[win] Chrome freezes (when accessibility is generated for large pages?)

[Carlos Lenz]

Hi,

I'm using CUIAutomation to extract minor data from Chrome's tool bar (not the page itself).

The problem is that once I try accessing anything but the window itself, if the page is large like https://chromium.googlesource.com/chromium/src/+/refs/heads/main/ui/accessibility/platform/ax_platform_node_win.cc, it takes a lot of time (4s) and all Chrome windows freeze after I try changing Chrome tabs. Sometimes the whole system also slows down.

After reading https://www.chromium.org/developers/design-documents/accessibility, my guess is that Accessibility is being generated for the entire page.

At the same time, I can inspect Chrome using Accessibility Insights for Windows and it works just fine. So there should be a way to avoid this problem.

- Is it a bug?

- Are there other APIs that I can use that avoid this problem?

Environment

Chrome: 92.0.4515.159 (64 bit)

Windows: 10.0.19043 Build 19043

CPU: i7-9750H

Memory: 32.0 GB

// VS 2017 Test Code:

#include <cassert>

#include <chrono>

#include <ios>

#include <iostream>

#include <windows.h>

#include <uiautomationclient.h>

#include <comutil.h>

#ifdef _DEBUG

# pragma comment(lib, "comsuppwd.lib")

#else

# pragma comment(lib, "comsuppw.lib")

#endif

# pragma comment(lib, "wbemuuid.lib")

int main()

{

HRESULT hr = CoInitialize(NULL);

assert(SUCCEEDED(hr));

IUIAutomation *pAutomation;

hr = CoCreateInstance(

__uuidof(CUIAutomation),

NULL,

CLSCTX_INPROC_SERVER,

__uuidof(IUIAutomation),

(void **)(&pAutomation)

);

assert(SUCCEEDED(hr));

std::cout << "Go to window..." << std::endl;

Sleep(2000);

HWND hWin = GetForegroundWindow();

assert(hWin != NULL);

std::cout << "Running..." << std::endl;

IUIAutomationElement *win;

hr = pAutomation->ElementFromHandle(hWin, &win);

assert(hWin != NULL);

VARIANT varCtrlL;

varCtrlL.vt = VT_BSTR;

varCtrlL.bstrVal = _com_util::ConvertStringToBSTR("Ctrl+L");

IUIAutomationCondition *ctrlLAccessKeyCondition = NULL;

hr = pAutomation->CreatePropertyCondition(UIA_AccessKeyPropertyId, varCtrlL, &ctrlLAccessKeyCondition);

assert(SUCCEEDED(hr));

IUIAutomationElement *address;

std::chrono::steady_clock::time_point before = std::chrono::steady_clock::now();

hr = win->FindFirst(

TreeScope_Descendants,

ctrlLAccessKeyCondition,

&address

);

std::chrono::steady_clock::time_point after = std::chrono::steady_clock::now();

std::cout << "Took "

<< (std::chrono::duration_cast<std::chrono::milliseconds>(after - before).count())

<< " ms"

<< std::endl;

assert(SUCCEEDED(hr));

}