Windows error 1400 (ERROR_INVALID_WINDOW

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: the supplied HWND is not valid for the requested USER32 operation.

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ERROR_CURRENT_DOMAIN_NOT_ALLOWED	ERROR_INVALID_MENU_HANDLE

ERROR_INVALID_WINDOW_HANDLE

The HWND does not identify a live window

An HWND is an opaque window-manager handle. This status is about the identity and lifetime of that GUI object, not about the window title, class name, or whether the window is currently visible.

Window handles can become stale after destruction, and code that caches a handle across asynchronous work can race the thread that owns the window. A numeric value that once represented a window is not a persistent object ID. Cross-process discovery also needs a fresh handle from an API such as window enumeration or lookup rather than a serialized old value.

What to check

Record the API that produced the HWND and the API that rejected it.
Check whether the owner thread destroyed or recreated the window before the failing call.
Treat a reused handle value as opaque; do not infer object identity from the number.
If the target is external, reacquire the handle immediately before the operation and account for the target process exiting.

This differs from ERROR_WINDOW_OF_OTHER_THREAD: the latter can describe a valid window whose thread ownership makes the requested operation invalid.

References

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