fix 3785 waterfall connectors on date axes

Author: archmoj

Diff for: src/traces/waterfall/cross_trace_calc.js

@@ -65,6 +65,11 @@ module.exports = function crossTraceCalc(gd, plotinfo) {
             if(di.isSum === false) {
                 di.s0 += (j === 0) ? 0 : cd[j - 1].s;
             }
+
+            if(j + 1 < cd.length) {
+                cd[j].nextP0 = cd[j + 1].p0;
+                cd[j].nextS0 = cd[j + 1].s0;
+            }
         }
     }
 };

Diff for: src/traces/waterfall/plot.js

@@ -60,11 +60,6 @@ function plotConnectors(gd, plotinfo, cdModule, traceLayer) {
             var x2, y2;
             var x3, y3;
 
-            var delta = 0;
-            if(i + 1 < len && Array.isArray(trace.offset)) {
-                delta -= trace.offset[i + 1] - trace.offset[i];
-            }
-
             if(isHorizontal) {
                 x0 = xa.c2p(di.s1, true);
                 y0 = ya.c2p(di.p1, true);
@@ -76,8 +71,8 @@ function plotConnectors(gd, plotinfo, cdModule, traceLayer) {
                 y2 = ya.c2p(di.p1, true);
 
                 if(i + 1 < len) {
-                    x3 = xa.c2p(di.s0 + 1 - delta, true);
-                    y3 = ya.c2p(di.p0 + 1 - delta, true);
+                    x3 = xa.c2p(di.nextS0, true);
+                    y3 = ya.c2p(di.nextP0, true);
                 }
             } else {
                 x0 = xa.c2p(di.p1, true);
@@ -90,8 +85,8 @@ function plotConnectors(gd, plotinfo, cdModule, traceLayer) {
                 y2 = ya.c2p(di.s1, true);
 
                 if(i + 1 < len) {
-                    x3 = xa.c2p(di.p0 + 1 - delta, true);
-                    y3 = ya.c2p(di.s0 + 1 - delta, true);
+                    x3 = xa.c2p(di.nextP0, true);
+                    y3 = ya.c2p(di.nextS0, true);
                 }
             }
 

Diff for: test/image/baselines/waterfall_date-axes.png

@@ -0,0 +1,28 @@
+{
+    "data": [{
+        "type": "waterfall",
+        "x": [
+            "2010-01-01",
+            "2010-07-01",
+            "2011-01-01",
+            "2012-01-01"
+        ],
+        "y": [
+            1,
+            -2,
+            3,
+            0
+        ],
+        "measure": [
+           "absolute",
+           "relative",
+           "relative",
+           "total"
+        ]
+
+    }],
+    "layout": {
+        "width": 500,
+        "height": 250
+    }
+}