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IsWindowVisible() may produce an error#2171

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Enyium wants to merge 1 commit intoMicrosoftDocs:docsfrom
Enyium:fix-iswndvisible
Open

IsWindowVisible() may produce an error#2171
Enyium wants to merge 1 commit intoMicrosoftDocs:docsfrom
Enyium:fix-iswndvisible

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@Enyium Enyium commented Feb 1, 2026

I was hesitant to commit the following text, which was based on tests, because it may sound like an unauthorized contract:

To be able to tell an absent WS_VISIBLE style apart from an error condition and retrieve extended error information, call SetLastError(ERROR_SUCCESS) in preparation to IsWindowVisible, and finally GetLastError.

(As Markdown) 
To be able to tell an absent <b>WS_VISIBLE</b> style apart from an error condition and retrieve extended error information, call <b><a href="/windows/win32/api/errhandlingapi/nf-errhandlingapi-setlasterror">SetLastError(ERROR_SUCCESS)</a></b> in preparation to <b>IsWindowVisible</b>, and finally <b><a href="/windows/win32/api/errhandlingapi/nf-errhandlingapi-getlasterror">GetLastError</a></b>.

Or, a bit stronger:

To get extended error information, call GetLastError. To be able to tell an absent WS_VISIBLE style apart from an error condition, call SetLastError(ERROR_SUCCESS) in preparation to IsWindowVisible.

(As Markdown) 
To get extended error information, call <b><a href="/windows/win32/api/errhandlingapi/nf-errhandlingapi-getlasterror">GetLastError</a></b>. To be able to tell an absent <b>WS_VISIBLE</b> style apart from an error condition, call <b><a href="/windows/win32/api/errhandlingapi/nf-errhandlingapi-setlasterror">SetLastError(ERROR_SUCCESS)</a></b> in preparation to <b>IsWindowVisible</b>.

Would it be okay to use one of those texts as the second paragraph under the "Return value" heading?

Tests I did on Windows 11 Home 24H2 (in another language, from memory):

SetLastError(ERROR_SUCCESS);
isVisible = IsWindowVisible((HWND)123);  // Invalid handle.
if (!isVisible) {
    DWORD lastError = GetLastError();
    // `lastError` is `ERROR_INVALID_WINDOW_HANDLE`.
}

///////////////////////////////////////

SetLastError(123);
isVisible = IsWindowVisible(validHwnd);
if (!isVisible) {
    DWORD lastError = GetLastError();
    // `lastError` is 123. So, preparation `SetLastError(ERROR_SUCCESS)` is needed.
}

@Enyium
IsWindowVisible() may produce an error.
8de4a70 
Passing in garbage makes `GetLastError()` return `ERROR_INVALID_WINDOW_HANDLE`.
@prmerger-automator prmerger-automator bot requested a review from jwmsft February 1, 2026 18:05
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prmerger-automator bot commented Feb 1, 2026

@Enyium : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

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