Question

So I have a color picker. Users can pick colors using RGB or HSB. There are sliders/properties for each value. When user sets Red for example, I will calculate HSB values to reflect new color value. When user sets Hue, the RGB value will be recalculated from the HSB values. But see there’s a loop there. When I set RGB it must recalculate HSB values, ok so far, but it also means that HSB values will change causing RGB values to be re updated again. I think this is where the problem is but how can I fix this?

UPDATE: One Possible Solution

One possible solution I used was flag, not very readable tho, but it works. Basically, when I set properties, I also set a flag to signify I am setting a value

public float Hue {
    get { return _hue; }
    set
    {
        if (_hue == value)
            return;
        CurrentlySetting = (CurrentlySetting.HasValue) ? CurrentlySetting : ColorType.HSB;
        _hue = value;
        NotifyPropertyChanged("Hue");
        NotifyPropertyChanged("Color");
        RecalculateRGB();
        CurrentlySetting = (CurrentlySetting == ColorType.HSB) ? null : CurrentlySetting;
    }
}

When I “Recalculate” Values, I check for that and ensure I am not currently setting them

protected void RecalculateRGB(Color color = new Color())
{
    if (CurrentlySetting == ColorType.RGB) // prevent stackoverflow
        return;

    if (color == new Color())
        color = HSBColorHelper.FromAHSB(255, Hue, Saturation, Brightness);
    Red = color.R;
    Green = color.G;
    Blue = color.B;
}

Not very straight forward, I still prefer @Marc Gravell’s, solution

Answer 1

I would have all the setters call into the same inner code:

public byte R {
    get {return r;}
    set { SetRGB(value, G, B); }
}
public byte G {
    get {return g;}
    set { SetRGB(R, value, B); }
}

etc – and that inner SetRGB method only talks to the fields (not the properties), including any HSB fields you need; so no recursion. You might also want a SetHSB, obviously – again, setting all the fields (not calling into any of the property setters).