IDC_STATIC 在resource.h 文件中意味着什么？

我有一个由 VS 2012 生成的简单 Win32 项目。resource.h文件，我看到了这个：

#ifndef IDC_STATIC
#define IDC_STATIC              -1
#endif

我发现它在几个地方被引用resource.rc文件。但我无法理解这意味着什么。我在网上也没有找到有关它的参考资料。任何想法？

通过调用创建子控件时CreateWindowEx https://msdn.microsoft.com/en-us/library/windows/desktop/ms632680.aspx，你必须分配一个控件ID（通过重载hMenu范围）。控件 ID 稍后可用于引用控件，而无需存储动态创建的控件HWND（例如，当调用GetDlgItem https://msdn.microsoft.com/en-us/library/windows/desktop/ms645481.aspx or GetDlgItemInt https://msdn.microsoft.com/en-us/library/windows/desktop/ms645485.aspx).

Some controls rarely need to be identified in code. A prominent example is the Static Control https://msdn.microsoft.com/en-us/library/windows/desktop/bb760769.aspx¹, that, if defined in a resource script, usually does not need to be referenced in code. You (or the dialog manager) still need to pass a control ID when creating the control, even though you don't use it later on. For those controls you can pass the IDC_STATIC control ID, that is defined in a wizard-generated Resource.h file².

¹ Other examples include the Icon Control https://msdn.microsoft.com/en-us/library/windows/desktop/aa369208.aspx (a static control with the SS_ICON style), the Line Control https://msdn.microsoft.com/en-us/library/windows/desktop/aa369760.aspx (a static control with the SS_ETCHEDHORZ and SS_SUNKEN styles), or the GroupBox Control https://msdn.microsoft.com/en-us/library/windows/desktop/aa368766.aspx.

² This is not a convention of the Windows API³. It is strictly a decision made by user code. You could use another ID value, or not define IDC_STATIC at all if you want, and use an integer literal in the LTEXT control statement https://msdn.microsoft.com/en-us/library/windows/desktop/aa381021.aspx instead: LTEXT "Filename", -1, 10, 10, 100, 100

³ Granted, the SDK header winres.h does define the preprocessor symbol IDC_STATIC as (-1), so if you do define it in your code, make sure to assign the same value to avoid any confusion.