Center modal dialog at all times

js/modal.js

@@ -56,11 +56,11 @@
     this.isShown = true
 
     this.checkScrollbar()
+    this.setScrollbar()
     this.$body.addClass('modal-open')
 
-    this.setScrollbar()
     this.escape()
-    if (this.options.backdrop) this.resize()
+    this.resize()
 
     this.$element.on('click.dismiss.bs.modal', '[data-dismiss="modal"]', $.proxy(this.hide, this))
 
@@ -75,7 +75,8 @@
         .show()
         .scrollTop(0)
 
-      if (that.options.backdrop) that.setBackdropHeight()
+      if (that.options.backdrop) that.adjustBackdrop()
+      that.adjustDialog()
 
       if (transition) {
         that.$element[0].offsetWidth // force reflow
@@ -111,7 +112,7 @@
     this.isShown = false
 
     this.escape()
-    if (this.options.backdrop) this.resize()
+    this.resize()
 
     $(document).off('focusin.bs.modal')
 
@@ -149,7 +150,7 @@
 
   Modal.prototype.resize = function () {
     if (this.isShown) {
-      $(window).on('resize.bs.modal', $.proxy(this.setBackdropHeight, this))
+      $(window).on('resize.bs.modal', $.proxy(this.handleUpdate, this))
     } else {
       $(window).off('resize.bs.modal')
     }
@@ -160,6 +161,7 @@
     this.$element.hide()
     this.backdrop(function () {
       that.$body.removeClass('modal-open')
+      that.resetAdjustments()
       that.resetScrollbar()
       that.$element.trigger('hidden.bs.modal')
     })
@@ -216,19 +218,43 @@
     }
   }
 
-  Modal.prototype.setBackdropHeight = function () {
+  // these following methods are used to handle overflowing modals
+
+  Modal.prototype.handleUpdate = function () {
+    if (this.options.backdrop) this.adjustBackdrop()
+    this.adjustDialog()
+  }
+
+  Modal.prototype.adjustBackdrop = function () {
     this.$backdrop
       .css('height', 0)
       .css('height', this.$element[0].scrollHeight)
   }
 
+  Modal.prototype.adjustDialog = function () {
+    var modalIsOverflowing = this.$element[0].scrollHeight > document.documentElement.clientHeight
+
+    this.$element.css({
+      paddingLeft:  !this.bodyIsOverflowing && modalIsOverflowing ? this.scrollbarWidth : '',
+      paddingRight: this.bodyIsOverflowing && !modalIsOverflowing ? this.scrollbarWidth : ''
+    })
+  }
+
+  Modal.prototype.resetAdjustments = function () {
+    this.$element.css({
+      paddingLeft: '',
+      paddingRight: ''
+    })
+  }
+
   Modal.prototype.checkScrollbar = function () {
+    this.bodyIsOverflowing = document.body.scrollHeight > document.documentElement.clientHeight
     this.scrollbarWidth = this.measureScrollbar()
   }
 
   Modal.prototype.setScrollbar = function () {
     var bodyPad = parseInt((this.$body.css('padding-right') || 0), 10)
-    if (this.scrollbarWidth) this.$body.css('padding-right', bodyPad + this.scrollbarWidth)
+    if (this.bodyIsOverflowing) this.$body.css('padding-right', bodyPad + this.scrollbarWidth)
   }
 
   Modal.prototype.resetScrollbar = function () {
@@ -236,7 +262,6 @@
   }
 
   Modal.prototype.measureScrollbar = function () { // thx walsh
-    if (document.body.clientWidth >= window.innerWidth) return 0
     var scrollDiv = document.createElement('div')
     scrollDiv.className = 'modal-scrollbar-measure'
     this.$body.append(scrollDiv)