASSERT_X(operation() == Operation::None, Q_FUNC_INFO,
+               "Resize must not start anew when one is in progress");
+
+    auto *window = m_screen->compositor()->windowAt(m_systemDragInitData.lastMouseMovePoint);
+    if (Q_UNLIKELY(!window))
+        return;
+
+    m_state.reset(new OperationState{
+        .pointerId = m_systemDragInitData.lastMousePointerId,
+        .window = window,
+        .operationSpecific =
+            ResizeState{
+                .m_resizeEdges = edges,
+                .m_originInScreenCoords = m_systemDragInitData.lastMouseMovePoint,
+                .m_initialWindowBounds = window->geometry(),
+                .m_minShrink =
+                    QPoint(window->minimumWidth() - window->geometry().width(),
+                        window->minimumHeight() - window->geometry().height()),
+                .m_maxGrow =
+                    QPoint(window->maximumWidth() - window->geometry().width(),
+                        window->maximumHeight() - window->geometry().height()),
+            },
+    });
+    m_screen->canvas().call<void>("setPointerCapture", m_systemDragInitData.lastMousePointerId);
+}
+
 bool QWasmCompositor::processKeyboard(int eventType, const EmscriptenKeyboardEvent *emKeyEvent)
 {
     constexpr bool ProceedToNativeEvent = false;
diff --git a/src/plugins/platforms/wasm/qwasmcompositor.h b/src/plugins/platforms/wasm/qwasmcompositor.h
index b2bb51fc52..07bce77a94 100644
--- a/src/plugins/platforms/wasm/qwasmcompositor.h
+++ b/src/plugins/platforms/wasm/qwasmcompositor.h
@@ -57,6 +57,7 @@ public:
     };
 
     void setEnabled(bool enabled);
+    void startResize(Qt::Edges edges);
 
     void addWindow(QWasmWindow *window);
     void removeWindow(QWasmWindow *window);
@@ -108,6 +109,7 @@ private:
         void onPointerDown(const PointerEvent& event, QWindow* windowAtPoint);
         void onPointerMove(const PointerEvent& event);
         void onPointerUp(const PointerEvent& event);
+        void startResize(Qt::Edges edges);
 
         Operation operation() const;
 
@@ -128,11 +130,18 @@ private:
             QPointer<QWindow> window;
             std::variant<ResizeState, MoveState> operationSpecific;
         };
+        struct SystemDragInitData
+        {
+            QPoint lastMouseMovePoint;
+            int lastMousePointerId = -1;
+        };
 
         void resizeWindow(const QPoint& amount);
+        ResizeState makeResizeState(Qt::Edges edges, const QPoint &startPoint, QWindow *window);
 
         QWasmScreen *m_screen;
 
+        SystemDragInitData m_systemDragInitData;
         std::unique_ptr<OperationState> m_state;
     };
 
diff --git a/src/plugins/platforms/wasm/qwasmwindow.cpp b/src/plugins/platforms/wasm/qwasmwindow.cpp
index 8e3bc3f72c..0ba7f44684 100644
--- a/src/plugins/platforms/wasm/qwasmwindow.cpp
+++ b/src/plugins/platforms/wasm/qwasmwindow.cpp
@@ -212,6 +212,13 @@ void QWasmWindow::propagateSizeHints()
     }
 }
 
+bool QWasmWindow::startSystemResize(Qt::Edges edges)
+{
+    m_compositor->startResize(edges);
+
+    return true;
+}
+
 void QWasmWindow::injectMousePressed(const QPoint &local, const QPoint &global,
                                       Qt::MouseButton button, Qt::KeyboardModifiers mods)
 {
diff --git a/src/plugins/platforms/wasm/qwasmwindow.h b/src/plugins/platforms/wasm/qwasmwindow.h
index 0148dc7d62..c86026cf1b 100644
--- a/src/plugins/platforms/wasm/qwasmwindow.h
+++ b/src/plugins/platforms/wasm/qwasmwindow.h
@@ -56,6 +56,7 @@ public:
                             Qt::MouseButton button, Qt::KeyboardModifiers mods);
     void injectMouseReleased(const QPoint &local, const QPoint &global,
                             Qt::MouseButton button, Qt::KeyboardModifiers mods);
+    bool startSystemResize(Qt::Edges edges) final;
 
     bool isPointOnTitle(QPoint point) const;
     bool isPointOnResizeRegion(QPoint point) const;