cube-game-plus-plus/client/FontRenderer.cpp

#include "client/FontRenderer.h"
#include "io/ImageReader.h"
#include "rendering/Shader.h"
#include "rendering/Texture.h"
#include "rendering/VertexBuffer.h"
#include "utils/Logger.h"

static constexpr float FONT_WIDTH = 8.0f;
static constexpr float FONT_HEIGHT = 8.0f;
static constexpr float FONT_STEP = 1.0f / 128.0f;

static Shader shader;
static VertexBuffer buffer;
static Texture texture;
static Buffer data{50};
static Color4 color;

struct Symbol {
    int offsetX = 8;
    int width = 0;
};
static Array<Symbol, 256> symbols;

bool FontRenderer::init() {
    Error e = shader.compile("resources/shader/fontTest.vs",
                             "resources/shader/fontTest.fs");
    if(e.has()) {
        LOG_ERROR(e.message);
        return true;
    }

    ImageReader::Image image;
    const char* path = "resources/font8x8.png";
    e = ImageReader::load(image, path);
    if(e.has()) {
        LOG_ERROR(e.message);
        return true;
    }
    if(image.channels < 1 || image.channels > 4 || image.bitdepth != 8 ||
       image.width != 128 || image.height != 128) {
        LOG_ERROR("font must have 1-4 channels, 8 bit per channel and a size "
                  "of 128x128");
        return true;
    }
    texture.init(Texture::Format::color8(image.channels), 0);
    int end = image.width * image.height;
    for(int i = 0; i < end; i++) {
        int c = image.data[i * image.channels];
        if(c != 255) {
            continue;
        }
        int px = i % image.width;
        int py = i / image.width;
        int index = (py / 8) * 16 + (px / 8);
        symbols[index].offsetX = std::min(symbols[index].offsetX, px % 8);
        symbols[index].width = std::max(symbols[index].width, px % 8);
    }
    texture.setData(image.width, image.height, image.data);

    for(Symbol& s : symbols) {
        s.width = std::max(s.width - s.offsetX + 2, 0);
    }
    symbols[' '].offsetX = 0;
    symbols[' '].width = 4;

    buffer.init(VertexBuffer::Attributes().addFloat(3).addFloat(2).addColor4());
    return false;
}

void FontRenderer::bind() {
    shader.use();
    texture.bindTo(0);
}

void FontRenderer::setProjection(const Matrix& m) {
    shader.setMatrix("proj", m);
}

void FontRenderer::setView(const Matrix& m) {
    shader.setMatrix("view", m);
}

void FontRenderer::setModel(const Matrix& m) {
    shader.setMatrix("model", m);
}

void FontRenderer::draw(const char* text, int alpha) {
    data.clear();
    color = Color4(255, 255, 255, alpha);
    int index = 0;
    Vector3 pos;
    int vertices = 0;
    while(text[index] != '\0') {
        int i = text[index];
        if(i < 0 && text[index + 1] != '\0') {
            index++;
            i = ((i & 0x1F) << 6) | (text[index] & 0x3F);
        }
        if(i < 0 || i >= 256) {
            continue;
        }

        Vector3 right = pos + Vector3(symbols[i].width, 0.0f, 0.0f);
        Vector3 down = pos + Vector3(0.0f, FONT_HEIGHT, 0.0f);
        Vector3 downRight = pos + Vector3(symbols[i].width, FONT_HEIGHT, 0.0f);

        Vector2 tPos((FONT_WIDTH * (i % 16) + symbols[i].offsetX) * FONT_STEP,
                     FONT_HEIGHT * (i / 16) * FONT_STEP);
        Vector2 tRight = tPos + Vector2(symbols[i].width * FONT_STEP, 0.0f);
        Vector2 tDown = tPos + Vector2(0.0f, FONT_HEIGHT * FONT_STEP);
        Vector2 tDownRight = tPos + Vector2(symbols[i].width * FONT_STEP,
                                            FONT_HEIGHT * FONT_STEP);

        Color4 dark =
            Color4(color[0] / 2, color[1] / 2, color[2] / 2, color[3]);
        Vector3 shift(0.25f, 0.25f, 0.0f);
        data.add(shift + pos).add(tPos).add(dark);
        data.add(shift + down).add(tDown).add(dark);
        data.add(shift + right).add(tRight).add(dark);
        data.add(shift + down).add(tDown).add(dark);
        data.add(shift + right).add(tRight).add(dark);
        data.add(shift + downRight).add(tDownRight).add(dark);

        data.add(pos).add(tPos).add(color);
        data.add(down).add(tDown).add(color);
        data.add(right).add(tRight).add(color);
        data.add(down).add(tDown).add(color);
        data.add(right).add(tRight).add(color);
        data.add(downRight).add(tDownRight).add(color);

        pos += Vector3(symbols[i].width, 0.0f, 0.0f);
        vertices += 12;
        index++;
    }
    buffer.setData(data, GL::DYNAMIC_DRAW);
    buffer.draw(vertices);
}

float FontRenderer::getWidth(const char* text, int max) {
    int index = 0;
    float width = 0.0f;
    while(text[index] != '\0' && (max < 0 || index < max)) {
        int i = text[index];
        if(i < 0 && text[index + 1] != '\0') {
            index++;
            i = ((i & 0x1F) << 6) | (text[index] & 0x3F);
        }
        if(i < 0 || i >= 256) {
            continue;
        }
        width += symbols[i].width;
        index++;
    }
    return width;
}

void FontRenderer::draw(const Vector2& size, Color4 c) {
    data.clear();
    Vector3 pos;
    Vector3 right = pos + Vector3(size[0], 0.0f, 0.0f);
    Vector3 down = pos + Vector3(0.0f, size[1], 0.0f);
    Vector3 downRight = pos + Vector3(size[0], size[1], 0.0f);

    Vector2 tPos;
    Vector2 tRight(FONT_STEP, 0.0f);
    Vector2 tDown(0.0f, FONT_STEP);
    Vector2 tDownRight(FONT_STEP, FONT_STEP);

    data.add(pos).add(tPos).add(c);
    data.add(down).add(tDown).add(c);
    data.add(right).add(tRight).add(c);
    data.add(down).add(tDown).add(c);
    data.add(right).add(tRight).add(c);
    data.add(downRight).add(tDownRight).add(c);

    buffer.setData(data, GL::DYNAMIC_DRAW);
    buffer.draw(6);
}