adding focusopacity attribute for symmetry

(cherry picked from commit f2a79a6)

Author: monfera

src/traces/parcoords/attributes.js

@@ -155,6 +155,15 @@ module.exports = {
                 description: 'Opacity of the context lines, on a scale of 0 (invisible) to 1 (fully opaque).'
             },
 
+            focusopacity: {
+                valType: 'number',
+                dflt: 1,
+                min: 0,
+                max: 1,
+                role: 'style',
+                description: 'Opacity of the focus lines, on a scale of 0 (invisible) to 1 (fully opaque).'
+            },
+
             pixelratio: {
                 valType: 'number',
                 dflt: 1,

src/traces/parcoords/defaults.js

@@ -84,6 +84,7 @@ module.exports = function supplyDefaults(traceIn, traceOut, defaultColor, layout
     coerce('domain.y');
 
     coerce('line.color');
+    coerce('line.focusopacity');
     coerce('line.contextopacity');
     coerce('line.pixelratio');
     coerce('line.focusalphablending');

src/traces/parcoords/lines.js

@@ -89,11 +89,11 @@ function adjustDepth(d) {
     return Math.max(depthLimitEpsilon, Math.min(1 - depthLimitEpsilon, d));
 }
 
-function palette(unitToColor, context, contextOpacity) {
+function palette(unitToColor, context, opacity) {
     var result = [];
     for(var j = 0; j < 256; j++) {
         var c = unitToColor(j / 255);
-        result.push((context ? contextColor : c).concat([context ? Math.round(contextOpacity * 255) : 255]));
+        result.push((context ? contextColor : c).concat(opacity));
     }
 
     return result;
@@ -158,7 +158,7 @@ module.exports = function(canvasGL, lines, canvasWidth, canvasHeight, dimensions
     var dimensionCount = dimensions.length;
     var sampleCount = dimensions[0].values.length;
 
-    var focusAlphaBlending = context; // controlConfig.focusAlphaBlending;
+    var focusAlphaBlending = context || lines.focusalphablending;
 
     var canvasPanelSizeY = canvasHeight;
 
@@ -183,7 +183,7 @@ module.exports = function(canvasGL, lines, canvasWidth, canvasHeight, dimensions
         type: 'uint8',
         mag: 'nearest',
         min: 'nearest',
-        data: palette(unitToColor, context, lines.contextopacity)
+        data: palette(unitToColor, context, Math.round((context ? lines.contextopacity : lines.focusopacity) * 255))
     });
 
     var glAes = regl({