simplify dragElement cursor handling & remove redundant initInteractions

The only reason we needed two initInteractions during Plotly.plot
is so the second one could pick up the `onmousemove` from the first
to cache as `initialMouseMove`, but it works fine now to remove that
junk entirely.

Author: alexcjohnson

src/components/dragelement/index.js

@@ -26,6 +26,15 @@ dragElement.unhoverRaw = unhover.raw;
 
 /**
  * Abstracts click & drag interactions
+ *
+ * During the interaction, a "coverSlip" element - a transparent
+ * div covering the whole page - is created, which has two key effects:
+ * - Lets you drag beyond the boundaries of the plot itself without
+ *   dropping (but if you drag all the way out of the browser window the
+ *   interaction will end)
+ * - Freezes the cursor: whatever mouse cursor the drag element had when the
+ *   interaction started gets copied to the coverSlip for use until mouseup
+ *
  * @param {object} options with keys:
  *      element (required) the DOM element to drag
  *      prepFn (optional) function(event, startX, startY)
@@ -44,10 +53,6 @@ dragElement.unhoverRaw = unhover.raw;
  *          numClicks is how many clicks we've registered within
  *          a doubleclick time
  *          e is the original event
- *      setCursor (optional) function(event)
- *          executed on mousemove before mousedown
- *          the purpose of this callback is to update the mouse cursor before
- *          the click & drag interaction has been initiated
  */
 dragElement.init = function init(options) {
     var gd = options.gd,
@@ -57,15 +62,11 @@ dragElement.init = function init(options) {
         startY,
         newMouseDownTime,
         dragCover,
-        initialTarget,
-        initialOnMouseMove;
+        initialTarget;
 
     if(!gd._mouseDownTime) gd._mouseDownTime = 0;
 
     function onStart(e) {
-        // disable call to options.setCursor(evt)
-        options.element.onmousemove = initialOnMouseMove;
-
         // make dragging and dragged into properties of gd
         // so that others can look at and modify them
         gd._dragged = false;
@@ -116,10 +117,6 @@ dragElement.init = function init(options) {
     }
 
     function onDone(e) {
-        // re-enable call to options.setCursor(evt)
-        initialOnMouseMove = options.element.onmousemove;
-        if(options.setCursor) options.element.onmousemove = options.setCursor;
-
         dragCover.onmousemove = null;
         dragCover.onmouseup = null;
         dragCover.onmouseout = null;
@@ -166,10 +163,6 @@ dragElement.init = function init(options) {
         return Lib.pauseEvent(e);
     }
 
-    // enable call to options.setCursor(evt)
-    initialOnMouseMove = options.element.onmousemove;
-    if(options.setCursor) options.element.onmousemove = options.setCursor;
-
     options.element.onmousedown = onStart;
     options.element.style.pointerEvents = 'all';
 };

src/components/shapes/draw.js

@@ -130,7 +130,6 @@ function setupDragElement(gd, shapePath, shapeOptions, index) {
     var xa, ya, x2p, y2p, p2x, p2y;
 
     var dragOptions = {
-            setCursor: updateDragMode,
             element: shapePath.node(),
             gd: gd,
             prepFn: startDrag,
@@ -141,6 +140,8 @@ function setupDragElement(gd, shapePath, shapeOptions, index) {
 
     dragElement.init(dragOptions);
 
+    shapePath.node().onmousemove = updateDragMode;
+
     function updateDragMode(evt) {
         // choose 'move' or 'resize'
         // based on initial position of cursor within the drag element

src/plot_api/plot_api.js

@@ -368,7 +368,6 @@ Plotly.plot = function(gd, data, layout, config) {
         drawFramework,
         marginPushers,
         marginPushersAgain,
-        initInteractions,
         positionAndAutorange,
         subroutines.layoutStyles,
         drawAxes,