donner::svg::TextEngine Class Reference

Shared SVG text engine. More...

#include "donner/svg/text/TextEngine.h"

Public Member Functions
	TextEngine (FontManager &fontManager, Registry &registry)
	Construct a text engine using the provided font manager and ECS registry.
	TextEngine (FontManager &fontManager, Registry &registry, std::unique_ptr< TextBackend > backend)
	Test-only constructor that injects a custom TextBackend.
	TextEngine (const TextEngine &)=delete
TextEngine &	operator= (const TextEngine &)=delete
void	addFontFace (const css::FontFace &face)
	Register a single face with the engine's font manager.
void	addFontFaces (std::span< const css::FontFace > faces)
	Register a batch of faces with the engine's font manager.
void	prepareForElement (EntityHandle handle, ParseWarningSink &warningSink)
	Prepare text dependencies for the text root containing handle.
std::vector< TextRun >	layout (const components::ComputedTextComponent &text, const TextLayoutParams &params)
	Lay out all spans, returning positioned glyph runs.
FontVMetrics	fontVMetrics (FontHandle font) const
	Return vertical font metrics for font.
float	scaleForPixelHeight (FontHandle font, float pixelHeight) const
	Return the scale factor mapping design units to pixelHeight pixels for font.
float	scaleForEmToPixels (FontHandle font, float pixelHeight) const
	Return the scale factor mapping one em to pixelHeight pixels for font.
std::optional< UnderlineMetrics >	underlineMetrics (FontHandle font) const
	Return underline position/thickness for font, if available.
std::optional< UnderlineMetrics >	strikeoutMetrics (FontHandle font) const
	Return strikeout position/thickness for font, if available.
std::optional< SubSuperMetrics >	subSuperMetrics (FontHandle font) const
	Return subscript/superscript offset metrics for font, if available.
Path	glyphOutline (FontHandle font, int glyphIndex, float scale) const
	Return the vector outline for glyphIndex in font at the given scale.
bool	isBitmapOnly (FontHandle font) const
	Return true if font only contains bitmap glyphs (e.g. color emoji).
std::optional< TextBackend::BitmapGlyph >	bitmapGlyph (FontHandle font, int glyphIndex, float scale) const
	Return a rasterized bitmap glyph for glyphIndex in font at the given scale.
std::optional< double >	measureChUnitInEm (std::span< const RcString > fontFamilies)
	Measure the ch unit in ems for the given font-family cascade.
void	resolvePerSpanLayoutStyles (EntityHandle textRootHandle, components::ComputedTextComponent &text) const
	Resolve per-span layout-affecting style state on a computed text tree.
const components::ComputedTextGeometryComponent &	ensureComputedTextGeometryComponent (EntityHandle handle) const
	Ensure cached text geometry exists for the text root containing handle.
std::vector< Path >	computedGlyphPaths (EntityHandle handle) const
	Return glyph outlines for the text subtree rooted at handle.
Box2d	computedInkBounds (EntityHandle handle) const
	Return the ink bounds for the text subtree rooted at handle.
Box2d	computedObjectBoundingBox (EntityHandle handle) const
	Return the object bounding box for the text subtree rooted at handle.
long	getNumberOfChars (EntityHandle handle) const
	Return the number of addressable characters for the text subtree rooted at handle.
double	getComputedTextLength (EntityHandle handle) const
	Return the computed text length for the text subtree rooted at handle.
double	getSubStringLength (EntityHandle handle, std::size_t charnum, std::size_t nchars) const
	Return the substring length for the text subtree rooted at handle.
Vector2d	getStartPositionOfChar (EntityHandle handle, std::size_t charnum) const
	Return the start position of a character for the text subtree rooted at handle.
Vector2d	getEndPositionOfChar (EntityHandle handle, std::size_t charnum) const
	Return the end position of a character for the text subtree rooted at handle.
Box2d	getExtentOfChar (EntityHandle handle, std::size_t charnum) const
	Return the extent of a character for the text subtree rooted at handle.
double	getRotationOfChar (EntityHandle handle, std::size_t charnum) const
	Return the rotation of a character for the text subtree rooted at handle.
long	getCharNumAtPosition (EntityHandle handle, const Vector2d &point) const
	Return the character index at the given point for the text subtree rooted at handle.

Detailed Description

Shared SVG text engine.

Owns the selected text backend and provides layout plus font-related operations while hiding backend selection from callers.

Usage:

Registry registry;
auto& fontManager = registry.ctx().emplace<FontManager>(registry);
auto& engine = registry.ctx().emplace<TextEngine>(fontManager, registry);
std::vector<TextRun> runs = engine.layout(text, params);

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The documentation for this class was generated from the following file:

• donner/svg/text/TextEngine.h