Java中，如何根据Font.canDisplay方法对String进行分片

问题描述 投票：0回答：1

给定首选字体列表，Main.main(...)

//simplified code
List<java.awt.Font> preferredFontList = List.of(
  "Roboto-Regular.ttf", "FreeSerif.ttf", "Quivira-A8VL.ttf", "Code2000-rdLO.ttf"
).stream().map(fontName->createFont(fontName)).toList();

我如何根据preferredFontList顺序分段字符串及其支持显示（Font.canDisplay（...））codePoints？ TS_FileTmcrFileHandler.addText(...)

//simplified code
var text = "Tuğalsan Karabacak ♠☀☁☃☎☛ ŞşİiIıÜüÖöÇ窺Ğğ";
fragment(text, preferredFontList).forEach((subText, decidedFontIdx)->{
  addText(subText, preferredFontList.get(decidedFontIdx));
});
java string list fonts java-stream
1个回答
0
投票

你对“碎片”这个词的使用让我感到困惑。这并没有错，但它含糊不清。我假设您希望将字符串分解（分段）为子字符串，每个子字符串都可以通过您喜欢的字体之一完全呈现。

“文本串”是具有共同属性的字符子序列。在这种情况下，该公共属性是将用于呈现字符的字体。 Java 有一个类可以存储具有基于属性的文本：AttributedString。

因此，我们可以创建一个循环，尝试在每种字体上调用 Font.canDisplayUpTo，直到该方法返回一个有效索引，表明该字体可以显示至少一个字符。我们可以使用返回的索引不仅将字体应用于 AttributedString 的部分，还可以前进通过字符串并使用相同的字体循环检查文本的下一部分，重复该过程直到到达字符串的末尾:

private AttributedString applyFontsTo(String text) {
    AttributedString attrText = new AttributedString(text);

    int len = text.length();
    int textRunStart = 0;
    CharacterIterator i = new StringCharacterIterator(text);
    while (textRunStart >= 0) {
        Font matchingFont = null;
        String runText = null;

        for (Font font : preferredFontList) {
            int textRunEnd = font.canDisplayUpTo(i, textRunStart, len);
            if (textRunEnd != textRunStart) {
                matchingFont = font.deriveFont(24f);
                attrText.addAttribute(TextAttribute.FONT, matchingFont,
                    textRunStart, textRunEnd >= 0 ? textRunEnd : len);

                textRunStart = textRunEnd;
                break;
            }
        }

        if (matchingFont == null) {
            int index = i.getIndex();
            throw new IllegalArgumentException(String.format(
                "Character at index %d (U+%04X) "
                + "cannot be displayed by any of %s",
                index, text.codePointAt(index), preferredFontList));
        }
    }

    return attrText;
}

我们现在可以通过几种不同的方式使用 AttributedString 的 iterator：

  • 我们可以通过将其传递给 Graphics.drawString，在绘画方法中渲染它。
  • 我们可以使用迭代器的 getRunLimit 方法及其继承的 setIndex 方法循环遍历迭代器的运行，以其他方式处理文本和字体。

这是第一种方法的示例：

public void show(String text) {
    AttributedString a = applyFontsTo(text);

    JPanel panel = new JPanel() {
        private static final long serialVersionUID = 1;

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(text.length() * 20, 50);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            ((Graphics2D) g).setRenderingHint(
                RenderingHints.KEY_TEXT_ANTIALIASING, 
                RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
            g.drawString(a.getIterator(), 6, getHeight() - 12);
        }
    };

    JFrame frame = new JFrame("Multi-Font Renderer");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(panel);
    frame.pack();
    frame.setLocationByPlatform(true);
    frame.setVisible(true);
}

这是第二种方法的示例：

public void showAsList(String text) {
    Box box = Box.createVerticalBox();

    AttributedString a = applyFontsTo(text);
    AttributedCharacterIterator i = a.getIterator();
    while (i.getIndex() < i.getEndIndex()) {
        int runLimit = i.getRunLimit();
        String runText = text.substring(i.getIndex(), runLimit);
        Font font = (Font) i.getAttribute(TextAttribute.FONT);

        JLabel label = new JLabel(runText);
        label.setFont(font);
        box.add(label);

        i.setIndex(runLimit);
    }

    JFrame frame = new JFrame("Multi-Font Renderer");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().add(new JScrollPane(box));
    frame.pack();
    frame.setLocationByPlatform(true);
    frame.setVisible(true);
}

这是一个完整的程序，演示了这两种方法：

import java.io.InputStream;
import java.io.IOException;

import java.text.CharacterIterator;
import java.text.StringCharacterIterator;
import java.text.AttributedCharacterIterator;
import java.text.AttributedString;

import java.util.List;
import java.util.ArrayList;
import java.util.stream.Collectors;

import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontFormatException;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.font.TextAttribute;

import javax.swing.Box;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JScrollPane;

public class MultiFontRenderer {
    private final List<Font> preferredFontList;

    public MultiFontRenderer() {
        preferredFontList = List.of(
            "Roboto-Regular.ttf",
            "FreeSerif.ttf",
            "Quivira.otf",
            "Code2000-rdLO.ttf"
        ).stream().map(fontName -> createFont(fontName)).collect(
            Collectors.toUnmodifiableList());
    }

    private static Font createFont(String name) {
        try (InputStream fontResource =
            MultiFontRenderer.class.getResourceAsStream(name)) {

            return Font.createFont(Font.TRUETYPE_FONT, fontResource);
        } catch (IOException | FontFormatException e) {
            throw new RuntimeException("Cannot load font \"" + name + "\"", e);
        }
    }

    private AttributedString applyFontsTo(String text) {
        AttributedString attrText = new AttributedString(text);

        int len = text.length();
        int textRunStart = 0;
        CharacterIterator i = new StringCharacterIterator(text);
        while (textRunStart >= 0) {
            Font matchingFont = null;
            String runText = null;

            for (Font font : preferredFontList) {
                int textRunEnd = font.canDisplayUpTo(i, textRunStart, len);
                if (textRunEnd != textRunStart) {
                    matchingFont = font.deriveFont(24f);
                    attrText.addAttribute(TextAttribute.FONT, matchingFont,
                        textRunStart, textRunEnd >= 0 ? textRunEnd : len);

                    textRunStart = textRunEnd;
                    break;
                }
            }

            if (matchingFont == null) {
                int index = i.getIndex();
                throw new IllegalArgumentException(String.format(
                    "Character at index %d (U+%04X) "
                    + "cannot be displayed by any of %s",
                    index, text.codePointAt(index), preferredFontList));
            }
        }

        return attrText;
    }

    public void show(String text) {
        AttributedString a = applyFontsTo(text);

        JPanel panel = new JPanel() {
            private static final long serialVersionUID = 1;

            @Override
            public Dimension getPreferredSize() {
                return new Dimension(text.length() * 20, 50);
            }

            @Override
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                ((Graphics2D) g).setRenderingHint(
                    RenderingHints.KEY_TEXT_ANTIALIASING, 
                    RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
                g.drawString(a.getIterator(), 6, getHeight() - 12);
            }
        };

        JFrame frame = new JFrame("Multi-Font Renderer");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(panel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public void showAsList(String text) {
        Box box = Box.createVerticalBox();

        AttributedString a = applyFontsTo(text);
        AttributedCharacterIterator i = a.getIterator();
        while (i.getIndex() < i.getEndIndex()) {
            int runLimit = i.getRunLimit();
            String runText = text.substring(i.getIndex(), runLimit);
            Font font = (Font) i.getAttribute(TextAttribute.FONT);

            JLabel label = new JLabel(runText);
            label.setFont(font);
            box.add(label);

            i.setIndex(runLimit);
        }

        JFrame frame = new JFrame("Multi-Font Renderer");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(new JScrollPane(box));
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        boolean showList = args.length > 0;

        EventQueue.invokeLater(() -> {
            var text = "Tuğalsan Karabacak ♠☀☁☃☎☛ ŞşİiIıÜüÖöÇ窺Ğğ";

            MultiFontRenderer renderer = new MultiFontRenderer();
            if (showList) {
                renderer.showAsList(text);
            } else {
                renderer.show(text);
            }
        });
    }
}
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