Get zoom level from the browser host instead

[merceyz]

Resolves #1778

• Get zoom level from the browser host instead of ZoomLevelProperty

[amaitland]

Is it safe to Wait for the task to execute? I really dislike Wait, I've seen far too many deadlocks

[merceyz]

In my tests it didn't deadlock, it can of course happen.

In my application (Offscreen processes doing work) I use Wait on JS execution and haven't seen a deadlock yet

EDIT:
I could make CefBrowserHostWrapper::GetZoomLevelOnUI() public, then the task wouldn't be needed

[amaitland]

I'm still not keen on this. It's also we would be blocking the UI thread.

[merceyz]

Another solution is to have the zoom commands send the new zoom value to all other browser instances on the same domain.

Though that wouldn't work if you were to open the page after the initial zoom as it would show 0 no matter what the value is

[amaitland]

Is a fix actually required? The simplest workaround is to isolate each browser and let them zoom independently.

[merceyz]

If one wants the domain shared zoom to work properly yes, if not, no.

we would be blocking the UI thread.

Waiting for GetZoomLevelAsync to finish took 00:00:00.000473

[amaitland]

How about providing an example of your idea as an attached property? Get some real world feedback. There is nothing stopping a user from implementing their own solution.

[merceyz]

How about providing an example of your idea as an attached property?

I'm not quite sure what you mean, could you attempt to clarify?

[amaitland]

Using this in conjunction with my proposed fix for #1915 causes a deadlock. The simplest fix may well be updating ZoomLevelProperty when the browser becomes visible. Something like:

if(isVisible)
{
	browser.GetHost().GetZoomLevelAsync().ContinueWith(previous =>
	{
		if (!IsDisposed)
		{
			SetCurrentValue(ZoomLevelProperty, previous.Result);
		}
	}, TaskContinuationOptions.OnlyOnRanToCompletion);
}

The ZoomReset issue still needs to be addressed, changing ZoomLevelProperty from using the property changed to the CoerceValueCallback is probably the easiest fix (always called even if the values are the same).

EDIT:
I could make CefBrowserHostWrapper::GetZoomLevelOnUI() public, then the task wouldn't be needed

Adding IBrowserHost.GetZoomLevel is fine with me. I think the GetZoomLevelOnUI method should be private with a new public method being added that includes the standard disposed checks. You would only be able to use that version when MultiThreadedMessageLoop = false though.

[merceyz]

I don't have any plans to do anything with this PR, so i'm closing this.