Correctly selects arrow placement for a tooltip

Fixes #13696.
Fixes #13696.
Fixes #14197.
Closes #13718.

js/tests/unit/tooltip.js

@@ -836,4 +836,35 @@ $(function () {
     equal(currentUid, $('#tt-content').text())
   })
 
+  test('should position arrow correctly when tooltip is moved to not appear offscreen', function () {
+    stop()
+
+    var styles = '<style>'
+        + '.tooltip, .tooltip *, .tooltip *:before, .tooltip *:after { box-sizing: border-box; }'
+        + '.tooltip { position: absolute; }'
+        + '.tooltip-arrow { position: absolute; width: 0; height: 0; }'
+        + '.tooltip .tooltip-inner { max-width: 200px; padding: 3px 8px; }'
+        + '</style>'
+    var $styles = $(styles).appendTo('head')
+
+    $('<a href="#" title="tooltip title" style="position: absolute; bottom: 0; right: 0;">Foobar</a>')
+      .appendTo('body')
+      .on('shown.bs.tooltip', function () {
+        var arrowStyles = $(this).data('bs.tooltip').$tip.find('.tooltip-arrow').attr('style')
+        ok(/left/i.test(arrowStyles) && !/top/i.test(arrowStyles), 'arrow positioned correctly')
+        $(this).bootstrapTooltip('hide')
+      })
+      .on('hidden.bs.tooltip', function () {
+        $styles.remove()
+        $(this).remove()
+        start()
+      })
+      .bootstrapTooltip({
+        container: 'body',
+        placement: 'top',
+        trigger: 'manual'
+      })
+      .bootstrapTooltip('show')
+  })
+
 })

js/tooltip.js

@@ -261,16 +261,18 @@
     if (delta.left) offset.left += delta.left
     else offset.top += delta.top
 
-    var arrowDelta          = delta.left ? delta.left * 2 - width + actualWidth : delta.top * 2 - height + actualHeight
-    var arrowPosition       = delta.left ? 'left'        : 'top'
-    var arrowOffsetPosition = delta.left ? 'offsetWidth' : 'offsetHeight'
+    var isVertical          = /top|bottom/.test(placement)
+    var arrowDelta          = isVertical ? delta.left * 2 - width + actualWidth : delta.top * 2 - height + actualHeight
+    var arrowOffsetPosition = isVertical ? 'offsetWidth' : 'offsetHeight'
 
     $tip.offset(offset)
-    this.replaceArrow(arrowDelta, $tip[0][arrowOffsetPosition], arrowPosition)
+    this.replaceArrow(arrowDelta, $tip[0][arrowOffsetPosition], isVertical)
   }
 
-  Tooltip.prototype.replaceArrow = function (delta, dimension, position) {
-    this.arrow().css(position, delta ? (50 * (1 - delta / dimension) + '%') : '')
+  Tooltip.prototype.replaceArrow = function (delta, dimension, isHorizontal) {
+    this.arrow()
+      .css(isHorizontal ? 'left' : 'top', 50 * (1 - delta / dimension) + '%')
+      .css(isHorizontal ? 'top' : 'left', '')
   }
 
   Tooltip.prototype.setContent = function () {