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#include "font.h"
#include <algorithm>
#include <cctype>
#include <format>
#include <ft2build.h>
#include FT_FREETYPE_H
#include "gl_traits.h"
#include <glRef.h>
#include <maths.h>
#include <optional>
#include <stdexcept>
#include <string>
#include <unicode.h>
#include <util.h>
#include <utility>
// IWYU pragma: no_forward_declare FT_LibraryRec_
namespace {
std::string
FT_Error_StringSafe(FT_Error err)
{
if (const auto errstr = FT_Error_String(err)) {
return {errstr};
}
return std::format("Unknown FT error: {}", err);
}
template<auto Func, typename... Args>
void
FT_Check(Args &&... args)
{
if (const auto err = Func(std::forward<Args>(args)...)) {
throw std::runtime_error {std::format("FreeType error: {}", FT_Error_StringSafe(err))};
}
}
const std::string BASIC_CHARS = []() {
std::string chars {"£€²³"};
for (char c {}; c >= 0; c++) {
if (isgraph(c)) {
chars += c;
}
}
return chars;
}();
using FT = glRef<FT_Library,
[]() {
FT_Library ft {};
FT_Check<FT_Init_FreeType>(&ft);
return ft;
},
FT_Done_FreeType>;
using Face = glRef<FT_Face,
[](FT_Library ft, const char * const name) {
FT_Face face {};
FT_Check<FT_New_Face>(ft, name, 0, &face);
return face;
},
FT_Done_Face>;
}
Font::Font(std::filesystem::path p, unsigned s) : path {std::move(p)}, size {getTextureSize(s)}
{
generateChars(BASIC_CHARS);
}
void
Font::generateChars(const utf8_string_view chars) const
{
std::optional<FT> ft;
std::optional<Face> face;
for (auto codepoint : chars) {
if (charsData.find(codepoint) == charsData.end()) {
if (!ft) {
ft.emplace();
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
}
if (!face) {
face.emplace(*ft, path.c_str());
FT_Set_Pixel_Sizes(*face, 0, size.z);
}
const FT_UInt glyph_index = FT_Get_Char_Index(*face, codepoint);
if (FT_Load_Glyph(*face, glyph_index, FT_LOAD_RENDER)) {
charsData.emplace(codepoint, CharData {});
continue;
}
const auto & glyph = (*face)->glyph;
const auto textureIdx = getTextureWithSpace(glyph->bitmap.width);
auto & texture = fontTextures[textureIdx];
glTexSubImage2D(GL_TEXTURE_2D, 0, static_cast<GLint>(texture.used), 0,
static_cast<GLsizei>(glyph->bitmap.width), static_cast<GLsizei>(glyph->bitmap.rows), GL_RED,
GL_UNSIGNED_BYTE, glyph->bitmap.buffer);
const auto & cd = charsData
.emplace(codepoint,
CharData {textureIdx, {glyph->bitmap.width, glyph->bitmap.rows},
{texture.used, 0}, {glyph->bitmap_left, glyph->bitmap_top},
glyph->advance.x >> 6})
.first->second;
texture.used += cd.size.x;
}
}
}
std::size_t
Font::getTextureWithSpace(unsigned int adv) const
{
if (auto itr = std::find_if(fontTextures.begin(), fontTextures.end(),
[adv, this](const FontTexture & ft) {
return (ft.used + adv) < size.x;
});
itr != fontTextures.end()) {
glBindTexture(GL_TEXTURE_2D, itr->texture);
return static_cast<std::size_t>(itr - fontTextures.begin());
}
auto & texture = fontTextures.emplace_back();
glBindTexture(GL_TEXTURE_2D, texture.texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RED, static_cast<GLsizei>(size.x), static_cast<GLsizei>(size.y), 0, GL_RED,
GL_UNSIGNED_BYTE, nullptr);
glTexParameter(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameter(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameter(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameter(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
return fontTextures.size() - 1;
}
glm::uvec3
Font::getTextureSize(unsigned int height)
{
auto pow2 = [](unsigned int target) {
unsigned int v {8};
do {
v <<= 1;
} while (v << 1 < GL_MAX_TEXTURE_SIZE && v < target);
return v;
};
constexpr const unsigned int WIDTH_PER_HEIGHT {64};
return {pow2(height * WIDTH_PER_HEIGHT), pow2(height), height};
}
Font::TextureQuads
Font::render(const utf8_string_view chars) const
{
constexpr static const std::array<std::pair<glm::vec2, glm::vec2>, 4> C {{
{{0, 0}, {0, 1}},
{{1, 0}, {1, 1}},
{{1, 1}, {1, 0}},
{{0, 1}, {0, 0}},
}};
generateChars(chars);
glm::vec2 pos {};
TextureQuads out;
for (auto codepoint : chars) {
if (std::isspace(static_cast<int>(codepoint))) {
pos.x += static_cast<float>(size.y) / 4.F;
continue;
}
const auto & ch = charsData.at(codepoint);
if (!ch.advance) {
continue;
}
const auto charPos = pos + glm::vec2 {ch.bearing.x, ch.bearing.y - static_cast<int>(ch.size.y)};
const auto chSize = glm::vec2 {ch.size};
out[fontTextures[ch.textureIdx].texture].emplace_back(
transform_array(C, [&chSize, &charPos, &ch, this](const auto & c) {
return (charPos + (chSize * c.first))
|| ((glm::vec2 {ch.position} + (glm::vec2 {ch.size} * c.second)) / glm::vec2 {this->size});
}));
pos.x += static_cast<float>(ch.advance);
}
return out;
}
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