- Jump To … +
  ./demo/canvas-001.js ./demo/canvas-002.js ./demo/canvas-003.js ./demo/canvas-004.js ./demo/canvas-005.js ./demo/canvas-006.js ./demo/canvas-007.js ./demo/canvas-008.js ./demo/canvas-009.js ./demo/canvas-010.js ./demo/canvas-011.js ./demo/canvas-012.js ./demo/canvas-013.js ./demo/canvas-014.js ./demo/canvas-015.js ./demo/canvas-015a.js ./demo/canvas-016.js ./demo/canvas-017.js ./demo/canvas-018.js ./demo/canvas-019.js ./demo/canvas-019a.js ./demo/canvas-020.js ./demo/canvas-021.js ./demo/canvas-022.js ./demo/canvas-023.js ./demo/canvas-024.js ./demo/canvas-025.js ./demo/canvas-026.js ./demo/canvas-027.js ./demo/canvas-028.js ./demo/canvas-029.js ./demo/canvas-030.js ./demo/canvas-031.js ./demo/canvas-032.js ./demo/canvas-033.js ./demo/canvas-034.js ./demo/canvas-035.js ./demo/canvas-036.js ./demo/canvas-037.js ./demo/canvas-038.js ./demo/canvas-039.js ./demo/canvas-040.js ./demo/canvas-041.js ./demo/canvas-042.js ./demo/canvas-043.js ./demo/canvas-044.js ./demo/canvas-045.js ./demo/canvas-046.js ./demo/canvas-047.js ./demo/canvas-048.js ./demo/canvas-049.js ./demo/canvas-050.js ./demo/canvas-051.js ./demo/canvas-052.js ./demo/canvas-053.js ./demo/canvas-054.js ./demo/canvas-055.js ./demo/canvas-056.js ./demo/canvas-058.js ./demo/canvas-059.js ./demo/canvas-060.js ./demo/canvas-061.js ./demo/canvas-062.js ./demo/canvas-063.js ./demo/canvas-064.js ./demo/core-001.js ./demo/delaunator-001.js ./demo/delaunator-002.js ./demo/dom-001.js ./demo/dom-002.js ./demo/dom-003.js ./demo/dom-004.js ./demo/dom-005.js ./demo/dom-006.js ./demo/dom-007.js ./demo/dom-008.js ./demo/dom-009.js ./demo/dom-010.js ./demo/dom-011.js ./demo/dom-012.js ./demo/dom-013.js ./demo/dom-015.js ./demo/dom-016.js ./demo/dom-017.js ./demo/dom-018.js ./demo/filters-001.js ./demo/filters-002.js ./demo/filters-002a.js ./demo/filters-003.js ./demo/filters-004.js ./demo/filters-005.js ./demo/filters-006.js ./demo/filters-007.js ./demo/filters-008.js ./demo/filters-009.js ./demo/filters-010.js ./demo/filters-011.js ./demo/filters-012.js ./demo/filters-013.js ./demo/filters-014.js ./demo/filters-015.js ./demo/filters-016.js ./demo/filters-017.js ./demo/filters-018.js ./demo/filters-019.js ./demo/filters-020.js ./demo/filters-021.js ./demo/filters-022.js ./demo/filters-023.js ./demo/filters-024.js ./demo/filters-025.js ./demo/filters-026.js ./demo/filters-027.js ./demo/filters-028.js ./demo/filters-101.js ./demo/filters-102.js ./demo/filters-103.js ./demo/filters-104.js ./demo/filters-105.js ./demo/filters-501.js ./demo/filters-502.js ./demo/filters-503.js ./demo/filters-504.js ./demo/filters-505.js ./demo/mediapipe-001.js ./demo/mediapipe-002.js ./demo/mediapipe-003.js ./demo/modules-001.js ./demo/modules-002.js ./demo/modules-003.js ./demo/modules-004.js ./demo/modules-005.js ./demo/modules-006.js ./demo/packets-001.js ./demo/packets-002.js ./demo/particles-001.js ./demo/particles-002.js ./demo/particles-003.js ./demo/particles-004.js ./demo/particles-005.js ./demo/particles-006.js ./demo/particles-007.js ./demo/particles-008.js ./demo/particles-009.js ./demo/particles-010.js ./demo/particles-011.js ./demo/particles-012.js ./demo/particles-013.js ./demo/particles-014.js ./demo/particles-015.js ./demo/particles-016.js ./demo/rapier-001.js ./demo/snippets-001.js ./demo/snippets-002.js ./demo/snippets-003.js ./demo/snippets-004.js ./demo/snippets-005.js ./demo/snippets-006.js ./demo/tensorflow-001.js ./demo/tensorflow-002.js ./demo/utilities.js

- §

  # Demo Canvas 003

  Linear gradients

- §

  Run code

      import {
          addNativeListener,
          library as L,
          makeBlock,
          makeGradient,
          makeRender,
          makeUpdater,
      } from '../source/scrawl.js'

      import { reportSpeed, killStyle } from './utilities.js';

- §

  #### Scene setup

  Get a handle to the Canvas wrapper

      const canvas = L.artefact.mycanvas;

- §

  Namespacing boilerplate

      const namespace = 'demo';
      const name = (n) => `${namespace}-${n}`;

- §

  Create the linear gradient - we will kill and resurrect it as the demo runs

  - Needs to be a let, not a const, because we’re going to kill/resurrect this gradient

      let graddy = makeGradient({
          name: name('mygradient'),
          endX: '100%',

          easing: 'linear',
          precision: 1,
      });

- §

  Test the ability to load a user-created easing algorithm into the gradient

      const bespokeEasings = {

          'user-steps': (val) => {

              if (val < 0.2) return 0.1;
              if (val < 0.4) return 0.3;
              if (val < 0.6) return 0.5;
              if (val < 0.8) return 0.7;
              return 0.9;
          },
          'user-repeat': (val) => (val * 4) % 1,
      };

- §

  Create a block entity which will use the gradient

      makeBlock({
          name: name('myblock'),
          width: '90%',
          height: '90%',
          startX: '5%',
          startY: '5%',

          fillStyle: graddy,
          lockFillStyleToEntity: true,
          strokeStyle: 'coral',
          lineWidth: 2,
          method: 'fillAndDraw',
      });

- §

  #### Scene animation

  Function to display frames-per-second data, and other information relevant to the demo

      const report = reportSpeed('#reportmessage', function () {

- §

  if (L.palette.mygradient_palette) console.log(L.palette.mygradient_palette.colors); @ts-expect-error

          return `    Palette - start: ${paletteStart.value}; end: ${paletteEnd.value}\n    Start - x: ${startX.value}%; y: ${startY.value}%\n    End - x: ${endX.value}%; y: ${endY.value}%\n    Precision: ${precision.value}`;
      });

- §

  Create the Display cycle animation

      makeRender({

          name: name('animation'),
          target: canvas,
          afterShow: report,
      });

- §

  #### User interaction

  Setup form observer functionality. We’re doing it this way (wrapped in a function) so we can test that it can be killed, and then recreated, later

      const makeObserver = () => {

          return makeUpdater({

              event: ['input', 'change'],
              origin: '.controlItem',

              target: graddy,

              useNativeListener: true,
              preventDefault: true,

              updates: {

                  paletteStart: ['paletteStart', 'int'],
                  paletteEnd: ['paletteEnd', 'int'],

                  startX: ['startX', '%'],
                  startY: ['startY', '%'],

                  endX: ['endX', '%'],
                  endY: ['endY', '%'],

                  precision: ['precision', 'int'],

                  cyclePalette: ['cyclePalette', 'boolean'],

                  colorSpace: ['colorSpace', 'raw'],
                  returnColorAs: ['returnColorAs', 'raw'],
              },
          });
      }

- §

  … Create the form observer

      let myobserver = makeObserver();

- §

  Adding and removing color stops to the gradient - we’re using updateColor and removeColor functions rather than setting them on the gradient, so need separate event listener(s) to action form changes.

      const events = (e) => {

          e.preventDefault();
          e.returnValue = false;
      };

      addNativeListener(['input', 'change'], (e) => {

          events(e);

          const val = parseInt(e.target.value, 10);

          switch (e.target.id) {

              case 'red' :
                  if (val) graddy.updateColor(350, 'red');
                  else graddy.removeColor(350);
                  break;

              case 'blue' :
                  if (val) graddy.updateColor(650, 'blue');
                  else graddy.removeColor(650);
                  break;
          }
      }, '.colorItems');

      addNativeListener(['input', 'change'], (e) => {

          events(e);

          const val = e.target.value;

          if (['user-steps', 'user-repeat'].includes(val)) {
              graddy.set({
                  easing: bespokeEasings[val],
              });
          }
          else {
              graddy.set({
                  easing: val,
              });
          }

      }, '#easing');

- §

  Set the DOM input values

      const paletteStart = document.querySelector('#paletteStart');
      const paletteEnd = document.querySelector('#paletteEnd');
      const startX = document.querySelector('#startX');
      const startY = document.querySelector('#startY');
      const endX = document.querySelector('#endX');
      const endY = document.querySelector('#endY');
      const precision = document.querySelector('#precision');

- §

  @ts-expect-error

      paletteStart.value = 0;

- §

  @ts-expect-error

      paletteEnd.value = 999;

- §

  @ts-expect-error

      startX.value = 0;

- §

  @ts-expect-error

      startY.value = 0;

- §

  @ts-expect-error

      endX.value = 100;

- §

  @ts-expect-error

      endY.value = 0;

- §

  @ts-expect-error

      precision.value = 1;

- §

  @ts-expect-error

      document.querySelector('#red').value = 0;

- §

  @ts-expect-error

      document.querySelector('#blue').value = 0;

- §

  @ts-expect-error

      document.querySelector('#easing').options.selectedIndex = 0;

- §

  @ts-expect-error

      document.querySelector('#cyclePalette').value = 0;

- §

  @ts-expect-error

      document.querySelector('#colorSpace').options.selectedIndex = 0;

- §

  @ts-expect-error

      document.querySelector('#returnColorAs').options.selectedIndex = 0;

- §

  #### Development and testing

      console.log(L);

      console.log('Performing tests ...');

      killStyle(canvas, name('mygradient'), 3000, () => {

- §

  Repopulate the graddy variable

          graddy = L.styles[name('mygradient')];

- §

  Reset the block fillStyle to the gradient

          L.entity[name('myblock')].set({
              fillStyle: name('mygradient'),
          });

- §

  Kill the form observer

          console.log('Kill form observer');
          myobserver();

- §

  … and recreate it

          myobserver = makeObserver();
          console.log('Form observer recreated');
      });