Flattened Text Group always has the identity abs_transform

resvg version: 0.41

The group returned by Text::flattened always has the default abs_transform. usvg::text::flatten::flatten does not propagate the containing Text's abs_transform.

This does not affect resvg since resvg::render::render_group re-calculates abs_transform (Line 56).

https://github.com/RazrFalcon/resvg/blob/b908baf1a2b7bd724a7896f29bf56e2d666b87ff/crates/resvg/src/render.rs#L50-L61

All tests pass even after modifying usvg::text::flatten::flatten as follows.

        if let Some(path) = span_builder.finish().and_then(|p| {
            Path::new(
                String::new(),
                span.visibility,
                span.fill.clone(),
                span.stroke.clone(),
                span.paint_order,
                rendering_mode,
                Arc::new(p),
+++             text.abs_transform,
---             Transform::default(),
            )
        }) {
            stroke_bbox = stroke_bbox.expand(path.stroke_bounding_box());
            new_paths.push(path);
        }

        if let Some(path) = span.line_through.as_ref() {
            stroke_bbox = stroke_bbox.expand(path.data.bounds());
            let mut path = path.clone();
            path.rendering_mode = rendering_mode;
            new_paths.push(path);
        }
    }

    let mut group = Group {
        id: text.id.clone(),
+++     abs_transform: text.abs_transform,
        ..Group::empty()
    };

Is it intended to re-calculate abs_transform in resvg and keep abs_transform in Text::flattened default?

Start in usvg::text::flatten::flatten and compare its construction of flattened paths and groups with resvg::render::render_group, referenced in the issue. Run the existing test suite and add or update coverage for a Text with a non-default abs_transform; done means the intended transform is preserved consistently without changing existing rendering behavior.