fix #1058 - make sure no date ever returns sub-100microsec precision

Author: alexcjohnson

src/plots/cartesian/axes.js

@@ -850,7 +850,8 @@ function autoTickRound(ax) {
         // not necessarily *all* the information in tick0 though, if it's really odd
         // minimal string length for tick0: 'd' is 10, 'M' is 16, 'S' is 19
         // take off a leading minus (year < 0 so length is consistent)
-        var tick0str = Lib.ms2DateTime(Lib.dateTime2ms(ax.tick0)).replace(/^-/, ''),
+        var tick0ms = Lib.dateTime2ms(ax.tick0),
+            tick0str = Lib.ms2DateTime(tick0ms).replace(/^-/, ''),
             tick0len = tick0str.length;
 
         if(String(dtick).charAt(0) === 'M') {
@@ -862,7 +863,12 @@ function autoTickRound(ax) {
         else if((dtick >= ONEDAY && tick0len <= 10) || (dtick >= ONEDAY * 15)) ax._tickround = 'd';
         else if((dtick >= ONEMIN && tick0len <= 16) || (dtick >= ONEHOUR)) ax._tickround = 'M';
         else if((dtick >= ONESEC && tick0len <= 19) || (dtick >= ONEMIN)) ax._tickround = 'S';
-        else ax._tickround = Math.max(3 - Math.round(Math.log(dtick / 2) / Math.LN10), tick0len - 20);
+        else {
+            // of any two adjacent ticks, at least one will have the maximum fractional digits
+            // of all possible ticks - so take the max. length of tick0 and the next one
+            var tick1len = Lib.ms2DateTime(tick0ms + dtick).replace(/^-/, '').length;
+            ax._tickround = Math.max(tick0len, tick1len) - 20;
+        }
     }
     else if(isNumeric(dtick) || dtick.charAt(0) === 'L') {
         // linear or log (except D1, D2)
@@ -1112,7 +1118,7 @@ function formatDate(ax, out, hover, extraPrecision) {
                 if(tr !== 'M') {
                     tt += secondFormat(d);
                     if(tr !== 'S') {
-                        tt += numFormat(mod(x / 1000, 1), ax, 'none', hover)
+                        tt += numFormat(d3.round(mod(x / 1000, 1), 4), ax, 'none', hover)
                             .substr(1);
                     }
                 }

test/jasmine/tests/axes_test.js

@@ -1397,6 +1397,7 @@ describe('Test axes', function() {
         function mockCalc(ax) {
             Axes.setConvert(ax);
             ax.tickfont = {};
+            ax._gd = {_fullLayout: {separators: '.,'}};
             return Axes.calcTicks(ax).map(function(v) { return v.text; });
         }
 
@@ -1475,5 +1476,28 @@ describe('Test axes', function() {
             ];
             expect(textOut).toEqual(expectedText);
         });
+
+        it('should never give dates more than 100 microsecond precision', function() {
+            var textOut = mockCalc({
+                type: 'date',
+                tickmode: 'linear',
+                tick0: '2000-01-01',
+                dtick: 1.1333,
+                range: ['2000-01-01', '2000-01-01 00:00:00.01']
+            });
+
+            var expectedText = [
+                '00:00:00<br>Jan 1, 2000',
+                '00:00:00.0011',
+                '00:00:00.0023',
+                '00:00:00.0034',
+                '00:00:00.0045',
+                '00:00:00.0057',
+                '00:00:00.0068',
+                '00:00:00.0079',
+                '00:00:00.0091'
+            ];
+            expect(textOut).toEqual(expectedText);
+        });
     });
 });