bloat-buster/bootstrap/std/font_provider.c

#pragma once

#include <std/font_provider.h>

#define STBTT_STATIC
#define STB_TRUETYPE_IMPLEMENTATION
#define stbtt_uint8  u8
#define stbtt_uint16 u16
#define stbtt_uint32 u32
#define stbtt_int8  s8
#define stbtt_int16 s16
#define stbtt_int32 s32

extern float sqrtf(float x);
extern float roundf(float x);
extern float floorf(float x);

extern double sqrt(double x);
extern double fabs(double x);
extern double floor(double x);
extern double ceil(double x);
extern double fmod(double x, double y);
extern double pow(double x, double y);
extern double acos(double x);
extern double cos(double x);

#define STBTT_ifloor(x)    ((int) floor(x))
#define STBTT_iceil(x)     ((int) ceil(x))
#define STBTT_sqrt(x)      sqrt(x)
#define STBTT_pow(x,y)     pow(x,y)
#define STBTT_fmod(x,y)    fmod(x,y)
#define STBTT_cos(x)       cos(x)
#define STBTT_acos(x)      acos(x)
#define STBTT_fabs(x)      fabs(x)
#define STBTT_malloc(x,u)  ((void)(u),malloc(x))
#define STBTT_free(x,u)    ((void)(u),free(x))
#define STBTT_assert(x)    assert(x)
#define STBTT_strlen(x)    strlen(x)
#define STBTT_memcpy       memcpy
#define STBTT_memset       memset

#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-function"
#endif
#include <stb_truetype.h>
#ifdef __clang__
#pragma clang diagnostic pop
#endif

fn TextureAtlas font_texture_atlas_create(Arena* arena, Renderer* renderer, TextureAtlasCreate create)
{
    let(font_file, file_read(arena, create.font_path));
    stbtt_fontinfo font_info;
    if (!stbtt_InitFont(&font_info, font_file.pointer, stbtt_GetFontOffsetForIndex(font_file.pointer, 0)))
    {
        failed_execution();
    }

    TextureAtlas result = {};
    u32 character_count = 256;
    result.characters = arena_allocate(arena, FontCharacter, character_count);
    result.kerning_tables = arena_allocate(arena, s32, character_count * character_count);
    result.height = (u32)sqrtf((f32)(create.text_height * create.text_height * character_count));
    result.width = result.height;
    result.pointer = arena_allocate(arena, u32, result.width * result.height);
    let(scale_factor, stbtt_ScaleForPixelHeight(&font_info, create.text_height));

    int ascent;
    int descent;
    int line_gap;
    stbtt_GetFontVMetrics(&font_info, &ascent, &descent, &line_gap);

    result.ascent = (u32)roundf(ascent * scale_factor);
    result.descent = (u32)roundf(descent * scale_factor);
    result.line_gap = (u32)roundf(line_gap * scale_factor);

    u32 x = 0;
    u32 y = 0;
    u32 max_row_height = 0;
    u32 first_character = ' ';
    u32 last_character = '~';

    for (let(i, first_character); i <= last_character; ++i)
    {
        u32 width;
        u32 height;
        int advance;
        int left_bearing;

        let(ch, (u8)i);
        let(character, &result.characters[i]);
        stbtt_GetCodepointHMetrics(&font_info, ch, &advance, &left_bearing);

        character->advance = (u32)roundf(advance * scale_factor);
        character->left_bearing = (u32)roundf(left_bearing * scale_factor);

        u8* bitmap = stbtt_GetCodepointBitmap(&font_info, 0.0f, scale_factor, ch, (int*)&width, (int*)&height, &character->x_offset, &character->y_offset);
        let(kerning_table, result.kerning_tables + i * character_count); 
        for (u32 j = first_character; j <= last_character; j += 1)
        {
            let(kerning_advance, stbtt_GetCodepointKernAdvance(&font_info, i, j));
            kerning_table[j] = (s32)roundf(kerning_advance * scale_factor);
        }

        if (x + width > result.width)
        {
            y += max_row_height;
            max_row_height = height;
            x = 0;
        }
        else
        {
            max_row_height = MAX(height, max_row_height);
        }

        character->x = x;
        character->y = y;
        character->width = width;
        character->height = height;

        let(source, bitmap);
        let(destination, result.pointer);

        for (u32 bitmap_y = 0; bitmap_y < height; bitmap_y += 1)
        {
            for (u32 bitmap_x = 0; bitmap_x < width; bitmap_x += 1)
            {
                let(source_index, bitmap_y * width + bitmap_x);
                let(destination_index, (bitmap_y + y) * result.width + (bitmap_x + x));
                let(value, source[source_index]);
                destination[destination_index] = ((u32)value << 24) | 0xffffff;
            }
        }

        x += width;

        stbtt_FreeBitmap(bitmap, 0);
    }

    result.texture = renderer_texture_create(renderer, (TextureMemory) {
        .pointer = result.pointer,
        .width = result.width,
        .height = result.height,
        .depth = 1,
        .format = TEXTURE_FORMAT_R8G8B8A8_SRGB,
    });

    return result;
}

fn uint2 texture_atlas_compute_string_rect(String string, const TextureAtlas* atlas)
{
    let(height, atlas->ascent - atlas->descent);
    u32 x_offset = 0;
    u32 y_offset = height;

    for (u64 i = 0; i < string.length; i += 1)
    {
        let(ch, string.pointer[i]);
        let(character, &atlas->characters[ch]);
        let(kerning, (atlas->kerning_tables + ch * 256)[string.pointer[i + 1]]);
        x_offset += character->advance + kerning;
    }

    return (uint2) { x_offset, y_offset };
}