nes-emu/ppu/renderers/_1_preLine.js

A NES emulator

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = preLine;
var _constants = _interopRequireDefault(require("../../constants"));
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
/** Runs on virtual scanline -1, which prepares the PPU for rendering. */
function preLine(_ref) {
  let {
    ppu,
    mapper
  } = _ref;
  if (!ppu.registers.ppuMask.isRenderingEnabled) return null;
  if (ppu.cycle === _constants.default.PPU_CYCLE_CLEAR_FLAGS) {
    const {
      ppuStatus
    } = ppu.registers;
    ppuStatus.spriteOverflow = 0;
    ppuStatus.sprite0Hit = 0;
    ppuStatus.isInVBlankInterval = 0;
  }
  ppu.loopy.onPreLine(ppu.cycle);
  ppu.loopy.onLine(ppu.cycle);
  return ppu.cycle === _constants.default.PPU_CYCLE_MAPPER_TICK ? mapper.tick() : null;
}