Re: [PATCH] ox-html.el: add option to embed SVG for CSS support in SVG

[gerard.vermeulen@posteo.net]

On 15.06.2023 22:51, Ihor Radchenko wrote:
> gerard.vermeulen@posteo.net writes:
> 
>> On 07.06.2023 19:57, Ihor Radchenko wrote:
> I am not expert in html. Maybe someone else (Timothy?) can chime in.
> 
> That said, I do not see why we cannot offer <object> strategy as an
> option regardless whether is can solve the problem with CSS.
> 
>> ;; For each SVG image during HTML export:
>> ;; 1. It checks `svg-as-object' and "image in-lining" whether to
>> ;;    embed the SVG image in an <object> tag.
>> ;; 2. If not, it checks `svg-inclusion' and "image in-lining"
>> ;;    whether to copy the SVG contents to the HTML output.
>> ;; 3. If not, it falls back to checking "image in-lining" whether to
>> ;;    embed the SVG image in an <img> tag (as any other image type).
>> ;; 4. It is possible to set `svg-as-object' and/or `svg-inclusion':
>> ;;    - For each SVG link by means of "#+ATTR_HTML: :svg-as-object t"
>> ;;      or "#+ATTR_HTML: :svg-inclusion t".
>> ;;    - Within file scope by means of "#+OPTIONS: svg-as-object:t" or
>> ;;      "#+OPTIONS: svg-inclusion:t".
>> ;;    - Within toplevel scope by means of the options
>> ;;      `org-html-svg-as-object' or `org-html-svg-inclusion'.
> 
> I think you missed `org-html-inline-image-rules' where users can
> include/exclude svg images from inlining.

The term "image in-lining" is a very terse description of what my code 
does.

In case of rules 1, 2, and 3 above: the code takes into account the two
relevant options `org-html-inline-image' and 
`org-html-inline-image-rules'
to decide  whether the image would be in-lined in an <img> tag.

For rule 1 above: in case `svg-as-object' is also true, the code 
in-lines
the image in an <object> tag instead of an <img> tag and returns
the <object> tag. In case `svg-as-object' is nil, apply rule 2.

For rule 2 above: in case `svg-inclusion' is also true,  return the SVG
contents as a result. In case `svg-inclusion' is nil, apply rule 3.

Rule 3 is applied by the normal "Image file" handling code from
org-html-link in ox-html which handles `org-html-image-inline-rules',
but my code for rules 1 and 2 do too.

My clone of org-html-link is a copy with the exception that I
added 4 lines of code (and 2 lines of comments) to implement
the rules 1 and 2 (but we should not implement rule 2).

Before going ahead with a patch to in-line images in <object> tags,
there remains the question of how to make those tags behave as
much as possible as <img> tags.  My knowledge of HTML is very thin
and Javascript even worse.

Best regards -- Gerard