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Text-Rendering.h
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Text-Rendering.h
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#pragma once
#include <map>
/// Holds all state information relevant to a character as loaded using FreeType
struct Character {
unsigned int TextureID; // ID handle of the glyph texture
glm::ivec2 Size; // Size of glyph
glm::ivec2 Bearing; // Offset from baseline to left/top of glyph
unsigned int Advance; // Horizontal offset to advance to next glyph
};
std::map<GLchar, Character> Characters;
unsigned int VAO, VBO;
// To render text on screen
void RenderText(Shader& shader, std::string text, float x, float y, float scale, glm::vec3 color)
{
// activate corresponding render state
shader.use();
glUniform3f(glGetUniformLocation(shader.ID, "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];
float xpos = x + ch.Bearing.x * scale;
float ypos = y - (ch.Size.y - ch.Bearing.y) * scale;
float w = ch.Size.x * scale;
float h = ch.Size.y * scale;
// update VBO for each character
float vertices[6][4] = {
{ xpos, ypos + h, 0.0f, 0.0f },
{ xpos, ypos, 0.0f, 1.0f },
{ xpos + w, ypos, 1.0f, 1.0f },
{ xpos, ypos + h, 0.0f, 0.0f },
{ xpos + w, ypos, 1.0f, 1.0f },
{ xpos + w, ypos + h, 1.0f, 0.0f }
};
// 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);
}
// Binding Text Texture with shader
int BindText(Shader shader)
{
// Using Blend mode to blend texture with background color
glEnable(GL_CULL_FACE);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glm::mat4 projection = glm::ortho(0.0f, static_cast<float>(Screen_Width), 0.0f, static_cast<float>(Screen_Height));
shader.use();
glUniformMatrix4fv(glGetUniformLocation(shader.ID, "projection"), 1, GL_FALSE, glm::value_ptr(projection));
// Initialize freetype library object
FT_Library ft;
if (FT_Init_FreeType(&ft))
{
std::cout << "ERROR::FREETYPE: Could not init FreeType Library" << std::endl;
std::cin.get();
return -1;
}
// Load Font from directory as a face
FT_Face face;
if (FT_New_Face(ft, "FreeType/fonts/arial.ttf", 0, &face))
{
std::cout << "ERROR::FREETYPE: Failed to load font" << std::endl;
std::cin.get();
return -1;
}
else {
// set size to load glyphs as
FT_Set_Pixel_Sizes(face, 0, 24);
// disable byte-alignment restriction
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
// load first 128 characters of ASCII set
for (unsigned char 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;
std::cin.get();
continue;
}
// generate texture
unsigned int 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<char, 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(float) * 6 * 4, NULL, GL_DYNAMIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(float), 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
}