// Mismatch between actual painting with gc.drawString() and the gc.stringExtent()
// info, for e.g., chars '\u0001' - \u0006'.  The extent returned is larger than the
// actual extent painted.
//
// This makes it impossible e.g., to match a mouse-click's x offset in the window
// to the correct index inside the displayed text string.
//
// These characters seem to be filtered out somehow by StyledText's rendering
// (they have a width of 0 pixels on the display)?!  What is the full set of these
// characters?

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.widgets.*;

public class Main {

public static void main (String[] args) {
   Display display = new Display();
   Shell shell = new Shell(display);
   shell.open();
   GC gc = new GC(shell);

   Font font = new Font(display, "Courier", 10, SWT.NORMAL);
   gc.setFont(font);

   String r  = "*23456789012345678901234567890....+....01234567890";
   String x1 = "




0....+....01234567890";
   String x2 = "





....01234567890";
   String x3 = "







890";

   int extr = gc.stringExtent(r).x;
   int ext1 = gc.stringExtent(x1).x;
   int ext2 = gc.stringExtent(x2).x;
   int ext3 = gc.stringExtent(x3).x;

   gc.drawString(r, 0, 0);
   for (int i = 0; i < 50; i++) {
      int x = gc.stringExtent(r.substring(0,i)).x;
      gc.drawLine(x, 15, x, 25);
      gc.drawString(String.valueOf(r.charAt(i)), x, 30);
      }

   gc.drawString(x1, 0, 60);
   for (int i = 0; i < 50; i++) {
      int x = gc.stringExtent(x1.substring(0,i)).x;
      gc.drawLine(x, 75, x, 85);
      gc.drawString(String.valueOf(x1.charAt(i)), x, 90);
      }

   gc.drawString(x2, 0, 120);
   for (int i = 0; i < 50; i++) {
      int x = gc.stringExtent(x2.substring(0,i)).x;
      gc.drawLine(x, 135, x, 145);
      gc.drawString(String.valueOf(x2.charAt(i)), x, 150);
      }

   gc.drawString(x3, 0, 180);
   for (int i = 0; i < 50; i++) {
      int x = gc.stringExtent(x3.substring(0,i)).x;
      gc.drawLine(x, 195, x, 205);
      gc.drawString(String.valueOf(x3.charAt(i)), x, 210);
      }

   gc.drawString("*** stringExtent()s: " + extr + ' ' + ext1 + ' ' + ext2 + ' ' + ext3,
                 0, 240);

   gc.dispose ();
   while (!shell.isDisposed ()) {
      if (!display.readAndDispatch ()) display.sleep ();
   }
   display.dispose ();
}
}