Support nested SVG text spans

[rowland]

Problem

The current parser warns svg: <text>: nested text elements are unsupported and were skipped. This means SVGs using <tspan> or more structured text runs lose portions of their text.

What implementation would require

• Extend text parsing to preserve nested text nodes instead of flattening only direct character data.
• Add support for <tspan> as the first practical target, including inherited style, per-span x/y/dx/dy, and anchor behavior.
• Decide the minimum text layout subset we need now versus full SVG text semantics.
• Make renderer state changes safe across nested spans so fill/font changes do not leak.
• Add tests for multi-span text, partial style changes, and positioned tspans.

Workarounds

• Convert text to outlines for logo/branding assets.
• Export SVGs with simpler single-node text when text remains editable.
• Use plain <text> without nested spans in PDF-targeted assets.

[rowland]

Status audit (2026-08-14): this issue remains open. The original collectText path is still in place and skips every nested element under <text>, including the nested character data, while emitting the warning described above. The checked-in SVG corpus contains no <tspan> elements, so current corpus rendering does not exercise this gap.

Some renderer prerequisites have improved since the issue was filed: SVG text now has better font-family resolution/fallback, opacity and blend-mode handling, gradient fills, clip-path support, and injectable stylesheet rules. Those changes should make per-run styling safer to implement, but they do not add a nested text scene model or span layout.

A reasonable first milestone would be:

• preserve mixed direct text and <tspan> children in source order;
• inherit and override fill, opacity, font family/size/style/weight per span;
• support single-value x, y, dx, and dy on <tspan>;
• keep text-anchor defined at the containing <text> level initially;
• add focused tests for mixed text, style changes, positioned spans, and state restoration.

Character-position lists, rotate, advanced baseline properties, textLength/lengthAdjust, and full SVG whitespace semantics can remain explicitly out of scope for that first pass.