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#include "symbols-gl.h"
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
enum { ATLAS_MAX = 4096 };
#define SHARED \
"#version 310 es\n" \
"precision highp float;\n" \
"precision highp int;\n"
/* Text: a quad per glyph at whole pixels, each pixel one atlas texel. */
static const char draw_vertex[] = SHARED
"layout(location = 0) in ivec4 rect; /* in the atlas */\n"
"layout(location = 1) in ivec2 at; /* its top left on the target */\n"
"uniform vec2 target;\n"
"out vec2 texel;\n"
"void main() {\n"
" vec2 corner = vec2(float(gl_VertexID & 1), float(gl_VertexID >> 1)), size = vec2(rect.zw);\n"
" vec2 pixel = vec2(at) + corner * size;\n"
" texel = vec2(rect.xy) + corner * size;\n"
" gl_Position = vec4(pixel.x / target.x * 2.0 - 1.0, 1.0 - pixel.y / target.y * 2.0, 0.0, 1.0);\n"
"}\n";
static const char draw_fragment[] = SHARED
"uniform highp sampler2D atlas;\n"
"in vec2 texel;\n"
"out vec4 color;\n"
"void main() { color = vec4(texelFetch(atlas, ivec2(texel), 0).r, 0.0, 0.0, 1.0); }\n";
static GLuint compile(GLenum type, const char *source, char *error, size_t error_size) {
GLuint shader = glCreateShader(type);
glShaderSource(shader, 1, &source, NULL);
glCompileShader(shader);
GLint ok;
glGetShaderiv(shader, GL_COMPILE_STATUS, &ok);
if (!ok) {
glGetShaderInfoLog(shader, (GLsizei)error_size, NULL, error);
glDeleteShader(shader);
return 0;
}
return shader;
}
bool vega_gl_open(VegaGl *gl, char *error, size_t error_size) {
*gl = (VegaGl){0};
GLuint vertex = compile(GL_VERTEX_SHADER, draw_vertex, error, error_size);
GLuint fragment = vertex ? compile(GL_FRAGMENT_SHADER, draw_fragment, error, error_size) : 0;
if (!fragment) {
if (vertex) glDeleteShader(vertex);
return false;
}
gl->draw = glCreateProgram();
glAttachShader(gl->draw, vertex);
glAttachShader(gl->draw, fragment);
glLinkProgram(gl->draw);
glDeleteShader(vertex);
glDeleteShader(fragment);
GLint ok;
glGetProgramiv(gl->draw, GL_LINK_STATUS, &ok);
if (!ok) {
glGetProgramInfoLog(gl->draw, (GLsizei)error_size, NULL, error);
vega_gl_close(gl);
return false;
}
glUseProgram(gl->draw);
glUniform1i(glGetUniformLocation(gl->draw, "atlas"), 0);
gl->target = glGetUniformLocation(gl->draw, "target");
glGenVertexArrays(1, &gl->array);
glGenBuffers(1, &gl->instances);
glBindVertexArray(gl->array);
glBindBuffer(GL_ARRAY_BUFFER, gl->instances);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glVertexAttribIPointer(0, 4, GL_INT, 24, (void *)0);
glVertexAttribIPointer(1, 2, GL_INT, 24, (void *)16);
glVertexAttribDivisor(0, 1);
glVertexAttribDivisor(1, 1);
glBindVertexArray(0);
if (glGetError() != GL_NO_ERROR) {
snprintf(error, error_size, "cannot set up the text program");
vega_gl_close(gl);
return false;
}
return true;
}
bool vega_gl_atlas(VegaGl *gl, const VegaSymbols *s, float scale, const uint32_t *wanted, uint32_t count, VegaAtlas *out,
char *error, size_t error_size) {
(void)gl;
*out = (VegaAtlas){.scale = scale, .symbols = s->symbols};
if (!wanted) count = s->symbols;
out->places = calloc(s->symbols ? s->symbols : 1, sizeof(*out->places));
if (!out->places) {
snprintf(error, error_size, "out of memory");
return false;
}
/* Shelves, as wide as the square the rectangles would fill (a power of
* two), the next shelf starting under the tallest of the one before. */
uint64_t area = 0;
for (uint32_t i = 0; i < count; ++i) {
uint32_t index = wanted ? wanted[i] : i;
if (index >= s->symbols) continue;
VegaSymbol symbol = vega_symbol_at(s, index);
VegaPlace p = vega_symbol_place(&symbol, scale);
area += (uint64_t)p.width * (uint64_t)p.height;
}
int width = 64;
while (width < ATLAS_MAX && (uint64_t)width * (uint64_t)width < area + area / 4) width *= 2;
int x = 0, y = 0, shelf = 0;
for (uint32_t i = 0; i < count; ++i) {
uint32_t index = wanted ? wanted[i] : i;
if (index >= s->symbols) continue;
VegaSymbol symbol = vega_symbol_at(s, index);
VegaPlace p = vega_symbol_place(&symbol, scale);
if (!p.width) continue;
if (p.width > width) width = p.width;
if (x + p.width > width) { x = 0; y += shelf; shelf = 0; }
p.x = x, p.y = y;
x += p.width;
shelf = p.height > shelf ? p.height : shelf;
out->places[index] = p;
}
int height = y + shelf;
if (width > ATLAS_MAX || height > ATLAS_MAX) {
snprintf(error, error_size, "%u symbols at %.4f pixels a unit need %dx%d, more than one %d-pixel atlas", count,
(double)scale, width, height, ATLAS_MAX);
vega_gl_atlas_close(out);
return false;
}
out->width = width, out->height = height ? height : 1;
unsigned char *pixels = calloc((size_t)out->width * (size_t)out->height, 1);
if (!pixels) {
snprintf(error, error_size, "out of memory");
vega_gl_atlas_close(out);
return false;
}
for (uint32_t i = 0; i < s->symbols; ++i) {
VegaPlace p = out->places[i];
if (!p.width) continue;
VegaSymbol symbol = vega_symbol_at(s, i);
vega_symbol_raster(s, &symbol, scale, p.left / scale, p.top / scale, p.width, p.height,
pixels + (size_t)p.y * (size_t)out->width + (size_t)p.x, (size_t)out->width);
}
glGenTextures(1, &out->texture);
glBindTexture(GL_TEXTURE_2D, out->texture);
glTexStorage2D(GL_TEXTURE_2D, 1, GL_R8, out->width, out->height);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, out->width, out->height, GL_RED, GL_UNSIGNED_BYTE, pixels);
free(pixels);
if (glGetError() != GL_NO_ERROR) {
snprintf(error, error_size, "cannot upload the atlas");
vega_gl_atlas_close(out);
return false;
}
return true;
}
void vega_gl_draw(VegaGl *gl, const VegaAtlas *atlas, const VegaGlyph *glyphs, uint32_t count, int width, int height) {
int32_t *instances = malloc((size_t)(count ? count : 1) * 6 * sizeof(*instances));
uint32_t n = 0;
for (uint32_t i = 0; instances && i < count; ++i) {
if (glyphs[i].symbol >= atlas->symbols) continue;
VegaPlace p = atlas->places[glyphs[i].symbol];
if (!p.width) continue;
int32_t *q = instances + (size_t)n++ * 6;
q[0] = p.x, q[1] = p.y, q[2] = p.width, q[3] = p.height;
q[4] = glyphs[i].x + p.left, q[5] = glyphs[i].y - p.top;
}
glUseProgram(gl->draw);
glUniform2f(gl->target, (float)width, (float)height);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, atlas->texture);
glBindVertexArray(gl->array);
glBindBuffer(GL_ARRAY_BUFFER, gl->instances);
glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)((size_t)n * 6 * sizeof(*instances)), instances, GL_STREAM_DRAW);
glEnable(GL_BLEND);
glBlendFunc(GL_ONE, GL_ONE);
if (n) glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, (GLsizei)n);
glBindVertexArray(0);
free(instances);
}
void vega_gl_atlas_close(VegaAtlas *atlas) {
if (atlas->texture) glDeleteTextures(1, &atlas->texture);
free(atlas->places);
*atlas = (VegaAtlas){0};
}
void vega_gl_close(VegaGl *gl) {
if (gl->instances) glDeleteBuffers(1, &gl->instances);
if (gl->array) glDeleteVertexArrays(1, &gl->array);
if (gl->draw) glDeleteProgram(gl->draw);
*gl = (VegaGl){0};
}
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