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Incorrect resolved paragraph direction #163

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niello opened this issue Feb 26, 2022 · 4 comments · May be fixed by #164
Open

Incorrect resolved paragraph direction #163

niello opened this issue Feb 26, 2022 · 4 comments · May be fixed by #164
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@niello
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niello commented Feb 26, 2022 •
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libraqm/src/raqm.c

Lines 1417 to 1420 in ce67a59

if (par_type == FRIBIDI_PAR_LTR)
rq->resolved_dir = RAQM_DIRECTION_LTR;
else
rq->resolved_dir = RAQM_DIRECTION_RTL;

An assumption is made that everything that is not explicitly LTR is RTL. It fails for direction-neutral paragraphs (FRIBIDI_PAR_ON). This leads to strange results, e.g. a number in a separate paragraph in a completely LTR text is considered RTL.

I suggest to turn FRIBIDI_PAR_ON into RAQM_DIRECTION_DEFAULT, so users can treat it accordingly to their preference. This value should not have any side meaning anyway, e.g. checking whether layouting was performed by inspecting raqm_get_par_resolved_direction is definitely a bad practice.

This sould also be fixed for SheenBIDI but I can't make exact suggestions as I didn't work with it.
@niello niello changed the title Incorrect paragraph direction Incorrect resolved paragraph direction Feb 26, 2022
@niello niello linked a pull request Mar 6, 2022 that will close this issue
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@niello
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niello commented Mar 6, 2022

@khaledhosny , please look at the PR. The fix works perfectly in my case. Now all necessary info is provided to the library user code.

@khaledhosny
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I think the code is assuming par direction is explicitly set, which I think is one way to handle this. Am I right that you are using auto par dir?

@vorlov-playrix
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Yes, I want a multiline editbox to detect text direction per paragraph and align them correctly. Direction-neutral paragraphs are aligned as the above text. But this is only a practical example. The problem is conceptual - there are direction-neutral paragraphs (i.e. "111") and middleware should not suppose any strict direction for them. It should be handled in user code.

@khaledhosny
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I understand that, I was trying to figure out how the original code came to be like that, but it was definitely wrong. Now I need to make sure the SeenBiDi code is fixed the same way.

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Direction neutral paragraph support for Fribidi niello/libraqm
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@khaledhosny @niello @vorlov-playrix