1.     QPoint QMouseEvent::pos()

     這個只是返回相對這個widget(過載了QMouseEvent的widget)的位置。

      const Returns the position of the mouse cursor, relative to the widgetthat received the event. If you move the widget as a result of the mouse event,use the global position returned by globalPos() to avoid a shaking motion.

2.     QPoint QMouseEvent::globalPos()

     視窗座標，這個是返回滑鼠的全域性座標

    const Returns the global position of the mouse cursor at the time of theevent. This is important on asynchronous window systems like X11. Whenever youmove your widgets around in response to mouse events, globalPos() may differ alot from the current pointer position QCursor::pos(), and fromQWidget::mapToGlobal(pos()).

3.     QPoint QCursor::pos() [static]

     返回相對顯示器的全域性座標

     Returns the position of the cursor (hot spot) of the primary screen inglobal screen coordinates. You can call QWidget::mapFromGlobal() to translateit to widget coordinates. Note: The position is queried from the windowingsystem. If mouse events are generated via other means (e.g., viaQWindowSystemInterface in a unit test), those fake mouse moves will not bereflected in the returned value. Note: On platforms where there is no windowingsystem or cursors are not available, the returned position is based on the mousemove events generated via QWindowSystemInterface.

4.     QPoint QWidget::mapToGlobal(const QPoint & pos)  const

      將視窗座標轉換成顯示器座標

      Translates the widget coordinate pos to global screen coordinates. Forexample, mapToGlobal(QPoint(0,0)) would give the global coordinates of thetop-left pixel of the widget. See also mapFromGlobal(), mapTo(), andmapToParent().

5.     QPoint QWidget::mapFromGlobal(const QPoint & pos) const

      將顯示器座標轉換成視窗座標

      Translates the global screen coordinate pos to widget coordinates.

6.     QPoint QWidget::mapToParent(const QPoint & pos) const

      將視窗座標獲得的pos轉換成父類widget的座標

Translates the widget coordinate pos to acoordinate in the parent widget.

7.     QPoint QWidget::mapFromParent(const QPoint & pos) const

       將父類視窗座標轉換成當前視窗座標

Translates the parent widget coordinate posto widget coordinates. Same as mapFromGlobal() if the widget has no parent.

8.     QPoint QWidget::mapTo(const QWidget * parent, const QPoint &pos) const

將當前視窗座標轉換成指定parent座標。

Translates the widget coordinate pos to thecoordinate system of parent. The parent must not be 0 and must be a parent ofthe calling widget. See also mapFrom(), mapToParent(), mapToGlobal(), andunderMouse().

9.     QWidget::pos() : QPoint

這個屬性獲得的是當前目前控制元件在父視窗中的位置，

This property holds the position of thewidget within its parent widget.

If the widget is a window, the position isthat of the widget on the desktop, including its frame.

When changing the position, the widget, ifvisible, receives a move event (moveEvent()) immediately. If the widget is notcurrently visible, it is guaranteed to receive an event before it is shown.

By default, this property contains aposition that refers to the origin.

Warning: Calling move() or setGeometry()inside moveEvent() can lead to infinite recursion.

See the Window Geometry documentation foran overview of geometry issues with windows.

10.    const QPointF &QMouseEvent::screenPos() const

Returns the position of the mouse cursor asa QPointF, relative to the screen that received the event.

和QPoint QMouseEvent::globalPos() 值相同，但是型別更高精度的QPointF

This function was introduced in Qt 5.0.

11.   QCursor::pos() == QMouseEvent::globalPos() 都是全域性座標

12.   將滑鼠的座標轉換成全域性座標。

QMouseEvent::globalPos() == ui.posBtn->mapToGlobal(ui.posBtn->pos());

13.   將全域性座標（滑鼠當前座標，QCursor::pos()）直接轉換成當前視窗相對座標

ui.posBtn->mapFromGlobal(QCursor::pos());