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

import { action } from "@ember/object";
import { bind, observes } from "discourse-common/utils/decorators";
import { chooseDarker, darkLightDiff } from "wizard/lib/preview";
import I18n from "I18n";
import WizardPreviewBaseComponent from "./wizard-preview-base";

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

export default WizardPreviewBaseComponent.extend({
  width: 628,
  height: 322,
  logo: null,
  avatar: null,
  previewTopic: true,
  draggingActive: false,
  startX: 0,
  scrollLeft: 0,

  init() {
    this._super(...arguments);
    this.wizard.on("homepageStyleChanged", this.onHomepageStyleChange);
  },

  willDestroy() {
    this._super(...arguments);
    this.wizard.off("homepageStyleChanged", this.onHomepageStyleChange);
  },

  didInsertElement() {
    this._super(...arguments);
    this.element.addEventListener("mouseleave", this.handleMouseLeave);
    this.element.addEventListener("mousemove", this.handleMouseMove);
  },

  willDestroyElement() {
    this._super(...arguments);
    this.element.removeEventListener("mouseleave", this.handleMouseLeave);
    this.element.removeEventListener("mousemove", this.handleMouseMove);
  },

  mouseDown(e) {
    const slider = this.element.querySelector(".previews");
    this.setProperties({
      draggingActive: true,
      startX: e.pageX - slider.offsetLeft,
      scrollLeft: slider.scrollLeft,
    });
  },

  @bind
  handleMouseLeave() {
    this.set("draggingActive", false);
  },

  mouseUp() {
    this.set("draggingActive", false);
  },

  @bind
  handleMouseMove(e) {
    if (!this.draggingActive) {
      return;
    }
    e.preventDefault();

    const slider = this.element.querySelector(".previews"),
      x = e.pageX - slider.offsetLeft,
      walk = (x - this.startX) * 1.5;

    slider.scrollLeft = this.scrollLeft - walk;

    if (slider.scrollLeft < 50) {
      this.set("previewTopic", true);
    }
    if (slider.scrollLeft > slider.offsetWidth - 50) {
      this.set("previewTopic", false);
    }
  },

  didUpdateAttrs() {
    this._super(...arguments);

    this.triggerRepaint();
  },

  @bind
  onHomepageStyleChange() {
    this.set("previewTopic", false);
  },

  @observes("previewTopic")
  scrollPreviewArea() {
    const el = this.element.querySelector(".previews");
    el.scrollTo({
      top: 0,
      left: this.previewTopic ? 0 : el.scrollWidth - el.offsetWidth,
      behavior: "smooth",
    });
  },

  images() {
    return {
      logo: this.wizard.getLogoUrl(),
      avatar: "/images/wizard/trout.png",
    };
  },

  paint({ ctx, colors, font, headingFont, width, height }) {
    const headerHeight = height * 0.3;

    this.drawFullHeader(colors, headingFont, this.logo);

    const margin = 20;
    const avatarSize = height * 0.15;
    const lineHeight = height / 14;

    // Draw a fake topic
    this.scaleImage(
      this.avatar,
      margin,
      headerHeight + height * 0.09,
      avatarSize,
      avatarSize
    );

    const titleFontSize = headerHeight / 55;

    ctx.beginPath();
    ctx.fillStyle = colors.primary;
    ctx.font = `bold ${titleFontSize}em '${headingFont}'`;
    ctx.fillText(I18n.t("wizard.previews.topic_title"), margin, height * 0.3);

    const bodyFontSize = height / 330.0;
    ctx.font = `${bodyFontSize}em '${font}'`;

    let line = 0;
    const lines = LOREM.split("\n");
    for (let i = 0; i < 5; i++) {
      line = height * 0.35 + i * lineHeight;
      ctx.fillText(lines[i], margin + avatarSize + margin, line);
    }

    // Share Button
    const shareButtonWidth = I18n.t("wizard.previews.share_button").length * 11;

    ctx.beginPath();
    ctx.rect(margin, line + lineHeight, shareButtonWidth, height * 0.1);
    // accounts for hard-set color variables in solarized themes
    ctx.fillStyle =
      colors.primary_low ||
      darkLightDiff(colors.primary, colors.secondary, 90, 65);
    ctx.fillStyle = chooseDarker(colors.primary, colors.secondary);
    ctx.font = `${bodyFontSize}em '${font}'`;
    ctx.fillText(
      I18n.t("wizard.previews.share_button"),
      margin + 10,
      line + lineHeight * 1.9
    );

    // Reply Button
    const replyButtonWidth = I18n.t("wizard.previews.reply_button").length * 11;

    ctx.beginPath();
    ctx.rect(
      shareButtonWidth + margin + 10,
      line + lineHeight,
      replyButtonWidth,
      height * 0.1
    );
    ctx.fillStyle = colors.tertiary;
    ctx.fill();
    ctx.fillStyle = colors.secondary;
    ctx.font = `${bodyFontSize}em '${font}'`;
    ctx.fillText(
      I18n.t("wizard.previews.reply_button"),
      shareButtonWidth + margin + 20,
      line + lineHeight * 1.9
    );

    // Draw Timeline
    const timelineX = width * 0.86;
    ctx.beginPath();
    ctx.strokeStyle = colors.tertiary;
    ctx.lineWidth = 0.5;
    ctx.moveTo(timelineX, height * 0.3);
    ctx.lineTo(timelineX, height * 0.7);
    ctx.stroke();

    // Timeline
    ctx.beginPath();
    ctx.strokeStyle = colors.tertiary;
    ctx.lineWidth = 2;
    ctx.moveTo(timelineX, height * 0.3);
    ctx.lineTo(timelineX, height * 0.4);
    ctx.stroke();

    ctx.font = `Bold ${bodyFontSize}em ${font}`;
    ctx.fillStyle = colors.primary;
    ctx.fillText("1 / 20", timelineX + margin, height * 0.3 + margin * 1.5);
  },

  @action
  setPreviewHomepage(event) {
    event?.preventDefault();
    this.set("previewTopic", false);
  },

  @action
  setPreviewTopic(event) {
    event?.preventDefault();
    this.set("previewTopic", true);
  },
});