Minimal SVG handling for the reflow ereader (#112). More...

#include <stddef.h>
#include <stdint.h>
#include "ra8_err.h"

Include dependency graph for reflow_svg.h:

This graph shows which files directly or indirectly include this file:

Functions
bool	ra8_svg_is_svg (const uint8_t *bytes, size_t len)
	Heuristically decide whether `bytes` are an SVG document.
ra8_err_t	ra8_svg_image_href (const uint8_t svg, size_t len, size_t out_off, size_t *out_len)
	Extract the href of a cover-wrapper <svg><image .../></svg>.
ra8_err_t	ra8_svg_size (const uint8_t svg, size_t len, int32_t out_w, int32_t *out_h)
	Report an SVG's intrinsic size (width/height, else viewBox dimensions).
ra8_err_t	ra8_svg_render (const uint8_t *svg, size_t len, int32_t x, int32_t y, int32_t w, int32_t h)
	Render an SVG's vector shapes into a box.

Detailed Description

Minimal SVG handling for the reflow ereader (#112).

A small, hand-written, zero-allocation SVG subset for the two forms that actually appear in EPUBs:

Cover wrappers – a <svg> whose only content is a single <image xlink:href="cover.jpg"/>. ra8_svg_image_href returns that href so the caller can decode the referenced raster through the existing ra8_img_decode_blit path (no new decoder needed).
Simple in-content vector graphics – <rect>, <circle>, <line>, <polygon> (scanline-filled), <polyline> (stroked), and <path> (filled; M/L/H/V/Z exact, the C/S/Q/T Bezier curves and the A elliptical arc flattened to line segments), with solid fill / stroke. A A full 2x3 affine transform= (translate / scale / rotate / skewX / skewY / matrix) – on a shape or a <g> group (nested, bounded depth) – repositions, resizes, rotates, and shears the result; axis-aligned shapes keep the exact ra8_gfx fast-path while rotated / sheared shapes are mapped through the affine and scanline-polygon-filled. ra8_svg_render maps them from the SVG viewBox (or width/height) into a caller box and draws them through the bound ra8_gfx framebuffer.

Out of scope (documented limitations, tracked as follow-ups): gradient fills (linearGradient / radialGradient), opacity, CSS styling, stroke width, and fractional coordinates (truncated to integers).

The parser is pure string scanning over the caller's byte buffer (no DOM, no heap); ra8_svg_render's only side effect is drawing through ra8_gfx.

[Ring 4 / Reflow] {World: NS}

Copyright: Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Since: 0.1.0

Definition in file reflow_svg.h.

Function Documentation

◆ ra8_svg_image_href()

ra8_err_t ra8_svg_image_href	(	const uint8_t *	svg,
		size_t	len,
		size_t *	out_off,
		size_t *	out_len )

nodiscard

Extract the href of a cover-wrapper <svg><image .../></svg>.

Scans for the first <image> element and returns its xlink:href / href attribute value as a slice into svg. The caller resolves + decodes that raster through its normal image path.

Parameters

[in]	svg	SVG document bytes.
[in]	len	Length of `svg`.
[out]	out_off	Receives the href slice offset into `svg`.
[out]	out_len	Receives the href slice length, bytes.

Returns: ra8_err_t

Return values

k_ra8_ok	An <image> href was found.
k_ra8_err_null_ptr	A required pointer is NULL.
k_ra8_err_not_found	No <image> with an href was present.

Precondition: svg, out_off, out_len non-NULL.; None.

Postcondition: On success the outputs slice svg.; On failure the outputs are unchanged.

Note: Pure; thread-safe.

Since: 0.1.0

Definition at line 741 of file reflow_svg_doc.c.

References internal_tag_span(), k_ra8_err_not_found, k_ra8_err_null_ptr, k_ra8_ok, and priv_ra8_svgp_attr().

Referenced by internal_render_svg().

◆ ra8_svg_is_svg()

bool ra8_svg_is_svg	(	const uint8_t *	bytes,
		size_t	len )

nodiscard

Heuristically decide whether bytes are an SVG document.

Skips a leading UTF-8 BOM + whitespace and checks for <?xml or a <svg element start (case-insensitive). Used by the image path to route SVG bytes here instead of to the raster decoder.

Parameters

[in]	bytes	Candidate image bytes.
[in]	len	Length of `bytes`.

Returns: true iff bytes look like SVG.

Return values

false bytes is NULL/empty or does not begin like SVG.

Precondition: None.; None.

Postcondition: No state modified.

Note: Pure; thread-safe.

Since: 0.1.0

Definition at line 723 of file reflow_svg_doc.c.

References k_svg_bom0, k_svg_bom1, k_svg_bom2, k_svg_bom_len, priv_ra8_svgp_starts_ci(), and priv_ra8_svgp_ws().

Referenced by internal_render_one_image(), and ra8_img_probe_size().

◆ ra8_svg_render()

ra8_err_t ra8_svg_render	(	const uint8_t *	svg,
		size_t	len,
		int32_t	x,
		int32_t	y,
		int32_t	w,
		int32_t	h )

nodiscard

Render an SVG's vector shapes into a box.

Establishes a coordinate transform from the SVG viewBox (or its width/height, defaulting to the box) onto the caller box (x,y,w,h), then walks the supported shapes (<rect> / <circle> / <polygon> filled, <line> / <polyline> stroked) and draws each through the bound ra8_gfx framebuffer with its fill or stroke colour. fill="none" shapes are skipped. Coordinates outside the box are clipped by ra8_gfx.

Parameters

[in]	svg	SVG document bytes.
[in]	len	Length of `svg`.
[in]	x	Box left, framebuffer pixels.
[in]	y	Box top, framebuffer pixels.
[in]	w	Box width, pixels (> 0).
[in]	h	Box height, pixels (> 0).

Returns: ra8_err_t

Return values

k_ra8_ok	Rendered (possibly zero shapes).
k_ra8_err_null_ptr	`svg` is NULL.
k_ra8_err_invalid_arg	`w` or `h` is non-positive.

Precondition: svg non-NULL; ra8_gfx_init() has bound a framebuffer.; w > 0 and h > 0.

Postcondition: Shapes are drawn into the bound framebuffer within (x,y,w,h).; No allocation performed.

Note: Not thread-safe relative to the bound ra8_gfx framebuffer.

Since: 0.1.0

Definition at line 799 of file reflow_svg_doc.c.

References svg_xform_t::grads, internal_draw_shapes(), internal_read_viewbox(), internal_scan_grads(), k_ra8_err_invalid_arg, k_ra8_err_null_ptr, and k_ra8_ok.

Referenced by es_render_svg_or_halt(), and internal_render_svg().

◆ ra8_svg_size()

ra8_err_t ra8_svg_size	(	const uint8_t *	svg,
		size_t	len,
		int32_t *	out_w,
		int32_t *	out_h )

nodiscard

Report an SVG's intrinsic size (width/height, else viewBox dimensions).

Lets the layout reserve an <img src="*.svg"> box without a raster decode. Prefers the <svg> width/height attributes (units ignored), and falls back to the viewBox width/height.

Parameters