Scaling drawing based on y-axis zoom level?

[overflowing]

I'm drawing a rectangle whose height I want to stay proportional to the y axis price scale. That is, as the user increases the the zoom on the price scale I want the rectangle height to grow larger and as the user decreases the zoom I want the rectangle height to grow smaller.

I have successfully achieved this effect by getting the y value of two prices and using their difference as a scale factor. And then using the yscale variable in the call to DrawRectangle

int y1 = ChartControl.GetYByValue(this, 1);
int y2 = ChartControl.GetYByValue(this, 2);
float yscale = (y1 - y2) * (float)tickSize;

(the 1 and 2 parameters above are simply the price $1 and $2). It works but it seems a little kludgy. Is there a standard way to do this?

[NinjaTrader_Bertrand]

Hi overflowing, there's unfortunately no other 'standard' way of achieving this available - congrats on the implementation and thanks for posting it here on our forums.