如何强制启用Java text抗锯齿？

Question

在Kubuntu 14.04中运行Xilinx Vivado FPGA设计工具，它只在UI的某些部分使用抗锯齿字体，这使得它更难使用，更不用说难看了。其他人似乎也有相同的issue。

因为它似乎至少部分是用Java编写的，所以我尝试了一些谷歌搜索后找到的建议解决方案

export _JAVA_OPTIONS="-Dawt.useSystemAAFontSettings=on -Dswing.aatext=true -Dsun.java2d.xrender=true"

没有任何视觉效果。

下面的一个小测试程序清楚地表明，除非显式地设置了字体呈现提示(但不是RenderingHints.KEY_TEXT_ANTIALIASING)，否则将得到非抗锯齿文本。这在OpenJDK和Oracle JDK中都会发生。

import java.awt.*;
import java.awt.event.*;

// partially taken from http://stackoverflow.com/questions/2018102/java-font-rendering                                                     

public class AwtAA extends Panel {

    private final Font font = new Font(Font.SANS_SERIF, Font.BOLD, 16);
    private final int line = 24;
    private final int medskip = 16;

    AwtAA() {
    setBackground(SystemColor.control);
    }

    public void paint(Graphics g) {
    Graphics2D g2d = (Graphics2D)g;
    int py = 0;

    py = paintText(g2d, py, null, null);
    py += medskip;

    py = paintText(g2d, py, null, RenderingHints.VALUE_ANTIALIAS_DEFAULT);
    py = paintText(g2d, py, null, RenderingHints.VALUE_ANTIALIAS_ON);
    py += medskip;

    py = paintText(g2d, py, RenderingHints.VALUE_TEXT_ANTIALIAS_DEFAULT, null);
    py = paintText(g2d, py, RenderingHints.VALUE_TEXT_ANTIALIAS_ON,      null);
    py += medskip;

    py = paintText(g2d, py, RenderingHints.VALUE_TEXT_ANTIALIAS_DEFAULT, RenderingHints.VALUE_ANTIALIAS_DEFAULT);
    py = paintText(g2d, py, RenderingHints.VALUE_TEXT_ANTIALIAS_ON,      RenderingHints.VALUE_ANTIALIAS_DEFAULT);
    py += medskip;

    py = paintText(g2d, py, RenderingHints.VALUE_TEXT_ANTIALIAS_DEFAULT, RenderingHints.VALUE_ANTIALIAS_ON);
    py = paintText(g2d, py, RenderingHints.VALUE_TEXT_ANTIALIAS_ON,      RenderingHints.VALUE_ANTIALIAS_ON);
    }

    private int paintText(Graphics2D g2d, int py, Object text, Object aa) {
    Graphics2D dgc = g2d;
    Image img = null;

    String text_aa = "none";
    if (text != null) {
        if (text.equals(RenderingHints.VALUE_TEXT_ANTIALIAS_DEFAULT)) text_aa = "VALUE_TEXT_ANTIALIAS_DEFAULT";
        if (text.equals(RenderingHints.VALUE_TEXT_ANTIALIAS_OFF)) text_aa = "VALUE_TEXT_ANTIALIAS_OFF";
        if (text.equals(RenderingHints.VALUE_TEXT_ANTIALIAS_ON)) text_aa = "VALUE_TEXT_ANTIALIAS_ON";
    }

    String value_aa = "none";
    if (aa != null) {
        if (aa.equals(RenderingHints.VALUE_ANTIALIAS_DEFAULT)) value_aa = "VALUE_ANTIALIAS_DEFAULT";
        if (aa.equals(RenderingHints.VALUE_ANTIALIAS_OFF)) value_aa = "VALUE_ANTIALIAS_OFF";
        if (aa.equals(RenderingHints.VALUE_ANTIALIAS_ON)) value_aa = "VALUE_ANTIALIAS_ON";
    }

    char[] txt = ("ABCDEFGHIJKLMNOPQRSTUVWXYZ (" + text_aa + ", " + value_aa + ")").toCharArray();
    GraphicsConfiguration cfg = getGraphicsConfiguration();
    img = cfg.createCompatibleImage(getWidth(), line);
    dgc = (Graphics2D)img.getGraphics();
    dgc.setColor(getBackground());
    dgc.fillRect(0, 0, getWidth(), line);
    dgc.setColor(g2d.getColor());

    if (text != null) dgc.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, text);
    if (aa != null) dgc.setRenderingHint(RenderingHints.KEY_ANTIALIASING, aa);

    dgc.setFont(font);
    dgc.drawChars(txt, 0, txt. length, 10, line-5);
    g2d.drawImage(img, 0, py, null);
    dgc.dispose();
    img.flush();

    return py + line;
    }

    public static void main(String[] args) {
    Frame wnd = new Frame("AWT Antialiased Text Sample");

    wnd.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });

    wnd.add(new AwtAA());
    wnd.setSize(new Dimension(850, 330));
    wnd.setVisible(true);
    }
}

因此，问题是如何更改默认值(未设置提示或设置为VALUE_TEXT_ANTIALIAS_DEFAULT)以在字体渲染中使用抗锯齿？

当我能找到的所有答案都围绕着上面的几个属性进行设置时，我开始查看源代码……并在SunGraphics2D类构造函数中对openjdk 7做了一些粗略的“修复”：

apt-get source openjdk-7-jre
cd openjdk-7-7u55-2.4.7
tar zxf jdk.tar.gz

cd jdk-9448fff93286/src/share/classes/sun/java2d
patch -p1 <<"__EOF__"
--- a/SunGraphics2D.java    2014-06-29 23:39:34.183177958 +0300
+++ b/SunGraphics2D.java    2014-06-29 23:39:18.675177667 +0300
@@ -244,7 +244,10 @@

         renderHint = SunHints.INTVAL_RENDER_DEFAULT;
         antialiasHint = SunHints.INTVAL_ANTIALIAS_OFF;
-        textAntialiasHint = SunHints.INTVAL_TEXT_ANTIALIAS_DEFAULT;
+        textAntialiasHint = SunHints.INTVAL_TEXT_ANTIALIAS_ON;
         fractionalMetricsHint = SunHints.INTVAL_FRACTIONALMETRICS_OFF;
         lcdTextContrast = lcdTextContrastDefaultValue;
         interpolationHint = -1;
__EOF__
javac SunGraphics2D.java
cd ../..
jar cvf /tmp/rt.jar sun/java2d/SunGraphics2D.class

然后将其运行为

java -Xbootclasspath/p:/tmp/rt.jar AwtAA

这对测试程序和Vivado工具都起到了作用(除了Vidado以某种方式启动，并且似乎不支持-Xbootclasspath，所以我真的必须在system rt.jar中更新SunGraphics2D类)。这似乎适用于OpenJDK和甲骨文。

最后一个问题..。除了猴子修补系统jars之外，还必须有其他方法强制将抗锯齿文本作为默认设置吗？

Answer 1

感谢您的补丁jar解决方案，它可以工作，即使有一点混乱。

我不知道是否有比修补jar更好的强制抗锯齿文本的方法，但可以在启动Vivado之前使用以下命令，使其使用修补后的rt.jar，而无需更换主系统：

export _JAVA_OPTIONS="-Xbootclasspath/p:<PATH TO JAR>/rt.jar"

将<PATH TO JAR>替换为您放置修补的rt.jar的位置(我使用/opt/Xilinx/Vivado/)