working but incomplete version with new build.

dist/editor/extensions/ext-grid.js

@@ -0,0 +1,168 @@
+/**
+ * @file ext-grid.js
+ *
+ * @license Apache-2.0
+ *
+ * @copyright 2010 Redou Mine, 2010 Alexis Deveria
+ *
+ */
+
+export default {
+  name: 'grid',
+  async init ({$, NS, getTypeMap, importLocale}) {
+    const strings = await importLocale();
+    const svgEditor = this;
+    const svgCanvas = svgEditor.canvas;
+    const svgdoc = document.getElementById('svgcanvas').ownerDocument,
+      {assignAttributes} = svgCanvas,
+      hcanvas = document.createElement('canvas'),
+      canvBG = $('#canvasBackground'),
+      units = getTypeMap(), // Assumes prior `init()` call on `units.js` module
+      intervals = [0.01, 0.1, 1, 10, 100, 1000];
+    let showGrid = svgEditor.curConfig.showGrid || false;
+
+    $(hcanvas).hide().appendTo('body');
+
+    const canvasGrid = svgdoc.createElementNS(NS.SVG, 'svg');
+    assignAttributes(canvasGrid, {
+      id: 'canvasGrid',
+      width: '100%',
+      height: '100%',
+      x: 0,
+      y: 0,
+      overflow: 'visible',
+      display: 'none'
+    });
+    canvBG.append(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);
+    $('#canvasGrid').append(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;'
+    });
+    $('#canvasGrid').append(gridBox);
+
+    /**
+     *
+     * @param {Float} zoom
+     * @returns {void}
+     */
+    function updateGrid (zoom) {
+      // TODO: Try this with <line> elements, then compare performance difference
+      const unit = units[svgEditor.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.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}
+     */
+    function gridUpdate () {
+      if (showGrid) {
+        updateGrid(svgCanvas.getZoom());
+      }
+      $('#canvasGrid').toggle(showGrid);
+      $('#view_grid').toggleClass('push_button_pressed tool_button');
+    }
+    const buttons = [{
+      id: 'view_grid',
+      icon: svgEditor.curConfig.extIconsPath + 'grid.png',
+      type: 'context',
+      panel: 'editor_panel',
+      events: {
+        click () {
+          svgEditor.curConfig.showGrid = showGrid = !showGrid;
+          gridUpdate();
+        }
+      }
+    }];
+    return {
+      name: strings.name,
+      svgicons: svgEditor.curConfig.extIconsPath + 'grid-icon.xml',
+
+      zoomChanged (zoom) {
+        if (showGrid) { updateGrid(zoom); }
+      },
+      callback () {
+        if (showGrid) {
+          gridUpdate();
+        }
+      },
+      buttons: strings.buttons.map((button, i) => {
+        return Object.assign(buttons[i], button);
+      })
+    };
+  }
+};