discourse/app/assets/javascripts/wizard/addon/components/wizard-preview-base.js

import Component from "@ember/component";
import { Promise } from "rsvp";
/*eslint no-bitwise:0 */
import getUrl from "discourse-common/lib/get-url";
import { htmlSafe } from "@ember/template";
import { scheduleOnce } from "@ember/runloop";
import { observes } from "discourse-common/utils/decorators";
import { darkLightDiff, drawHeader } from "wizard/lib/preview";

export const LOREM = `
Lorem ipsum dolor sit amet,
consectetur adipiscing elit.
Nullam eget sem non elit
tincidunt rhoncus. Fusce
velit nisl, porttitor sed
nisl ac, consectetur interdum
metus. Fusce in consequat
augue, vel facilisis felis.`;

const scaled = {};

function canvasFor(image, w, h) {
  w = Math.ceil(w);
  h = Math.ceil(h);

  const scale = window.devicePixelRatio;

  const can = document.createElement("canvas");
  can.width = w * scale;
  can.height = h * scale;

  const ctx = can.getContext("2d");
  ctx.scale(scale, scale);
  ctx.drawImage(image, 0, 0, w, h);
  return can;
}

const scale = window.devicePixelRatio;
export default Component.extend({
  get elementWidth() {
    return this.width * scale;
  },

  get elementHeight() {
    return this.height * scale;
  },

  get canvasStyle() {
    return htmlSafe(`width:${this.width}px;height:${this.height}px`);
  },

  ctx: null,
  loaded: false,

  didInsertElement() {
    this._super(...arguments);
    const c = this.element.querySelector("canvas");
    this.ctx = c.getContext("2d");
    this.ctx.scale(scale, scale);
    this.reload();
  },

  @observes(
    "step.fieldsById.{color_scheme,body_font,heading_font,homepage_style}.value"
  )
  themeChanged() {
    this.triggerRepaint();
  },

  images() {},

  loadFonts() {
    return document.fonts.ready;
  },

  loadImages() {
    const images = this.images();
    if (images) {
      return Promise.all(
        Object.keys(images).map((id) => {
          return loadImage(images[id]).then((img) => (this[id] = img));
        })
      );
    }
    return Promise.resolve();
  },

  reload() {
    Promise.all([this.loadFonts(), this.loadImages()]).then(() => {
      this.loaded = true;
      this.triggerRepaint();
    });
  },

  triggerRepaint() {
    scheduleOnce("afterRender", this, "repaint");
  },

  repaint() {
    if (!this.loaded) {
      return false;
    }

    const colorsArray = this.wizard.currentColors;
    if (!colorsArray) {
      return;
    }

    let colors = {};
    colorsArray.forEach(function (c) {
      const name = c.name;
      colors[name] = `#${c.hex}`;
    });

    const { font, headingFont } = this.wizard;
    if (!font) {
      return;
    }

    const { ctx } = this;

    ctx.fillStyle = colors.secondary;
    ctx.fillRect(0, 0, this.width, this.height);

    const options = {
      ctx,
      colors,
      font,
      headingFont,
      width: this.width,
      height: this.height,
    };
    this.paint(options);
  },

  categories() {
    return [
      { name: "consecteteur", color: "#652D90" },
      { name: "ultrices", color: "#3AB54A" },
      { name: "placerat", color: "#25AAE2" },
    ];
  },

  scaleImage(image, x, y, w, h) {
    w = Math.floor(w);
    h = Math.floor(h);

    const { ctx } = this;

    const key = `${image.src}-${w}-${h}`;

    if (!scaled[key]) {
      let copy = image;
      let ratio = copy.width / copy.height;
      let newH = copy.height * 0.5;
      while (newH > h) {
        copy = canvasFor(copy, ratio * newH, newH);
        newH = newH * 0.5;
      }

      scaled[key] = copy;
    }

    ctx.drawImage(scaled[key], x, y, w, h);
  },

  drawFullHeader(colors, font, logo) {
    const { ctx } = this;

    const headerHeight = this.height * 0.15;
    drawHeader(ctx, colors, this.width, headerHeight);

    const avatarSize = this.height * 0.1;
    const headerMargin = headerHeight * 0.2;

    if (logo) {
      const logoHeight = headerHeight - headerMargin * 2;

      const ratio = logoHeight / logo.height;
      this.scaleImage(
        logo,
        headerMargin,
        headerMargin,
        logo.width * ratio,
        logoHeight
      );

      this.scaleImage(logo, this.width, headerMargin);
    }

    // Top right menu
    this.scaleImage(
      this.avatar,
      this.width - avatarSize - headerMargin,
      headerMargin,
      avatarSize,
      avatarSize
    );
    // accounts for hard-set color variables in solarized themes
    ctx.fillStyle =
      colors.primary_low_mid ||
      darkLightDiff(colors.primary, colors.secondary, 45, 55);

    const pathScale = headerHeight / 1200;
    // search icon SVG path
    const searchIcon = new Path2D(
      "M505 442.7L405.3 343c-4.5-4.5-10.6-7-17-7H372c27.6-35.3 44-79.7 44-128C416 93.1 322.9 0 208 0S0 93.1 0 208s93.1 208 208 208c48.3 0 92.7-16.4 128-44v16.3c0 6.4 2.5 12.5 7 17l99.7 99.7c9.4 9.4 24.6 9.4 33.9 0l28.3-28.3c9.4-9.4 9.4-24.6.1-34zM208 336c-70.7 0-128-57.2-128-128 0-70.7 57.2-128 128-128 70.7 0 128 57.2 128 128 0 70.7-57.2 128-128 128z"
    );
    // hamburger icon
    const hamburgerIcon = new Path2D(
      "M16 132h416c8.837 0 16-7.163 16-16V76c0-8.837-7.163-16-16-16H16C7.163 60 0 67.163 0 76v40c0 8.837 7.163 16 16 16zm0 160h416c8.837 0 16-7.163 16-16v-40c0-8.837-7.163-16-16-16H16c-8.837 0-16 7.163-16 16v40c0 8.837 7.163 16 16 16zm0 160h416c8.837 0 16-7.163 16-16v-40c0-8.837-7.163-16-16-16H16c-8.837 0-16 7.163-16 16v40c0 8.837 7.163 16 16 16z"
    );
    ctx.save(); // Save the previous state for translation and scale
    ctx.translate(
      this.width - avatarSize * 3 - headerMargin * 0.5,
      avatarSize / 2
    );
    // need to scale paths otherwise they're too large
    ctx.scale(pathScale, pathScale);
    ctx.fill(searchIcon);
    ctx.restore();
    ctx.save();
    ctx.translate(
      this.width - avatarSize * 2 - headerMargin * 0.5,
      avatarSize / 2
    );
    ctx.scale(pathScale, pathScale);
    ctx.fill(hamburgerIcon);
    ctx.restore();
  },

  drawPills(colors, font, headerHeight, opts) {
    opts = opts || {};

    const { ctx } = this;

    const categoriesSize = headerHeight * 2;
    const badgeHeight = categoriesSize * 0.25;
    const headerMargin = headerHeight * 0.2;

    ctx.beginPath();
    ctx.strokeStyle = colors.primary;
    ctx.lineWidth = 0.5;
    ctx.rect(
      headerMargin,
      headerHeight + headerMargin,
      categoriesSize,
      badgeHeight
    );
    ctx.stroke();

    const fontSize = Math.round(badgeHeight * 0.5);

    ctx.font = `${fontSize}px '${font}'`;
    ctx.fillStyle = colors.primary;
    ctx.fillText(
      "all categories",
      headerMargin * 1.5,
      headerHeight + headerMargin * 1.4 + fontSize
    );

    const pathScale = badgeHeight / 1000;
    // caret icon
    const caretIcon = new Path2D(
      "M0 384.662V127.338c0-17.818 21.543-26.741 34.142-14.142l128.662 128.662c7.81 7.81 7.81 20.474 0 28.284L34.142 398.804C21.543 411.404 0 402.48 0 384.662z"
    );

    ctx.save();
    ctx.translate(
      categoriesSize - headerMargin / 4,
      headerHeight + headerMargin + badgeHeight / 4
    );
    ctx.scale(pathScale, pathScale);
    ctx.fill(caretIcon);
    ctx.restore();

    const text = opts.categories ? "Categories" : "Latest";

    const activeWidth = categoriesSize * (opts.categories ? 0.8 : 0.55);
    ctx.beginPath();
    ctx.fillStyle = colors.quaternary;
    ctx.rect(
      headerMargin * 2 + categoriesSize,
      headerHeight + headerMargin,
      activeWidth,
      badgeHeight
    );
    ctx.fill();

    ctx.font = `${fontSize}px '${font}'`;
    ctx.fillStyle = colors.secondary;
    let x = headerMargin * 3.0 + categoriesSize;
    ctx.fillText(
      text,
      x - headerMargin * 0.1,
      headerHeight + headerMargin * 1.5 + fontSize
    );

    ctx.fillStyle = colors.primary;
    x += categoriesSize * (opts.categories ? 0.8 : 0.6);
    ctx.fillText("New", x, headerHeight + headerMargin * 1.5 + fontSize);

    x += categoriesSize * 0.4;
    ctx.fillText("Unread", x, headerHeight + headerMargin * 1.5 + fontSize);

    x += categoriesSize * 0.6;
    ctx.fillText("Top", x, headerHeight + headerMargin * 1.5 + fontSize);
  },
});

function loadImage(src) {
  if (!src) {
    return Promise.resolve();
  }

  const img = new Image();
  img.src = getUrl(src);
  return new Promise((resolve) => (img.onload = () => resolve(img)));
}