qpa: enhance mouse event with type and button data

... and deprecate QWSI APIs that accepts mouse event without mouse button/
type data.

In the early days of Qt5 it was decided to centralize mouse button/type
handling in QGuiApplication (because of limitation of some now unknown
platform). This has proven to be problematic as mouse handling details
differ across platforms (e.g on X11 we do not receive mouse release event
when closing popup windows or ordinary windows that are closed from the
mouse press event). Instead of hacking around platform specific behaviors
in Qt Gui, we should move this task back to platform plugins (similar to
how this was done in Qt4 with native APIs sending mouse details directly
to QApplication). There are even cases where it simply is not possible
to deduce (from QGuiApplication) which button caused the event (e.g. when
more than one button is involved and some event goes missing). Besisdes,
throwing away information which is already available at QPA level (for free)
and trying to deduce it again at Qt Gui level seems impractical, fagile
(as probably noticed by people fixing all the unexpected issues) and adds
unnecessary complexity.

Note:

Removing the deprecated QWSI APIs from offscreen plugin depends on fixing
autotests that rely on QOffscreenCursor::setPos() logic.

For the convenience of testing use QT_QPA_DISABLE_ENHANCED_MOUSE to restore
to the old code path where QGuiApplication does the mouse state deducing.

Other platforms have similar issues. I do not have all supported platform
available on my desk, so other platform maintainers will need to take care
of porting those platforms to the new APIs. And mainly, I don't want to deal
with all the hacks that other platforms have added to workaround this broken
mouse logic.

In Qt6 we need to remove deprecated code path from QGuiApplication.

This patch:

- Extends QWindowSystemInterfacePrivate::MouseEvent ctor with QEvent::Type
and Qt::MouseButton. We use this extra data when processing mouse events in
QGuiApplication. This actually is similar to KeyEvent, where we do pass the
type (press or release) to QtGui.

- Refactors QGuiApplicationPrivate::processMouseEvent and qtestlib to use
the new APIs.

Task-number: QTBUG-59277
Task-number: QTBUG-62329
Task-number: QTBUG-63467
Change-Id: If94fd46a7cccfea8264dcb1368804c73334558b8
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

4 files changed, 39 insertions, 21 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index de11ecfb6e..c5eae20266 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -983,6 +983,12 @@ static Qt::MouseButtons translateMouseButtons(int s)
     return ret;
 }
 
+void QXcbConnection::setButtonState(Qt::MouseButton button, bool down)
+{
+    m_buttonState.setFlag(button, down);
+    m_button = button;
+}
+
 Qt::MouseButton QXcbConnection::translateMouseButton(xcb_button_t s)
 {
     switch (s) {
@@ -1055,7 +1061,7 @@ void QXcbConnection::handleXcbEvent(xcb_generic_event_t *event)
             // the event explicitly contains the state of the three first buttons,
             // the rest we need to manage ourselves
             m_buttonState = (m_buttonState & ~0x7) | translateMouseButtons(ev->state);
-            m_buttonState |= translateMouseButton(ev->detail);
+            setButtonState(translateMouseButton(ev->detail), true);
             if (Q_UNLIKELY(lcQpaXInputEvents().isDebugEnabled()))
                 qCDebug(lcQpaXInputEvents, "legacy mouse press, button %d state %X", ev->detail, static_cast<unsigned int>(m_buttonState));
             HANDLE_PLATFORM_WINDOW_EVENT(xcb_button_press_event_t, event, handleButtonPressEvent);
@@ -1064,7 +1070,7 @@ void QXcbConnection::handleXcbEvent(xcb_generic_event_t *event)
             xcb_button_release_event_t *ev = (xcb_button_release_event_t *)event;
             m_keyboard->updateXKBStateFromCore(ev->state);
             m_buttonState = (m_buttonState & ~0x7) | translateMouseButtons(ev->state);
-            m_buttonState &= ~translateMouseButton(ev->detail);
+            setButtonState(translateMouseButton(ev->detail), false);
             if (Q_UNLIKELY(lcQpaXInputEvents().isDebugEnabled()))
                 qCDebug(lcQpaXInputEvents, "legacy mouse release, button %d state %X", ev->detail, static_cast<unsigned int>(m_buttonState));
             HANDLE_PLATFORM_WINDOW_EVENT(xcb_button_release_event_t, event, handleButtonReleaseEvent);
diff --git a/src/plugins/platforms/xcb/qxcbconnection.h b/src/plugins/platforms/xcb/qxcbconnection.h
index efc5e666fc..725c01f77d 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.h
+++ b/src/plugins/platforms/xcb/qxcbconnection.h
@@ -485,8 +485,9 @@ public:
     xcb_window_t getSelectionOwner(xcb_atom_t atom) const;
     xcb_window_t getQtSelectionOwner();
 
-    void setButtonState(Qt::MouseButton button, bool down) { m_buttonState.setFlag(button, down); }
+    void setButtonState(Qt::MouseButton button, bool down);
     Qt::MouseButtons buttonState() const { return m_buttonState; }
+    Qt::MouseButton button() const { return m_button; }
     Qt::MouseButton translateMouseButton(xcb_button_t s);
 
     QXcbWindow *focusWindow() const { return m_focusWindow; }
@@ -700,6 +701,7 @@ private:
     bool has_render_extension = false;
 
     Qt::MouseButtons m_buttonState = 0;
+    Qt::MouseButton m_button = Qt::NoButton;
 
     QXcbWindow *m_focusWindow = nullptr;
     QXcbWindow *m_mouseGrabber = nullptr;
diff --git a/src/plugins/platforms/xcb/qxcbwindow.cpp b/src/plugins/platforms/xcb/qxcbwindow.cpp
index eeaed86e98..475a4e37f3 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.cpp
+++ b/src/plugins/platforms/xcb/qxcbwindow.cpp
@@ -2111,7 +2111,8 @@ void QXcbWindow::handleUnmapNotifyEvent(const xcb_unmap_notify_event_t *event)
 }
 
 void QXcbWindow::handleButtonPressEvent(int event_x, int event_y, int root_x, int root_y,
-                                        int detail, Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp, Qt::MouseEventSource source)
+                                        int detail, Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp,
+                                        QEvent::Type type, Qt::MouseEventSource source)
 {
     const bool isWheel = detail >= 4 && detail <= 7;
     if (!isWheel && window() != QGuiApplication::focusWindow()) {
@@ -2160,11 +2161,12 @@ void QXcbWindow::handleButtonPressEvent(int event_x, int event_y, int root_x, in
 
     connection()->setMousePressWindow(this);
 
-    handleMouseEvent(timestamp, local, global, modifiers, source);
+    handleMouseEvent(timestamp, local, global, modifiers, type, source);
 }
 
 void QXcbWindow::handleButtonReleaseEvent(int event_x, int event_y, int root_x, int root_y,
-                                          int detail, Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp, Qt::MouseEventSource source)
+                                          int detail, Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp,
+                                          QEvent::Type type, Qt::MouseEventSource source)
 {
     QPoint local(event_x, event_y);
     QPoint global(root_x, root_y);
@@ -2177,7 +2179,7 @@ void QXcbWindow::handleButtonReleaseEvent(int event_x, int event_y, int root_x,
     if (connection()->buttonState() == Qt::NoButton)
         connection()->setMousePressWindow(nullptr);
 
-    handleMouseEvent(timestamp, local, global, modifiers, source);
+    handleMouseEvent(timestamp, local, global, modifiers, type, source);
 }
 
 static inline bool doCheckUnGrabAncestor(QXcbConnection *conn)
@@ -2278,7 +2280,8 @@ void QXcbWindow::handleLeaveNotifyEvent(int root_x, int root_y,
 }
 
 void QXcbWindow::handleMotionNotifyEvent(int event_x, int event_y, int root_x, int root_y,
-                                         Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp, Qt::MouseEventSource source)
+                                         Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp,
+                                         QEvent::Type type, Qt::MouseEventSource source)
 {
     QPoint local(event_x, event_y);
     QPoint global(root_x, root_y);
@@ -2292,27 +2295,28 @@ void QXcbWindow::handleMotionNotifyEvent(int event_x, int event_y, int root_x, i
     else if (hasMousePressWindow && !isMouseButtonPressed)
         connection()->setMousePressWindow(nullptr);
 
-    handleMouseEvent(timestamp, local, global, modifiers, source);
+    handleMouseEvent(timestamp, local, global, modifiers, type, source);
 }
 
 void QXcbWindow::handleButtonPressEvent(const xcb_button_press_event_t *event)
 {
     Qt::KeyboardModifiers modifiers = connection()->keyboard()->translateModifiers(event->state);
     handleButtonPressEvent(event->event_x, event->event_y, event->root_x, event->root_y, event->detail,
-                           modifiers, event->time);
+                           modifiers, event->time, QEvent::MouseButtonPress);
 }
 
 void QXcbWindow::handleButtonReleaseEvent(const xcb_button_release_event_t *event)
 {
     Qt::KeyboardModifiers modifiers = connection()->keyboard()->translateModifiers(event->state);
     handleButtonReleaseEvent(event->event_x, event->event_y, event->root_x, event->root_y, event->detail,
-                             modifiers, event->time);
+                             modifiers, event->time, QEvent::MouseButtonRelease);
 }
 
 void QXcbWindow::handleMotionNotifyEvent(const xcb_motion_notify_event_t *event)
 {
     Qt::KeyboardModifiers modifiers = connection()->keyboard()->translateModifiers(event->state);
-    handleMotionNotifyEvent(event->event_x, event->event_y, event->root_x, event->root_y, modifiers, event->time);
+    handleMotionNotifyEvent(event->event_x, event->event_y, event->root_x, event->root_y, modifiers,
+                            event->time, QEvent::MouseMove);
 }
 
 #if QT_CONFIG(xinput2)
@@ -2363,18 +2367,18 @@ void QXcbWindow::handleXIMouseEvent(xcb_ge_event_t *event, Qt::MouseEventSource
         if (Q_UNLIKELY(lcQpaXInputEvents().isDebugEnabled()))
             qCDebug(lcQpaXInputEvents, "XI2 mouse press, button %d, time %d, source %s", button, ev->time, sourceName);
         conn->setButtonState(button, true);
-        handleButtonPressEvent(event_x, event_y, root_x, root_y, ev->detail, modifiers, ev->time, source);
+        handleButtonPressEvent(event_x, event_y, root_x, root_y, ev->detail, modifiers, ev->time, QEvent::MouseButtonPress, source);
         break;
     case XI_ButtonRelease:
         if (Q_UNLIKELY(lcQpaXInputEvents().isDebugEnabled()))
             qCDebug(lcQpaXInputEvents, "XI2 mouse release, button %d, time %d, source %s", button, ev->time, sourceName);
         conn->setButtonState(button, false);
-        handleButtonReleaseEvent(event_x, event_y, root_x, root_y, ev->detail, modifiers, ev->time, source);
+        handleButtonReleaseEvent(event_x, event_y, root_x, root_y, ev->detail, modifiers, ev->time, QEvent::MouseButtonRelease, source);
         break;
     case XI_Motion:
         if (Q_UNLIKELY(lcQpaXInputEvents().isDebugEnabled()))
             qCDebug(lcQpaXInputEvents, "XI2 mouse motion %d,%d, time %d, source %s", event_x, event_y, ev->time, sourceName);
-        handleMotionNotifyEvent(event_x, event_y, root_x, root_y, modifiers, ev->time, source);
+        handleMotionNotifyEvent(event_x, event_y, root_x, root_y, modifiers, ev->time, QEvent::MouseMove, source);
         break;
     default:
         qWarning() << "Unrecognized XI2 mouse event" << ev->evtype;
@@ -2419,10 +2423,13 @@ void QXcbWindow::handleXIEnterLeave(xcb_ge_event_t *event)
 QXcbWindow *QXcbWindow::toWindow() { return this; }
 
 void QXcbWindow::handleMouseEvent(xcb_timestamp_t time, const QPoint &local, const QPoint &global,
-        Qt::KeyboardModifiers modifiers, Qt::MouseEventSource source)
+        Qt::KeyboardModifiers modifiers, QEvent::Type type, Qt::MouseEventSource source)
 {
     connection()->setTime(time);
-    QWindowSystemInterface::handleMouseEvent(window(), time, local, global, connection()->buttonState(), modifiers, source);
+    Qt::MouseButton button = type == QEvent::MouseMove ? Qt::NoButton : connection()->button();
+    QWindowSystemInterface::handleMouseEvent(window(), time, local, global,
+                                             connection()->buttonState(), button,
+                                             type, modifiers, source);
 }
 
 void QXcbWindow::handleEnterNotifyEvent(const xcb_enter_notify_event_t *event)
diff --git a/src/plugins/platforms/xcb/qxcbwindow.h b/src/plugins/platforms/xcb/qxcbwindow.h
index 176f9a234c..b89dddf72f 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.h
+++ b/src/plugins/platforms/xcb/qxcbwindow.h
@@ -146,7 +146,7 @@ public:
     QXcbWindow *toWindow() override;
 
     void handleMouseEvent(xcb_timestamp_t time, const QPoint &local, const QPoint &global,
-                          Qt::KeyboardModifiers modifiers, Qt::MouseEventSource source);
+                          Qt::KeyboardModifiers modifiers, QEvent::Type type, Qt::MouseEventSource source);
 
     void updateNetWmUserTime(xcb_timestamp_t timestamp);
 
@@ -221,13 +221,16 @@ protected:
     bool compressExposeEvent(QRegion &exposeRegion);
 
     void handleButtonPressEvent(int event_x, int event_y, int root_x, int root_y,
-                                int detail, Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp, Qt::MouseEventSource source = Qt::MouseEventNotSynthesized);
+                                int detail, Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp,
+                                QEvent::Type type, Qt::MouseEventSource source = Qt::MouseEventNotSynthesized);
 
     void handleButtonReleaseEvent(int event_x, int event_y, int root_x, int root_y,
-                                  int detail, Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp, Qt::MouseEventSource source = Qt::MouseEventNotSynthesized);
+                                  int detail, Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp,
+                                  QEvent::Type type, Qt::MouseEventSource source = Qt::MouseEventNotSynthesized);
 
     void handleMotionNotifyEvent(int event_x, int event_y, int root_x, int root_y,
-                                 Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp, Qt::MouseEventSource source = Qt::MouseEventNotSynthesized);
+                                 Qt::KeyboardModifiers modifiers, xcb_timestamp_t timestamp,
+                                 QEvent::Type type, Qt::MouseEventSource source = Qt::MouseEventNotSynthesized);
 
     void handleEnterNotifyEvent(int event_x, int event_y, int root_x, int root_y,
                                 quint8 mode, quint8 detail, xcb_timestamp_t timestamp);