#1051 Aggressive Font Fallback doesn't work on Java 11

[Aaron Madlon-Kay]

When running with Java 11 on macOS 11.4, Aggressive Font Fallback doesn't work even in cases where it does work with Java 8.

It appears that the methods we use to check whether a font supports a codepoint (Font#canDisplay, Font#canDisplayUpTo) always report true or -1 respectively.

There are related reports on the internet but no known fixes or workarounds that I have seen:

• https://bugs.java.com/bugdatabase/view_bug.do?bug_id=JDK-8223834
• https://stackoverflow.com/questions/17008081/font-candisplay-always-returns-true-on-mac

[Hiroshi Miura]

Inspired from Intellij-community(Apache-2.0).

import java.awt.Font;
import java.awt.font.FontRenderContext;

import org.omegat.util.Platform;
import sun.font.CompositeGlyphMapper;

    public static FontRenderContext DEFAULT_CONTEXT = new FontRenderContext(null, false, false);

    public boolean canDisplay(Font font, final int codePoint) {
        if (!Character.isValidCodePoint(codePoint)) return false;
        if (Platform.isMacOSX()) {
            int glyphCode = font.createGlyphVector(DEFAULT_CONTEXT, new String(new int[]{codePoint}, 0, 1)).getGlyphCode(0);
            return (glyphCode & CompositeGlyphMapper.GLYPHMASK) != 0 && (glyphCode & CompositeGlyphMapper.SLOTMASK) == 0;
        } else {
            return font.canDisplay(codePoint);
        }
   }

[Hiroshi Miura]

Does https://github.com/omegat-org/omegat/pull/118 work on macOS?

[Hiroshi Miura]

Fix merged.

[Aaron Madlon-Kay]

A workaround is implemented in [39e2da]. The workaround attempts to detect when Font#canDisplay is unreliable, and in that case uses a slower, but accurate, codepath. Hence affected systems may see decreased performance of Agressive Font Fallback.

[Jean-Christophe Helary]

documented in changes.txt

[Aaron Madlon-Kay]

Released in OmegaT 5.6.0.