How to render text into a box and replace excess with three dots

Question

I render text with a custom table cell renderer and I want to trim the text drawn if it would exceed the current cell width, switching to a "This text is to long..." kind of representation, where the three dots at the end never leaves the bounding box. My current algorithm is the following:

FontMetrics fm0 = g2.getFontMetrics(); 
int h = fm0.getHeight();
int ellw = fm0.stringWidth("\u2026");
int titleWidth = fm0.stringWidth(se.title);
if (titleWidth > getWidth()) {
    for (int i = se.title.length() - 1; i > 0; i--) {
        String tstr = se.title.substring(0, i);
        int tstrw = fm0.stringWidth(tstr);
        if (tstrw + ellw < getWidth()) {
            g2.drawString(tstr, 2, h);
            g2.drawString("\u2026", 2 + tstrw, h);
            break;
        }
    }
} else {
    g2.drawString(se.title, 2, h);
}

Is there a better way of determining how many characters should I drawString() before switching to the ... (u2026) character?

Answer 1

I can't think of another way to achieve the desired effect, but you should be able to replace the 2 drawString() calls with one. It's been a while since I've written Java but I think the following should work.

BTW, I changed the variable names so I can read the code. :p

FontMetrics metrics = g2.getFontMetrics(); 
int fontHeight = metrics.getHeight();
int titleWidth = metrics.stringWidth(se.title);

if (titleWidth > getWidth()) {
    String titleString;

    for (int i = se.title.length() - 1; i > 0; i --) {
        titleString = se.title.substring(0, i) + "\u2026";
        titleWidth = metrics.stringWidth(titleString);

        if (titleWidth < getWidth()) {
            g2.drawString(titleString, 2, fontHeight);

            break;
        }
    }
} else {
    g2.drawString(se.title, 2, fontHeight);
}

Answer 2

This is the default behaviour of the default renderer for a table so I'm not sure I understand the reason for doing this.

But I've created a renderer for dots on the left ("... text is too long") which shows a more complete way to do what you want since it takes into account a possible Border on the renderer and the intercell spacing of the renderer. Check out the LeftDotRenderer.