"Recently google gave a few devices the feature to cast your screen to chromecast, sadly opo isn't among the list.
But if you're rooted, you can do this mod and it will work, and it's pretty simple. You just have to trick the OS into thinking you have a nexus 5.
Edit the /system/build.prop
Find the line where says ro.product.device
Change "A0001" to "hammerhead" (without quotes)
Open your quick toggles, and press the cast screen button
Thanks in advance !
EDIT : Resolved , you can close this post , thanks.