[vis/tooltip] modify the placement if we can't swap direction

src/kibana/components/vislib/lib/tooltip.js

@@ -63,7 +63,7 @@ define(function (require) {
 
     Tooltip.prototype.getTooltipPlacement = function (event) {
       var self = this;
-      var OFFSET = 15;
+      var OFFSET = 10;
 
       var chart = $(self.el).find('.' + self.containerClass);
       if (!chart.size()) return;
@@ -82,22 +82,44 @@ define(function (require) {
         west: event.clientX - tipWidth - OFFSET
       };
 
-      var eastOverEdge = left.east + tipWidth > chartPos.right;
-      var westOverEdge = left.west + tipWidth < chartPos.left;
-
       // the placements if we were to place the tip north or south
       var top = {
         south: event.clientY + OFFSET,
         north: event.clientY - tipHeight - OFFSET
       };
 
-      var northOverEdge = top.north + tipHeight < chartPos.top;
-      var southOverEdge = top.south + tipHeight > chartPos.bottom;
-
-      return {
-        top: (southOverEdge && !northOverEdge) ? top.north : top.south,
-        left: (eastOverEdge && !westOverEdge) ? left.west : left.east
+      // number of pixels that the toolip would overflow it's far
+      // side, if we placed it that way. (negative === no overflow)
+      var overflow = {
+        north: chartPos.top - top.north,
+        east: (left.east + tipWidth) - chartPos.right,
+        south: (top.south + tipHeight) - chartPos.bottom,
+        west: chartPos.left - left.west
       };
+
+      var placement = {};
+
+      if (overflow.south > 0) {
+        if (overflow.north < 0) {
+          placement.top = top.north;
+        } else {
+          placement.top = top.south - overflow.south;
+        }
+      } else {
+        placement.top = top.south;
+      }
+
+      if (overflow.east > 0) {
+        if (overflow.west < 0) {
+          placement.left = left.west;
+        } else {
+          placement.left = left.east - overflow.east;
+        }
+      } else {
+        placement.left = left.east;
+      }
+
+      return placement;
     };
 
     return Tooltip;