feat: add targetLine

justgage.js

@@ -207,6 +207,17 @@
         dataset,
         ">"
       ),
+      // targetLine : float
+      // value for the target line (optional)
+      targetLine: kvLookup("targetLine", config, dataset, null, "float"),
+
+      // targetLineColor : string
+      // color of the target line
+      targetLineColor: kvLookup("targetLineColor", config, dataset, "#000000"),
+
+      // targetLineWidth : float
+      // width of the target line
+      targetLineWidth: kvLookup("targetLineWidth", config, dataset, 1.5),
 
       // donutStartAngle : int
       // angle to start from when in donut mode
@@ -765,6 +776,9 @@
       ],
     });
 
+    // Draw the Target Line
+    obj.drawTargetLine();
+
     if (obj.config.donut) {
       obj.level.transform(
         "r" +
@@ -1376,6 +1390,62 @@
     }
   };
 
+  JustGage.prototype.drawTargetLine = function() {
+      const obj = this;
+
+      if (obj.config.targetLine === null) {
+        return;
+      }
+
+      let path;
+      const w = obj.params.widgetW;
+      const h = obj.params.widgetH;
+      const dx = obj.params.dx;
+      const dy = obj.params.dy;
+      const gws = obj.config.gaugeWidthScale;
+      const donut = obj.config.donut;
+
+      let alpha = (1 - (obj.config.targetLine - obj.config.min) / (obj.config.max - obj.config.min)) * Math.PI;
+      let Ro = w / 2 - w / 10;
+      let Ri = Ro - w / 6.666666666666667 * gws;
+
+      let Cx, Cy, Xo, Yo, Xi, Yi;
+
+      if (donut) {
+        Ro = w / 2 - w / 30;
+        Ri = Ro - w / 6.666666666666667 * gws;
+
+        Cx = w / 2 + dx;
+        Cy = h / 2 + dy;
+
+        Xo = Cx + Ro * Math.cos(alpha);
+        Yo = Cy - Ro * Math.sin(alpha);
+        Xi = Cx + Ri * Math.cos(alpha);
+        Yi = Cy - Ri * Math.sin(alpha);
+
+        path = "M" + Xi + "," + Yi + " L" + Xo + "," + Yo;
+      } else {
+        Cx = w / 2 + dx;
+        Cy = h / 1.25 + dy;
+
+        Xo = Cx + Ro * Math.cos(alpha);
+        Yo = Cy - Ro * Math.sin(alpha);
+        Xi = Cx + Ri * Math.cos(alpha);
+        Yi = Cy - Ri * Math.sin(alpha);
+
+        path = "M" + Xi + "," + Yi + " L" + Xo + "," + Yo;
+      }
+
+      obj.targetLine = obj.canvas.path(path).attr({
+        "stroke": obj.config.targetLineColor,
+        "stroke-width": obj.config.targetLineWidth
+      });
+
+      if (donut) {
+        obj.targetLine.transform("r" + obj.config.donutStartAngle + "," + (w / 2 + dx) + "," + (h / 2 + dy));
+      }
+    };
+
   //
   // tiny helper function to lookup value of a key from two hash tables
   // if none found, return defaultvalue