Qt获取控件位置，坐标总结

QMouseEvent中两类坐标系统，一类是窗口坐标，一类是显示器坐标。

总结一：经过试验，QMouseEvent::globalPos()  和 QCursor::pos()效果一样，但是Qt帮助文档说不一样，可是我获得值确实相同的。

QCursor::pos() == QMouseEvent::globalPos() 都是全局坐标；

总结二：将button：posBtn直接转换成全局坐标。

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

总结三：将全局坐标（鼠标当前坐标，QCursor::pos()）直接转换成当前

当前窗口相对坐标 ==  ui.posBtn->mapFromGlobal(QCursor::pos());

 

上面的mouseEvent.globalPos()和QCursor::pos()永远相同，都是全局坐标。

上面绿色按钮的当前坐标：ui.pushButton->pos() 、转换父窗口坐标后mapToParent()、转换成全局坐标后mapToGlobal();如果当前鼠标坐标摸到按钮，按钮上面的文字会发生变化，经过比较。确实得到：QCursor::pos() == ui.posBtn->mapFromGlobal(QCursor::pos());

代码如下，跟踪任何控件，记得设置跟踪轨迹为真setMouseTracking(true)

1. void TestWidget::mouseMoveEvent(QMouseEvent* event)  
2. {  
3.     QPoint m = event->globalPos();  
4.     ui.lblMouseEventGlobalPos->setText(QString("(%1,%2)").arg(m.x()).arg(m.y()));  
5.     QPoint n = QCursor::pos();  
6.     ui.lblCursorPos->setText(QString("(%1,%2)").arg(n.x()).arg(n.y()));  
7.     QPoint k = ui.posBtn->pos();  
8.     QPoint h = ui.posBtn->mapToGlobal(ui.posBtn->pos());  
9.     QPoint i = ui.posBtn->mapToGlobal(ui.posBtn->pos());  
10.   
11.     ui.lblPushBttonPos->setText(QString("(%1,%2)").arg(k.x()).arg(k.y()));  
12.     ui.lblToParentPos->setText(QString("(%1,%2)").arg(h.x()).arg(h.y()));  
13.     ui.lblToGlobalPos->setText(QString("(%1,%2)").arg(i.x()).arg(i.y()));  
14.   
15.   
16.     QRect widgetRect = ui.posBtn->geometry();  
17.     QPoint mousePos = ui.posBtn->mapFromGlobal(QCursor::pos());  
18.     if (widgetRect.contains(mousePos))  
19.     {  
20.         ui.posBtn->setText("摸到我了");  
21.     }  
22.     else  
23.     {  
24.         ui.posBtn->setText("....");  
25.     }  
26.   
27. }  

 

==========================基础知识=================

1、QPoint QMouseEvent::pos() 

      这个只是返回相对这个widget(重载了QMouseEvent的widget)的位置。

       const Returns the position of the mouse cursor, relative to the widget that 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() 

     窗口坐标，这个是返回鼠标的全局坐标

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

3、QPoint QCursor::pos() [static] 

      返回相对显示器的全局坐标

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

4.1  QPoint QWidget::mapToGlobal(const QPoint & pos)  const 

       将窗口坐标转换成显示器坐标

       Translates the widget coordinate pos to global screen coordinates. For example, mapToGlobal(QPoint(0,0)) would give the global coordinates of the top-left pixel of the widget. See also mapFromGlobal(), mapTo(), and mapToParent().

4.2   QPoint QWidget::mapFromGlobal(const QPoint & pos) const 

       将显示器坐标转换成窗口坐标

       Translates the global screen coordinate pos to widget coordinates.

5.1 QPoint QWidget::mapToParent(const QPoint & pos) const

       将窗口坐标获得的pos转换成父类widget的坐标

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

5.2 QPoint QWidget::mapFromParent(const QPoint & pos) const 

       将父类窗口坐标转换成当前窗口坐标

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

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

       将当前窗口坐标转换成指定parent坐标。

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

7、QWidget::pos() : QPoint

这个属性获得的是当前目前控件在父窗口中的位置，

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

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

When changing the position, the widget, if visible, receives a move event (moveEvent()) immediately. If the widget is not currently visible, it is guaranteed to receive an event before it is shown.

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

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

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

8、const QPointF & QMouseEvent::screenPos() const

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

和QPoint QMouseEvent::globalPos() 值相同，但是类型更高精度的QPointF

This function was introduced in Qt 5.0.