CFont.h/CFont.cpp

//================================================CFONT.H=============================================
#ifndef __C_FONT_H__
#define __C_FONT_H__

#include <ft2build.h>
#include FT_FREETYPE_H

class ShaderProgram;

class CFont
{
private:
    static FT_Library library;
    static ShaderProgram* textShader;

private:
    unsigned int texID; //The texture id that stores the texture this font uses
    unsigned int vboID; //The vbo id that holds the combined vertex and texture coordinates
    FT_Face face; //The face used by this font
    FT_GlyphSlot slot; //The shortcut to the active glyph in the face

public:
    CFont(const char* file, unsigned int size);
    ~CFont();

    void SetSize(unsigned int);
    void RenderText(const char* text, float x, float y, float color[4]);
};

#endif

//=============================================CFONT.CPP==========================================
#include "cfont.h"
#include "shader_program.h"
#include "globals.h"

#include <GL\glew.h>

#include <stdexcept>

FT_Library CFont::library = nullptr;
ShaderProgram* CFont::textShader = nullptr;

CFont::CFont(const char* file, unsigned int size)
{
    //Static init
    if (!library)
    {
        int err = FT_Init_FreeType(&library);
        if (err)
            throw std::runtime_error("Failed to load FreeType font library.");

        textShader = new ShaderProgram("data\\shaders\\TextRenderer.vert", "data\\shaders\\TextRenderer.frag");
    }

    //Load face and set size
    int err;
    err = FT_New_Face(library, file, 0, &face);
    if (err)
        throw std::runtime_error("Could not load font " + *file);
    err = FT_Set_Pixel_Sizes(face, 0, size);
    if (err)
        throw std::runtime_error("Could not change fint size.");

    slot = face->glyph;

    //Load graphics stuff
    glGenTextures(1, &texID);
    glBindTexture(GL_TEXTURE_2D, texID);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    glBindTexture(GL_TEXTURE_2D, 0);
    glGenBuffers(1, &vboID);
}

CFont::~CFont()
{

}

void CFont::SetSize(unsigned int size)
{
    int err = FT_Set_Pixel_Sizes(face, 0, size);
    if (err)
        throw std::runtime_error("Could not set font size.");
}

void CFont::RenderText(const char* text, float x, float y, float color[4])
{
    float penX = x, penY = y;

    ShaderProgram::SetActive(textShader);
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, texID);
    textShader->Uniform1i("glyphTex", 0);
    textShader->Uniform4f("color", color[0], color[1], color[2], color[3]);
    glBindBuffer(GL_ARRAY_BUFFER, vboID);
    glEnableVertexAttribArray(glGetAttribLocation(textShader->GetProgramID(), "coord"));
    glVertexAttribPointer(glGetAttribLocation(textShader->GetProgramID(), "coord"), 4, GL_FLOAT, GL_FALSE, 0, (void*)0);

    const char* p;
    for (p = text; *p; p++)
    {
        int err = FT_Load_Char(face, *p, FT_LOAD_RENDER);
        if (err)
            continue;

        glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, slot->bitmap.width, slot->bitmap.rows, 0, GL_ALPHA, GL_UNSIGNED_BYTE, slot->bitmap.buffer);

        float x2 = penX + slot->bitmap_left * (2.0f / g_screenWidth);
        float y2 = -penY - slot->bitmap_top * (2.0f / g_screenHeight);
        float w = slot->bitmap.width * (2.0f / g_screenWidth);
        float h = slot->bitmap.rows * (2.0f / g_screenHeight);

        GLfloat data[4][4] =
        {
            {x2, -y2, 0, 0},
            {x2 + w, -y2, 1, 0},
            {x2, -y2 - h, 0, 1},
            {x2 + w, -y2 - h, 1, 1},
        };

        glBufferData(GL_ARRAY_BUFFER, sizeof(data), data, GL_DYNAMIC_DRAW);
        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

        penX += (slot->advance.x >> 6) * (2.0f / g_screenWidth);
        penY += (slot->advance.y >> 6) * (2.0f / g_screenHeight);
    }

    glDisableVertexAttribArray(glGetAttribLocation(textShader->GetProgramID(), "coord"));
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindTexture(GL_TEXTURE_2D, 0);
}