update has** optimization flags on mousedown

... as opposed to on every mousemove.

Author: etpinard

src/plots/cartesian/dragbox.js

@@ -82,6 +82,8 @@ function makeDragBox(gd, plotinfo, x, y, w, h, ns, ew) {
     var isSubplotConstrained;
     // do we need to edit x/y ranges?
     var editX, editY;
+    // graph-wide optimization flags
+    var hasScatterGl, hasOnlyLargeSploms, hasSplom, hasSVG;
 
     function recomputeAxisLists() {
         xa0 = plotinfo.xaxis;
@@ -117,6 +119,12 @@ function makeDragBox(gd, plotinfo, x, y, w, h, ns, ew) {
         isSubplotConstrained = links.isSubplotConstrained;
         editX = ew || isSubplotConstrained;
         editY = ns || isSubplotConstrained;
+
+        var fullLayout = gd._fullLayout;
+        hasScatterGl = fullLayout._has('scattergl');
+        hasOnlyLargeSploms = fullLayout._hasOnlyLargeSploms;
+        hasSplom = hasOnlyLargeSploms || fullLayout._has('splom');
+        hasSVG = fullLayout._has('svg');
     }
 
     recomputeAxisLists();
@@ -696,14 +704,6 @@ function makeDragBox(gd, plotinfo, x, y, w, h, ns, ew) {
         var fullLayout = gd._fullLayout;
         var plotinfos = fullLayout._plots;
         var subplots = fullLayout._subplots.cartesian;
-
-        // TODO can we move these to outer scope?
-        var hasScatterGl = fullLayout._has('scattergl');
-        var hasOnlyLargeSploms = fullLayout._hasOnlyLargeSploms;
-        var hasSplom = hasOnlyLargeSploms || fullLayout._has('splom');
-        var hasSVG = fullLayout._has('svg');
-        var hasDraggedPts = fullLayout._has('draggedPts');
-
         var i, sp, xa, ya;
 
         if(hasSplom || hasScatterGl) {