Take screenshot and use it as texture using ScreenCapture

I need to take screenshot and hold it in memory so later I can serialise it in save file with all the other information I need to save. We’re using Unity 2019.3.0a8 and as documentation says for taking screenshots there is class ScreenCapture for which I wasn’t able to find any information except for Unity Scripting API. So I have two questions.

First, as documentation says I need to wait till the end of frame rendering and the proper way of doing so is (taken from ScreenCapture.CaptureScreenshotAsTexture)

`IEnumerator TakeScreenshot()
yield return new WaitForEndOfFrame();
var texture = ScreenCapture.CaptureScreenshotAsTexture();
// do something with texture

    // cleanup

However if I’m using yield return, I can’t have neither return value for the method nor ref parameter thus I can’t use the screenshot inside the method in which I call StartCoroutine(TakeScreenshot());. I was thinking of using async/await but it allows me to wait only for some amount of seconds and not exactly till the end of frame. How can I wait for end of frame rendering without using yield?

Second question here.

One way to solve the issue with returning values from Coroutines is passing a Callback to the Coroutine method.

The Callback can be called after the screenshot is taken, and receive the result as a Parameter.

For example:

 void HandleScreenshot()
     StartCoroutine(TakeScreenshot((result) => {
 IEnumerator TakeScreenShot(System.Action<ResultType> callback)
     yield return new WaitForEndOfFrame();
     var result = new ResultType(ScreenCapture.CaptureScreenshotAsTexture());

Don’t forget to destroy the texture aftwards.

I get this error that is a known bug but only has 2 upvotes:

Metal: GrabIntoRenderTexture mismatched grab pass: 80 / 70