Material-ui: Arrow Icons are not flipped in RTL

[AhmedSayed77]

I followed the steps in the website to create an Arabic web application. Everything works great until I use any of the (directional) arrow icons.

• [X] The issue is present in the latest release.
• [X] I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

The back arrow still points left, and the forward arrows still points right.

Expected Behavior 🤔

They should be flipped

Steps to Reproduce 🕹

reproduction

Steps:

1. Follow the steps in the website to support RTL
2. use any directional arrow icon

Your Environment 🌎

| Tech | Version |
| ----------- | ------- |
| Material-UI | v4.11.0 |
| React | v16.9.49 |
| Browser | Firefox 80.0.1 (64-bit)|
| TypeScript | v3.9.7 |
| Material-UI Icons | v4.9.1 |

[mbrookes]

The React SVG icon component names describe the icons as produced by Google, and assume forward is to the right, and back is to the left.

You can use import aliases to rename the imports.

[AhmedSayed77]

@mbrookes but the arrows will not be flipped automatically if the direction is changed dynamically. all the styles of the page will be flipped except for the arrow, which will need to be handled in userland.

And according to the specs the arrows should be flipped

Edit: Sorry that the link is not to the specific paragraph. It's titled "When to mirror" and the examples used are the back and forward arrows

[oliviertassinari]

@AhmedSayed77 See an example on how to do such:

https://github.com/mui-org/material-ui/blob/0acf4de98e45b0fd481f36a30ec3e66bed735fce/packages/material-ui/src/TablePagination/TablePaginationActions.js#L65

RTL isn't very frequently used by the community. If we can trust the npm downloads, it's used by less than 2% of the developers we reach. This market share influences the tradeoffs we are willing to make.

[mbrookes]

@mbrookes but the arrows will not be flipped automatically if the direction is changed dynamically.

Apologies, it wasn't obvious from your issue description that you needed to support both. In addition to @oliviertassinari's suggestion, you could perhaps alternatively try applying transform: flipX(-1) in conjunction with the :dir(rtl) pseudo selector.

[AhmedSayed77]

@oliviertassinari @mbrookes Thanks for your time

[ryancogswell]

Here's a related StackOverflow question: https://stackoverflow.com/questions/64307165/material-ui-icons-wont-flip-when-i-change-to-rtl/64307950#64307950.

In my answer I suggested that this could be handled in the theme with:

overrides: {
  MuiSvgIcon: {
    root: {
      "body[dir=rtl] &": {
        transform: "scaleX(-1)"
      }
    }
  }
}

I have a little concern about this potentially conflicting with usages of transform within Material-UI, but the two main cases I'm aware of (AccordionSummary expanded styles and SelectInput iconOpen styles) seemed to still work fine. We could potentially add something along these lines to the RTL documentation.

[oliviertassinari]

@ryancogswell What's the impact on the components that already handle RTL for the icons, like the TablePagination?

[ryancogswell]

What's the impact on the components that already handle RTL for the icons, like the TablePagination?

@oliviertassinari The cases of this I found just now are in TablePaginationActions and PaginationItem. There are some additional cases in examples in the docs, but these two were the only cases I found in the component code (though I'm not confident that my search would have found all cases). It would definitely have an undesirable effect in these cases since it would flip an already flipped icon.

One possibility would be to add transform: theme.direction === 'rtl' ? 'scaleX(-1)' : undefined, directly into SvgIcon and remove all the code for swapping icons. This would be a breaking change, since it would mean that any similar icon swapping in user code would need to be removed, but I think people would welcome this being handled automatically. The application I work on deals with about 40 languages including Arabic and Hebrew, so I have some experience with this in our application.

[oliviertassinari]

Is this a behavior we want by default? on YouTube, I have only seen one icon swapped.

[ryancogswell]

Is this a behavior we want by default?

Looking at some of these examples, probably not. For most icons, flipping is neither necessary nor harmful, but the "Help" icon would be one that shouldn't flip and same with "Paid memberships" and "YouTube Studio". Probably best for users to deal with on a case-by-case basis since it depends on the nature of the icon whether flipping is appropriate.

[oliviertassinari]

Maybe we could add a prop for that? https://fontawesome.com/how-to-use/on-the-web/styling/power-transforms

[ryancogswell]

Maybe we could add a prop for that?

Yes, I think that would be nice. Perhaps a flipForRtl boolean prop?

[AhmedSayed77]

It should be the default behaviour, but only for the directional icons - back and forward, not left, right, up or down

[ryancogswell]

It should be the default behaviour, but only for the directional icons - back and forward, not left, right, up or down

@AhmedSayed77 I don't think it would be practical (from a maintenance standpoint) to change the default behavior icon-by-icon and it would be difficult to document this clearly. I think people choose icons primarily by how they look with less concern about how they are named -- the name just helps people find the icon. Icons with names including "left" and "right" could easily be used for "back" and "forward" purposes and vice versa. It would be very confusing for similar icons to behave differently in this regard.

If we add a flipForRtl prop, it makes it very easy for developers to control this explicitly in their own code. The prop could also be used internally within Material-UI components such as TablePaginationActions and PaginationItem rather than swapping in different icons for rtl.

[AhmedSayed77]

I'm expressing what I think is best from a DX standpoint. Left always means left, but back doesn't always mean left. Thank god we only have two setting: ltr and rtl. So handling it case by case makes sense, and shouldn't be difficult, since there are only 2 settings. How to do it in a maintainable way, is our job as developers, that's what we do for a living. Of course I'm not a maintainer, and I don't have the right to tell you what to do, or how to do it. If you decide that you will leave it as it is, and let the users handle it, I can only thank you for time, and your work, that I acknowledge I'm using for free - and I'm sincerely thankful to every one of you. But I felt that you were caught up discussing the issue from maintenance standpoint, but didn't think of what's intuitive for the library users. Yes, as an arabic speaker, I expect "back" and "front' arrows to be flipped in an arabic website, but I don't expect play buttons, logos, or other icons to be flipped too.

[ryancogswell]

Left always means left, but back doesn't always mean left.

@AhmedSayed77 My point is that from a DX standpoint, developers will use ArrowLeft and ArrowBack for overlapping purposes (largely choosing based on aesthetics, not name) and I don't think it would be intuitive for them to behave differently with regard to whether they automatically flip. For instance, TablePaginationActions uses KeyboardArrowLeft and KeyboardArrowRight for "back" and "forward" purposes. In this case, "left" doesn't mean "left", it means "back".

[AhmedSayed77]

Maybe if they knew that back arrow and front arrow handles the direction, they would've used it, instead of handling it themselves, while using ArrowLeft and ArrowRight? I don't want to be insistent, I really don't think I can add anything to what I've said before. Do what you think is best for you and your users, and after all, handling it in userland is not too hard anyways