FULL PRODUCT VERSION :
java version "9-ea"
Java(TM) SE Runtime Environment (build 9-ea+107-2016-02-24-182456.javare.4520.nc)
Java HotSpot(TM) 64-Bit Server VM (build 9-ea+107-2016-02-24-182456.javare.4520.nc, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Tested on Windows 8.1:
Microsoft Windows [Version 6.3.9600]
but this seems to be a platform-independent issue.

A DESCRIPTION OF THE PROBLEM :
In Java 9 latest builds getGlyphCharIndex method for a GlyphVector instance can return a wrong value in some cases. The problem is related to Harfbuzz integration, as the issue is not observed when the application is run with 'sun.font.layoutengine' system property set to 'icu'.

REGRESSION. Last worked in version 8u74

ADDITIONAL REGRESSION INFORMATION:
java version "1.8.0_74"
Java(TM) SE Runtime Environment (build 1.8.0_74-b02)
Java HotSpot(TM) 64-Bit Server VM (build 25.74-b02, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the sample program

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
0 is printed.
ACTUAL -
1 is printed.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.Font;
import java.awt.font.FontRenderContext;
import java.awt.font.GlyphVector;

public class GlyphVectorTest {
    public static void main(String[] args) {
        Font font = new Font(Font.MONOSPACED, Font.PLAIN, 12);
        FontRenderContext frc = new FontRenderContext(null, false, false);
        GlyphVector gv = font.layoutGlyphVector(frc, "abc".toCharArray(), 1, 3, Font.LAYOUT_LEFT_TO_RIGHT);
        System.out.println(gv.getGlyphCharIndex(0));
    }
}

---------- END SOURCE ----------