textRenderer.cpp

#include <SDL2/SDL.h>
#include <math.h>
#include <stdio.h>
#include <textRenderer.h>

// class members
unsigned int TextRenderer::referenceCounter = 0;

TextRenderer::TextRenderer(char *fontPath, unsigned int fontSize) {
  // Init font for text drawing
  if (!TextRenderer::referenceCounter) {
    if (TTF_Init() == -1) {
      fprintf(stderr, "TTF_Init: %s\n", TTF_GetError());
      exit(1);
    }
  }
  font = TTF_OpenFont(fontPath, fontSize);
  if (!font) {
    fprintf(stderr, "TTF_OpenFont: %s\n", TTF_GetError());
  }
  // disable kerning since we are not able to make any use of it
  TTF_SetFontKerning(font, 0);
  // get font outline
  outline = TTF_GetFontOutline(font);
  fontHeight = TTF_FontHeight(font);
  initTextures();
  TextRenderer::referenceCounter++;
}

void TextRenderer::initTextures() {
  SDL_Surface *surface;
  SDL_Color color = {255, 255, 255, 255};
  int maxy, miny, advance, minx, maxx;
  GLuint texture;
  for (char i = 0x20; i < 0x7F; ++i) {
    // cache glyph metrics and texture
    TTF_GlyphMetrics(font, i, &minx, &maxx, &miny, &maxy, &advance);
    if (!(surface = TTF_RenderGlyph_Blended(font, i, color))) {
      fprintf(stderr, "%s\n", TTF_GetError());
    }
    glGenTextures(1, &texture);
    Glyph glyph(i, advance, miny, maxy, minx, maxx, texture);
    glBindTexture(GL_TEXTURE_2D, glyph.getTextureID());
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, surface->w, surface->h, 0, GL_RGBA,
                 GL_UNSIGNED_BYTE, surface->pixels);
    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_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glyphs.push_back(glyph);
    SDL_FreeSurface(surface);
  }
}

void TextRenderer::renderText(char *str, int x, int y) {
  for (char *c = str; (*c) != '\0'; c++) {
    renderChar(*c, x, y);
    x += getGlyph(*c).getAdvance();
  }
}

// x, y is the top-left origin
void TextRenderer::renderChar(char letter, int x, int y) {
  Glyph glyph = getGlyph(letter);
  glDisable(GL_DEPTH_TEST);
  glDisable(GL_LIGHTING);
  glEnable(GL_TEXTURE_2D);
  glEnable(GL_BLEND);
  glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
  glBindTexture(GL_TEXTURE_2D, glyph.getTextureID());
  glBegin(GL_QUADS);
  glTexCoord2f(0, 0);
  glVertex2f(x - outline, y + fontHeight - outline);
  glTexCoord2f(0, 1);
  glVertex2f(x - outline, y - outline);
  glTexCoord2f(1, 1);
  glVertex2f(x + glyph.getMaxX() - outline, y - outline);
  glTexCoord2f(1, 0);
  glVertex2f(x + glyph.getMaxX() - outline, y + fontHeight - outline);
  glEnd();
  glDisable(GL_BLEND);
  glDisable(GL_TEXTURE_2D);
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_LIGHTING);
}

int TextRenderer::getWidth(const char *str) {
  int w;
  TTF_SizeText(font, str, &w, NULL);
  return w;
}

int TextRenderer::getHeight() { return fontHeight; }

void TextRenderer::quit() {
  TextRenderer::referenceCounter--;
  TTF_CloseFont(font);
  if (!TextRenderer::referenceCounter) {
    TTF_Quit();
  }
}