Follow-up: How to deal with existing <title> elements in SVG (icons) in function image_add_svg_attributes()

[indigoxela]

Description of the task

In a code comment on backdrop/backdrop#4797 a request has been made to take care of existing titles in SVG elements:

I realize that this is not part of the scope here, but is this whole code here making an assumption that the given svg does not have an existing <title>? 🤔

^^ raised by @klonos

This concern's valid - given, this function is available for other SVG types, not only icons (which usually don't have any title child elements).

But as it is/was out of scope in #6613, and desired behavior's still to determine - and to not block the bugfix - we decided to discuss this in a follow-up.

Additional information

• Function image_add_svg_attributes() has been added in Backdrop 1.28.0, core/includes/image.inc
• Its current purpose and only usage is to deal with alt attributes in SVG icons, core/includes/icon.inc
• But the function name suggests, that there could be additional use cases

To have something to play with:

$svg_content = '<svg width="400" height="400" version="1.1" viewBox="0 0 400 400" xmlns="http://www.w3.org/2000/svg"><rect width="400" height="400" fill="#93a7ac"/></svg>';

And now with a title child:

$svg_content = '<svg width="400" height="400" version="1.1" viewBox="0 0 400 400" xmlns="http://www.w3.org/2000/svg"><title>Hello</title><rect width="400" height="400" fill="#93a7ac"/></svg>';

Now, if calling image_add_svg_attributes() like that, with alt set to an empty string - what should happen?
And what should happen, if it's a non-empty string?

$attributes = array('alt' => 'Hello');
$foo = image_add_svg_attributes($svg_content, $attributes);

And for completeness: what are the use-cases to deal with?