wasmboy/core/graphics/palette.ts

Gameboy / Gameboy Color Emulator written for Web Assembly using AssemblyScript. Shell/Debugger in Preact

import { GBC_PALETTE_LOCATION } from '../constants';
import { Cpu } from '../cpu/index';
import { eightBitLoadFromGBMemory, eightBitStoreIntoGBMemory } from '../memory/index';
import { checkBitOnByte, resetBitOnByte, setBitOnByte, concatenateBytes } from '../helpers/index';

import { Colors } from './colors';

// Class for GBC Color palletes
// http://gbdev.gg8.se/wiki/articles/Video_Display#FF68_-_BCPS.2FBGPI_-_CGB_Mode_Only_-_Background_Palette_Index
export class Palette {
  static memoryLocationBackgroundPaletteIndex: i32 = 0xff68;
  static memoryLocationBackgroundPaletteData: i32 = 0xff69;
  static memoryLocationSpritePaletteIndex: i32 = 0xff6a;
  static memoryLocationSpritePaletteData: i32 = 0xff6b;

  // Palettes
  static readonly memoryLocationBackgroundPalette: i32 = 0xff47;
  static readonly memoryLocationSpritePaletteOne: i32 = 0xff48;
  static readonly memoryLocationSpritePaletteTwo: i32 = 0xff49;
}

// Inlined because closure compiler inlines
export function initializePalette(): void {
  if (Cpu.GBCEnabled) {
    // GBC Palettes
    eightBitStoreIntoGBMemory(0xff68, 0xc0);
    eightBitStoreIntoGBMemory(0xff69, 0xff);
    eightBitStoreIntoGBMemory(0xff6a, 0xc1);
    eightBitStoreIntoGBMemory(0xff6b, 0x0d);
  } else {
    // GBC Palettes
    eightBitStoreIntoGBMemory(0xff68, 0xff);
    eightBitStoreIntoGBMemory(0xff69, 0xff);
    eightBitStoreIntoGBMemory(0xff6a, 0xff);
    eightBitStoreIntoGBMemory(0xff6b, 0xff);
  }

  // Override some values if using the bootrom
  if (Cpu.BootROMEnabled && Cpu.GBCEnabled) {
    // GBC Palettes
    eightBitStoreIntoGBMemory(0xff69, 0x20);
    eightBitStoreIntoGBMemory(0xff6b, 0x8a);
  }
}

// Simple get pallete color or monochrome GB
// shouldRepresentColorByColorId is good for debugging tile data for GBC games that don't have
// monochromePalettes
// Inlined because closure compiler inlines
export function getMonochromeColorFromPalette(
  colorId: i32,
  paletteMemoryLocation: i32,
  shouldRepresentColorByColorId: boolean = false
): i32 {
  // Shift our paletteByte, 2 times for each color ID
  // And off any extra bytes
  // Return our Color (00 - white, 01 - light grey, 10 Dark grey, or 11 - Black)
  let color = colorId;
  if (!shouldRepresentColorByColorId) {
    color = ((<i32>eightBitLoadFromGBMemory(paletteMemoryLocation)) >> (colorId << 1)) & 0x03;
  }

  // Since our max is 254, and max is 3.
  // monochrome color palette is modified from bgb
  // TODO: Make these colors into a constant
  let rgbColor = 242;

  switch (color) {
    case 0:
      break;
    case 1:
      rgbColor = 160;
      break;
    case 2:
      rgbColor = 88;
      break;
    case 3:
      rgbColor = 8;
      break;
  }

  return rgbColor;
}

// Function to returns the Colorized color for a GB games
export function getColorizedGbHexColorFromPalette(colorId: i32, paletteMemoryLocation: i32): i32 {
  // Shift our paletteByte, 2 times for each color ID
  // And off any extra bytes
  // Return our Color (00 - white, 01 - light grey, 10 Dark grey, or 11 - Black)
  let color = ((<i32>eightBitLoadFromGBMemory(paletteMemoryLocation)) >> (colorId * 2)) & 0x03;

  // Check which palette we got, to apply the right color layer
  let hexColor = 0;
  if (paletteMemoryLocation === Palette.memoryLocationSpritePaletteOne) {
    hexColor = Colors.obj0White;

    switch (color) {
      case 0:
        break;
      case 1:
        hexColor = Colors.obj0LightGrey;
        break;
      case 2:
        hexColor = Colors.obj0DarkGrey;
        break;
      case 3:
        hexColor = Colors.obj0Black;
        break;
    }
  } else if (paletteMemoryLocation === Palette.memoryLocationSpritePaletteTwo) {
    hexColor = Colors.obj1White;

    switch (color) {
      case 0:
        break;
      case 1:
        hexColor = Colors.obj1LightGrey;
        break;
      case 2:
        hexColor = Colors.obj1DarkGrey;
        break;
      case 3:
        hexColor = Colors.obj1Black;
        break;
    }
  } else {
    hexColor = Colors.bgWhite;

    switch (color) {
      case 0:
        break;
      case 1:
        hexColor = Colors.bgLightGrey;
        break;
      case 2:
        hexColor = Colors.bgDarkGrey;
        break;
      case 3:
        hexColor = Colors.bgBlack;
        break;
    }
  }

  return hexColor;
}

// Inlined because closure compiler inlines
export function writeColorPaletteToMemory(offset: i32, value: i32): void {
  // FF68
  //  Bit 0-5   Index (00-3F)
  let memoryLocationSpritePaletteData = Palette.memoryLocationSpritePaletteData;
  if (offset === Palette.memoryLocationBackgroundPaletteData || offset === memoryLocationSpritePaletteData) {
    // Get the palette index
    let paletteIndex: i32 = eightBitLoadFromGBMemory(offset - 1);

    // Clear the 6th bit, as it does nothing
    paletteIndex = resetBitOnByte(6, paletteIndex);

    // Check if we are changing the sprite pallete data
    let isSprite = offset === memoryLocationSpritePaletteData;
    storePaletteByteInWasmMemory(paletteIndex, value, isSprite);
    incrementPaletteIndexIfSet(paletteIndex, offset - 1);
  }
}

// Functions to Handle Write to pallete data registers
// http://gbdev.gg8.se/wiki/articles/Video_Display#FF68_-_BCPS.2FBGPI_-_CGB_Mode_Only_-_Background_Palette_Index
// Function to handle incrementing the pallete index if required
// Inlined because closure compiler inlines
function incrementPaletteIndexIfSet(paletteIndex: i32, offset: i32): void {
  // Check ther auto increment box
  if (checkBitOnByte(7, paletteIndex)) {
    // Increment the index, and return the value before the increment
    // Ensure we don't ouverflow our auto increment bit
    paletteIndex += 1;
    paletteIndex = setBitOnByte(7, paletteIndex);

    eightBitStoreIntoGBMemory(offset, paletteIndex);
  }
}

// FF68
// Bit 0-5   Index (00-3F)
// Bit 7     Auto Increment  (0=Disabled, 1=Increment after Writing)
// Index is 00-0x3F because the means 0 - 63 (64),
// and apparently there are 8 bytes per pallete to describe Color 0-3 (4 colors),
// and 0-7 (8 palltetes). Therefore, 64!
export function getRgbColorFromPalette(paletteId: i32, colorId: i32, isSprite: boolean): i32 {
  // Each Pallete takes 8 bytes, so multiply by 8 to get the pallete
  // And Each color takes 2 bytes, therefore, multiple by 2 for the correct color bytes in the palette
  let paletteIndex = paletteId * 8 + colorId * 2;

  // Load the Color that is seperated into two bytes
  let paletteHighByte: i32 = loadPaletteByteFromWasmMemory(paletteIndex + 1, isSprite);
  let paletteLowByte: i32 = loadPaletteByteFromWasmMemory(paletteIndex, isSprite);

  // Return the concatenated color byte
  return <i32>concatenateBytes(paletteHighByte, paletteLowByte);
}

// Function to return the color from a passed 16 bit color pallette
export function getColorComponentFromRgb(colorId: i32, colorRgb: i32): i32 {
  // Get our bitmask for the color ID
  // bit mask tested good :)
  colorId *= 5;
  let bitMask = 0x1f << colorId;
  let colorValue = (colorRgb & bitMask) >> colorId;

  // Goal is to reach 254 for each color, so 255 / 31 (0x1F) ~8 TODO: Make exact
  // Want 5 bits for each
  return colorValue * 8;
}

// Function to load a byte from our Gbc Palette memory
export function loadPaletteByteFromWasmMemory(paletteIndexByte: i32, isSprite: boolean): u8 {
  // Clear the top two bits to just get the bottom palette Index
  let paletteIndex = paletteIndexByte & 0x3f;

  // Move over the palette index to not overlap the background has 0x3F, so Zero for Sprites is 0x40)
  if (isSprite) {
    paletteIndex += 0x40;
  }

  return load<u8>(GBC_PALETTE_LOCATION + paletteIndex);
}

// Function to store a byte to our Gbc Palette memory
// Inlined because closure compiler inlines
export function storePaletteByteInWasmMemory(paletteIndexByte: i32, value: i32, isSprite: boolean): void {
  // Clear the top two bits to just get the bottom palette Index
  let paletteIndex = paletteIndexByte & 0x3f;

  // Move over the palette index to not overlap the background (has 0x3F, so Zero for Sprites is 0x40)
  if (isSprite) {
    paletteIndex += 0x40;
  }

  store<u8>(GBC_PALETTE_LOCATION + paletteIndex, <u8>value);
}