# 2024.04.19

<pre class="language-cpp"><code class="lang-cpp">inline QRect rect() const;
<strong>
</strong><strong>inline QRect QWidget::rect() const
</strong>{ return QRect(0,0,data->crect.width(),data->crect.height()); }
</code></pre>

* inline关键字，不太清楚好处，但inline函数的定义一般放在头文件中（怪不得在cpp里没找到
* 返回一个QRect类型的变量
* const关键字，表示该成员函数是一个常量成员函数，即在函数体内部不能修改对象的成员变量。这个关键字在成员函数声明和定义时都需要添加
* data是QWidget的一个QWidgetData类型指针变量，crect又是一个QRect类型变量

```cpp
Q_DECL_CONSTEXPR inline QRect::QRect(int aleft, int atop, int awidth, int aheight) Q_DECL_NOTHROW
    : x1(aleft), y1(atop), x2(aleft + awidth - 1), y2(atop + aheight - 1) {}
```

* 猜测aleft代表最左侧的坐标，atop代表最上方的坐标，awidth代表宽度，aheight代表高度，然后x1 y1代表左上角的横纵坐标，x2 y2代表右下角的横纵坐标
* 这段语法可参考<https://blog.csdn.net/xzli8_geo/article/details/85037530>

```cpp
class QWidgetData
{
public:
    WId winid;
    uint widget_attributes;
    Qt::WindowFlags window_flags;
    uint window_state : 4;
    uint focus_policy : 4;
    uint sizehint_forced :1;
    uint is_closing :1;
    uint in_show : 1;
    uint in_set_window_state : 1;
    mutable uint fstrut_dirty : 1;
    uint context_menu_policy : 3;
    uint window_modality : 2;
    uint in_destructor : 1;
    uint unused : 13;
    QRect crect;
    mutable QPalette pal;
    QFont fnt;
    QRect wrect;
};

class Q_WIDGETS_EXPORT QWidget : public QObject, public QPaintDevice
{
private:
    QWidgetData *data;
}
```

```cpp
void QWidget::update()
{
    update(rect());
}
```

如果调用update时没有传递参数，则再调用重载的update函数

```cpp
void QWidget::update(const QRect &rect)
{
    Q_D(QWidget);
    d->update(rect);
}
```


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