class TQtClientWidget: public QFrame

 fprintf(stderr, "TQtClientWidget::~TQtClientWidget dtor %p\n", this);
 remove the event filter

 This Qt QCloseEvent event handler

 Color to paint widget background with our PainEvent

 pixmap to paint widget background with our PainEvent

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 XGrabButton(3X11)         XLIB FUNCTIONS        XGrabButton(3X11)
   *    The pointer is not grabbed, and the specified button is logically
        pressed when the specified modifier keys are logically down,
        and no other buttons or modifier keys are logically down.
   *    The grab_window contains the pointer.
   *    The confine_to window (if any) is viewable.
   *    A passive grab on the same button/key combination does not exist
        on any ancestor of grab_window.
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 Check ROOT Event_t ev structure for the KeyGrab mask

 replace the original Windows_t  with the grabbing id and
 re-caclulate the mouse coordinate
 to respect the new Windows_t id if any

 Select input and chech whether qwe nat mouse tracking

 Set the Button mask

 Unset the Button mask

 Set the key button mask
 insert   = -1 - remove
             0 - test
            +1 - insert

 Associate this widget with the parent ROOT gui widget

 Unset the key button mask

 Qt slot to respond to the "Keyboard accelerator signal"

 Disconnect the Canvas and ROOT gui widget before destroy.