diff --git a/browser/base/content/tabcandy/app/trench.js b/browser/base/content/tabcandy/app/trench.js
index 05e36988928..c3ed1f24cc4 100644
--- a/browser/base/content/tabcandy/app/trench.js
+++ b/browser/base/content/tabcandy/app/trench.js
@@ -105,7 +105,23 @@ Trench.prototype = {
 		var xRange = {min: rect.left, max: rect.left + rect.width};
 		var yRange = {min: rect.top, max: rect.top + rect.height};
 		
-		switch (edge) {
+		var edgeToCheck;
+		if (this.type == "border") {
+			if (this.edge == "left")
+				edgeToCheck = "right";
+			else if (this.edge == "right")
+				edgeToCheck = "left";
+			else if (this.edge == "top")
+				edgeToCheck = "bottom";
+			else if (this.edge == "bottom")
+				edgeToCheck = "top";
+		} else if (this.type == "guide") {
+			edgeToCheck = this.edge;
+		}
+
+		rect.adjustedEdge = edgeToCheck;
+		
+		switch (edgeToCheck) {
 			case "left":
 				if (this.ruleOverlaps(rect.left, yRange)) {
 					rect.left = this.position;
@@ -178,44 +194,13 @@ var Trenches = {
 			delete self.trenches[id];
 		});
 	},
-	comparePosition: function Trenches_comparePosition(a,b) {
-		return a.position - b.position;
-	},
 	activateOthersTrenches: function Trenches_activateOthersTrenches(element) {
-		var aT = this.activeTrenches;
-		aT.left = [];
-		aT.right = [];
-		aT.top = [];
-		aT.bottom = [];
-		this.safeRegionCache = {left:{},right:{},top:{},bottom:{}};
 		this.trenches.forEach(function(t) {
 			if (t.el === element)
 				return;
 			t.active = true;
 			t.show(); // debug
-			
-			var relevantEdge;
-			if (t.type == "border") {
-				if (t.edge == "left")
-					relevantEdge = "right";
-				else if (t.edge == "right")
-					relevantEdge = "left";
-				else if (t.edge == "top")
-					relevantEdge = "bottom";
-				else if (t.edge == "bottom")
-					relevantEdge = "top";
-			} else if (t.type == "guide" || t.type == "barrier") {
-				relevantEdge = t.edge;
-			}
-			
-			aT[relevantEdge].push({id: t.id, position: t.position, toString: function(){return '' + t.id + ':' + t.position}});
-			
 		});
-
-		aT.left.sort(this.comparePosition);
-		aT.right.sort(this.comparePosition);
-		aT.top.sort(this.comparePosition);
-		aT.bottom.sort(this.comparePosition);		
 	},
 	disactivate: function Trenches_disactivate() {
 		this.trenches.forEach(function(t) {
@@ -223,74 +208,6 @@ var Trenches = {
 			t.show();
 		});
 	},
-	snapEdge: function Trenches_snapEdge(rect,edge,assumeConstantSize,keepProportional) {
-
-		var aT = this.activeTrenches;
-
-		var position;
-		switch (edge) {
-			case 'left':
-				position = rect.left; break;
-			case 'right':
-				position = rect.left + rect.width; break;
-			case 'top':
-				position = rect.top; break;
-			case 'bottom':
-				position = rect.top + rect.height; break;
-		}
-		
-		var safeRegionCache = this.safeRegionCache;
-		
-		if ('min' in safeRegionCache[edge] && 'max' in safeRegionCache[edge]) {
-			if (safeRegionCache[edge].min < position && position < safeRegionCache[edge].max) {
-				return false;
-			}
-		}
-
-		// Find the relevant trenches to compare to:
-		// What we're doing here is planting a "rat" within the ordered list of edges that matter
-		// We then sort the resulting array, use indexOf on the rat, and figure out which trenches
-		// are closest to the edge in question.
-		var rat = {id:'rat',position:position};
-		var index = aT[edge].concat(rat).sort(this.comparePosition).indexOf(rat);
-
-		// Now we know to check aT[edge][index-1] and aT[edge][index]
-
-		var newRect;
-		var updated = false;
-		if (index-1 >= 0) {
-			var trench = this.getById(aT[edge][index-1].id);
-			newRect = trench.rectOverlaps(rect,edge,assumeConstantSize,keepProportional);
-			if (newRect) {
-				rect = newRect;
-				updated = true;
-				delete safeRegionCache[edge].min;
-			} else {
-				safeRegionCache[edge].min = trench.position + trench.radius;
-			}
-		} else {
-			safeRegionCache[edge].min = -10;
-		}
-		if (index < aT[edge].length) {
-			var trench = this.getById(aT[edge][index].id);
-			newRect = trench.rectOverlaps(rect,edge,assumeConstantSize,keepProportional);
-			if (newRect) {
-				rect = newRect;
-				updated = true;
-				delete safeRegionCache[edge].max;
-			} else {
-				safeRegionCache[edge].max = trench.position - trench.radius;
-			}
-		} else {
-			safeRegionCache[edge].max = Infinity;
-		}
-		
-		if (updated)
-			return rect;
-		else
-			return false;
-		
-	},
 	snap: function Trenches_snap(rect,assumeConstantSize,keepProportional) {
 		var aT = this.activeTrenches;
 		
@@ -298,39 +215,38 @@ var Trenches = {
 		var updatedX = false;
 		var updatedY = false;
 		
-		var newRect;
-		newRect = this.snapEdge(rect,(this.preferLeft?'left':'right'),assumeConstantSize,keepProportional);
-		if (newRect) {
-			rect = newRect;
-			updated = true;
-			updatedX = true;
-		}
-		
-		if (!assumeConstantSize || !updatedX) {
-			newRect = this.snapEdge(rect,(this.preferLeft?'right':'left'),assumeConstantSize,keepProportional);
+		for (let i in this.trenches) {
+			var t = this.trenches[i];
+			if (!t.active)
+				continue;
+			// newRect will be a new rect, or false
+			var newRect = t.rectOverlaps(rect,assumeConstantSize,keepProportional);
+
 			if (newRect) {
-				rect = newRect;
-				updated = true;
-				updatedX = true;
+				if (assumeConstantSize && updatedX && updatedY)
+					break;
+				if (assumeConstantSize && updatedX && (newRect.adjustedEdge == "left"||newRect.adjustedEdge == "right"))
+					continue;
+				if (assumeConstantSize && updatedY && (newRect.adjustedEdge == "top"||newRect.adjustedEdge == "bottom"))
+					continue;
+ 				rect = newRect;
+ 				updated = true;
+	
+				// if updatedX, we don't need to update x any more.
+				if (newRect.adjustedEdge == "left" && this.preferLeft)
+					updatedX = true;
+				if (newRect.adjustedEdge == "right" && !this.preferLeft)
+					updatedX = true;
+	
+				// if updatedY, we don't need to update x any more.
+				if (newRect.adjustedEdge == "top" && this.preferTop)
+					updatedY = true;
+				if (newRect.adjustedEdge == "bottom" && !this.preferTop)
+					updatedY = true;
+
 			}
-		}
-		
-		newRect = this.snapEdge(rect,(this.preferTop?'top':'bottom'),assumeConstantSize,keepProportional);
-		if (newRect) {
-			rect = newRect;
-			updated = true;
-			updatedY = true;
-		}
-		
-		if (!assumeConstantSize || !updatedY) {
-			newRect = this.snapEdge(rect,(this.preferTop?'bottom':'top'),assumeConstantSize,keepProportional);
-			if (newRect) {
-				rect = newRect;
-				updated = true;
-				updatedY = true;
-			}
-		}
-		
+		}		
+
 		if (updated)
 			return rect;
 		else