Avoid repeatedly allocating frame line buffer in stack

src/chip8.cpp

@@ -386,12 +386,12 @@ void Chip8::RenderFrame() {
  const std::string border_down = u8"\u2514" + horizontal + u8"\u2518" + "\n";
  std::string pixels = border_up;
  for (size_t row = 0; row < ROWS; ++row) {
- std::array<uint8_t, COLS> line {};
+ static std::array<char, COLS> line_buffer {};
  for (size_t col = 0; col < COLS; ++col) {
  size_t index = row * COLS + col;
- frame_buffer_[index] != 0 ? line[col] = 24 : line[col] = ' ';
+ frame_buffer_[index] != 0 ? line_buffer[col] = 24 : line_buffer[col] = ' ';
  }
- std::string frame_row(line.begin(), line.end());
+ std::string frame_row(line_buffer.begin(), line_buffer.end());
  const std::string border_left_right = u8"\u2502";
  pixels += border_left_right + frame_row + border_left_right;
  pixels += "\n";
@@ -403,13 +403,13 @@ void Chip8::RenderFrame() {
  Frontend::WritePC(pixels, PC_);
  Frontend::WriteSP(pixels, SP_);
  Frontend::WriteStack(pixels, stack_);
- int line = 10;
- Frontend::WriteRight(pixels, line++, "[P]ause/resume [S]tep [R]un [Esc]ape\n");
- Frontend::WriteRight(pixels, line++, "[-] " + std::to_string(freq_) + " Hz [+]\n");
+ int line_num = 10;
+ Frontend::WriteRight(pixels, line_num++, "[P]ause/resume [S]tep [R]un [Esc]ape\n");
+ Frontend::WriteRight(pixels, line_num++, "[-] " + std::to_string(freq_) + " Hz [+]\n");
  for (const auto& key_descr: cfg_parser_->key_descrs()) {
  std::string key = key_descr.first;
  std::string descr = key_descr.second;
- Frontend::WriteRight(pixels, line++, "[" + key + "] " + descr + "\n");
+ Frontend::WriteRight(pixels, line_num++, "[" + key + "] " + descr + "\n");
  }
  std::cout << pixels << std::endl << std::flush;
  std::this_thread::sleep_for(std::chrono::microseconds(1400));