RenderWidgetHostViewQtDelegateItem: keep grabs

If a WebView or WebEngineView gets a mouse or touch grab, we don't want
to give it up to any handlers that may be lurking on Items underneath.
WebView is opaque, so we don't know whether the user is trying to drag a
scrollbar or something else, but interactive items outside shouldn't
interfere, in general.

[ChangeLog][QtWebEngineQuick] WebEngineView (or WebView backed by Qt
WebEngine) no longer allows components outside to take over the mouse or
touch exclusive grab. For example if the user starts dragging a
scrollbar inside the web view, that continues until release, regardless
of any DragHandler, Flickable etc.

Fixes: QTBUG-103518
Pick-to: 6.5 6.6
Change-Id: I4352dc8482020f0efc7a0901e94ccf7fc147fa1b
Reviewed-by: Michal Klocek <michal.klocek@qt.io>

2 files changed, 68 insertions, 0 deletions

diff --git a/tests/auto/quick/qmltests/CMakeLists.txt b/tests/auto/quick/qmltests/CMakeLists.txt
index acd783bd5..6301e5ab6 100644
--- a/tests/auto/quick/qmltests/CMakeLists.txt
+++ b/tests/auto/quick/qmltests/CMakeLists.txt
@@ -25,6 +25,7 @@ set(testList
     tst_datalist.qml
     tst_desktopBehaviorLoadHtml.qml
     tst_download.qml
+    tst_dragHandlerUnderView.qml
     tst_favicon.qml
     tst_faviconDatabase.qml
     tst_filePicker.qml
diff --git a/tests/auto/quick/qmltests/data/tst_dragHandlerUnderView.qml b/tests/auto/quick/qmltests/data/tst_dragHandlerUnderView.qml
new file mode 100644
index 000000000..c22bd44c2
--- /dev/null
+++ b/tests/auto/quick/qmltests/data/tst_dragHandlerUnderView.qml
@@ -0,0 +1,67 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0
+
+import QtQuick
+import QtTest
+import QtWebEngine
+
+Item {
+    id: parentItem
+    width: 400
+    height: 300
+
+    Rectangle {
+        id: draggableDownUnder
+        color: "wheat"
+        width: 350
+        height: 250
+
+        DragHandler { id: dragHandler }
+    }
+
+    TestWebEngineView {
+        id: webEngineView
+        width: 300
+        height: 250
+
+        property var testUrl: Qt.resolvedUrl("test4.html")
+
+        SignalSpy {
+            id: scrollPositionSpy
+            target: webEngineView
+            signalName: "onScrollPositionChanged"
+        }
+
+        SignalSpy {
+            id: dragActiveSpy
+            target: dragHandler
+            signalName: "activeChanged"
+        }
+
+        TestCase {
+            id: testCase
+            name: "KeepMouseGrabDuringScrolling"
+            when: windowShown
+
+            function test_scroll() {
+                webEngineView.url = Qt.resolvedUrl("test4.html");
+                verify(webEngineView.waitForLoadSucceeded());
+
+                mousePress(webEngineView, 295, 20);
+                mouseMove(webEngineView, 295, 200);
+                mouseRelease(webEngineView, 295, 200);
+
+                // WebEngineView scrolled if the scrollbar was visible.
+                // But on macOS, the scrollbar is hidden, so text gets selected.
+                tryVerify(function() {
+                    return (scrollPositionSpy.count === 1 && webEngineView.scrollPosition.y > 100)
+                            || webEngineView.getTextSelection().length > 0;
+                });
+
+                // DragHandler didn't take over and drag
+                compare(dragActiveSpy.count, 0);
+                compare(draggableDownUnder.y, 0);
+            }
+        }
+    }
+}