features height is not 0 (#513)

* features height is not 0

* features not in example code, height not modified in AbstractCachef

* remove comment

Author: geenakim

src/main/viz/FeatureTrack.js

@@ -46,7 +46,7 @@ class FeatureTiledCanvas extends TiledCanvas {
   }
 
   heightForRef(ref: string): number {
-    return this.cache.pileupHeightForRef(ref) *
+    return Math.max(this.cache.pileupHeightForRef(ref),1) *
                     (style.READ_HEIGHT + style.READ_SPACING);
   }
 
@@ -207,7 +207,7 @@ class FeatureTrack extends React.Component<VizProps<DataSource<Feature>>, State>
     var parent = ((d3utils.findParent(canvas, "features") : any) : HTMLCanvasElement);
 
     // Height can only be computed after the pileup has been updated.
-    var height = yForRow(this.cache.pileupHeightForRef(this.props.range.contig));
+    var height = this.tiles.heightForRef(this.props.range.contig);
 
     // resize height for device
     height = d3utils.heightForCanvas(canvas, height);

style/pileup.css

@@ -7,7 +7,7 @@
 .pileup-root {
   display: flex;
   flex-direction: column;
-  height: 100%;
+  height: inherit; /* height 100% makes featureTrack too small */
 }
 
 .pileup-root > .track {
@@ -201,6 +201,7 @@
 
 /* features track */
 .pileup-root > .features {
+  flex-basis: auto; /* sets track size based on track height */
   max-height: 200px; /* prevents track from becoming too large */
 }