Fix contrasting text color for bars without explicit marker color [2951]

Author: rmoestl

src/traces/bar/plot.js

@@ -176,7 +176,7 @@ function appendBarText(gd, bar, calcTrace, i, x0, x1, y0, y1) {
     }
 
     var layoutFont = gd._fullLayout.font;
-    var barColor = calcTrace[i].mc;
+    var barColor = style.getBarColor(calcTrace[i], trace);
     var insideTextFont = style.getInsideTextFont(trace, i, layoutFont, barColor);
     var outsideTextFont = style.getOutsideTextFont(trace, i, layoutFont);
 

src/traces/bar/style.js

@@ -104,7 +104,7 @@ function determineFont(tx, d, trace, gd) {
     var textFont = trace.textfont;
 
     if(tx.classed('bartext-inside')) {
-        var barColor = d.mc;
+        var barColor = getBarColor(d, trace);
         textFont = getInsideTextFont(trace, d.i, layoutFont, barColor);
     } else if(tx.classed('bartext-outside')) {
         textFont = getOutsideTextFont(trace, d.i, layoutFont);
@@ -159,9 +159,14 @@ function getFontValue(attributeDefinition, attributeValue, index, defaultValue)
     };
 }
 
+function getBarColor(cd, trace) {
+    return cd.mc || trace.marker.color;
+}
+
 module.exports = {
     style: style,
     styleOnSelect: styleOnSelect,
     getInsideTextFont: getInsideTextFont,
-    getOutsideTextFont: getOutsideTextFont
+    getOutsideTextFont: getOutsideTextFont,
+    getBarColor: getBarColor
 };

test/image/baselines/bar_attrs_relative.png

@@ -1081,8 +1081,16 @@ describe('A bar plot', function() {
     };
 
     it('should use inside text colors contrasting to bar colors by default', function(done) {
-        Plotly.plot(gd, [insideTextTestsTrace])
-          .then(assertTextFontColors([DARK, DARK, LIGHT, LIGHT, DARK, LIGHT]))
+        var noMarkerTrace = Lib.extendFlat({}, insideTextTestsTrace);
+        delete noMarkerTrace.marker;
+
+        Plotly.plot(gd, [insideTextTestsTrace, noMarkerTrace])
+          .then(function() {
+              var trace1Colors = [DARK, DARK, LIGHT, LIGHT, DARK, LIGHT];
+              var trace2Colors = Lib.repeat(DARK, 6);
+              var allExpectedColors = trace1Colors.concat(trace2Colors);
+              assertTextFontColors(allExpectedColors)();
+          })
           .catch(failTest)
           .then(done);
     });