Funkin/source/funkin/graphics/rendering/SustainTrail.hx

package funkin.graphics.rendering;

import flixel.FlxSprite;
import flixel.graphics.FlxGraphic;
import flixel.graphics.tile.FlxDrawTrianglesItem;
import flixel.math.FlxMath;

/**
 * This is based heavily on the `FlxStrip` class. It uses `drawTriangles()` to clip a sustain note
 * trail at a certain time.
 * The whole `FlxGraphic` is used as a texture map. See the `NOTE_hold_assets.fla` file for specifics
 * on how it should be constructed.
 *
 * @author MtH
 */
class SustainTrail extends FlxSprite
{
  /**
   * Used to determine which note color/direction to draw for the sustain.
   */
  public var noteData:Int = 0;

  /**
   * The zoom level to render the sustain at.
   * Defaults to 1.0, increased to 6.0 for pixel notes.
   */
  public var zoom(default, set):Float = 1;

  /**
   * The strumtime of the note, in milliseconds.
   */
  public var strumTime:Float = 0; // millis

  /**
   * The sustain length of the note, in milliseconds.
   */
  public var sustainLength(default, set):Float = 0; // millis

  /**
   * The scroll speed of the note, as a multiplier.
   */
  public var scrollSpeed(default, set):Float = 1.0; // stand-in for PlayState scroll speed

  /**
   * Whether the note was missed.
   */
  public var missed:Bool = false; // maybe BlendMode.MULTIPLY if missed somehow, drawTriangles does not support!

  /**
   * A `Vector` of floats where each pair of numbers is treated as a coordinate location (an x, y pair).
   */
  var vertices:DrawData<Float> = new DrawData<Float>();

  /**
   * A `Vector` of integers or indexes, where every three indexes define a triangle.
   */
  var indices:DrawData<Int> = new DrawData<Int>();

  /**
   * A `Vector` of normalized coordinates used to apply texture mapping.
   */
  var uvtData:DrawData<Float> = new DrawData<Float>();

  var processedGraphic:FlxGraphic;

  /**
   * What part of the trail's end actually represents the end of the note.
   * This can be used to have a little bit sticking out.
   */
  public var endOffset:Float = 0.5; // 0.73 is roughly the bottom of the sprite in the normal graphic!

  /**
   * At what point the bottom for the trail's end should be clipped off.
   * Used in cases where there's an extra bit of the graphic on the bottom to avoid antialiasing issues with overflow.
   */
  public var bottomClip:Float = 0.9;

  /**
   * Normally you would take strumTime:Float, noteData:Int, sustainLength:Float, parentNote:Note (?)
   * @param NoteData 
   * @param SustainLength 
   * @param FileName 
   */
  public function new(NoteData:Int, SustainLength:Float, Path:String, ?Alpha:Float = 0.6, ?Pixel:Bool = false)
  {
    super(0, 0, Path);

    // BASIC SETUP
    this.sustainLength = SustainLength;
    this.noteData = NoteData;

    // CALCULATE SIZE
    if (Pixel)
    {
      this.endOffset = bottomClip = 1;
      this.antialiasing = false;
      this.zoom = 6.0;
    }
    else
    {
      this.antialiasing = true;
      this.zoom = 1.0;
    }
    // width = graphic.width / 8 * zoom; // amount of notes * 2
    height = sustainHeight(sustainLength, scrollSpeed);
    // instead of scrollSpeed, PlayState.SONG.speed

    alpha = Alpha; // setting alpha calls updateColorTransform(), which initializes processedGraphic!

    updateClipping();
    indices = new DrawData<Int>(12, true, [0, 1, 2, 2, 3, 0, 4, 5, 6, 6, 7, 4]);
  }

  /**
   * Calculates height of a sustain note for a given length (milliseconds) and scroll speed.
   * @param	susLength	The length of the sustain note in milliseconds.
   * @param	scroll		The current scroll speed.
   */
  public static inline function sustainHeight(susLength:Float, scroll:Float)
  {
    return (susLength * 0.45 * scroll);
  }

  function set_zoom(z:Float)
  {
    this.zoom = z;
    width = graphic.width / 8 * z;
    updateClipping();
    return this.zoom;
  }

  function set_sustainLength(s:Float)
  {
    height = sustainHeight(s, scrollSpeed);
    return sustainLength = s;
  }

  function set_scrollSpeed(s:Float)
  {
    height = sustainHeight(sustainLength, s);
    return scrollSpeed = s;
  }

  /**
   * Sets up new vertex and UV data to clip the trail.
   * If flipY is true, top and bottom bounds swap places.
   * @param songTime	The time to clip the note at, in milliseconds.
   */
  public function updateClipping(songTime:Float = 0):Void
  {
    var clipHeight:Float = FlxMath.bound(sustainHeight(sustainLength - (songTime - strumTime), scrollSpeed), 0, height);
    if (clipHeight == 0)
    {
      visible = false;
      return;
    }
    else
      visible = true;
    var bottomHeight:Float = graphic.height * zoom * endOffset;
    var partHeight:Float = clipHeight - bottomHeight;
    // == HOLD == //
    // left bound
    vertices[6] = vertices[0] = 0.0;
    // top bound
    vertices[3] = vertices[1] = flipY ? clipHeight : height - clipHeight;
    // right bound
    vertices[4] = vertices[2] = width;
    // bottom bound (also top bound for hold ends)
    if (partHeight > 0) vertices[7] = vertices[5] = flipY ? 0.0 + bottomHeight : vertices[1] + partHeight;
    else
      vertices[7] = vertices[5] = vertices[1];

    // same shit with da bounds, just in relation to the texture
    uvtData[6] = uvtData[0] = 1 / 4 * (noteData % 4);
    // height overflows past image bounds so wraps around, looping the texture
    // flipY bounds are not swapped for UV data, so the graphic is actually flipped
    // top bound
    uvtData[3] = uvtData[1] = (-partHeight) / graphic.height / zoom;
    uvtData[4] = uvtData[2] = uvtData[0] + 1 / 8; // 1
    // bottom bound
    uvtData[7] = uvtData[5] = 0.0;

    // == HOLD ENDS == //
    // left bound
    vertices[14] = vertices[8] = vertices[0];
    // top bound
    vertices[11] = vertices[9] = vertices[5];
    // right bound
    vertices[12] = vertices[10] = vertices[2];
    // bottom bound, mind the bottomClip because it clips off bottom of graphic!!
    vertices[15] = vertices[13] = flipY ? graphic.height * (-bottomClip + endOffset) : height + graphic.height * (bottomClip - endOffset);

    uvtData[14] = uvtData[8] = uvtData[2];
    if (partHeight > 0) uvtData[11] = uvtData[9] = 0.0;
    else
      uvtData[11] = uvtData[9] = (bottomHeight - clipHeight) / zoom / graphic.height;
    uvtData[12] = uvtData[10] = uvtData[8] + 1 / 8;
    // again, clips off bottom !!
    uvtData[15] = uvtData[13] = bottomClip;
  }

  @:access(flixel.FlxCamera)
  override public function draw():Void
  {
    if (alpha == 0 || graphic == null || vertices == null) return;

    for (camera in cameras)
    {
      if (!camera.visible || !camera.exists || !isOnScreen(camera)) continue;

      getScreenPosition(_point, camera).subtractPoint(offset);
      camera.drawTriangles(processedGraphic, vertices, indices, uvtData, null, _point, blend, true, antialiasing);
    }
  }

  override public function destroy():Void
  {
    vertices = null;
    indices = null;
    uvtData = null;
    processedGraphic.destroy();

    super.destroy();
  }

  override function updateColorTransform():Void
  {
    super.updateColorTransform();
    if (processedGraphic != null) processedGraphic.destroy();
    processedGraphic = FlxGraphic.fromGraphic(graphic, true);
    processedGraphic.bitmap.colorTransform(processedGraphic.bitmap.rect, colorTransform);
  }
}