How to specify maxLength on the text size while getting the text from text box supporting ValuePattern?

Ashwin Mittal 5

I'm using the IUIAutomation textRange GetText method if my text box supports the text pattern. There, I can specify the maxLength as given here: https://video2.skills-academy.com/en-us/windows/win32/api/uiautomationclient/nf-uiautomationclient-iuiautomationtextrange-gettext.

However, if a text box doesn't support TextPattern but ValuePattern, then I'm using IValueProvider. Unfortunately, this doesn't allow specifying the limit on the text to be retrieved.

    IValueProvider* pValueProvider;
    hr = pFocusedElement->GetCurrentPattern(UIA_ValuePatternId, reinterpret_cast<IUnknown**> (&pValueProvider));
    if (S_OK != hr)
    {
        printf("GetCurrentPattern error: %d\n", GetLastError());
        return FALSE;
    }

    BSTR text;
    hr = pValueProvider->get_Value(&text);
    if (S_OK != hr)
    {
        printf("get_Value error: %d\n", GetLastError());
        return FALSE;
    }
    wprintf(L"%s\n", text);
    SysFreeString(text);

I want to set the limit because I want to optimize my code and avoid spending too much time retrieving text from the box.

RLWA32 42,286 Reputation points

2024-06-22T09:46:42.7666667+00:00

I can understand why setting a limit makes sense for multi-line controls when retrieving text with IUIAutomationTextRange::GetText. On the other hand, since IValueProvider or IUIAutomationValuePattern is used with single-line controls perhaps this limit was deemed unnecessary.
Ashwin Mittal 5 Reputation points

2024-06-22T10:11:58.45+00:00

However, a text box supporting the ValuePattern can allow a large amount of text as well, which is why I think there should be a way to limit it while extracting it.
RLWA32 42,286 Reputation points

2024-06-22T10:30:38.4566667+00:00

Well, I don't see any simple, documented way to set the limit that you want. You can always make your suggestion to Microsoft that's such a limit should be provided by UI automation. Or maybe create a custom control and implement your own provider.
RLWA32 42,286 Reputation points

2024-06-22T12:37:26.5233333+00:00

By the way, if the automation element from which you want to retrieve text supports UIA_NativeWindowHandlePropertyId you could retrieve the HWND and send the window a WM_GETTEXT message which allows you to specify the number of characters to be returned.
Xiaopo Yang - MSFT 12,071 Reputation points Microsoft Vendor

2024-06-24T05:46:29.43+00:00

It is mentioned by IValueProvider::get_Value.

IValueProvider does not support the retrieval of formatting information or substring values. Implement ITextProvider in these scenarios.

Single-line edit controls support programmatic access to their contents by implementing IValueProvider (in addition to ITextProvider). However, multi-line edit controls do not implement IValueProvider.

Also see Text Control Type

A text control never supports the Value control pattern. If the text is editable, it is the Edit control type.

So,

However, if a text box doesn't support TextPattern but ValuePattern,...

It could be a design issue of your text box.

Share via

How to specify maxLength on the text size while getting the text from text box supporting ValuePattern?