Derive scaling from axes

Author: degzhaus

src/traces/quiver/attributes.js

@@ -73,12 +73,6 @@ var attrs = {
         editType: 'calc',
         description: 'Angle of arrowhead in radians. Default = π/9'
     },
-    scaleratio: {
-        valType: 'number',
-        min: 0,
-        editType: 'calc',
-        description: 'The ratio between the scale of the y-axis and the scale of the x-axis (scale_y / scale_x). Default = null, the scale ratio is not fixed.'
-    },
     hoverdistance: {
         valType: 'number',
         min: -1,

src/traces/quiver/defaults.js

@@ -46,7 +46,6 @@ module.exports = function supplyDefaults(traceIn, traceOut, defaultColor, layout
     // back-compat
     coerce('arrow_scale');
     coerce('angle', Math.PI / 9);
-    coerce('scaleratio');
     coerce('hoverdistance', 20);
 
     // Line styling

src/traces/quiver/plot.js

@@ -106,7 +106,10 @@ function plotOne(gd, idx, plotinfo, cdscatter, cdscatterAll, element, transition
         }
 
         // Compute arrow in data space
-        var scaleRatio = trace.scaleratio || 1;
+        // Derive pixel-per-data scaling from axes at this point
+        var pxPerX = Math.abs(xa.c2p(cdi.x + 1) - xa.c2p(cdi.x));
+        var pxPerY = Math.abs(ya.c2p(cdi.y + 1) - ya.c2p(cdi.y));
+        var scaleRatio = (pxPerX && pxPerY) ? (pxPerY / pxPerX) : 1;
         var baseHeadScale = 0.2;
         var arrowScale = (trace.arrowsize !== undefined)
             ? (baseHeadScale * trace.arrowsize)