windows 处理鼠标拖动的正确方法是什么？
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What is the proper way of handling a mouse drag?
提问by Mike Morum
I need to implement mouse drag events which look something like this:
我需要实现如下所示的鼠标拖动事件：
class MouseDragEvent
{
public:
uint m_btn;
uint m_x, m_y;
uint m_delta_x, m_delta_y;
};
I think I will need to check for WM_LBUTTONDOWN and WM_LBUTTONUP messages and manually find the change in x and y. Is there a drag message or a better way?
我想我需要检查 WM_LBUTTONDOWN 和 WM_LBUTTONUP 消息并手动找到 x 和 y 的变化。有没有拖拽消息或者更好的方法？
回答by Mark Ransom
Start by detecting WM_LBUTTONDOWN. Record the starting coordinates where the mouse button was pressed. Check for WM_MOUSEMOVE, and when the mouse has moved outside the rectangle determined by GetSystemParameters(SM_CXDRAG)and GetSystemParameters(SM_CYDRAG)use SetCaptureto capture the mouse. At this point continue responding to WM_MOUSEMOVEand check for WM_LBUTTONUP. You might want to change the mouse cursor at this point. Also check for WM_CAPTURECHANGED, which means the drag has been aborted. After the drag is complete call ReleaseCapture.
从检测开始WM_LBUTTONDOWN。记录按下鼠标按钮的起始坐标。检查WM_MOUSEMOVE, 以及当鼠标移到由GetSystemParameters(SM_CXDRAG)和GetSystemParameters(SM_CYDRAG)用于SetCapture捕获鼠标所确定的矩形之外时。此时继续响应WM_MOUSEMOVE并检查WM_LBUTTONUP。此时您可能想要更改鼠标光标。还要检查WM_CAPTURECHANGED，这意味着拖动已中止。拖动完成后调用ReleaseCapture。
Edit:Most of this process can be automated with the DragDetectfunction. Call this function from the WM_LBUTTONDOWN handler.
编辑：这个过程的大部分都可以通过该DragDetect功能实现自动化。从 WM_LBUTTONDOWN 处理程序调用此函数。
回答by Ben Voigt
There are drag-and-drop APIs in Windows (e.g. RegisterDragDrop), but concerned with the from- and to- windows (often in different applications), not the coordinates.
Windows 中有拖放 API（例如RegisterDragDrop），但关注的是 from- 和 to- 窗口（通常在不同的应用程序中），而不是坐标。
If you want to deal with delta-x and delta-y coordinated, then processing button down and button up messages is appropriate.
如果你想处理 delta-x 和 delta-y 协调，那么处理 button down 和 button up 消息是合适的。
回答by bayCoder
Did you try this: http://www.codeproject.com/KB/miscctrl/rdragdropfiles.aspx
你试过这个吗：http: //www.codeproject.com/KB/miscctrl/rdragdropfiles.aspx
This may also be helpful: http://msdn.microsoft.com/en-us/magazine/cc163915.aspx
这也可能有帮助：http: //msdn.microsoft.com/en-us/magazine/cc163915.aspx
