datepicker: Fixes regression in #3232 [datepicker position problem in…

… IE 6/7]: added back functionality to detect whether the datepicker displays outside a viewpoint. Additionally if the viewpoint is too small to fit the datepicker it will show in its usual position regardless. I have also added a visual test case for this.

tests/visual/datepicker.html

@@ -56,7 +56,9 @@
 
 		// disabled input datepicker
 		$('#d3').datepicker();		
-
+
+		// bottom-right datepicker
+		$('#d4').datepicker({numberOfMonths: 3});		
 	});
 	</script>
 </head>
@@ -96,6 +98,12 @@
 		<div>
 			<input type="text" id="d3" disabled="disabled" />
 		</div>
+	</li>
+	<li class="plugin" style="position: absolute; right: 0; bottom: 0; height: 40px">
+		Datepicker - positioned bottom-right
+		<div>
+			<input type="text" id="d4">
+		</div>
 	</li>	
 </ul>
 

ui/ui.datepicker.js

@@ -608,10 +608,22 @@ $.extend(Datepicker.prototype, {
 	},
 
 	/* Check positioning to remain on screen. */
-	_checkOffset: function(inst, offset, isFixed) {
-		offset.left -= (this._get(inst, 'isRTL') ? (inst.dpDiv.outerWidth() - inst.input.outerWidth()) : 0);
+	_checkOffset: function(inst, offset, isFixed) {		
+		var dpWidth = inst.dpDiv.outerWidth();
+		var dpHeight = inst.dpDiv.outerHeight();
+		var inputWidth = inst.input ? inst.input.outerWidth() : 0;
+		var inputHeight = inst.input ? inst.input.outerHeight() : 0;
+		var viewWidth = window.innerWidth || document.documentElement.clientWidth;
+		var viewHeight = window.innerHeight || document.documentElement.clientHeight;
+
+		offset.left -= (this._get(inst, 'isRTL') ? (dpWidth - inputWidth) : 0);
 		offset.left -= (isFixed && offset.left == inst.input.offset().left) ? $(document).scrollLeft() : 0;
-		offset.top -= (isFixed && offset.top == (inst.input.offset().top + inst.input.outerHeight())) ? $(document).scrollTop() : 0;			
+		offset.top -= (isFixed && offset.top == (inst.input.offset().top + inputHeight)) ? $(document).scrollTop() : 0;
+
+		// now check if datepicker is showing outside window viewpoint - move to a better place if so.
+		offset.left -= (offset.left + dpWidth > viewWidth && viewWidth > dpWidth) ? Math.abs(offset.left + dpWidth - viewWidth) : 0;
+		offset.top -= (offset.top + dpHeight > viewHeight && viewHeight > dpHeight) ? Math.abs(offset.top + dpHeight + inputHeight*2 - viewHeight) : 0;
+
 		return offset;
 	},