modebar: use axis r21 and l2r to compute zoom +/- ranges

- so that zoomed ranges are computed consistently
  for all axis types

Author: etpinard

src/components/modebar/buttons.js

@@ -204,9 +204,18 @@ function handleCartesian(gd, ev) {
                     }
                 }
                 else {
-                    var rangeNow = ax.range;
-                    aobj[axName + '.range[0]'] = Math.floor(r0 * rangeNow[0] + r1 * rangeNow[1]);
-                    aobj[axName + '.range[1]'] = Math.floor(r0 * rangeNow[1] + r1 * rangeNow[0]);
+                    var rangeNow = [
+                        ax.r2l(ax.range[0]),
+                        ax.r2l(ax.range[1]),
+                    ];
+
+                    var rangeNew = [
+                        r0 * rangeNow[0] + r1 * rangeNow[1],
+                        r0 * rangeNow[1] + r1 * rangeNow[0]
+                    ];
+
+                    aobj[axName + '.range[0]'] = ax.l2r(rangeNew[0]);
+                    aobj[axName + '.range[1]'] = ax.l2r(rangeNew[1]);
                 }
             }
         }