broken-neees/ppu/SpriteRenderer.js

A really broken NEEES emulator that introduces glitches and random bugs on purpose!

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _Sprite = _interopRequireDefault(require("../lib/ppu/Sprite"));
var _Tile = _interopRequireDefault(require("./Tile"));
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
const TILE_SIZE_PIXELS = 8;
const SPRITE_SIZE_BYTES = 4;
const SPRITE_BYTE_Y = 0;
const SPRITE_BYTE_TILE_ID = 1;
const SPRITE_BYTE_ATTRIBUTES = 2;
const SPRITE_BYTE_X = 3;
const SPRITE_8x16_PATTERN_TABLE_MASK = 0b1;
const SPRITE_8x16_TILE_ID_MASK = 0xfe;
const MAX_SPRITES = 64;
const MAX_SPRITES_PER_SCANLINE = 8;
class SpriteRenderer {
  constructor(ppu) {
    this.ppu = ppu;
  }
  renderScanline() {
    if (!this.ppu.registers.ppuMask.showSprites) return;
    const sprites = this._evaluate();
    const buffer = this._render(sprites);
    this._draw(buffer);
  }
  _evaluate() {
    const sprites = [];
    for (let spriteId = 0; spriteId < MAX_SPRITES; spriteId++) {
      const sprite = this._createSprite(spriteId);
      if (sprite.shouldRenderInScanline(this.ppu.scanline) && sprites.length < MAX_SPRITES_PER_SCANLINE + 1) {
        if (sprites.length < MAX_SPRITES_PER_SCANLINE) {
          sprites.push(sprite);
        } else {
          this.ppu.registers.ppuStatus.spriteOverflow = 1;
          break;
        }
      }
    }
    if (this.ppu.cpu.unbroken) {
      return sprites.reverse();
    } else {
      // [!!!]
      return sprites;
    }
  }
  _render(sprites) {
    const y = this.ppu.scanline;
    const buffer = [];
    for (let sprite of sprites) {
      const insideY = sprite.diffY(y);
      const tileInsideY = insideY % TILE_SIZE_PIXELS;
      const tile = new _Tile.default(this.ppu, sprite.patternTableId, sprite.tileIdFor(insideY), sprite.flipY ? TILE_SIZE_PIXELS - 1 - tileInsideY : tileInsideY);
      const paletteColors = this.ppu.getPaletteColors(sprite.paletteId);
      for (let insideX = 0; insideX < TILE_SIZE_PIXELS; insideX++) {
        const x = sprite.x + insideX;
        if (!this.ppu.registers.ppuMask.showSpritesInFirst8Pixels && x < 8) continue;
        const colorIndex = tile.getColorIndex(sprite.flipX ? TILE_SIZE_PIXELS - 1 - insideX : insideX);
        if (colorIndex > 0) {
          const color = paletteColors[colorIndex];
          buffer[x] = {
            x,
            color,
            isInFrontOfBackground: sprite.isInFrontOfBackground
          };
          if (sprite.id === 0 && this.ppu.isBackgroundPixelOpaque(x, y) && this.ppu.registers.ppuMask.showBackground && this.ppu.registers.ppuMask.showSprites) this.ppu.registers.ppuStatus.sprite0Hit = 1;
        }
      }
    }
    return buffer;
  }
  _draw(buffer) {
    const y = this.ppu.scanline;
    for (let object of buffer) {
      if (!object) continue;
      const {
        x,
        color,
        isInFrontOfBackground
      } = object;
      const isBackgroundPixelOpaque = this.ppu.isBackgroundPixelOpaque(x, y);
      const shouldDraw = isInFrontOfBackground || !isBackgroundPixelOpaque;
      if (shouldDraw) this.ppu.plot(x, y, color);
    }
  }
  _createSprite(id) {
    const oamRam = this.ppu.memory.oamRam;
    const ppuCtrl = this.ppu.registers.ppuCtrl;
    const is8x16 = ppuCtrl.spriteSize === 1;
    const address = id * SPRITE_SIZE_BYTES;
    let yByte;
    if (this.ppu.cpu.unbroken) {
      yByte = oamRam[address + SPRITE_BYTE_Y];
    } else {
      // [!!!]
      yByte = oamRam[address + SPRITE_BYTE_Y] + (id > 0 ? 10 : 0);
    }
    const tileIdByte = oamRam[address + SPRITE_BYTE_TILE_ID];
    const attributes = oamRam[address + SPRITE_BYTE_ATTRIBUTES];
    const x = oamRam[address + SPRITE_BYTE_X];
    const y = yByte + 1;
    const patternTableId = is8x16 ? tileIdByte & SPRITE_8x16_PATTERN_TABLE_MASK : ppuCtrl.sprite8x8PatternTableId;
    const tileId = is8x16 ? tileIdByte & SPRITE_8x16_TILE_ID_MASK : tileIdByte;
    return new _Sprite.default(this.ppu, id, x, y, is8x16, patternTableId, tileId, attributes);
  }
}
exports.default = SpriteRenderer;