/// <summary>
/// Sort images by global style
/// </summary>
/// <remarks>
/// <see cref="GetImage(IEnumerable{string})"/> is optimized for performace and therefore
/// just loops over the images and selects the first best matching one based on given styles.
/// The result is not predictable if the image list is not sorted and several alternatives
/// match different global and explicit styles.
/// Since we want to prioritize explicit styles first (<see cref="Image.WithStyles(string[])"/>),
/// we need to make sure that we don't select an image with a given global style
/// (<see cref="Context.SetGlobalStyle(string)"/>) but without an explicit match.
/// The simplest approach without slowing down rendering by a sophisticated lookup is to
/// sort images matching global styles last, so that <see cref="GetImage(IEnumerable{string})"/>
/// would always select an alternative with an explicit rather than a global style.
/// </remarks>
static int StylePriorityComparison(Tuple <Image, string []> img1, Tuple <Image, string []> img2)
{
var hasGlobal1 = img1.Item2.Any(style => Context.HasGlobalStyle(style));
var hasGlobal2 = img2.Item2.Any(style => Context.HasGlobalStyle(style));
if (hasGlobal1 && hasGlobal2)
{
return(0);
}
if (hasGlobal1)
{
return(1); // sort global styles last
}
return(-1); // explicit styles go first
}