Improve window dragging on WASM

Window dragging has been considerably improved by replacing the mouse
events by pointer events and placing a pointer lock on WASM canvas, so
that off-browser window events are delivered to us.

Translation of the drag origin has been limited to inside the canvas, so
that a window cannot be dragged so far that it becomes offscreen and is
unreachable.

Change-Id: Id177c630a6466f04464a513371d6b97d3a098b6a
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/src/plugins/platforms/wasm/qwasmevent.cpp b/src/plugins/platforms/wasm/qwasmevent.cpp
new file mode 100644
index 0000000000..b094dbfe14
--- /dev/null
+++ b/src/plugins/platforms/wasm/qwasmevent.cpp
@@ -0,0 +1,53 @@
+// Copyright (C) 2022 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
+
+#include "qwasmevent.h"
+
+QT_BEGIN_NAMESPACE
+
+namespace KeyboardModifier
+{
+template <>
+QFlags<Qt::KeyboardModifier> getForEvent<EmscriptenKeyboardEvent>(
+    const EmscriptenKeyboardEvent& event)
+{
+    return internal::Helper<EmscriptenKeyboardEvent>::getModifierForEvent(event) |
+        (event.location == DOM_KEY_LOCATION_NUMPAD ? Qt::KeypadModifier : Qt::NoModifier);
+}
+}  // namespace KeyboardModifier
+
+std::optional<PointerEvent> PointerEvent::fromWeb(emscripten::val event)
+{
+    PointerEvent ret;
+
+    const auto eventType = ([&event]() -> std::optional<EventType> {
+        const auto eventTypeString = event["type"].as<std::string>();
+
+        if (eventTypeString == "pointermove")
+            return EventType::PointerMove;
+        else if (eventTypeString == "pointerup")
+            return EventType::PointerUp;
+        else if (eventTypeString == "pointerdown")
+            return EventType::PointerDown;
+        else if (eventTypeString == "pointerenter")
+            return EventType::PointerEnter;
+        else if (eventTypeString == "pointerleave")
+            return EventType::PointerLeave;
+        return std::nullopt;
+    })();
+    if (!eventType)
+        return std::nullopt;
+
+    ret.type = *eventType;
+    ret.pointerType = event["pointerType"].as<std::string>() == "mouse" ?
+        PointerType::Mouse : PointerType::Other;
+    ret.mouseButton = MouseEvent::buttonFromWeb(event["button"].as<int>());
+    ret.mouseButtons = MouseEvent::buttonsFromWeb(event["buttons"].as<unsigned short>());
+    ret.point = QPoint(event["x"].as<int>(), event["y"].as<int>());
+    ret.pointerId = event["pointerId"].as<int>();
+    ret.modifiers = KeyboardModifier::getForEvent(event);
+
+    return ret;
+}
+
+QT_END_NAMESPACE