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#ifndef VEGA_SYMBOLS_H
#define VEGA_SYMBOLS_H
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
/* Symbols: glyphs and icons as outlines of quadratic curves in one file,
* verified once and then read where it lies (docs/design/002-symbol-format.md).
* An outline is a chain of points, on or off the curve, as in TrueType: two
* off points in a row imply the on point halfway between them. */
enum { VEGA_SYMBOLS_HEADER = 28, VEGA_SYMBOL_BYTES = 24, VEGA_POINT_BYTES = 4 };
typedef struct {
int16_t x, y;
bool off; /* a control point */
bool move; /* starts a contour */
} VegaPoint;
typedef struct { float x0, y0, x1, y1, x2, y2; } VegaCurve; /* a line has its middle as control */
typedef struct {
uint32_t code, first, count; /* its points: [first, first + count) */
int16_t left, bottom, right, top; /* bounds, in units, y up */
int16_t advance;
} VegaSymbol;
typedef struct {
const unsigned char *bytes;
size_t size;
uint16_t units; /* per em */
int16_t ascent, descent; /* a font's line, in units from the baseline, y up (0 and 0 for icons) */
uint32_t symbols, points;
} VegaSymbols;
/* Verify bytes as a symbol file (kept, not copied); false with why. What
* reading needs is checked, per symbol: after this no read leaves the file
* or its symbol. The points themselves are not: one outside its symbol's
* bounds draws wrong. */
bool vega_symbols_open(VegaSymbols *, const unsigned char *bytes, size_t size, char *error, size_t error_size);
/* The symbol of code (a binary search), or false. */
bool vega_symbol(const VegaSymbols *, uint32_t code, VegaSymbol *out);
VegaSymbol vega_symbol_at(const VegaSymbols *, uint32_t index);
VegaPoint vega_symbols_point(const VegaSymbols *, uint32_t index);
/* The curve that point index of symbol begins, if any: an off point is the
* control of one, and an on point followed by another on point in the same
* contour starts a line. Every curve of a symbol is had once this way, from
* the point and its two neighbours alone (as a GPU would fetch it). */
bool vega_symbol_curve(const VegaSymbols *, const VegaSymbol *, uint32_t index, VegaCurve *out);
/* All of a symbol's curves, in one pass over its points; out has room for
* symbol->count (a symbol has no more curves than points). */
uint32_t vega_symbol_curves(const VegaSymbols *, const VegaSymbol *, VegaCurve *out);
/* The coverage (0 to 1) of the pixel whose center is (x, y) in units, at
* scale pixels per unit: the exact area the curves' outline covers. */
double vega_coverage(const VegaCurve *, uint32_t count, double scale, double x, double y);
/* The pixels a symbol reaches at scale (pixels per unit), one more on each
* side: width and height, and the offset of the box's top left from the
* symbol's origin (right, up). x and y are where a set of bitmaps (an atlas)
* keeps it. A symbol with nothing to draw has an empty box. */
typedef struct { int32_t x, y, width, height, left, top; } VegaPlace;
VegaPlace vega_symbol_place(const VegaSymbol *, float scale);
/* width x height 8-bit coverage, rows top first, stride bytes apart; pixel
* (i, j) has its center at (left + (i + 0.5) / scale, top - (j + 0.5) / scale)
* in units. */
void vega_symbol_raster(const VegaSymbols *, const VegaSymbol *, double scale, double left, double top, int width,
int height, unsigned char *out, size_t stride);
/* Symbols drawn once at one scale and kept, for surfaces that compose them
* on the CPU: each the first time it is asked for. */
typedef struct { VegaPlace place; const unsigned char *pixels; } VegaBitmap; /* pixels: place.width per row */
typedef struct VegaGlyphs VegaGlyphs;
VegaGlyphs *vega_glyphs_open(const VegaSymbols *, float scale);
/* The bitmap of code, or NULL when the file has no such symbol. */
const VegaBitmap *vega_glyph(VegaGlyphs *, uint32_t code);
void vega_glyphs_close(VegaGlyphs *);
#endif
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