Custom Gauge Controls for Windows Phone 7: Part II

using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Diagnostics;

namespace WPScadaControlsV2
{
    public class LinearBarIndicator:BarIndicator
    {
        public LinearBarIndicator()
        {
            DefaultStyleKey = typeof(LinearBarIndicator);
        }

        protected override void OnValueChanged(double newVal, double oldVal)
        {
            //every time the value changes set the width and the hight of
            //the indicator.
            //setting these properties will trigger the measure and arrange passes
            LinearScale scale = Owner as LinearScale;
            if (scale != null)
            {
                Size sz = GetIndicatorSize(scale);
                Debug.WriteLine("val changed: "+sz);
                Width = sz.Width;
                Height = sz.Height;
            }
        }
        protected override Size MeasureOverride(Size availableSize)
        {
            //call the base version to set the owner
            base.MeasureOverride(availableSize);
            Size size = new Size();
            //get the desired size of the indicator based on the owner size
            LinearScale owner = Owner as LinearScale;
            if (owner != null)
            {
                size = GetIndicatorSize(owner);
            }
            return size;
        }
        protected override Size ArrangeOverride(Size arrangeBounds)
        {//with every arrange pass the size of the indicator should 
            //be set again. this is important if the orientation is
            //vertical as the start position changes every time the value changes
            //so the indicator should be rearranged
            LinearScale scale = Owner as LinearScale;
            Size sz = base.ArrangeOverride(arrangeBounds);
            if (scale != null)
            {
                //reset the indicator size after each arrange phase
                sz = GetIndicatorSize(scale);
                Width = sz.Width;
                Height = sz.Height;
                Point pos = scale.GetIndicatorOffset(this);
                TranslateTransform tt = new TranslateTransform();
                tt.X = pos.X;
                tt.Y = pos.Y;
                this.RenderTransform = tt;
            }
            return sz;
        }
        private Size GetIndicatorSize(LinearScale owner)
        {//gets the size of the indicator based on the current value and the
            //owner dimensions
            double width = 0, height = 0;
            if (owner.Orientation == Orientation.Horizontal)
            {
                height = BarThickness;
                width = GetExtent(owner.ActualWidth, Value, owner.Maximum, owner.Minimum);
            }
            else
            {
                width = BarThickness;
                height = GetExtent(owner.ActualHeight, Value, owner.Maximum, owner.Minimum);
            }
            return new Size(width, height);
        }
        
        //gets the length the indicator should have
        private double GetExtent(double length, double value, double max, double min)
        {
            return length * (value - min) / (max - min);
        }

    }
}