[QGIS-Developer] [Qgis-user] Looking for assistance with fixing RTL label bugs

[Nyall Dawson]

Thanks for your insights Micha!

Unfortunately I can't solve this one given my lack of language
knowledge. I'll step aside and let a native RTL language developer
take over. I've introduced some tests in
https://github.com/qgis/QGIS/pull/57586 which could be a starting
point for someone.

Nyall

On Tue, 28 May 2024 at 19:13, Micha Silver <tsvibar at gmail.com> wrote:
>
>
> On 28/05/2024 11:34, Nyall Dawson wrote:
>
> Hi Micha,
>
>
> On Tue, 28 May 2024, 6:28 pm Micha Silver, <tsvibar at gmail.com> wrote
>>
>> Thanks for following up on this.
>>
>> The few details (that are mentioned in the issue tracker) that might help track down the root of the problem:
>>
>>
>> 1- There was no issue up to 3.28. The reports appeared only on 3.30 and above.
>>
>> 2- I'm pretty sure that it occurs only on Windows, and only Win 11. Just now checked again on my Debian machine, with 3.36, and the problem does not appear, and never has.
>>
>> 3- Somehow I think this might be a Qt problem. Do you know if there were any Qt changes in Win installs between 3.28 and 3.30.x?
>
>
> Actually, if it works on a given platform, it's by accident and not design 😁. There's no tests covering this and I don't think it's been actually thought out by design.
>
> So my questions related to high level design decisions, like:
>
> - should the switch to rtl layout determined by the content of a label alone? Or is it determined by the font choice? Or the users locale? Or should it be an explicit choice set per layer, so that the project will appear
>
> In my opinion, by the content alone. Not font choice since many fonts have glyphs in both RTL and LTR languages. Not user's locale, since a map can contain text in different RTL languages even if the locale LANG setting is Western LTR. Not by layer, since user's can have multiple text attributes with text in different languages in each.  In full featured word processors there is, of course, a button to choose text directionality on a per-paragraph level. But I don't think implementing that is required for map labels.
>
>
> identical when shared with a user using a different locale for their qgis?
> - how should mixed ltr and rtl string work? Should users be required to manually insert rtl / ltr unicode markers?
>
> Traditionally that has been handled by the underlying bidi library. All the problematic edge cases of (i.e. a period within a string of numbers should be LTR but a period at the end of RTL language string should be assumed to be at the end of the RTL string), are taken care of by that library. I'm pretty sure this was the case with <=3.28.x. I wouldn't expect users to know how to insert RTL unicode. We just switch the keyboard language.
>
>
> - how should rtl be handled with respect to multiline text alignment?
>
> Ideally, alignment (as opposed to RTL directionality) should be user configurable. I believe you have already done this with the legend that allows aligning legend items to the right or left.
>
> But, regarding map labels, a minimalist approach would be to always align RTL text to the right, and LTR text to the left. (Don't let "perfect be the enemy of good")
>
>
> - is rtl placement of characters determined by graphemes? Ie do we split the string to graphemes and then lay these out right to left? Or is it done on individual characters?
>
> Not sure I understand. But as above, the underlying bidi library should be handling the cases of individual characters that might be RTL in some cases, and LTR in others.
>
>
> Cheers
>
>
>
> Nyall
>>
>>
>> If I can be of any further help testing, let me know. i.e. I can update a colleague's machine, and prepare a very simple test project...
>>
>>
>> Best, Micha
>>
>>
>> On 28/05/2024 5:56, Nyall Dawson via QGIS-User wrote:
>>
>> Hi lists,
>>
>> I'm looking for some assistance in fixing the right-to-left labeling
>> issues described in https://github.com/qgis/QGIS/issues/54098 . While
>> I can fix the code issues, I don't have the linguistic understanding
>> to know how right-to-left text SHOULD behave in QGIS labels!
>>
>> Is there anyone out there from a RTL language background who can add
>> the missing information to the above ticket and help get this bug
>> fixed?
>>
>> Nyall
>> _______________________________________________
>> QGIS-User mailing list
>> QGIS-User at lists.osgeo.org
>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user
>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
>>
>> --
>> Micha Silver
>> Ben Gurion Univ.
>> Sde Boker, Remote Sensing Lab
>> cell: +972-523-665918
>
> --
> Micha Silver
> Ben Gurion Univ.
> Sde Boker, Remote Sensing Lab
> cell: +972-523-665918