rpi-rgb-led-matrix/examples-api-use/text-example.cc

// -*- mode: c++; c-basic-offset: 2; indent-tabs-mode: nil; -*-
// Small example how write text.
//
// This code is public domain
// (but note, that the led-matrix library this depends on is GPL v2)

#include "led-matrix.h"
#include "graphics.h"

#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

using namespace rgb_matrix;

static int usage(const char *progname) {
  fprintf(stderr, "usage: %s [options]\n", progname);
  fprintf(stderr, "Reads text from stdin and displays it. "
          "Empty string: clear screen\n");
  fprintf(stderr, "Options:\n");
  rgb_matrix::PrintMatrixFlags(stderr);
  fprintf(stderr,
          "\t-f <font-file>    : Use given font.\n"
          "\t-b <brightness>   : Sets brightness percent. Default: 100.\n"
          "\t-x <x-origin>     : X-Origin of displaying text (Default: 0)\n"
          "\t-y <y-origin>     : Y-Origin of displaying text (Default: 0)\n"
          "\t-C <r,g,b>        : Color. Default 255,255,0\n");
  return 1;
}

static bool parseColor(Color *c, const char *str) {
  return sscanf(str, "%hhu,%hhu,%hhu", &c->r, &c->g, &c->b) == 3;
}

int main(int argc, char *argv[]) {
  RGBMatrix *canvas = rgb_matrix::CreateMatrixFromFlags(&argc, &argv);

  Color color(255, 255, 0);
  const char *bdf_font_file = NULL;
  int x_orig = 0;
  int y_orig = -1;
  int brightness = 100;

  int opt;
  while ((opt = getopt(argc, argv, "x:y:f:C:b:")) != -1) {
    switch (opt) {
    case 'b': brightness = atoi(optarg); break;
    case 'x': x_orig = atoi(optarg); break;
    case 'y': y_orig = atoi(optarg); break;
    case 'f': bdf_font_file = strdup(optarg); break;
    case 'C':
      if (!parseColor(&color, optarg)) {
        fprintf(stderr, "Invalid color spec.\n");
        return usage(argv[0]);
      }
      break;
    default:
      return usage(argv[0]);
    }
  }

  if (bdf_font_file == NULL) {
    fprintf(stderr, "Need to specify BDF font-file with -f\n");
    return usage(argv[0]);
  }

  if (canvas == NULL)
    return 1;

  /*
   * Load font. This needs to be a filename with a bdf bitmap font.
   */
  rgb_matrix::Font font;
  if (!font.LoadFont(bdf_font_file)) {
    fprintf(stderr, "Couldn't load font '%s'\n", bdf_font_file);
    return usage(argv[0]);
  }

  if (brightness < 1 || brightness > 100) {
    fprintf(stderr, "Brightness is outside usable range.\n");
    return 1;
  }

  canvas->SetBrightness(brightness);

  bool all_extreme_colors = brightness == 100;
  all_extreme_colors &= color.r == 0 || color.r == 255;
  all_extreme_colors &= color.g == 0 || color.g == 255;
  all_extreme_colors &= color.b == 0 || color.b == 255;
  if (all_extreme_colors)
    canvas->SetPWMBits(1);

  const int x = x_orig;
  int y = y_orig;

  if (isatty(STDIN_FILENO)) {
    // Only give a message if we are interactive. If connected via pipe, be quiet
    printf("Enter lines. Full screen or empty line clears screen.\n"
           "Supports UTF-8. CTRL-D for exit.\n");
  }

  char line[1024];
  while (fgets(line, sizeof(line), stdin)) {
    const size_t last = strlen(line);
    if (last > 0) line[last - 1] = '\0';  // remove newline.
    bool line_empty = strlen(line) == 0;
    if ((y + font.height() > canvas->height()) || line_empty) {
      canvas->Clear();
      y = y_orig;
    }
    if (line_empty)
      continue;
    rgb_matrix::DrawText(canvas, font, x, y + font.baseline(), color, line);
    y += font.height();
  }

  // Finished. Shut down the RGB matrix.
  canvas->Clear();
  delete canvas;

  return 0;
}