c++ - SetWindowPos 是否立即绘制

Question

在每次鼠标移动事件中，我都在移动我的窗口。从文档中可以看出，如果移动成功，SetWindowPos 会返回一个非零值。

我想证实我的推断，即每次 SetWindowPos 返回一个非零值时，移动都已经发生。这意味着，窗口实际上已经在新位置重新绘制，然后函数才返回。函数返回后不久(处理某种消息时)不会发生移动。

Answer 1

I wanted to confirm my inference that every time SetWindowPos returns a non-zero value, the move has already happened. Which means, the window has actually been re-painted

这是错误的假设。成功的移动和非零返回与绘画无关。

API 改变位置和非零返回值确认新值被接受。 API 不 promise ，不将完整的重绘周期作为其执行的一部分。更重要的是，位置、Z 顺序等的变化也可能影响其他窗口的可见性，这又需要重新绘制，而这又必须在各自的线程上发生。重绘是有计划的，它们与 SetWindowPos 返回不同步。 MSDN 上的文档没有任何关于重绘/更新的 promise 。然后从 API 返回零表示您的参数根本不被接受(尤其是无效的窗口句柄)。

Bonus reading :

When you call the Set­Window­Pos function, the window manager updates the window size, position, whatever, and then it goes around repainting the windows that were affected by the operation. By default, the Set­Window­Pos function does a quick-repaint of the windows before returning. After the function returns, the normal WM_PAINT message does the real work of painting the window. The quick-repaint is done so that there is immediate feedback that the window did change its size, position, whatever.