set period0 to be on first Monday of 2000

- and improve test for the case of stack and default weekly period on Monday

Author: archmoj

src/traces/scatter/attributes.js

@@ -29,20 +29,22 @@ function axisPeriod(axis) {
             'Only relevant when the axis `type` is *date*.',
             'Sets the period positioning in milliseconds or *M<n>* on the ' + axis + ' axis.',
             'Special values in the form of *M<n>* could be used to declare',
-            'the number of "average" months. In this case `n` must be a positive integer.'
+            'the number of months. In this case `n` must be a positive integer.'
         ].join(' ')
     };
 }
 
 function axisPeriod0(axis) {
     return {
         valType: 'any',
-        dflt: 0,
         role: 'info',
         editType: 'calc',
         description: [
             'Only relevant when the axis `type` is *date*.',
-            'Sets the base for period positioning in milliseconds or date string on the ' + axis + ' axis.'
+            'Sets the base for period positioning in milliseconds or date string on the ' + axis + ' axis.',
+            'When `' + axis + 'period` is round number of weeks,',
+            'the `' + axis + 'period0` by default would be on a Monday i.e. 1970-01-05,',
+            'otherwise it would be at 1970-01-01.'
         ].join(' ')
     };
 }

src/traces/scatter/period_defaults.js

@@ -8,6 +8,17 @@
 
 'use strict';
 
+var numConstants = require('../../constants/numerical');
+var ONEWEEK = numConstants.ONEWEEK;
+
+function getPeriod0Dflt(period) {
+    var n = period / ONEWEEK;
+
+    return Math.round(n) === n ?
+        '1970-01-05' : // a Monday
+        '1970-01-01';
+}
+
 module.exports = function handlePeriodDefaults(traceIn, traceOut, layout, coerce, opts) {
     if(!opts) {
         opts = {
@@ -19,15 +30,15 @@ module.exports = function handlePeriodDefaults(traceIn, traceOut, layout, coerce
     if(opts.x) {
         var xperiod = coerce('xperiod');
         if(xperiod) {
-            coerce('xperiod0');
+            coerce('xperiod0', getPeriod0Dflt(xperiod));
             coerce('xperiodalignment');
         }
     }
 
     if(opts.y) {
         var yperiod = coerce('yperiod');
         if(yperiod) {
-            coerce('yperiod0');
+            coerce('yperiod0', getPeriod0Dflt(yperiod));
             coerce('yperiodalignment');
         }
     }

test/image/baselines/period_positioning8.png

@@ -0,0 +1,67 @@
+{
+    "data": [
+        {
+            "marker": {
+                "opacity": 0.5,
+                "line": {
+                    "width": 2,
+                    "color": "white"
+                }
+            },
+            "textposition": "inside",
+            "textangle": 0,
+            "texttemplate": "%{x|%A %d %b %Y}",
+            "hovertemplate": "%{x|%A}, %{y}",
+            "type": "bar",
+            "y": [
+                21,
+                21,
+                21,
+                21,
+                12,
+                12,
+                12,
+                12,
+                12,
+                12,
+                12,
+                28,
+                28,
+                28
+            ],
+            "x": [
+                "2020-01-16",
+                "2020-01-17",
+                "2020-01-18",
+                "2020-01-19",
+                "2020-01-20",
+                "2020-01-21",
+                "2020-01-22",
+                "2020-01-23",
+                "2020-01-24",
+                "2020-01-25",
+                "2020-01-26",
+                "2020-01-27",
+                "2020-01-28",
+                "2020-01-29"
+            ],
+            "xperiod": 604800000
+        }
+    ],
+    "layout": {
+        "width": 600,
+        "height": 400,
+        "margin": {
+            "t": 50
+        },
+        "hovermode": "closest",
+        "barmode": "stack",
+        "bargap": 0,
+        "xaxis": {
+            "dtick": 86400000,
+            "ticklabelmode": "period",
+            "tickformat": "%a %m-%d",
+            "tickcolor": "black"
+        }
+    }
+}

test/image/mocks/period_positioning8.json

@@ -761,6 +761,7 @@ var list = [
     'period_positioning5',
     'period_positioning6',
     'period_positioning7',
+    'period_positioning8',
     'picnic_heatmap',
     'pie_aggregated',
     'pie_automargin',
@@ -1821,6 +1822,7 @@ figs['period_positioning4'] = require('@mocks/period_positioning4');
 figs['period_positioning5'] = require('@mocks/period_positioning5');
 figs['period_positioning6'] = require('@mocks/period_positioning6');
 figs['period_positioning7'] = require('@mocks/period_positioning7');
+figs['period_positioning8'] = require('@mocks/period_positioning8');
 figs['picnic_heatmap'] = require('@mocks/picnic_heatmap');
 figs['pie_aggregated'] = require('@mocks/pie_aggregated');
 figs['pie_automargin'] = require('@mocks/pie_automargin');