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>

1 files changed, 0 insertions, 1 deletions

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;