UIAutomation GetTopLevelWindowByName - c++

Question

Trying to follow the example found here:
https://learn.microsoft.com/en-us/windows/win32/winauto/uiauto-howto-find-ui-elements
WCHAR window_name[250] = L"tools";
IUIAutomationElement *window = GetTopLevelWindowByName(window_name);
IUIAutomationElement* GetTopLevelWindowByName(LPWSTR windowName)
{
if (windowName == NULL)
return NULL;
CComPtr<IUIAutomation> g_pAutomation;
VARIANT varProp;
varProp.vt = VT_BSTR;
varProp.bstrVal = SysAllocString(windowName);
if (varProp.bstrVal == NULL)
return NULL;
IUIAutomationElement* pRoot = NULL;
IUIAutomationElement* pFound = NULL;
IUIAutomationCondition* pCondition = NULL;
// Get the desktop element.
HRESULT hr = g_pAutomation->GetRootElement(&pRoot);
if (FAILED(hr) || pRoot == NULL)
goto cleanup;
// Get a top-level element by name, such as "Program Manager"
hr = g_pAutomation->CreatePropertyCondition(UIA_NamePropertyId, varProp, &pCondition);
if (FAILED(hr))
goto cleanup;
pRoot->FindFirst(TreeScope_Children, pCondition, &pFound);
cleanup:
if (pRoot != NULL)
pRoot->Release();
if (pCondition != NULL)
pCondition->Release();
VariantClear(&varProp);
return pFound;
}
But the application is crashing at the line HRESULT hr = g_pAutomation->GetRootElement(&pRoot);
With the error:
File: C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\VC\Tools\MSVC\14.28.29333\atlmfc\include\atlcomcli.h
Line: 204
Expression: p!=0
What I'm trying is, learn how to iterate through the elements like name, description, etc of the given window.

Answer 1

You must create g_pAutomation, it cannot be null, for example like this:
CoCreateInstance(
__uuidof(CUIAutomation),
NULL,
CLSCTX_ALL,
_uuidof(IUIAutomation),
(void**)&g_pAutomation);