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#ifndef VEGA_SYMBOLS_GL_H
#define VEGA_SYMBOLS_GL_H
#include "symbols.h"
#include <GLES3/gl31.h>
/* Symbols on the GPU (OpenGL ES 3.1): the symbols wanted at one scale are
* drawn on the CPU into an atlas, each pixel the exact area its curves cover
* (vega_symbol_raster), and text is quads reading it. On the Pi 5 the CPU
* draws the atlas faster than the GPU's compute could, and the GPU composes
* a 1080p page of text in about a millisecond (docs/design/002). A scale that
* keeps changing (a zoom) draws its atlas again. Needs a current context. */
typedef struct {
GLuint draw, array, instances;
GLint target;
} VegaGl;
/* Where each symbol is in an atlas: its rectangle there (x, y, width, height)
* and the pixel offset of that rectangle's top left from the symbol's origin
* (right, up). A symbol with nothing to draw has an empty rectangle. */
typedef struct { int32_t x, y, width, height, left, top; } VegaPlace;
typedef struct {
GLuint texture; /* 8-bit coverage */
int width, height;
float scale; /* pixels per unit */
uint32_t symbols;
VegaPlace *places; /* per symbol index */
} VegaAtlas;
/* A symbol at a pen position (whole pixels from the target's top left, on the
* baseline). */
typedef struct { int32_t x, y; uint32_t symbol; } VegaGlyph;
bool vega_gl_open(VegaGl *, char *error, size_t error_size);
/* Draw symbols (their indices; all when wanted is NULL) at scale into a new
* atlas; false when they do not fit one texture. */
bool vega_gl_atlas(VegaGl *, const VegaSymbols *, float scale, const uint32_t *wanted, uint32_t count, VegaAtlas *out,
char *error, size_t error_size);
/* Coverage added into the red channel of the bound framebuffer. */
void vega_gl_draw(VegaGl *, const VegaAtlas *, const VegaGlyph *, uint32_t count, int width, int height);
void vega_gl_atlas_close(VegaAtlas *);
void vega_gl_close(VegaGl *);
#endif
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