Contour label extra pad and correct minus sign

src/traces/contour/constants.js

@@ -72,5 +72,8 @@ module.exports = {
         INITIALSEARCHPOINTS: 10,
         // number of binary search iterations after the initial wide search
         ITERATIONS: 5
-    }
+    },
+
+    // number of px around labels text clip out of contour lines below
+    LABEL_LINE_CLIP_PAD: 2
 };

src/traces/contour/plot.js

@@ -26,6 +26,7 @@ var convertToConstraints = require('./convert_to_constraints');
 var closeBoundaries = require('./close_boundaries');
 var constants = require('./constants');
 var costConstants = constants.LABELOPTIMIZER;
+var LABEL_LINE_CLIP_PAD = constants.LABEL_LINE_CLIP_PAD;
 
 exports.plot = function plot(gd, plotinfo, cdcontours, contourLayer) {
     var xa = plotinfo.xaxis;
@@ -394,21 +395,21 @@ exports.labelFormatter = function(gd, cd0) {
     var trace = cd0.trace;
     var contours = trace.contours;
 
+    var formatAxis = {
+        type: 'linear',
+        _id: 'ycontour',
+        showexponent: 'all',
+        exponentformat: 'B'
+    };
+
     if(contours.labelformat) {
-        return fullLayout._d3locale.numberFormat(contours.labelformat);
+        formatAxis.tickformat = contours.labelformat;
+        setConvert(formatAxis, fullLayout);
     } else {
-        var formatAxis;
         var cOpts = Colorscale.extractOpts(trace);
         if(cOpts && cOpts.colorbar && cOpts.colorbar._axis) {
             formatAxis = cOpts.colorbar._axis;
         } else {
-            formatAxis = {
-                type: 'linear',
-                _id: 'ycontour',
-                showexponent: 'all',
-                exponentformat: 'B'
-            };
-
             if(contours.type === 'constraint') {
                 var value = contours.value;
                 if(Array.isArray(value)) {
@@ -429,10 +430,9 @@ exports.labelFormatter = function(gd, cd0) {
             formatAxis._tmin = null;
             formatAxis._tmax = null;
         }
-        return function(v) {
-            return Axes.tickText(formatAxis, v).text;
-        };
     }
+
+    return function(v) { return Axes.tickText(formatAxis, v).text; };
 };
 
 exports.calcTextOpts = function(level, contourFormat, dummyText, gd) {
@@ -544,8 +544,8 @@ function locationCost(loc, textOpts, labelData, bounds) {
 }
 
 exports.addLabelData = function(loc, textOpts, labelData, labelClipPathData) {
-    var halfWidth = textOpts.width / 2;
-    var halfHeight = textOpts.height / 2;
+    var halfWidth = textOpts.width / 2 + LABEL_LINE_CLIP_PAD;
+    var halfHeight = textOpts.height / 2 + LABEL_LINE_CLIP_PAD;
 
     var x = loc.x;
     var y = loc.y;