From 88a34aacbee09417252c804f7cded926a496904a Mon Sep 17 00:00:00 2001
From: Jason Golieb <jgolieb@hortonworks.com>
Date: Mon, 28 Jan 2019 22:55:21 +0200
Subject: [PATCH] Add support for tooltip offset option to be a function.

---
 js/src/tooltip.js                    | 16 +++++++++---
 js/tests/unit/tooltip.js             | 37 ++++++++++++++++++++++++++++
 site/docs/4.2/components/tooltips.md |  8 ++++--
 3 files changed, 55 insertions(+), 6 deletions(-)

diff --git a/js/src/tooltip.js b/js/src/tooltip.js
index 366781b3e8..0b6e21085f 100644
--- a/js/src/tooltip.js
+++ b/js/src/tooltip.js
@@ -32,7 +32,7 @@ const DefaultType = {
   html              : 'boolean',
   selector          : '(string|boolean)',
   placement         : '(string|function)',
-  offset            : '(number|string)',
+  offset            : '(number|string|function)',
   container         : '(string|element|boolean)',
   fallbackPlacement : '(string|array)',
   boundary          : '(string|element)'
@@ -273,6 +273,16 @@ class Tooltip {
       const attachment = this._getAttachment(placement)
       this.addAttachmentClass(attachment)
 
+      const offsetConf = {}
+      if (typeof this.config.offset === 'function') {
+        offsetConf.fn = (data) => {
+          data.offsets = $.extend({}, data.offsets, this.config.offset(data.offsets, this.element) || {})
+          return data
+        }
+      } else {
+        offsetConf.offset = this.config.offset
+      }
+
       const container = this._getContainer()
       $(tip).data(this.constructor.DATA_KEY, this)
 
@@ -285,9 +295,7 @@ class Tooltip {
       this._popper = new Popper(this.element, tip, {
         placement: attachment,
         modifiers: {
-          offset: {
-            offset: this.config.offset
-          },
+          offset: offsetConf,
           flip: {
             behavior: this.config.fallbackPlacement
           },
diff --git a/js/tests/unit/tooltip.js b/js/tests/unit/tooltip.js
index 54dbe57bd8..30829d24d5 100644
--- a/js/tests/unit/tooltip.js
+++ b/js/tests/unit/tooltip.js
@@ -1069,4 +1069,41 @@ $(function () {
 
     assert.strictEqual(tooltip._isEnabled, true)
   })
+
+  QUnit.test('should create offset modifier correctly when offset option is a function', function (assert) {
+    assert.expect(2)
+
+    var getOffset = function (offsets) {
+      return offsets
+    }
+
+    var $trigger = $('<a href="#" rel="tooltip" data-trigger="click" title="Another tooltip"/>')
+      .appendTo('#qunit-fixture')
+      .bootstrapTooltip({
+        offset: getOffset
+      })
+
+    var tooltip = $trigger.data('bs.tooltip')
+    var offset = tooltip._getOffset()
+
+    assert.ok(typeof offset.offset === 'undefined')
+    assert.ok(typeof offset.fn === 'function')
+  })
+
+  QUnit.test('should create offset modifier correctly when offset option is not a function', function (assert) {
+    assert.expect(2)
+
+    var myOffset = 42
+    var $trigger = $('<a href="#" rel="tooltip" data-trigger="click" title="Another tooltip"/>')
+      .appendTo('#qunit-fixture')
+      .bootstrapTooltip({
+        offset: myOffset
+      })
+
+    var tooltip = $trigger.data('bs.tooltip')
+    var offset = tooltip._getOffset()
+
+    assert.strictEqual(offset.offset, myOffset)
+    assert.ok(typeof offset.fn === 'undefined')
+  })
 })
diff --git a/site/docs/4.2/components/tooltips.md b/site/docs/4.2/components/tooltips.md
index e49db56347..0a6be47588 100644
--- a/site/docs/4.2/components/tooltips.md
+++ b/site/docs/4.2/components/tooltips.md
@@ -234,9 +234,13 @@ Options can be passed via data attributes or JavaScript. For data attributes, ap
     </tr>
     <tr>
       <td>offset</td>
-      <td>number | string</td>
+      <td>number | string | function</td>
       <td>0</td>
-      <td>Offset of the tooltip relative to its target. For more information refer to Popper.js's <a href="https://popper.js.org/popper-documentation.html#modifiers..offset.offset">offset docs</a>.</td>
+      <td>
+        <p>Offset of the tooltip relative to its target.</p>
+        <p>When a function is used to determine the offset, it is called with an object containing the offset data as its first argument. The function must return an object with the same structure. The triggering element DOM node is passed as the second argument.</p>
+        <p>For more information refer to Popper.js's <a href="https://popper.js.org/popper-documentation.html#modifiers..offset.offset">offset docs</a>.</p>
+      </td>
     </tr>
     <tr>
       <td>fallbackPlacement</td>