o performBatchOperations:

@@ -49,6 +49,7 @@
 
     CGMutablePathRef path;
     CGRect pathBoundingBox;
+    BOOL ignorePathUpdates;
 
     /// Width of the line, units unknown; pixels maybe?
     float lineWidth;
@@ -106,6 +107,9 @@
 - (void)addLineToScreenPoint:(CGPoint)point;
 - (void)addLineToLatLong:(CLLocationCoordinate2D)point;
 
+// Change the path without recalculating the geometry (performance!)
+- (void)performBatchOperations:(void (^)(RMPath *aPath))block;
+
 /// This closes the path, connecting the last point to the first.
 /// After this action, no further points can be added to the path.
 /// There is no requirement that a path be closed.

@@ -53,6 +53,7 @@
 
     path = CGPathCreateMutable();
     pathBoundingBox = CGRectZero;
+    ignorePathUpdates = NO;
 
     lineWidth = kDefaultLineWidth;
     drawingMode = kCGPathFillStroke;
@@ -104,6 +105,8 @@
 
 - (void)recalculateGeometry
 {
+    if (ignorePathUpdates) return;
+
     RMMercatorToScreenProjection *projection = [mapContents mercatorToScreenProjection];
     float scale = [projection metersPerPixel];
     float scaledLineWidth;
@@ -228,6 +231,14 @@
     [self addLineToXY:mercator];
 }
 
+- (void)performBatchOperations:(void (^)(RMPath *aPath))block
+{
+    ignorePathUpdates = YES;
+    block(self);
+    ignorePathUpdates = NO;
+    [self recalculateGeometry];
+}
+
 - (void)drawInContext:(CGContextRef)theContext
 {
     renderedScale = [mapContents metersPerPixel];