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我怎么知道它是有效的gdi区域句柄？

[英]How do I know it's a valid gdi region handle?

原文 2010-11-21 21:23:37 6 3 c++/ windows/ user-interface/ gdi/ winapi

or other gdi handle, such as pen brush. 或其他gdi手柄，例如笔刷。 how do i know is it valid? 我怎么知道这是有效的？

3 个解决方案

You should never get yourself into a situation where you might be holding onto a handle that isn't valid. 切勿陷入可能握住无效手柄的情况。 If necessary, set the handle to NULL after calling DeleteObject() so it is completely obvious. 如有必要，在调用DeleteObject（）之后将句柄设置为NULL，这样就很明显了。 Assuming that a GDI function will give you a FALSE return value because you passed a bad handle isn't safe. 假设由于传递了错误的句柄，GDI函数将为您提供FALSE返回值是不安全的。

The answer is: where did you get the handle from? 答案是：您从哪里得到的？

Simply speaking, it's like with the art: how do you know it's authentic, not a fake? 简而言之，就像艺术一样：您怎么知道它是真实的，而不是假的？ There're some "heuristics", but the only 100%-working way is to know where is it from. 有一些“启发式”方法，但是唯一可行的方法是知道它从哪里来。

So, regarding the GDI regions: you should only trust those region handles that are returned by GDI functions. 因此，关于GDI区域：您应该只信任GDI函数返回的那些区域句柄。

:) :)

Try GetObject() or GetObjectType() . 尝试GetObject()或GetObjectType() 。 They should return NULL if the object handle is invalid. 如果对象句柄无效，则它们应返回NULL。

I can see where you'd want to use this for debugging. 我可以看到您想在哪里使用它进行调试。 In a perfect world, we keep track of our objects and know where they are at all times. 在一个完美的世界中，我们跟踪对象并始终知道它们在哪里。

Ours is not a perfect world. 我们的世界不是一个完美的世界。