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

[Ihor Radchenko <yantar92@posteo.net>]

gerard.vermeulen@posteo.net writes:

> I have been trying to export SVG images having links to CSS from Org to 
> HTML
> and I have found that the this CSS is not active in Firefox (only 
> browser I tried).
>
> I have found that the CCS is only active under two conditions:
> 1. The HTML page should manage the CSS that the SVG image links to.
> 2. The SVG image should be embedded in the HTML page.

CCing Timothy, the maintainer.

Also, does the above mean that Firefox does not support custom CSS user
stylesheets? What am I missing?

> I wrote an ox-html derived export backend to embed SVG images:
> https://forge.chapril.org/gav451/emacs.d/src/branch/main/site-lisp/ox-my-html/ox-my-html.el
> and merged the SVG embedding functionality into ox-html.el leading to 
> the
> attached patch.

Thanks! I will provide high-level comments from general ox.el
perspective.

> +    (:html-embed-svg-excludes "HTML_EMBED_SVG_EXCLUDES" nil
> +                              org-html-embed-svg-excludes split)
> +    (:html-embed-svg-includes "HTML_EMBED_SVG_INCLUDES" nil
> +                              org-html-embed-svg-includes split)

This is awkward. To do per-image export adjustments, we usually use
export attributes (#+ATTR_HTML: ...). And why "split"?

> +    (:with-html-svg-embedding nil "html-embed-svg" org-html-embed-svg)

We have :html-inline-images. Maybe better :html-embed-svg ?

> +(defcustom org-html-embed-svg nil
> ...
> +  :version "30.0"

We do not use :version tag. Please use :package-version.
See Elisp manual section "15.1 Common Item Keywords".

Also, maybe instead of t/nil boolean values here, we may allow the value
to be a list of regular expressions or a string representing regular
expression. This will allow what you are trying to do with
HTML_EMBED_SVG_INCLUDES. The list elements might also be (not "..."),
replicating HTML_EMBED_SVG_EXLCUDES.

Even more generally, we may turn this into HTML_EMBED_IMAGES and embed
all the images (possibly filtered by regexp). This will be slightly
beyond the scope of this patch though.

> +(defun org-html--embed-svg-p (link path info)
> +  "Check whether LINK and INFO specify to embed the SVG file named PATH.
> +LINK must have no contents and link to an SVG file.  INFO may contain
> +lists of SVG files to include in and/or to exclude from embedding."
> +  (and (not (org-element-contents link))

Please use `org-export-inline-image-p'.

> +(defun org-html-svg-contents (path)
> +  "Return the SVG contents of the file named PATH."
> +  (with-temp-buffer
> +    (insert-file-contents path)
> +    ;; Delete text preceding something starting as an SVG root element.
> +    ;; The intent is to remove XML declarations (and XML comments).
> +    ;; This breaks in case of a preceding XML comment with <svg inside
> +    ;; or a preceding XML element with an SVG element inside.
> +    ;; See https://emacs.stackexchange.com/a/57433 for the original code.

But the original code is different, no?

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>