private static FlexSpacingMeasurement CalculateLineSpacing(FlexSpacing spacing, int remainingEmptySpace, int lineItemCount)
{
var betweenCount = lineItemCount > 1
? lineItemCount - 1
: 0;
var layout = new FlexSpacingMeasurement();
switch (spacing)
{
case FlexSpacing.Start:
layout.End = remainingEmptySpace;
break;
case FlexSpacing.End:
layout.Start = remainingEmptySpace;
break;
case FlexSpacing.Center:
layout.Start = (int)Math.Floor(remainingEmptySpace / 2.0);
layout.End = (int)Math.Ceiling(remainingEmptySpace / 2.0);
break;
case FlexSpacing.Around:
var halved = remainingEmptySpace / 2.0;
var elementSpace = (int)Math.Ceiling(halved);
var startEndSpace = remainingEmptySpace - elementSpace;
layout.Between = betweenCount > 0 ? elementSpace / betweenCount : 0;
layout.Start = (int)Math.Floor(startEndSpace / 2.0);
layout.End = (int)Math.Ceiling(startEndSpace / 2.0);
break;
case FlexSpacing.Between:
layout.Between = betweenCount > 0 ? remainingEmptySpace / betweenCount : 0;
break;
case FlexSpacing.Evenly:
var spaceCount = betweenCount + 2; // the space in front and at the end
var distributed = remainingEmptySpace / spaceCount;
layout.Between = distributed;
layout.Start = distributed;
layout.End = distributed;
break;
default:
break;
}
return(layout);
}
private static void LayoutLine(MeasuredLayout layout, FlexSpacing spacing, Axis axis, BoxConstraint constraint)
{
int total = 0;
try
{
total = layout
.Elements
.Select(l => l.Size.GetAxis(axis))
.Sum();
}
catch (ArithmeticException ex)
{
throw;
}
// if !isbounded, it's just a total + maxsize on offset
// if isbounded, then calc the flex spacing
// add it all together for the size
var lineSpacing = constraint.IsBounded(axis)
? CalculateLineSpacing(spacing, constraint.GetMaxSize().GetAxis(axis) - total, layout.Elements.Count)
: new FlexSpacingMeasurement()
{
Between = 0, End = 0, Start = 0
};
var used = lineSpacing.Start;
var crossMax = 0;
for (var x = 0; x < layout.Elements.Count; x++)
{
var item = layout.Elements[x];
item.Offset = used;
used += item.Size.GetAxis(axis);
if (x != layout.Elements.Count - 1)
{
// add between for every item that's not 'last'
used += lineSpacing.Between;
}
var cross = item.Size.GetAxis(axis.CrossAxis());
if (cross < int.MaxValue && cross > crossMax)
{
crossMax = cross;
}
}
used += lineSpacing.End;
foreach (var i in layout.Elements)
{
i.Constraint = i.Constraint.Set(axis.CrossAxis(), crossMax);
}
layout.Size = axis == Axis.Horizontal
? new Size(used, crossMax)
: new Size(crossMax, used);
}
