Check harder before enabling Accessibility support on Win32

[anaisbetts]

Fixes #7208

TODO:

• Verify with a touch screen
• Verify that NVDA still works

[kevinsawicki]

Just curious, what is this include used for?

[anaisbetts]

@kevinsawicki Without it, the next header barfs a thousand lines of COM nonsense

[kevinsawicki]

On this branch (compared with master), I'm not seeing the 'accessibility-support-changed' event fire when you launch NVDA after launching your app:

To reproduce:

• Launch Electron
• Open the dev tools and run the following

require('electron').remote.app.on('accessibility-support-changed', function(e, axs) {console.log('changed', axs)})

• Launch NVDA
• 'changed true` is not logged on this branch (it is logged on master)

Should the checked_for_a11y_support_ = true; be done after the if (obj_id != OBJID_CLIENT) { check? If I move it below that check, then I do see it fire.

[anaisbetts]

We can do that, I was trying to make this as efficient as possible but I didn't know we had an event for this, 👍

[kevinsawicki]

This should be initialized to false in the constructor like enabled_a11y_support_ is in atom/browser/native_window_views.cc

[kevinsawicki]

I think this variable can be removed now, it looks like it is no longer read anywhere.

[anaisbetts]

👍

[kevinsawicki]

Thanks so much for fixing this 💻 🔍

[miniak]

@paulcbetts, why didn't you do it like this?

static bool IsScreenReaderActive()
{
  UINT screenReader = 0;
  SystemParametersInfo(SPI_GETSCREENREADER, 0, &screenReader, 0);

  return screenReader && UiaClientsAreListening();
}

...
      if (obj_id == OBJID_CLIENT && IsScreenReaderActive()) {
...

That would be much cleaner.

[miniak]

@paulcbetts did you try running Electron first and then running the screen reader? You only check if it's running once.

[kevinsawicki]

did you try running Electron first and then running the screen reader?

I did try this and it worked as expected but I wasn't on a touch screen. I launched Electron, then opened NVDA, and saw the accessibility state changed event fire.

[miniak]

@kevinsawicki, I am experimenting with this. Looks like the whole WM_GETOBJECT handling code may not be even necessary. JAWS, NVDA and Window-Eyes trigger the accessible mode without that. Narrator and ZoomText only work if they were running before Electron was launched.

[miniak]

Also the accessibility-support-changed event should be fired when BrowserAccessibilityState::IsAccessibleBrowser() value changes, BrowserAccessibilityState::OnScreenReaderDetected() does not have to be called by Electron code (https://github.com/adobe/chromium/blob/cfe5bf0b51b1f6b9fe239c2a3c2f2364da9967d7/content/browser/renderer_host/render_widget_host_view_win.cc#L2307)

[miniak]

Unfortunately there is no notification for BrowserAccessibilityState::IsAccessibleBrowser() changes

[miniak]

Also, on my Windows 10 in Parallels on Mac, UiaClientsAreListening returns true even if I don't have any screen reader running.

[alexdima]

@paulcbetts Thank you very much for the fix! ❤️