constrained override for -[RMMapContents moveBy:] in route-me

gistfile1.m

- (void)moveBy:(CGSize)delta
{
    // Adjust delta as necessary to constrain latitude, but not longitude.
    //
    // This is largely borrowed from -[RMMapView setConstraintsSW:NE:] and -[RMMapView moveBy:]
    //
    RMProjectedRect sourceBounds = [self.mercatorToScreenProjection projectedBounds];
    RMProjectedSize XYDelta      = [self.mercatorToScreenProjection projectScreenSizeToXY:delta];

    CGSize sizeRatio = CGSizeMake(((delta.width == 0)  ? 0 : XYDelta.width  / delta.width),
                                  ((delta.height == 0) ? 0 : XYDelta.height / delta.height));

    RMProjectedRect destinationBounds = sourceBounds;
    
    destinationBounds.origin.northing -= XYDelta.height;
    destinationBounds.origin.easting  -= XYDelta.width; 
    
    BOOL constrained = NO;
    
    RMProjectedPoint SWconstraint = [self.projection latLongToPoint:CLLocationCoordinate2DMake(kLowerLatitudeBounds, 0)];
    RMProjectedPoint NEconstraint = [self.projection latLongToPoint:CLLocationCoordinate2DMake(kUpperLatitudeBounds, 0)];
    
    if (destinationBounds.origin.northing < SWconstraint.northing)
    {
        destinationBounds.origin.northing = SWconstraint.northing;
        constrained = YES;
    }
    
    if (destinationBounds.origin.northing + sourceBounds.size.height > NEconstraint.northing)
    {
        destinationBounds.origin.northing = NEconstraint.northing - destinationBounds.size.height;
        constrained = YES;
    }

    if (constrained) 
    {
        XYDelta.height = sourceBounds.origin.northing - destinationBounds.origin.northing;
        XYDelta.width  = sourceBounds.origin.easting  - destinationBounds.origin.easting;
        
        delta = CGSizeMake(((sizeRatio.width == 0)  ? 0 : XYDelta.width  / sizeRatio.width), 
                           ((sizeRatio.height == 0) ? 0 : XYDelta.height / sizeRatio.height));
    }

    [super moveBy:delta];
}