biskuteri-cafe-JKomasto2/RichTextPane.java

import javax.swing.JComponent;
import javax.swing.ImageIcon;
import java.awt.Graphics;
import java.awt.FontMetrics;
import java.awt.Image;
import java.awt.Color;
import java.util.List;
import java.util.LinkedList;
import java.util.ListIterator;

class
RichTextPane extends JComponent {

	private List<Segment>
	text;

//	---%-@-%---

	public void
	setText(List<Segment> text) { this.text = text; }

//	 -	-%-	 -

	protected void
	paintComponent(Graphics g)
	{
		g.setFont(getFont());
		FontMetrics fm = g.getFontMetrics(getFont());
		g.clearRect(0, 0, getWidth(), getHeight());

		for (Segment segment: text)
		{
			if (segment.image != null) {
				int ow = segment.image.getIconWidth();
				int oh = segment.image.getIconHeight();
				int h = fm.getHeight();
				int w = h * ow / oh;
				int x = segment.x, y = segment.y;
				Image img = segment.image.getImage();
				g.drawImage(img, x, y - h, w, h, this);
				continue;
			}
			
			if (segment.link != null) g.setColor(Color.BLUE);
			g.drawString(segment.text, segment.x, segment.y);
			g.setColor(getForeground());
		}
	}

//	 -	-%-	 -

	public static List<Segment>
	layout(List<Segment> text, FontMetrics fm, int width)
	{
		List<Segment> copy = new LinkedList<>();
		for (Segment segment: text) copy.add(segment.clone());
		text = copy;
		ListIterator<Segment> cursor = text.listIterator();
		int x = 0, y = fm.getAscent();
		int dy = fm.getHeight();
		while (cursor.hasNext())
		{
			Segment curr = cursor.next();
			
			int dx;
			if (curr.image != null) {
				int ow = curr.image.getIconWidth();
				int oh = curr.image.getIconHeight();
				dx = dy * ow / oh;
			}
			else if (curr.text != null) {
				dx = fm.stringWidth(curr.text);
			}
			else if (curr.link != null) {
				curr.text = curr.link;
				dx = fm.stringWidth(curr.link);
			}
			else {
				assert false;
				dx = 0;
			}

			boolean fits = x + dx < width;
			
			if (fits || curr.spacer)
			{
				curr.x = x;
				curr.y = y;
				x += dx;
				if (curr.spacer && curr.text.equals("\n")) {
					y += dy;
					x = 0;
				}
				continue;
			}

			boolean tooLong = dx > width;
			boolean canFitChar = width >= fm.getMaxAdvance();
			boolean splittable = curr.image == null;
			/*
			* A bit of redundancy in my conditions, but the point is
			* to exactly express the triggers in my mental model.
			* The conditions should read more like English.
			*/

			if (!tooLong || (tooLong && !splittable))
			{
				curr.x = 0;
				curr.y = y += dy;
				x = dx;
				continue;
			}

			assert tooLong && splittable;

			String s = curr.text;
			int splitOffset;
			for (splitOffset = 0; splitOffset < s.length(); ++splitOffset)
			{
				String substring = s.substring(0, splitOffset + 1);
				if (fm.stringWidth(substring) > width) break;
			}
			if (splitOffset == 0) splitOffset = 1;
			/*
			* I force a split even if our width supports no characters.
			* Because if I don't split, the only alternatives to infinitely
			* looping downwards is to emplace this segment or ignore it.
			*/
			Segment fitted = new Segment();
			fitted.text = s.substring(0, splitOffset);
			fitted.link = curr.link;
			fitted.x = x;
			fitted.y = y;
			cursor.add(fitted);
			curr.text = s.substring(splitOffset);
			y += dy;
			x = 0;
			cursor.add(curr); cursor.previous();
			/*
			* I had to use a stack and return a new list because,
			* splitting can turn a long segment into several spread
			* over different lines. Here curr becomes the "after-split"
			* and I push it back to the stack.
			*
			* If #layout wasn't a separate method, but rather only for
			* graphical painting. Then I don't need a stack nor return
			* a new list. I iterate over the given one, filling the
			* nodes' geometric information, if a split occurs I save the
			* "after-split" in a variable, which in the next iteration
			* I use as curr instead of list.next(). The caller doesn't
			* need to know the geometry of these intermediate segments.
			*/
			continue;
		}

		return text;
	}

//	---%-@-%---

	public static class
	Segment {

		public ImageIcon
		image;

		public String
		link;

		public String
		text;

		public boolean
		spacer;

		public int
		x, y;

//		-=%=-

		public String
		toString()
		{
			StringBuilder b = new StringBuilder();
			b.append(getClass().getName() + "[");
			b.append("image=" + image);
			b.append(",link=" + link);
			b.append(",text=" + text);
			b.append(",x=" + x);
			b.append(",y=" + y);
			b.append("]");
			return b.toString();
		}

		public Segment
		clone()
		{
			Segment segment = new Segment();
			segment.image = this.image;
			segment.link = this.link;
			segment.text = this.text;
			segment.spacer = this.spacer;
			segment.x = this.x;
			segment.y = this.y;
			return segment;
		}

	}

	public static class
	Builder {

		private List<Segment>
		returnee;

//		-=%=-

		public
		Builder() { returnee = new LinkedList<>(); }

		public Builder
		image(ImageIcon image, String text)
		{
			Segment segment = new Segment();
			segment.image = image;
			segment.text = text;
			returnee.add(segment);
			return this;
		}

		public Builder
		link(String link, String text)
		{
			Segment segment = new Segment();
			segment.link = link;
			segment.text = text;
			returnee.add(segment);
			return this;
		}

		public Builder
		text(String text)
		{
			Segment segment = new Segment();
			segment.text = text;
			returnee.add(segment);
			return this;
		}

		public Builder
		spacer(String text)
		{
			Segment segment = new Segment();
			segment.text = text;
			segment.spacer = true;
			returnee.add(segment);
			return this;
		}

		public List<Segment>
		finish() { return returnee; }

	}

//	---%-@-%---

	RichTextPane()
	{
		text = new LinkedList<>();
	}

}