Proposing new arrow characters with Bidi_Mirrored=Yes

[Mark E. Shoulson]

My initial reaction on reading the subject was "*eyeroll* like we need 
MORE arrow characters!" But then again, there is some point to these 
arrows (sorry).  I do feel like there are already _so many_ arrow 
characters that duplicating all the ones with a horizontal component to 
have a mirrored version would be a bit much, but there does seem to be 
some utility in what is being proposed here.  Naturally, this makes me 
think, "well, how about we just make a _few_ such duplicates?" but 
that's a slippery slope and will only lead to people protesting "But 
there's a mirrored →, why can't I have a mirrored ⇰???"  Not sure what 
the best answer is.  (Unless maybe mirrored characters were a Bad Idea 
to start with?)

Here's a possibly disastrous idea: arrows mirror when they are within 
the domain of a Directional Override character (U+202D, U+202E).  This 
would entail creating a new category of character which is subject to 
this optional mirroring behavior, which then might be applied to other 
characters (hmm, like some emoji, to get people running to the left or 
something?) and I get the feeling that anything that touches the BiDi 
algorithm might just be asking for trouble.

A similar[ly bad] idea might be to have markup-type characters, 
something like <MIRRORED SELECTOR> or some such, to indicate that an 
attached character should be mirrored (or a pair of them that indicate 
direction).

I don't even want to know about handling this in TTB contexts...

~mark

On 4/8/25 10:34 AM, NeatNit via Unicode wrote:
> Hi, I hope this is the right place to bring this up. I could not find 
> any discussions on this other than the document I quote.
>
> Quick intro: characters with the property Bidi_Mirrored=Yes will be 
> visually mirrored within RTL text, such as Hebrew or Arabic. An easy 
> example is the Greater Than symbol: A>B and א>ב.
>
> Arrow characters do not have this property: A→B but א→ב.
>
> I've found this discrepancy mentioned in this document:
>
> https://www.unicode.org/L2/L2022/22026r-non-bidi-mirroring.pdf
>
>> In particular, arrow and arrow-like characters
>> each often has a mirror character. One could
>> argue that they should have had the
>> Bidi_Mirrored=Yes property value, but they
>> don’t, and cannot now get that.
> Even if it weren't for Unicode's stability policies, there are two 
> distinct usages of arrow symbols:
>
> To indicate directions, e.g. "Turn left (←) and then right (→)" - in 
> this case the arrow refers to the physical direction and should not be 
> mirrored in RTL. The existing arrow characters serve this purpose 
> well: "פנה שמאלה (←) ואז ימינה (→)‏"
>
> As an operator: "Convert A->B and assign C<-D" - in this case the 
> arrow direction should be mirrored if it appears in RTL text. 
> Currently this can only be emulated with ASCII "->" as I've just 
> demonstrated. Result: "המר א->ב וקבע ג<-ד".
>
> Therefore I think there should be new characters, "Forward Arrow" and 
> "Backward Arrow", to serve the latter case. They would use the same 
> glyphs as existing arrows, but have the Bidi_Mirrored=Yes property.
>
> Please let me know if this is likely to happen, and what I would have 
> to do to make a proper proposal. And if any of you are convinced 
> enough that you would like to make a proposal on my behalf, you are 
> welcome to do so!
>
> The same reasoning can be applied to many other characters besides 
> these basic arrows. At minimum, all arrow and arrow-like characters 
> should be included. I haven't made a thorough search to find all 
> affected characters, at least not yet.
>
> Note that some software, such as the Discourse forum software, convert 
> "->" to "→" in user content, obviously unaware of this issue. These 
> proposed bidi-mirrored arrow characters would be an appropriate 
> replacement in such cases. Today, that simple search-and-replace must 
> be replaced with parsing the text using the full Unicode Bidi 
> algorithm to select the correct arrow, and even then some cases would 
> be impossible to determine without knowing the base direction or more 
> context which is not always available.
>
> Awaiting your comments.
>
> Thanks,
> Nitai
>
On 4/8/25 10:34 AM, NeatNit via Unicode wrote:
> Hi, I hope this is the right place to bring this up. I could not find any discussions on this other than the document I quote.
>
> Quick intro: characters with the property Bidi_Mirrored=Yes will be visually mirrored within RTL text, such as Hebrew or Arabic. An easy example is the Greater Than symbol: A>B and א>ב.
>
> Arrow characters do not have this property: A→B but א→ב.
>
> I've found this discrepancy mentioned in this document:
>
> https://www.unicode.org/L2/L2022/22026r-non-bidi-mirroring.pdf
>
>> In particular, arrow and arrow-like characters
>> each often has a mirror character. One could
>> argue that they should have had the
>> Bidi_Mirrored=Yes property value, but they
>> don’t, and cannot now get that.
> Even if it weren't for Unicode's stability policies, there are two distinct usages of arrow symbols:
>
> To indicate directions, e.g. "Turn left (←) and then right (→)" - in this case the arrow refers to the physical direction and should not be mirrored in RTL. The existing arrow characters serve this purpose well: "פנה שמאלה (←) ואז ימינה (→)‏"
>
> As an operator: "Convert A->B and assign C<-D" - in this case the arrow direction should be mirrored if it appears in RTL text. Currently this can only be emulated with ASCII "->" as I've just demonstrated. Result: "המר א->ב וקבע ג<-ד".
>
> Therefore I think there should be new characters, "Forward Arrow" and "Backward Arrow", to serve the latter case. They would use the same glyphs as existing arrows, but have the Bidi_Mirrored=Yes property.
>
> Please let me know if this is likely to happen, and what I would have to do to make a proper proposal. And if any of you are convinced enough that you would like to make a proposal on my behalf, you are welcome to do so!
>
> The same reasoning can be applied to many other characters besides these basic arrows. At minimum, all arrow and arrow-like characters should be included. I haven't made a thorough search to find all affected characters, at least not yet.
>
> Note that some software, such as the Discourse forum software, convert "->" to "→" in user content, obviously unaware of this issue. These proposed bidi-mirrored arrow characters would be an appropriate replacement in such cases. Today, that simple search-and-replace must be replaced with parsing the text using the full Unicode Bidi algorithm to select the correct arrow, and even then some cases would be impossible to determine without knowing the base direction or more context which is not always available.
>
> Awaiting your comments.
>
> Thanks,
> Nitai
>