// Std. Includes
#include <iostream>
#include <map>
#include <string>
// GLEW
#define GLEW_STATIC
#include <GL/glew.h>
// GLFW
#include <GLFW/glfw3.h>
// GLM
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
// FreeType
#include <ft2build.h>
#include FT_FREETYPE_H
// GL includes
#include "Shader.h"
// Properties
const GLuint WIDTH = 800, HEIGHT = 600;
/// Holds all state information relevant to a character as loaded using FreeType
struct Character {
GLuint TextureID; // ID handle of the glyph texture
glm::ivec2 Size; // Size of glyph
glm::ivec2 Bearing; // Offset from baseline to left/top of glyph
GLuint Advance; // Horizontal offset to advance to next glyph
};
std::map<GLchar, Character> Characters;
GLuint VAO, VBO;
void RenderText(Shader &shader, std::string text, GLfloat x, GLfloat y, GLfloat scale, glm::vec3 color);
// The MAIN function, from here we start our application and run the Game loop
int main()
{
// Init GLFW
glfwInit();
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, "LearnOpenGL", nullptr, nullptr); // Windowed
glfwMakeContextCurrent(window);
// Initialize GLEW to setup the OpenGL Function pointers
glewExperimental = GL_TRUE;
glewInit();
// Define the viewport dimensions
glViewport(0, 0, WIDTH, HEIGHT);
// Set OpenGL options
glEnable(GL_CULL_FACE);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
// Compile and setup the shader
Shader shader("shaders/text.vs", "shaders/text.frag");
glm::mat4 projection = glm::ortho(0.0f, static_cast<GLfloat>(WIDTH), 0.0f, static_cast<GLfloat>(HEIGHT));
shader.Use();
glUniformMatrix4fv(glGetUniformLocation(shader.Program, "projection"), 1, GL_FALSE, glm::value_ptr(projection));
// FreeType
FT_Library ft;
// All functions return a value different than 0 whenever an error occurred
if (FT_Init_FreeType(&ft))
std::cout << "ERROR::FREETYPE: Could not init FreeType Library" << std::endl;
// Load font as face
FT_Face face;
if (FT_New_Face(ft, "fonts/arial.ttf", 0, &face))
std::cout << "ERROR::FREETYPE: Failed to load font" << std::endl;
// Set size to load glyphs as
FT_Set_Pixel_Sizes(face, 0, 48);
// Disable byte-alignment restriction
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
// Load first 128 characters of ASCII set
for (GLubyte c = 0; c < 128; c++)
{
// Load character glyph
if (FT_Load_Char(face, c, FT_LOAD_RENDER))
{
std::cout << "ERROR::FREETYTPE: Failed to load Glyph" << std::endl;
continue;
}
// Generate texture
GLuint texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(
GL_TEXTURE_2D,
0,
GL_RED,
face->glyph->bitmap.width,
face->glyph->bitmap.rows,
0,
GL_RED,
GL_UNSIGNED_BYTE,
face->glyph->bitmap.buffer
);
// Set texture options
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);
// Now store character for later use
Character character = {
texture,
glm::ivec2(face->glyph->bitmap.width, face->glyph->bitmap.rows),
glm::ivec2(face->glyph->bitmap_left, face->glyph->bitmap_top),
face->glyph->advance.x
};
Characters.insert(std::pair<GLchar, Character>(c, character));
}
glBindTexture(GL_TEXTURE_2D, 0);
// Destroy FreeType once we're finished
FT_Done_Face(face);
FT_Done_FreeType(ft);
// Configure VAO/VBO for texture quads
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat) * 6 * 4, NULL, GL_DYNAMIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
// Game loop
while (!glfwWindowShouldClose(window))
{
// Check and call events
glfwPollEvents();
// Clear the colorbuffer
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
RenderText(shader, "This is sample text", 25.0f, 25.0f, 1.0f, glm::vec3(0.5, 0.8f, 0.2f));
RenderText(shader, "(C) LearnOpenGL.com", 540.0f, 570.0f, 0.5f, glm::vec3(0.3, 0.7f, 0.9f));
// Swap the buffers
glfwSwapBuffers(window);
}
glfwTerminate();
return 0;
}
void RenderText(Shader &shader, std::string text, GLfloat x, GLfloat y, GLfloat scale, glm::vec3 color)
{
// Activate corresponding render state
shader.Use();
glUniform3f(glGetUniformLocation(shader.Program, "textColor"), color.x, color.y, color.z);
glActiveTexture(GL_TEXTURE0);
glBindVertexArray(VAO);
// Iterate through all characters
std::string::const_iterator c;
for (c = text.begin(); c != text.end(); c++)
{
Character ch = Characters[*c];
GLfloat xpos = x + ch.Bearing.x * scale;
GLfloat ypos = y - (ch.Size.y - ch.Bearing.y) * scale;
GLfloat w = ch.Size.x * scale;
GLfloat h = ch.Size.y * scale;
// Update VBO for each character
GLfloat vertices[6][4] = {
{ xpos, ypos + h, 0.0, 0.0 },
{ xpos, ypos, 0.0, 1.0 },
{ xpos + w, ypos, 1.0, 1.0 },
{ xpos, ypos + h, 0.0, 0.0 },
{ xpos + w, ypos, 1.0, 1.0 },
{ xpos + w, ypos + h, 1.0, 0.0 }
};
// Render glyph texture over quad
glBindTexture(GL_TEXTURE_2D, ch.TextureID);
// Update content of VBO memory
glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices); // Be sure to use glBufferSubData and not glBufferData
glBindBuffer(GL_ARRAY_BUFFER, 0);
// Render quad
glDrawArrays(GL_TRIANGLES, 0, 6);
// Now advance cursors for next glyph (note that advance is number of 1/64 pixels)
x += (ch.Advance >> 6) * scale; // Bitshift by 6 to get value in pixels (2^6 = 64 (divide amount of 1/64th pixels by 64 to get amount of pixels))
}
glBindVertexArray(0);
glBindTexture(GL_TEXTURE_2D, 0);
}
HI