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- §

  # Spiral factory

  A factory for generating spiral shape-based entitys

  Path-defined entitys represent a diverse range of shapes rendered onto a DOM <canvas> element using the Canvas API’s Path2D interface. They use the shapeBasic and shapePathCalculation (some also use shapeCurve) mixins to define much of their functionality.

  All path-defined entitys can be positioned, cloned, filtered etc:

  - Positioning functionality for the entity is supplied by the position mixin, while rendering functionality comes from the entity mixin.
  - Dimensions, however, have little meaning for path-defined entitys - their width and height are determined by their SVG path data Strings; use `scale` instead.
  - Path-defined entitys can use CSS color Strings for their fillStyle and strokeStyle values, alongside Gradient, RadialGradient, Color and Pattern objects.
  - They will also accept Filter objects.
  - They can use Anchor objects for user navigation.
  - They can be rendered to the canvas by including them in a Cell object’s Group.
  - They can be animated directly, or using delta animation, or act as the target for Tween animations.
  - Path-defined entitys can be cloned, and killed.
- §

  #### Using path-defined entitys as Scrawl-canvas paths

  A path is a track - straight, or curved, or as complex as required - placed across a container which artefacts can use as a source of their positioning data. We can animate an artifact to move along the path:

  - To enable a path-defined entity to be used as a path by other artefacts, set its `useAsPath` flag to `true`.
  - The artefact can then set its `path` attribute to the path-defined entity’s name-String (or the entity itself), and set its `lockTo` Array values to `"path"`.
  - We position the artefact by setting its `pathPosition` attribute to a float Number value between `0.0 - 1.0`, with `0` being the start of the path, and `1` being its end.
  - Path-defined entitys can use other path-defined entitys as a path.
  - Phrase entitys can use a path to position their text block; they can also use a path to position each letter individually along the path.
  - Artefacts (and letters) can be rotated so that they match the rotation at that point along the path - tangential rotation by setting their `addPathRotation` flag to `true`.
  - Animate an artefact along the path by either using the artefact’s `delta` object, or triggering a Tween to perform the movement.
- §

  #### Demos:

  - Canvas-011 - Shape entity (make, clone, method); drag and drop shape entitys
  - Canvas-012 - Shape entity position; shape entity as a path for other artefacts to follow
  - Canvas-013 - Path-defined entitys: oval, rectangle, line, quadratic, bezier, tetragon, polygon, star, spiral
  - Canvas-014 - Line, quadratic and bezier entitys - control lock alternatives
  - Canvas-018 - Phrase entity - text along a path
  - Canvas-024 - Loom entity functionality
  - Canvas-030 - Polyline entity functionality
  - Canvas-038 - Responsive Shape-based entitys
  - DOM-015 - Use stacked DOM artefact corners as pivot points
  - Packets-002 - Scrawl-canvas packets - save and load a range of different entitys
- §

  #### Imports

      import { constructors } from '../core/library.js';

      import { doCreate, mergeOver, Ωempty } from '../core/utilities.js';

      import { releaseArray, requestArray } from './array-pool.js';

      import baseMix from '../mixin/base.js';
      import shapeMix from '../mixin/shape-basic.js';

      import { _floor, _freeze, ENTITY, SPIRAL, T_SPIRAL, ZERO_PATH } from '../core/shared-vars.js';

- §

  Local constants

      const FIRST_TURN = _freeze([
          _freeze([0.043, 0, 0.082, -0.035, 0.088, -0.088]),
          _freeze([0.007, -0.057, -0.024, -0.121, -0.088, -0.162]),
          _freeze([-0.07, -0.045, -0.169, -0.054, -0.265, -0.015]),
          _freeze([-0.106, 0.043, -0.194, 0.138, -0.235, 0.265]),
          _freeze([-0.044, 0.139, -0.026, 0.3, 0.058, 0.442]),
          _freeze([0.091, 0.153, 0.25, 0.267, 0.442, 0.308]),
          _freeze([0.206, 0.044, 0.431, -0.001, 0.619, -0.131]),
          _freeze([0.2, -0.139, 0.34, -0.361, 0.381, -0.619])
      ]);
      const SUBSEQUENT_TURNS = _freeze([
          _freeze([0, -0.27, -0.11, -0.52, -0.29, -0.71]),
          _freeze([-0.19, -0.19, -0.44, -0.29, -0.71, -0.29]),
          _freeze([-0.27, 0, -0.52, 0.11, -0.71, 0.29]),
          _freeze([-0.19, 0.19, -0.29, 0.44, -0.29, 0.71]),
          _freeze([0, 0.27, 0.11, 0.52, 0.29, 0.71]),
          _freeze([0.19, 0.19, 0.44, 0.29, 0.71, 0.29]),
          _freeze([0.27, 0, 0.52, -0.11, 0.71, -0.29]),
          _freeze([0.19, -0.19, 0.29, -0.44, 0.29, -0.71])
      ]);

- §

  #### Spiral constructor

      const Spiral = function (items = Ωempty) {

          this.shapeInit(items);
          return this;
      };

- §

  #### Spiral prototype

      const P = Spiral.prototype = doCreate();
      P.type = T_SPIRAL;
      P.lib = ENTITY;
      P.isArtefact = true;
      P.isAsset = false;

- §

  #### Mixins

  - base
  - shapeBasic

      baseMix(P);
      shapeMix(P);

- §

  #### Spiral attributes

  - Attributes defined in the base mixin: name.
  - Attributes defined in the position mixin: group, visibility, order, calculateOrder, stampOrder, start, startX, startY, handle, handleX, handleY, offset, offsetX, offsetY, dimensions, width, height, pivoted, mimicked, lockTo, lockXTo, lockYTo, scale, roll, noUserInteraction, noPositionDependencies, noCanvasEngineUpdates, noFilters, noPathUpdates, purge, bringToFrontOnDrag.
  - Attributes defined in the delta mixin: delta, noDeltaUpdates.
  - Attributes defined in the pivot mixin: pivot, pivotCorner, addPivotHandle, addPivotOffset, addPivotRotation.
  - Attributes defined in the mimic mixin: mimic, useMimicDimensions, useMimicScale, useMimicStart, useMimicHandle, useMimicOffset, useMimicRotation, useMimicFlip, addOwnDimensionsToMimic, addOwnScaleToMimic, addOwnStartToMimic, addOwnHandleToMimic, addOwnOffsetToMimic, addOwnRotationToMimic.
  - Attributes defined in the path mixin: path, pathPosition, addPathHandle, addPathOffset, addPathRotation, constantPathSpeed.
  - Attributes defined in the entity mixin: method, pathObject, winding, flipReverse, flipUpend, scaleOutline, lockFillStyleToEntity, lockStrokeStyleToEntity, onEnter, onLeave, onDown, onUp, fillStyle, strokeStyle, globalAlpha, globalCompositeOperation, lineWidth, lineCap, lineJoin, lineDash, lineDashOffset, miterLimit, shadowOffsetX, shadowOffsetY, shadowBlur, shadowColor, filter.
  - Attributes defined in the anchor mixin: anchor.
  - Attributes defined in the filter mixin: filters, isStencil.
  - Attributes defined in the shapeBasic mixin: species, useAsPath, precision, pathDefinition, showBoundingBox, boundingBoxColor, minimumBoundingBoxDimensions, constantPathSpeed.

      const defaultAttributes = {

          loops: 1,
          loopIncrement: 1,
          drawFromLoop: 0,
      };
      P.defs = mergeOver(P.defs, defaultAttributes);

- §

  #### Packet management

  No additional packet functionality required

- §

  #### Clone management

  No additional clone functionality required

- §

  #### Kill management

  No additional kill functionality required

- §

  #### Get, Set, deltaSet

      const S = P.setters,
          D = P.deltaSetters;

- §

  loops

      S.loops = function (item) {

          this.loops = item;
          this.updateDirty();
      };
      D.loops = function (item) {

          this.loops += item;
          this.updateDirty();
      };

- §

  loopIncrement

      S.loopIncrement = function (item) {

          this.loopIncrement = item;
          this.updateDirty();
      };
      D.loopIncrement = function (item) {

          this.loopIncrement += item;
          this.updateDirty();
      };

- §

  drawFromLoop

      S.drawFromLoop = function (item) {

          this.drawFromLoop = _floor(item);
          this.updateDirty();
      };
      D.drawFromLoop = function (item) {

          this.drawFromLoop = _floor(this.drawFromLoop + item);
          this.updateDirty();
      };

- §

  #### Prototype functions

- §

  `cleanSpecies` - internal helper function - called by `prepareStamp`

      P.cleanSpecies = function () {

          this.dirtySpecies = false;
          this.pathDefinition = this.makeSpiralPath();
      };

- §

  `makeSpiralPath` - internal helper function - called by `cleanSpecies`

      P.makeSpiralPath = function () {

          const loops = _floor(this.loops),
              loopIncrement = this.loopIncrement,
              drawFromLoop = _floor(this.drawFromLoop),
              currentTurn = requestArray();

          let x1, y1, x2, y2, x3, y3,
              sx1, sy1, sx2, sy2, sx3, sy3;

          for (let i = 0, iz = FIRST_TURN.length; i < iz; i++) {

              [x1, y1, x2, y2, x3, y3] = FIRST_TURN[i];
              currentTurn.push([x1 * loopIncrement, y1 * loopIncrement, x2 * loopIncrement, y2 * loopIncrement, x3 * loopIncrement, y3 * loopIncrement]);
          }

          let path = ZERO_PATH;

          for (let j = 0; j < loops; j++) {

              for (let i = 0, iz = currentTurn.length; i < iz; i++) {

                  [x1, y1, x2, y2, x3, y3] = currentTurn[i];

                  if (j >= drawFromLoop) path += `c${x1},${y1} ${x2},${y2} ${x3},${y3}`;

                  [sx1, sy1, sx2, sy2, sx3, sy3] = SUBSEQUENT_TURNS[i];
                  currentTurn[i] = [x1 + (sx1 * loopIncrement), y1 + (sy1 * loopIncrement), x2 + (sx2 * loopIncrement), y2 + (sy2 * loopIncrement), x3 + (sx3 * loopIncrement), y3 + (sy3 * loopIncrement)];
              }
          }
          releaseArray(currentTurn);

          return path;
      };

      P.calculateLocalPathAdditionalActions = function () {

          const [x, y] = this.localBox,
              scale = this.scale;

          this.pathDefinition = this.pathDefinition.replace(ZERO_PATH, `m${-x / scale},${-y / scale}`);

          this.pathCalculatedOnce = false;

- §

  ALWAYS, when invoking `calculateLocalPath` from `calculateLocalPathAdditionalActions`, include the second argument, set to `true`! Failure to do this leads to an infinite loop which will make your machine weep.

  - We need to recalculate the local path to take into account the offset required to put the Spiral entity’s start coordinates at the top-left of the local box, and to recalculate the data used by other artefacts to place themselves on, or move along, its path.

          this.calculateLocalPath(this.pathDefinition, true);
      };

- §

  #### Factories

- §

  ##### makeSpiral

  A spiral drawn from an inner-radius outwards by a given number of loops, with the distance between each loop determined by a given increment. Accepts argument with attributes:

  - loops (required) - positive float Number representing the number of times the Shape line will wind arount the Shape’s center point
  - loopIncrement - float Number representative of the distance between successive loops; negative values have the effect of rotating the spiral 180 degrees
  - drawFromLoop - positive integer Number representing the loop on which the spiral starts to be drawn

      scrawl.makeSpiral({

          name: 'mySpiral',

          strokeStyle: 'darkgreen',
          method: 'draw',

          startX: 50,
          startY: 100,

          loops: 5,
          loopIncrement: 0.8,
          drawFromLoop: 1,
      });

      export const makeSpiral = function (items) {

          if (!items) return false;
          items.species = SPIRAL;
          return new Spiral(items);
      };

      constructors.Spiral = Spiral;