bar: Implement layout.barbase

* Fix: do not normalise bars with no size

* Fix: update minDtick if barmode is group and bars overlap.

Closes plotly#475

Author: n-riesco

src/traces/bar/layout_attributes.js

@@ -10,6 +10,12 @@
 
 
 module.exports = {
+    barbase: {
+        valType: 'number',
+        dflt: 0,
+        role: 'style',
+        description: 'Sets where the bar base is drawn (in axis units).'
+    },
     barmode: {
         valType: 'enumerated',
         values: ['stack', 'group', 'overlay', 'relative'],

src/traces/bar/layout_defaults.js

@@ -48,6 +48,8 @@ module.exports = function(layoutIn, layoutOut, fullData) {
 
     if(!hasBars) return;
 
+    coerce('barbase');
+
     var mode = coerce('barmode');
     if(mode !== 'overlay') coerce('barnorm');
 

src/traces/bar/set_positions.js

@@ -76,18 +76,12 @@ function setGroupPositionsInOverlayMode(gd, pa, sa, traces) {
     // update position axis and set bar offsets and widths
     traces.forEach(function(trace) {
         var sieve = new Sieve(
-                    [trace], separateNegativeValues, dontMergeOverlappingData
-                ),
-            minDiff = sieve.minDiff,
-            distinctPositions = sieve.distinctPositions;
+            [trace], separateNegativeValues, dontMergeOverlappingData
+        );
 
-        // set bar offsets and widths
+        // set bar offsets and widths and update position axis
         setOffsetAndWidth(gd, pa, sieve);
 
-        // update position axis
-        Axes.minDtick(pa, minDiff, distinctPositions[0]);
-        Axes.expand(pa, distinctPositions, {vpad: minDiff / 2});
-
         // update size axis and set bar bases and sizes
         if(barnorm) {
             stackBars(gd, sa, sieve);
@@ -102,6 +96,8 @@ function setGroupPositionsInOverlayMode(gd, pa, sa, traces) {
             Axes.expand(sa, trace.map(fs), {tozero: true, padded: true});
         }
     });
+
+    applyBarbase(gd, sa, traces);
 }
 
 
@@ -112,17 +108,11 @@ function setGroupPositionsInGroupMode(gd, pa, sa, traces) {
         dontMergeOverlappingData = !barnorm,
         sieve = new Sieve(
                 traces, separateNegativeValues, dontMergeOverlappingData
-            ),
-        minDiff = sieve.minDiff,
-        distinctPositions = sieve.distinctPositions;
+            );
 
-    // set bar offsets and widths
+    // set bar offsets and widths and update position axis
     setOffsetAndWidthInGroupMode(gd, pa, sieve);
 
-    // update position axis
-    Axes.minDtick(pa, minDiff, distinctPositions[0]);
-    Axes.expand(pa, distinctPositions, {vpad: minDiff / 2});
-
     // update size axis and set bar bases and sizes
     if(barnorm) {
         stackBars(gd, sa, sieve);
@@ -138,6 +128,8 @@ function setGroupPositionsInGroupMode(gd, pa, sa, traces) {
             Axes.expand(sa, traces[i].map(fs), {tozero: true, padded: true});
         }
     }
+
+    applyBarbase(gd, sa, traces);
 }
 
 
@@ -151,18 +143,12 @@ function setGroupPositionsInStackOrRelativeMode(gd, pa, sa, traces) {
         dontMergeOverlappingData = !(barnorm || stack || relative),
         sieve = new Sieve(
                 traces, separateNegativeValues, dontMergeOverlappingData
-            ),
-        minDiff = sieve.minDiff,
-        distinctPositions = sieve.distinctPositions;
+            );
 
-    // set bar offsets and widths
+    // set bar offsets and widths and update position axis
     setOffsetAndWidth(gd, pa, sieve);
 
-    // update position axis
-    Axes.minDtick(pa, minDiff, distinctPositions[0]);
-    Axes.expand(pa, distinctPositions, {vpad: minDiff / 2});
-
-    // set bar bases and sizes
+    // set bar bases and sizes and update size axis
     stackBars(gd, sa, sieve);
 }
 
@@ -199,6 +185,11 @@ function setOffsetAndWidth(gd, pa, sieve) {
             bar[pLetter] = bar.p + barCenter;
         }
     }
+
+    // update position axis
+    var distinctPositions = sieve.distinctPositions;
+    Axes.minDtick(pa, minDiff, distinctPositions[0]);
+    Axes.expand(pa, distinctPositions, {vpad: minDiff / 2});
 }
 
 
@@ -243,6 +234,10 @@ function setOffsetAndWidthInGroupMode(gd, pa, sieve) {
             bar[pLetter] = bar.p + barCenter;
         }
     }
+
+    // update position axis
+    Axes.minDtick(pa, minDiff, distinctPositions[0], overlap);
+    Axes.expand(pa, distinctPositions, {vpad: minDiff / 2});
 }
 
 
@@ -318,9 +313,11 @@ function normalizeBars(gd, sa, sieve) {
         var trace = traces[i];
 
         for(var j = 0; j < trace.length; j++) {
-            var bar = trace[j],
-                scale = Math.abs(sTop / sieve.get(bar.p, bar.s));
+            var bar = trace[j];
+
+            if(!isNumeric(bar.s)) continue;
 
+            var scale = Math.abs(sTop / sieve.get(bar.p, bar.s));
             bar.b *= scale;
             bar.s *= scale;
             var barEnd = bar.b + bar.s;
@@ -343,6 +340,27 @@ function normalizeBars(gd, sa, sieve) {
 }
 
 
+function applyBarbase(gd, sa, traces) {
+    var barbase = gd._fullLayout.barbase;
+    if(!barbase || !isNumeric(sa.c2l(barbase))) return;
+
+    for(var i = 0; i < traces.length; i++) {
+        var trace = traces[i];
+
+        for(var j = 0; j < trace.length; j++) {
+            var bar = trace[j],
+                bartop = bar.b + bar.s;
+            if(isNumeric(sa.c2l(bartop))) {
+                bar.b = barbase;
+                bar.s = bartop - barbase;
+            }
+        }
+    }
+
+    Axes.expand(sa, [barbase], {tozero: true, padded: true});
+}
+
+
 function getAxisLetter(ax) {
     return ax._id.charAt(0);
 }