Re: [PATCH] Highlight ANSI sequences in the whole buffer (was [PATCH] ANSI color on example blocks and fixed width elements)

[Nathaniel Nicandro <nathanielnicandro@gmail.com>]

Ihor Radchenko <yantar92@posteo.net> writes:

> Nathaniel Nicandro <nathanielnicandro@gmail.com> writes:
>
>>> 1. Do not allow ANSI sequences to intersect markup boundaries of the
>>>    same AST depth:
>>>    *bold <ANSI>* plain text <ANSI> should not trigger fontification
>>>    *bold <ANSI> /italic/ <ANSI>* should trigger
>>>    plain text <ANSI> *bold* plain text <ANSI> also should
>>
>> Just to make sure I'm getting you right.  You're saying that
>> fontification should trigger if the sequences live in the same
>> org-element-context?
>
>> What about cases like:
>>
>>     *<ANSI>bold* plain text <ANSI>
>>     plain <ANSI>text *bold <ANSI>* paragraph end
>>
>> In the first case, should only "bold" be fontified? Since the sequence
>> lives in the bold context.
>
>> In the second, should only "text"? Since the sequence lives at a higher
>> depth (the paragraph context, compared to the bold context). Or should
>> it be that the fontification should extend to the end of the paragraph
>> because the sequence lives at a higher depth?
>
> I completely missed the point that <ANSI> codes are not <open ... close>
> pairs, but switches; this is completely different from Org syntax.
>
> So, let me re-consider where <ANSI> codes are likely to be used in
> practice:
>
> 1. Inside shell code blocks (src-block element)
> 2. Inside results of evaluation, which are usually fixed-width element,
>    but might also be example-block, export-block, drawer, table, or
>    other element.
> 3. Inside shell inline code blocks (inline-src-block object)
> 4. Inside results of evaluation of an inline code block - usually
>    code/verbatim markup.
>
> I think that the most reasonable approach to fontify ANSI sequences will
> be the following:
>
> 1. We will consider ANSI within (a) all greater elements and lesser
>    elements that have RESULTS affiliated keyword (indicating that they
>    are result of code block evaluation); (b) otherwise, just lesser
>    elements, like paragraph, src block, example block, export block,
>    etc., but _not_ tables (c) otherwise, within verbatim-like objects,
>    like code, export-snippet, inline-src-block, table-cell, verbatim.
>
>    The three groups above should be declared via variables, so that
>    users can tweak them as necessary.
>
> 2. If ANSI sequence is encountered inside a verbatim-like object and we
>    did not see any ANSI sequences within parent element or greater
>    element, limit ANSI triggers to the current object.
>
>    Example:
>
>    #+RESULTS:
>    Lorem upsum =<ANSI>valor=. Some more text.
>
>    (only "valor" will be affected)
>
> 3. If the first ANSI sequence is encountered inside element and outside
>    verbatim-like object, the rest of the element is affected, including
>    all the objects.
>
>    Example:
>
>    #+RESULTS:
>    <ANSI>Lorem upsum =<ANSI>valor=. Some more text.
>
>    (the first ANSI affects everything, including verbatim; the second
>    ANSI also affects everything)
>
> 4. If the first ANSI sequence is encountered inside greater element with
>    RESULTS affiliated keyword, all the lesser elements inside will be
>    affected.
>
>    Example:
>
>    #+RESULTS:
>    :drawer:
>    <ANSI>Lorem upsum =valor=. Some more text.
>
>    Another paragraph inside drawer.
>    :end:
>
>    (everything down to :end: is affected)
>
>    or
>
>    #+RESULTS:
>    - <ANSI>list
>    - one
>    - two
>    - three
>
>    (everything is affected down to the end of the list)
>
> Does it make sense?
>

Sounds good to me.

>>>> +        (cl-letf (((symbol-function #'delete-region)
>>>> +                   (lambda (beg end)
>>>> +                     (add-text-properties beg end '(invisible t))))
>>>
>>> This is fragile and relies on internal implementation details of
>>> ansi-color.el. Is there another way?
>>
>> Since the context in which the sequences live in need to be considered,
>> it doesn't look like ansi-color-apply-on-region can be used any more
>> since it isn't aware of Org objects.
>>
>> I've come up with a function that calculates the highlightable regions
>> (considering contexts) and fontifies them, but it requires the use of
>> private functions from ansi-color. Specifically
>> ansi-color--face-vec-face, ansi-color--update-face-vec, and
>> ansi-color--code-as-hex (used internally by ansi-color--face-vec-face).
>> Does it make sense to copy over these functions into Org for the
>> purposes of handling ANSI escapes? There would be some backward
>> compatibility issues, e.g. ansi-color only started using faces as colors
>> in Emacs 28.
>
> If we really need to, we can propose an extension of
> ansi-color-apply-on-region upstream for Emacs itself.


-- 
Nathaniel