Add and use a _smithlayer

Author: waxlamp

src/plot_api/plot_api.js

@@ -3729,6 +3729,9 @@ function makePlotFramework(gd) {
     // single polar layer for the whole plot
     fullLayout._polarlayer = fullLayout._paper.append('g').classed('polarlayer', true);
 
+    // single smith layer for the whole plot
+    fullLayout._smithlayer = fullLayout._paper.append('g').classed('smithlayer', true);
+
     // single ternary layer for the whole plot
     fullLayout._ternarylayer = fullLayout._paper.append('g').classed('ternarylayer', true);
 

src/plots/smith/smith.js

@@ -54,7 +54,7 @@ function Smith(gd, id) {
         .attr('id', this.clipIds.forTraces);
     this.clipPaths.forTraces.append('path');
 
-    this.framework = fullLayout._polarlayer.append('g')
+    this.framework = fullLayout._smithlayer.append('g')
         .attr('class', id);
 
     // unfortunately, we have to keep track of some axis tick settings