scrolling-text-example.cc

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

// For a utility with a few more features see
// ../utils/text-scroller.cc

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

#include <string>

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

using namespace rgb_matrix;

volatile bool interrupt_received = false;
static void InterruptHandler(int signo) {
  interrupt_received = true;
}

static int usage(const char *progname) {
  fprintf(stderr, "usage: %s [options] <text>\n", progname);
  fprintf(stderr, "Takes text and scrolls it with speed -s\n");
  fprintf(stderr, "Options:\n");
  rgb_matrix::PrintMatrixFlags(stderr);
  fprintf(stderr,
          "\t-s <speed>        : Approximate letters per second. "
          "(Zero for no scrolling)\n"
          "\t-l <loop-count>   : Number of loops through the text. "
          "-1 for endless (default)\n"
          "\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-t <track=spacing>: Spacing pixels between letters (Default: 0)\n"
          "\n"
          "\t-C <r,g,b>        : Text-Color. Default 255,255,0\n"
          "\t-B <r,g,b>        : Background-Color. Default 0,0,0\n"
          );
  return 1;
}

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

static bool FullSaturation(const Color &c) {
  return (c.r == 0 || c.r == 255)
    && (c.g == 0 || c.g == 255)
    && (c.b == 0 || c.b == 255);
}

int main(int argc, char *argv[]) {
  RGBMatrix::Options matrix_options;
  rgb_matrix::RuntimeOptions runtime_opt;
  if (!rgb_matrix::ParseOptionsFromFlags(&argc, &argv,
                                         &matrix_options, &runtime_opt)) {
    return usage(argv[0]);
  }

  Color color(255, 255, 0);
  Color bg_color(0, 0, 0);

  const char *bdf_font_file = NULL;
  std::string line;
  /* x_origin is set by default just right of the screen */
  const int x_default_start = (matrix_options.chain_length
                               * matrix_options.cols) + 5;
  int x_orig = x_default_start;
  int y_orig = 0;
  int brightness = 100;
  int letter_spacing = 0;
  float speed = 7.0f;
  int loops = -1;

  int opt;
  while ((opt = getopt(argc, argv, "x:y:f:C:B:b:t:s:l:")) != -1) {
    switch (opt) {
    case 's': speed = atof(optarg); break;
    case 'l': loops = atoi(optarg); break;
    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 't': letter_spacing = atoi(optarg); break;
    case 'C':
      if (!parseColor(&color, optarg)) {
        fprintf(stderr, "Invalid color spec: %s\n", optarg);
        return usage(argv[0]);
      }
      break;
    case 'B':
      if (!parseColor(&bg_color, optarg)) {
        fprintf(stderr, "Invalid background color spec: %s\n", optarg);
        return usage(argv[0]);
      }
      break;
    default:
      return usage(argv[0]);
    }
  }

  for (int i = optind; i < argc; ++i) {
    line.append(argv[i]).append(" ");
  }

  if (line.empty()) {
    fprintf(stderr, "Add the text you want to print on the command-line.\n");
    return usage(argv[0]);
  }

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

  /*
   * 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 1;
  }

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

  RGBMatrix *canvas = rgb_matrix::CreateMatrixFromOptions(matrix_options,
                                                          runtime_opt);
  if (canvas == NULL)
    return 1;

  canvas->SetBrightness(brightness);

  const bool all_extreme_colors = (brightness == 100)
    && FullSaturation(color)
    && FullSaturation(bg_color);
  if (all_extreme_colors)
    canvas->SetPWMBits(1);

  signal(SIGTERM, InterruptHandler);
  signal(SIGINT, InterruptHandler);

  printf("CTRL-C for exit.\n");

  // Create a new canvas to be used with led_matrix_swap_on_vsync
  FrameCanvas *offscreen_canvas = canvas->CreateFrameCanvas();

  int delay_speed_usec = 1000000;
  if (speed > 0) {
    delay_speed_usec = 1000000 / speed / font.CharacterWidth('W');
  } else if (x_orig == x_default_start) {
    // There would be no scrolling, so text would never appear. Move to front.
    x_orig = 0;
  }

  int x = x_orig;
  int y = y_orig;
  int length = 0;

  while (!interrupt_received && loops != 0) {
    offscreen_canvas->Fill(bg_color.r, bg_color.g, bg_color.b);
    // length = holds how many pixels our text takes up
    length = rgb_matrix::DrawText(offscreen_canvas, font,
                                  x, y + font.baseline(),
                                  color, nullptr,
                                  line.c_str(), letter_spacing);

    if (speed > 0 && --x + length < 0) {
      x = x_orig;
      if (loops > 0) --loops;
    }

    // Swap the offscreen_canvas with canvas on vsync, avoids flickering
    offscreen_canvas = canvas->SwapOnVSync(offscreen_canvas);
    usleep(delay_speed_usec);
  }

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

  return 0;
}