some experimental changes to try to get it working at the trace level (does not work yet)

Author: emilykl

src/components/fx/calc.js

@@ -40,6 +40,7 @@ module.exports = function calc(gd) {
         fillFn(trace.hoverlabel.font.variant, cd, 'htv');
         fillFn(trace.hoverlabel.namelength, cd, 'hnl');
         fillFn(trace.hoverlabel.align, cd, 'hta');
+        fillFn(trace.hoverlabel.showarrow, cd, 'hsa');
     }
 };
 

src/components/fx/hover.js

@@ -913,7 +913,7 @@ function _hover(gd, evt, subplot, noHoverEvent, eventTarget) {
 
     if(!helpers.isUnifiedHover(hovermode)) {
         hoverAvoidOverlaps(hoverLabels, rotateLabels, fullLayout, hoverText.commonLabelBoundingBox);
-        alignHoverText(hoverLabels, rotateLabels, fullLayout._invScaleX, fullLayout._invScaleY, fullLayout.hoverlabel.showarrow);
+        alignHoverText(hoverLabels, rotateLabels, fullLayout._invScaleX, fullLayout._invScaleY);
     }    // TODO: tagName hack is needed to appease geo.js's hack of using eventTarget=true
     // we should improve the "fx" API so other plots can use it without these hack.
     if(eventTarget && eventTarget.tagName) {
@@ -1903,7 +1903,7 @@ function getTextShiftX(hoverLabel) {
     };
 }
 
-function alignHoverText(hoverLabels, rotateLabels, scaleX, scaleY, showArrow) {
+function alignHoverText(hoverLabels, rotateLabels, scaleX, scaleY) {
     var pX = function(x) { return x * scaleX; };
     var pY = function(y) { return y * scaleY; };
 
@@ -1928,7 +1928,7 @@ function alignHoverText(hoverLabels, rotateLabels, scaleX, scaleY, showArrow) {
             // middle aligned: rect centered on data
             pathStr = 'M-' + pX(d.bx / 2 + d.tx2width / 2) + ',' + pY(offsetY - d.by / 2) +
                       'h' + pX(d.bx) + 'v' + pY(d.by) + 'h-' + pX(d.bx) + 'Z';
-        } else if(showArrow !== false) {
+        } else if(d.showarrow !== false) {
             // left or right aligned: side rect with arrow to data
             pathStr = 'M0,0L' + pX(horzSign * HOVERARROWSIZE + offsetX) + ',' + pY(HOVERARROWSIZE + offsetY) +
                       'v' + pY(d.by / 2 - HOVERARROWSIZE) +
@@ -2013,6 +2013,7 @@ function cleanPoint(d, hovermode) {
     fill('fontVariant', 'htv', 'hoverlabel.font.variant');
     fill('nameLength', 'hnl', 'hoverlabel.namelength');
     fill('textAlign', 'hta', 'hoverlabel.align');
+    fill('showarrow', 'hsa', 'hoverlabel.showarrow');
 
     d.posref = (hovermode === 'y' || (hovermode === 'closest' && trace.orientation === 'h')) ?
         (d.xa._offset + (d.x0 + d.x1) / 2) :