From de0bb1e0522d14bcdef70746da277992f992f83c Mon Sep 17 00:00:00 2001
From: Shohei Yoshida <fellows3@gmail.com>
Date: Mon, 21 Jan 2019 06:28:16 +0900
Subject: Scrollable modal (#27769)

---
 js/src/modal.js                   |   9 +++-
 js/tests/unit/modal.js            |  27 ++++++++++
 scss/_modal.scss                  |  50 +++++++++++++++++--
 site/docs/4.2/components/modal.md | 102 +++++++++++++++++++++++++++++++++++++-
 4 files changed, 182 insertions(+), 6 deletions(-)

diff --git a/js/src/modal.js b/js/src/modal.js
index 125182e136..f658201306 100644
--- a/js/src/modal.js
+++ b/js/src/modal.js
@@ -51,6 +51,7 @@ const Event = {
 }
 
 const ClassName = {
+  SCROLLABLE         : 'modal-dialog-scrollable',
   SCROLLBAR_MEASURER : 'modal-scrollbar-measure',
   BACKDROP           : 'modal-backdrop',
   OPEN               : 'modal-open',
@@ -60,6 +61,7 @@ const ClassName = {
 
 const Selector = {
   DIALOG         : '.modal-dialog',
+  MODAL_BODY     : '.modal-body',
   DATA_TOGGLE    : '[data-toggle="modal"]',
   DATA_DISMISS   : '[data-dismiss="modal"]',
   FIXED_CONTENT  : '.fixed-top, .fixed-bottom, .is-fixed, .sticky-top',
@@ -244,7 +246,12 @@ class Modal {
     this._element.style.display = 'block'
     this._element.removeAttribute('aria-hidden')
     this._element.setAttribute('aria-modal', true)
-    this._element.scrollTop = 0
+
+    if ($(this._dialog).hasClass(ClassName.SCROLLABLE)) {
+      this._dialog.querySelector(Selector.MODAL_BODY).scrollTop = 0
+    } else {
+      this._element.scrollTop = 0
+    }
 
     if (transition) {
       Util.reflow(this._element)
diff --git a/js/tests/unit/modal.js b/js/tests/unit/modal.js
index 4d7682aaa7..1762904803 100644
--- a/js/tests/unit/modal.js
+++ b/js/tests/unit/modal.js
@@ -790,4 +790,31 @@ $(function () {
     })
       .bootstrapModal('show')
   })
+
+  QUnit.test('should scroll to top of the modal body if the modal has .modal-dialog-scrollable class', function (assert) {
+    assert.expect(2)
+    var done = assert.async()
+
+    var $modal = $([
+      '<div id="modal-test">',
+      '  <div class="modal-dialog modal-dialog-scrollable">',
+      '    <div class="modal-content">',
+      '      <div class="modal-body" style="height: 100px; overflow-y: auto;">',
+      '        <div style="height: 200px" />',
+      '      </div>',
+      '    </div>',
+      '  </div>',
+      '</div>'
+    ].join('')).appendTo('#qunit-fixture')
+
+    var $modalBody = $('.modal-body')
+    $modalBody.scrollTop(100)
+    assert.strictEqual($modalBody.scrollTop(), 100)
+
+    $modal.on('shown.bs.modal', function () {
+      assert.strictEqual($modalBody.scrollTop(), 0, 'modal body scrollTop should be 0 when opened')
+      done()
+    })
+      .bootstrapModal('show')
+  })
 })
diff --git a/scss/_modal.scss b/scss/_modal.scss
index 65b61d90c2..0c4a68d0be 100644
--- a/scss/_modal.scss
+++ b/scss/_modal.scss
@@ -50,17 +50,51 @@
   }
 }
 
+.modal-dialog-scrollable {
+  display: flex; // IE10/11
+  max-height: calc(100% - #{$modal-dialog-margin * 2});
+
+  .modal-content {
+    max-height: calc(100vh - #{$modal-dialog-margin * 2}); // IE10/11
+    overflow: hidden;
+  }
+
+  .modal-header,
+  .modal-footer {
+    flex-shrink: 0;
+  }
+
+  .modal-body {
+    overflow-y: auto;
+  }
+}
+
 .modal-dialog-centered {
   display: flex;
   align-items: center;
-  min-height: calc(100% - (#{$modal-dialog-margin} * 2));
+  min-height: calc(100% - #{$modal-dialog-margin * 2});
 
   // Ensure `modal-dialog-centered` extends the full height of the view (IE10/11)
   &::before {
     display: block; // IE10
-    height: calc(100vh - (#{$modal-dialog-margin} * 2));
+    height: calc(100vh - #{$modal-dialog-margin * 2});
     content: "";
   }
+
+  // Ensure `.modal-body` shows scrollbar (IE10/11)
+  &.modal-dialog-scrollable {
+    flex-direction: column;
+    justify-content: center;
+    height: 100%;
+
+    .modal-content {
+      max-height: none;
+    }
+
+    &::before {
+      content: none;
+    }
+  }
 }
 
 // Actual modal
@@ -159,11 +193,19 @@
     margin: $modal-dialog-margin-y-sm-up auto;
   }
 
+  .modal-dialog-scrollable {
+    max-height: calc(100% - #{$modal-dialog-margin-y-sm-up * 2});
+
+    .modal-content {
+      max-height: calc(100vh - #{$modal-dialog-margin-y-sm-up * 2});
+    }
+  }
+
   .modal-dialog-centered {
-    min-height: calc(100% - (#{$modal-dialog-margin-y-sm-up} * 2));
+    min-height: calc(100% - #{$modal-dialog-margin-y-sm-up * 2});
 
     &::before {
-      height: calc(100vh - (#{$modal-dialog-margin-y-sm-up} * 2));
+      height: calc(100vh - #{$modal-dialog-margin-y-sm-up * 2});
     }
   }
 
diff --git a/site/docs/4.2/components/modal.md b/site/docs/4.2/components/modal.md
index 86996ecda4..e95a57b9cd 100644
--- a/site/docs/4.2/components/modal.md
+++ b/site/docs/4.2/components/modal.md
@@ -210,6 +210,79 @@ When modals become too long for the user's viewport or device, they scroll indep
 </div>
 {% endhighlight %}
 
+You can also create a scrollable modal that allows scroll the modal body by adding `.modal-dialog-scrollable` to `.modal-dialog`.
+
+<div id="exampleModalScrollable" class="modal fade" tabindex="-1" role="dialog" aria-labelledby="exampleModalScrollableTitle" aria-hidden="true">
+  <div class="modal-dialog modal-dialog-scrollable" role="document">
+    <div class="modal-content">
+      <div class="modal-header">
+        <h5 class="modal-title" id="exampleModalScrollableTitle">Modal title</h5>
+        <button type="button" class="close" data-dismiss="modal" aria-label="Close">
+          <span aria-hidden="true">&times;</span>
+        </button>
+      </div>
+      <div class="modal-body">
+        <p>Cras mattis consectetur purus sit amet fermentum. Cras justo odio, dapibus ac facilisis in, egestas eget quam. Morbi leo risus, porta ac consectetur ac, vestibulum at eros.</p>
+        <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Vivamus sagittis lacus vel augue laoreet rutrum faucibus dolor auctor.</p>
+        <p>Aenean lacinia bibendum nulla sed consectetur. Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Donec sed odio dui. Donec ullamcorper nulla non metus auctor fringilla.</p>
+        <p>Cras mattis consectetur purus sit amet fermentum. Cras justo odio, dapibus ac facilisis in, egestas eget quam. Morbi leo risus, porta ac consectetur ac, vestibulum at eros.</p>
+        <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Vivamus sagittis lacus vel augue laoreet rutrum faucibus dolor auctor.</p>
+        <p>Aenean lacinia bibendum nulla sed consectetur. Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Donec sed odio dui. Donec ullamcorper nulla non metus auctor fringilla.</p>
+        <p>Cras mattis consectetur purus sit amet fermentum. Cras justo odio, dapibus ac facilisis in, egestas eget quam. Morbi leo risus, porta ac consectetur ac, vestibulum at eros.</p>
+        <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Vivamus sagittis lacus vel augue laoreet rutrum faucibus dolor auctor.</p>
+        <p>Aenean lacinia bibendum nulla sed consectetur. Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Donec sed odio dui. Donec ullamcorper nulla non metus auctor fringilla.</p>
+        <p>Cras mattis consectetur purus sit amet fermentum. Cras justo odio, dapibus ac facilisis in, egestas eget quam. Morbi leo risus, porta ac consectetur ac, vestibulum at eros.</p>
+        <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Vivamus sagittis lacus vel augue laoreet rutrum faucibus dolor auctor.</p>
+        <p>Aenean lacinia bibendum nulla sed consectetur. Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Donec sed odio dui. Donec ullamcorper nulla non metus auctor fringilla.</p>
+        <p>Cras mattis consectetur purus sit amet fermentum. Cras justo odio, dapibus ac facilisis in, egestas eget quam. Morbi leo risus, porta ac consectetur ac, vestibulum at eros.</p>
+        <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Vivamus sagittis lacus vel augue laoreet rutrum faucibus dolor auctor.</p>
+        <p>Aenean lacinia bibendum nulla sed consectetur. Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Donec sed odio dui. Donec ullamcorper nulla non metus auctor fringilla.</p>
+        <p>Cras mattis consectetur purus sit amet fermentum. Cras justo odio, dapibus ac facilisis in, egestas eget quam. Morbi leo risus, porta ac consectetur ac, vestibulum at eros.</p>
+        <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Vivamus sagittis lacus vel augue laoreet rutrum faucibus dolor auctor.</p>
+        <p>Aenean lacinia bibendum nulla sed consectetur. Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Donec sed odio dui. Donec ullamcorper nulla non metus auctor fringilla.</p>
+      </div>
+      <div class="modal-footer">
+        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
+        <button type="button" class="btn btn-primary">Save changes</button>
+      </div>
+    </div>
+  </div>
+</div>
+
+<div class="bd-example">
+  <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModalScrollable">
+    Launch demo modal
+  </button>
+</div>
+
+{% highlight html %}
+<!-- Button trigger modal -->
+<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModalScrollable">
+  Launch demo modal
+</button>
+
+<!-- Modal -->
+<div class="modal fade" id="exampleModalScrollable" tabindex="-1" role="dialog" aria-labelledby="exampleModalScrollableTitle" aria-hidden="true">
+  <div class="modal-dialog" role="document">
+    <div class="modal-content">
+      <div class="modal-header">
+        <h5 class="modal-title" id="exampleModalScrollableTitle">Modal title</h5>
+        <button type="button" class="close" data-dismiss="modal" aria-label="Close">
+          <span aria-hidden="true">&times;</span>
+        </button>
+      </div>
+      <div class="modal-body">
+        ...
+      </div>
+      <div class="modal-footer">
+        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
+        <button type="button" class="btn btn-primary">Save changes</button>
+      </div>
+    </div>
+  </div>
+</div>
+{% endhighlight %}
+
 ### Vertically centered
 
 Add `.modal-dialog-centered` to `.modal-dialog` to vertically center the modal.
@@ -234,9 +307,36 @@ Add `.modal-dialog-centered` to `.modal-dialog` to vertically center the modal.
   </div>
 </div>
 
+<div id="exampleModalCenteredScrollable" class="modal fade" tabindex="-1" role="dialog" aria-labelledby="exampleModalCenteredScrollableTitle" aria-hidden="true">
+  <div class="modal-dialog modal-dialog-scrollable modal-dialog-centered" role="document">
+    <div class="modal-content">
+      <div class="modal-header">
+        <h5 class="modal-title" id="exampleModalCenteredScrollableTitle">Modal title</h5>
+        <button type="button" class="close" data-dismiss="modal" aria-label="Close">
+          <span aria-hidden="true">&times;</span>
+        </button>
+      </div>
+      <div class="modal-body">
+        <p>Cras mattis consectetur purus sit amet fermentum. Cras justo odio, dapibus ac facilisis in, egestas eget quam. Morbi leo risus, porta ac consectetur ac, vestibulum at eros.</p>
+        <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Vivamus sagittis lacus vel augue laoreet rutrum faucibus dolor auctor.</p>
+        <p>Aenean lacinia bibendum nulla sed consectetur. Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Donec sed odio dui. Donec ullamcorper nulla non metus auctor fringilla.</p>
+        <p>Cras mattis consectetur purus sit amet fermentum. Cras justo odio, dapibus ac facilisis in, egestas eget quam. Morbi leo risus, porta ac consectetur ac, vestibulum at eros.</p>
+        <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur et. Vivamus sagittis lacus vel augue laoreet rutrum faucibus dolor auctor.</p>
+      </div>
+      <div class="modal-footer">
+        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
+        <button type="button" class="btn btn-primary">Save changes</button>
+      </div>
+    </div>
+  </div>
+</div>
+
 <div class="bd-example">
   <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModalCenter">
-    Launch demo modal
+    Vertically centered modal
+  </button>
+  <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModalCenteredScrollable">
+    Vertically centered scrollable modal
   </button>
 </div>
 
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