poc: don't write empty nodes

[Its-Just-Nans]

This is more like a Proof of concept about not writing nodes.

But it's very bad great for performance

let mut fake_xml = XmlWriter::new(Options::default());
write_group_element(g, is_clip_path, opt, &mut fake_xml);
let fake_xml_str = fake_xml.end_document();
if fake_xml_str != "<g/>\n" {
    write_group_element(g, is_clip_path, opt, xml);
}

[Its-Just-Nans]

Any others ideas to not write empty nodes ?

[Its-Just-Nans]

I'm also thinking on "start_svg_element" only when necessary, ie

Before

xml.start_svg_element(EId::G);
if !g.id.is_empty() {
    xml.write_id_attribute(&g.id, opt);
};
// ...
xml.end_element();

After

let mut element_started = false;
if !g.id.is_empty() {
    xml.start_svg_element(EId::G);
    element_started = true;
    xml.write_id_attribute(&g.id, opt);
};

// ...
if element_started {
    xml.end_element();
}

[Its-Just-Nans]

Hi @LaurenzV pinging you for question

Do you think the second option ("after") is suitable?

[LaurenzV]

I'm not sure... But I can't say I'm a fan, to be honest. I'll try to think about it a bit more when I find some time.

[LaurenzV]

Probably there should be some method that based on the group node checks whether it will be empty, and then only do the check once. Otherwise, we would have to do the check every time we write a new attribute.

[Its-Just-Nans]

I'm not sure... But I can't say I'm a fan, to be honest. I'll try to think about it a bit more when I find some time.

I implemented the lazy writer version. What do you think about it?