wasm: add dragleave event handling

Fixes: QTBUG-129149
Change-Id: I946f43e3a696c801a60a9a209a70ccaf57252a60
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
Reviewed-by: Piotr Wierciński <piotr.wiercinski@qt.io>
(cherry picked from commit 8a93093271329f1fb867c0627e63f61ed7330860)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/plugins/platforms/wasm/qwasmdrag.cpp

@@ -187,6 +187,12 @@ void QWasmDrag::onNativeDragFinished(DragEvent *event)
     m_dragState->quitEventLoopClosure();
 }
 
+void QWasmDrag::onNativeDragLeave(DragEvent *event)
+{
+    m_dragState->dropAction = event->dropAction;
+    event->dataTransfer.setDropAction(Qt::DropAction::IgnoreAction);
+}
+
 QWasmDrag::DragState::DragImage::DragImage(const QPixmap &pixmap, const QMimeData *mimeData,
                                            QWindow *window)
     : m_temporaryImageElementParent(QWasmWindow::fromWindow(window)->containerElement())

src/plugins/platforms/wasm/qwasmdrag.h

@@ -32,6 +32,7 @@ public:
     void onNativeDrop(DragEvent *event);
     void onNativeDragStarted(DragEvent *event);
     void onNativeDragFinished(DragEvent *event);
+    void onNativeDragLeave(DragEvent *event);
 
     // QPlatformDrag:
     Qt::DropAction drag(QDrag *drag) final;

src/plugins/platforms/wasm/qwasmevent.cpp

@@ -260,7 +260,6 @@ std::optional<DragEvent> DragEvent::fromWeb(emscripten::val event, QWindow *targ
 {
     const auto eventType = ([&event]() -> std::optional<EventType> {
         const auto eventTypeString = event["type"].as<std::string>();
-
         if (eventTypeString == "dragend")
             return EventType::DragEnd;
         if (eventTypeString == "dragover")
@@ -269,6 +268,8 @@ std::optional<DragEvent> DragEvent::fromWeb(emscripten::val event, QWindow *targ
             return EventType::DragStart;
         if (eventTypeString == "drop")
             return EventType::Drop;
+        if (eventTypeString == "dragleave")
+            return EventType::DragLeave;
         return std::nullopt;
     })();
     if (!eventType)

src/plugins/platforms/wasm/qwasmevent.h

@@ -25,6 +25,7 @@ enum class EventType {
     DragEnd,
     DragOver,
     DragStart,
+    DragLeave,
     Drop,
     KeyDown,
     KeyUp,

src/plugins/platforms/wasm/qwasmwindowclientarea.cpp

@@ -60,6 +60,13 @@ ClientArea::ClientArea(QWasmWindow *window, QWasmScreen *screen, emscripten::val
                             QWasmDrag::instance()->onNativeDragFinished(&event);
                         });
 
+        m_dragLeaveCallback = std::make_unique<qstdweb::EventCallback>(
+                    element, "dragleave", [this](emscripten::val webEvent) {
+                            webEvent.call<void>("preventDefault");
+                            auto event = *DragEvent::fromWeb(webEvent, m_window->window());
+                            QWasmDrag::instance()->onNativeDragLeave(&event);
+                        });
+
 }
 
 bool ClientArea::processPointer(const PointerEvent &event)

src/plugins/platforms/wasm/qwasmwindowclientarea.h

@@ -40,6 +40,7 @@ private:
     std::unique_ptr<qstdweb::EventCallback> m_dragStartCallback;
     std::unique_ptr<qstdweb::EventCallback> m_dragEndCallback;
     std::unique_ptr<qstdweb::EventCallback> m_dropCallback;
+    std::unique_ptr<qstdweb::EventCallback> m_dragLeaveCallback;
 
     QMap<int, QWindowSystemInterface::TouchPoint> m_pointerIdToTouchPoints;