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Quickstart: Prepare and Layout

The smallest useful flow is:

using Pretext;

const string text = "Hello soft\u00ADwrapped world";
const string font = "16px Inter";
const double lineHeight = 20;

var prepared = PretextLayout.PrepareWithSegments(text, font);
var metrics = PretextLayout.Layout(prepared, maxWidth: 160, lineHeight);
var lines = PretextLayout.LayoutWithLines(prepared, maxWidth: 160, lineHeight);

Console.WriteLine(metrics.LineCount);
Console.WriteLine(metrics.Height);
foreach (var line in lines.Lines)
{
    Console.WriteLine($"{line.Text} ({line.Width})");
}

If normalization leaves the prepared text empty, Layout returns new LayoutResult(0, 0). When your container sizing wants to reserve at least one visual row, clamp in the caller with Math.Max(1, metrics.LineCount) instead of expecting Pretext to invent a blank line.

What this does

  • PrepareWithSegments analyzes the text, measures it, and preserves segment metadata.
  • Layout answers the cheapest high-level question: how many lines fit, and how tall is the result if each line uses your chosen lineHeight.
  • LayoutWithLines materializes the text and width of every line.

The same prepared object is reused by both layout calls. That is the main performance model of Pretext.

Why PrepareWithSegments here?

This quickstart uses PrepareWithSegments because it unlocks all later APIs:

  • LayoutWithLines
  • LayoutNextLine
  • WalkLineRanges
  • segment inspection through Segments, Kinds, and BreakableWidths

If you only need Layout, use Prepare instead and skip the extra segment data.

Reuse matters

Prepare once and reuse the PreparedText object. Recreate it when text, font, whitespace mode, or locale changes. Do not recreate it just because width or line height changed.

Streaming version

When you are building a custom layout engine, iterate line by line instead of materializing the whole paragraph:

var cursor = new LayoutCursor(0, 0);

while (true)
{
    var line = PretextLayout.LayoutNextLine(prepared, cursor, maxWidth: 160);
    if (line is null)
    {
        break;
    }

    Console.WriteLine($"{line.Start} -> {line.End}: {line.Text}");
    cursor = line.End;
}