cleanup: remove redundant QGuiApplicationPrivate::buttons

This variable was introducing during Qt 5.0 Q{Gui}Application
refactoring days (2011 or even before) and since then has been
used interchangeably with QGuiApplicationPrivate::mouse_buttons.

This patch removes the duplicate member variable as it is
redundant and could be a source of potential errors.

Initially I was thinking that ::buttons might be used for
the purpose of QTestLib, but it is not. QTestLib delivers
mouse events directly via qApp->notify() (mouse button state
is update via QGuiApplicationPrivate::mouse_buttons from notify()),
or via window system interface QWindowSystemInterface::handleMouseEvent
(which goes through QGuiApplication::processMouseEvent).
Looking at QGuiApplication, it is clear that ::buttons
and ::mouse_buttons always have the same value, as there
is only one assignment to these members in QGuiApplication:

mouse_buttons = buttons = e->buttons;

And there are no other places that would assign to
QGuiApplicationPrivate::buttons.

Change-Id: Ib60d366bf056a98b15bb4538a569693e7bd022e2
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

3 files changed, 13 insertions, 13 deletions

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 23c11fe212..79f2fb4f1b 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -164,8 +164,6 @@ QString *QGuiApplicationPrivate::desktopFileName = 0;
 
 QPalette *QGuiApplicationPrivate::app_pal = 0;        // default application palette
 
-Qt::MouseButtons QGuiApplicationPrivate::buttons = Qt::NoButton;
-
 ulong QGuiApplicationPrivate::mousePressTime = 0;
 Qt::MouseButton QGuiApplicationPrivate::mousePressButton = Qt::NoButton;
 int QGuiApplicationPrivate::mousePressX = 0;
@@ -1830,7 +1828,7 @@ void QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePriv
 void QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::MouseEvent *e)
 {
     QEvent::Type type;
-    Qt::MouseButtons stateChange = e->buttons ^ buttons;
+    Qt::MouseButtons stateChange = e->buttons ^ mouse_buttons;
     if (e->globalPos != QGuiApplicationPrivate::lastCursorPosition && (stateChange != Qt::NoButton)) {
         // A mouse event should not change both position and buttons at the same time. Instead we
         // should first send a move event followed by a button changed event. Since this is not the case
@@ -1839,7 +1837,7 @@ void QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::Mo
                     e->window.data(), e->timestamp, e->type, e->localPos, e->globalPos, e->buttons, e->modifiers, e->source);
         if (e->flags & QWindowSystemInterfacePrivate::WindowSystemEvent::Synthetic)
             mouseButtonEvent.flags |= QWindowSystemInterfacePrivate::WindowSystemEvent::Synthetic;
-        e->buttons = buttons;
+        e->buttons = mouse_buttons;
         processMouseEvent(e);
         processMouseEvent(&mouseButtonEvent);
         return;
@@ -1893,7 +1891,7 @@ void QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::Mo
             // Ignore mouse events that don't change the current state.
             return;
         }
-        mouse_buttons = buttons = e->buttons;
+        mouse_buttons = e->buttons;
         if (button & e->buttons) {
             ulong doubleClickInterval = static_cast<ulong>(QGuiApplication::styleHints()->mouseDoubleClickInterval());
             doubleClick = e->timestamp - mousePressTime < doubleClickInterval && button == mousePressButton;
@@ -1918,14 +1916,14 @@ void QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::Mo
                 const QPointF nativeLocalPoint = QHighDpi::toNativePixels(localPoint, screen);
                 const QPointF nativeGlobalPoint = QHighDpi::toNativePixels(globalPoint, screen);
                 QMouseEvent ev(type, nativeLocalPoint, nativeLocalPoint, nativeGlobalPoint,
-                                          button, buttons, e->modifiers, e->source);
+                                          button, mouse_buttons, e->modifiers, e->source);
                 ev.setTimestamp(e->timestamp);
                 cursor->pointerEvent(ev);
             }
     }
 #endif
 
-    QMouseEvent ev(type, localPoint, localPoint, globalPoint, button, buttons, e->modifiers, e->source);
+    QMouseEvent ev(type, localPoint, localPoint, globalPoint, button, mouse_buttons, e->modifiers, e->source);
     ev.setTimestamp(e->timestamp);
 
     if (window->d_func()->blockedByModalWindow && !qApp->d_func()->popupActive()) {
@@ -1959,7 +1957,7 @@ void QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::Mo
             point.state = Qt::TouchPointPressed;
         } else if (type == QEvent::MouseButtonRelease && button == Qt::LeftButton) {
             point.state = Qt::TouchPointReleased;
-        } else if (type == QEvent::MouseMove && (buttons & Qt::LeftButton)) {
+        } else if (type == QEvent::MouseMove && (mouse_buttons & Qt::LeftButton)) {
             point.state = Qt::TouchPointMoved;
         } else {
             return;
@@ -1980,7 +1978,7 @@ void QGuiApplicationPrivate::processMouseEvent(QWindowSystemInterfacePrivate::Mo
         if (!e->window.isNull() || e->nullWindow()) { // QTBUG-36364, check if window closed in response to press
             const QEvent::Type doubleClickType = frameStrut ? QEvent::NonClientAreaMouseButtonDblClick : QEvent::MouseButtonDblClick;
             QMouseEvent dblClickEvent(doubleClickType, localPoint, localPoint, globalPoint,
-                                      button, buttons, e->modifiers, e->source);
+                                      button, mouse_buttons, e->modifiers, e->source);
             dblClickEvent.setTimestamp(e->timestamp);
             QGuiApplication::sendSpontaneousEvent(window, &dblClickEvent);
         }
@@ -2014,7 +2012,7 @@ void QGuiApplicationPrivate::processWheelEvent(QWindowSystemInterfacePrivate::Wh
     }
 
      QWheelEvent ev(localPoint, globalPoint, e->pixelDelta, e->angleDelta, e->qt4Delta, e->qt4Orientation,
-                    buttons, e->modifiers, e->phase, e->source, e->inverted);
+                    mouse_buttons, e->modifiers, e->phase, e->source, e->inverted);
      ev.setTimestamp(e->timestamp);
      QGuiApplication::sendSpontaneousEvent(window, &ev);
 #else
@@ -2471,7 +2469,7 @@ void QGuiApplicationPrivate::processTouchEvent(QWindowSystemInterfacePrivate::To
                                                                e->timestamp,
                                                                synthIt->pos,
                                                                synthIt->screenPos,
-                                                               buttons & ~Qt::LeftButton,
+                                                               mouse_buttons & ~Qt::LeftButton,
                                                                e->modifiers,
                                                                Qt::MouseEventSynthesizedByQt);
                 fake.flags |= QWindowSystemInterfacePrivate::WindowSystemEvent::Synthetic;
@@ -2686,7 +2684,7 @@ void QGuiApplicationPrivate::processTouchEvent(QWindowSystemInterfacePrivate::To
                         QWindowSystemInterfacePrivate::MouseEvent fake(w, e->timestamp,
                                                                        touchPoint.pos(),
                                                                        touchPoint.screenPos(),
-                                                                       b | (buttons & ~Qt::LeftButton),
+                                                                       b | (mouse_buttons & ~Qt::LeftButton),
                                                                        e->modifiers,
                                                                        Qt::MouseEventSynthesizedByQt);
                         fake.flags |= QWindowSystemInterfacePrivate::WindowSystemEvent::Synthetic;
diff --git a/src/gui/kernel/qguiapplication_p.h b/src/gui/kernel/qguiapplication_p.h
index 3804667ef3..014ed861df 100644
--- a/src/gui/kernel/qguiapplication_p.h
+++ b/src/gui/kernel/qguiapplication_p.h
@@ -201,7 +201,6 @@ public:
     virtual bool isWindowBlocked(QWindow *window, QWindow **blockingWindow = 0) const;
     virtual bool popupActive() { return false; }
 
-    static Qt::MouseButtons buttons;
     static ulong mousePressTime;
     static Qt::MouseButton mousePressButton;
     static int mousePressX;
diff --git a/src/widgets/kernel/qapplication.cpp b/src/widgets/kernel/qapplication.cpp
index d7282d8c26..e22be2bd39 100644
--- a/src/widgets/kernel/qapplication.cpp
+++ b/src/widgets/kernel/qapplication.cpp
@@ -2955,6 +2955,9 @@ bool QApplication::notify(QObject *receiver, QEvent *e)
         // required in order to support Qt Test synthesized events. Real mouse
         // and keyboard state updates from the platform plugin are managed by
         // QGuiApplicationPrivate::process(Mouse|Wheel|Key|Touch|Tablet)Event();
+        // ### FIXME: Qt Test should not call qapp->notify(), but rather route
+        // the events through the proper QPA interface. This is required to
+        // properly generate all other events such as enter/leave etc.
         switch (e->type()) {
         case QEvent::MouseButtonPress:
             {