We will need this size value while composing MMS, so I query and store it at the message app start-up. Since the MMS composing is still pending, I wrap up this part into a function for the fallowing composing patch. We might be able to add some logic in window manager for bootstrap the message app with certain parameters, but I'd prefer to handle the MMS settings inside the app itself instead of system, thanks. @borjasalguero , do you have any suggestion about this issue?