I like the idea of letting “thin” characters count as half a character. Simple and a good approximation.
The main issue with most ellipsizings however, are (imho) that they chop of words in the middle. Here is a solution taking word-boundaries into account (but does not dive into pixel-math and the Swing-API).
private final static String NON_THIN = "[^iIl1\\.,']";
private static int textWidth(String str) {
return (int) (str.length() - str.replaceAll(NON_THIN, "").length() / 2);
}
public static String ellipsize(String text, int max) {
if (textWidth(text) <= max)
return text;
// Start by chopping off at the word before max
// This is an over-approximation due to thin-characters...
int end = text.lastIndexOf(' ', max - 3);
// Just one long word. Chop it off.
if (end == -1)
return text.substring(0, max-3) + "...";
// Step forward as long as textWidth allows.
int newEnd = end;
do {
end = newEnd;
newEnd = text.indexOf(' ', end + 1);
// No more spaces.
if (newEnd == -1)
newEnd = text.length();
} while (textWidth(text.substring(0, newEnd) + "...") < max);
return text.substring(0, end) + "...";
}
A test of the algorithm looks like this:
