[Dialog] Better mobile default margin?

When I set the dialog as fullWidth={true} I expect it to take whole screen up to maxWidth. On mobile, width is calculated as width: calc(100% - 96px);, the 96px coming from the rule just below margin: 48px;. So, it actually does not take full width and it just looks bad.

• This is not a v0.x issue.
• I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior 🤔

Current Behavior 😯

It takes width minus margin, which in the case is 48px at each side ( well, top and bottom as well, but that does not matter)

Steps to Reproduce 🕹

Link: to sandbox

Context 🔦

Just trying to have a full width feature to work properly. I did try to change the paperFullWidth: property, but that ends up changing the root element.

Your Environment 🌎

Tech	Version
Material-UI	v4.1.3
React	16.8.6
Browser	Firefox development latest
TypeScript
etc.

[vipertechofficial]

dialog: {
        [theme.breakpoints.down('sm')]: {
            "& .MuiDialog-container .MuiDialog-paper": {
                margin: "24px 0px",
                borderRadius: 0
            },
        }
    }

[m2mathew]

I made a dialog yesterday that looks like this on mobile.

I did it by passing down this prop to the Dialog component:

classes={{ paper: classes.dialogPaper }}

Which is applying this style from jss:

dialogPaper: {
  [theme.breakpoints.down(480)]: {
    margin: 24,
  },
},

It seems in line with what @BernardA is wanting. I am overriding the margin for the dialog on a smaller screen (he would want margin: 0, seemingly) and also using a maxWidth of xs for the dialog.

From the MUI Docs

fullWidth will cause the content inside the dialog to stretch to meet one of the enumerated maxWidth values (“xs”, “sm”, et al.). I find no confusion with the way that this API is named considering it matches the way that CSS works since those enumerations are stand-ins for real width values (300px, 440px, et all).

That being said, perhaps @oliviertassinari’s proposed wording update would help, too.