svgedit/src/editor/extensions/ext-grid/ext-grid.js

/**
 * @file ext-grid.js
 *
 * @license Apache-2.0
 *
 * @copyright 2010 Redou Mine, 2010 Alexis Deveria
 *
 */

const loadExtensionTranslation = async function (lang) {
  let translationModule;
  try {
    // eslint-disable-next-line no-unsanitized/method
    translationModule = await import(`./locale/${encodeURIComponent(lang)}.js`);
  } catch (_error) {
    // eslint-disable-next-line no-console
    console.error(`Missing translation (${lang}) - using 'en'`);
    translationModule = await import(`./locale/en.js`);
  }
  return translationModule.default;
};

export default {
  name: 'grid',
  async init ({NS, getTypeMap}) {
    const svgEditor = this;
    const strings = await loadExtensionTranslation(svgEditor.configObj.pref('lang'));
    const {svgCanvas} = svgEditor;
    const {$id} = svgCanvas;
    const svgdoc = document.getElementById('svgcanvas').ownerDocument;
    const {assignAttributes} = svgCanvas;
    const hcanvas = document.createElement('canvas');
    const canvBG = $id('canvasBackground');
    const units = getTypeMap(); // Assumes prior `init()` call on `units.js` module
    const intervals = [0.01, 0.1, 1, 10, 100, 1000];
    let showGrid = svgEditor.configObj.curConfig.showGrid || false;

    hcanvas.style.display = 'none';
    document.body.appendChild(hcanvas);

    const canvasGrid = svgdoc.createElementNS(NS.SVG, 'svg');
    assignAttributes(canvasGrid, {
      id: 'canvasGrid',
      width: '100%',
      height: '100%',
      x: 0,
      y: 0,
      overflow: 'visible',
      display: 'none'
    });
    canvBG.appendChild(canvasGrid);
    const gridDefs = svgdoc.createElementNS(NS.SVG, 'defs');
    // grid-pattern
    const gridPattern = svgdoc.createElementNS(NS.SVG, 'pattern');
    assignAttributes(gridPattern, {
      id: 'gridpattern',
      patternUnits: 'userSpaceOnUse',
      x: 0, // -(value.strokeWidth / 2), // position for strokewidth
      y: 0, // -(value.strokeWidth / 2), // position for strokewidth
      width: 100,
      height: 100
    });

    const gridimg = svgdoc.createElementNS(NS.SVG, 'image');
    assignAttributes(gridimg, {
      x: 0,
      y: 0,
      width: 100,
      height: 100
    });
    gridPattern.append(gridimg);
    gridDefs.append(gridPattern);
    $id('canvasGrid').appendChild(gridDefs);

    // grid-box
    const gridBox = svgdoc.createElementNS(NS.SVG, 'rect');
    assignAttributes(gridBox, {
      width: '100%',
      height: '100%',
      x: 0,
      y: 0,
      'stroke-width': 0,
      stroke: 'none',
      fill: 'url(#gridpattern)',
      style: 'pointer-events: none; display:visible;'
    });
    $id('canvasGrid').appendChild(gridBox);

    /**
     *
     * @param {Float} zoom
     * @returns {void}
     */
    const updateGrid = (zoom) => {
      // TODO: Try this with <line> elements, then compare performance difference
      const unit = units[svgEditor.configObj.curConfig.baseUnit]; // 1 = 1px
      const uMulti = unit * zoom;
      // Calculate the main number interval
      const rawM = 100 / uMulti;
      let multi = 1;
      intervals.some((num) => {
        multi = num;
        return rawM <= num;
      });
      const bigInt = multi * uMulti;

      // Set the canvas size to the width of the container
      hcanvas.width = bigInt;
      hcanvas.height = bigInt;
      const ctx = hcanvas.getContext('2d');
      const curD = 0.5;
      const part = bigInt / 10;

      ctx.globalAlpha = 0.2;
      ctx.strokeStyle = svgEditor.configObj.curConfig.gridColor;
      for (let i = 1; i < 10; i++) {
        const subD = Math.round(part * i) + 0.5;
        // const lineNum = (i % 2)?12:10;
        const lineNum = 0;
        ctx.moveTo(subD, bigInt);
        ctx.lineTo(subD, lineNum);
        ctx.moveTo(bigInt, subD);
        ctx.lineTo(lineNum, subD);
      }
      ctx.stroke();
      ctx.beginPath();
      ctx.globalAlpha = 0.5;
      ctx.moveTo(curD, bigInt);
      ctx.lineTo(curD, 0);

      ctx.moveTo(bigInt, curD);
      ctx.lineTo(0, curD);
      ctx.stroke();

      const datauri = hcanvas.toDataURL('image/png');
      gridimg.setAttribute('width', bigInt);
      gridimg.setAttribute('height', bigInt);
      gridimg.parentNode.setAttribute('width', bigInt);
      gridimg.parentNode.setAttribute('height', bigInt);
      svgCanvas.setHref(gridimg, datauri);
    };

    /**
     *
     * @returns {void}
     */
    const gridUpdate = () => {
      if (showGrid) {
        updateGrid(svgCanvas.getZoom());
      }
      $id('canvasGrid').style.display = (showGrid) ? 'block' : 'none';
      document.getElementById('view_grid').pressed = showGrid;
    };
    return {
      name: strings.name,
      zoomChanged (zoom) {
        if (showGrid) { updateGrid(zoom); }
      },
      callback () {
        // Add the button and its handler(s)
        const buttonTemplate = document.createElement("template");
        buttonTemplate.innerHTML = `
          <se-button id="view_grid" title="Show grid" src="./images/grid.svg"></se-button>
        `;
        $id('editor_panel').append(buttonTemplate.content.cloneNode(true));
        $id('view_grid').addEventListener("click", () => {
          svgEditor.configObj.curConfig.showGrid = showGrid = !showGrid;
          gridUpdate();
        }); 

        if (showGrid) {
          gridUpdate();
        }
      }
    };
  }
};