add highlight when mouseover matrix rect

components/content/pdockqMatrix.vue

@@ -156,6 +156,15 @@ function on(mark) {
             displayStructure(data[index])
         })
 
+        r.on("mouseover", function (event) {
+            const elem = d3.select(event.srcElement)
+            const elemFill = d3.color(elem.attr("fill")).darker()
+            elem.attr("stroke-width", 4).attr("stroke", elemFill)
+        })
+        r.on("mouseout", function (event) {
+            d3.select(event.srcElement).attr("stroke-width", undefined).attr("stroke", undefined)
+        })
+
         return g;
     };
     return mark;