Position north side placements using bottom css

As requested in #151 referencing issue #31 for rationale

Author: Joel Steres

src/placementcalculator.js

@@ -39,7 +39,7 @@ function PlacementCalculator() {
 		switch (placement) {
 			case 'n':
 				coords.set('left', position.left - (tipWidth / 2) - session.positionCompensation.left);
-				coords.set('top', position.top - tipHeight - offset - session.positionCompensation.top);
+				coords.set('bottom', session.windowHeight - position.top + offset - session.positionCompensation.bottom);
 				break;
 			case 'e':
 				coords.set('left', position.left + offset - session.positionCompensation.left);
@@ -54,19 +54,19 @@ function PlacementCalculator() {
 				coords.set('right', session.windowWidth - position.left + offset - session.positionCompensation.right);
 				break;
 			case 'nw':
-				coords.set('top', position.top - tipHeight - offset - session.positionCompensation.top);
+				coords.set('bottom', session.windowHeight - position.top + offset - session.positionCompensation.bottom);
 				coords.set('right', session.windowWidth - position.left - session.positionCompensation.right - 20);
 				break;
 			case 'nw-alt':
 				coords.set('left', position.left - session.positionCompensation.left);
-				coords.set('top', position.top - tipHeight - offset - session.positionCompensation.top);
+				coords.set('bottom', session.windowHeight - position.top + offset - session.positionCompensation.bottom);
 				break;
 			case 'ne':
 				coords.set('left', position.left - session.positionCompensation.left - 20);
-				coords.set('top', position.top - tipHeight - offset - session.positionCompensation.top);
+				coords.set('bottom', session.windowHeight - position.top + offset - session.positionCompensation.bottom);
 				break;
 			case 'ne-alt':
-				coords.set('top', position.top - tipHeight - offset - session.positionCompensation.top);
+				coords.set('bottom', session.windowHeight - position.top + offset - session.positionCompensation.bottom);
 				coords.set('right', session.windowWidth - position.left - session.positionCompensation.right);
 				break;
 			case 'sw':

test/unit/placementcalculator.js

@@ -40,6 +40,11 @@ $(function() {
 				case 'n':
 				case 'ne':
 				case 'nw-alt':
+					assert.strictEqual(coords.top, 'auto', key + ': top property is set to auto');
+					assert.strictEqual($.isNumeric(coords.left), true, key + ': left property is set to a number');
+					assert.strictEqual(coords.right, 'auto', key + ': right property is set to auto');
+					assert.strictEqual($.isNumeric(coords.bottom), true, key + ': bottom property is set to a number');
+					break;
 				case 'e':
 				case 's':
 				case 'se':
@@ -52,13 +57,18 @@ $(function() {
 				case 'w':
 				case 'sw':
 				case 'se-alt':
-				case 'nw':
-				case 'ne-alt':
 					assert.strictEqual($.isNumeric(coords.top), true, key + ': top property is set to a number');
 					assert.strictEqual(coords.left, 'auto', key + ': left property is set to auto');
 					assert.strictEqual($.isNumeric(coords.right), true, key + ': right property is set to a number');
 					assert.strictEqual(coords.bottom, 'auto', key + ': bottom property is set to auto');
 					break;
+				case 'nw':
+				case 'ne-alt':
+					assert.strictEqual(coords.top, 'auto', key + ': top property is set to auto');
+					assert.strictEqual(coords.left, 'auto', key + ': left property is set to auto');
+					assert.strictEqual($.isNumeric(coords.right), true, key + ': right property is set to a number');
+					assert.strictEqual($.isNumeric(coords.bottom), true, key + ': bottom property is set to a number');
+					break;
 			}
 		});
 	});