Question: Multiple styles in code area

Hi Tomas, I was looking at the code highlighting example. I have a question.
How do get multiple colors per keyword.
I did this:

private static final String[] GOLD = new String[]{
    "abstract", "assert", "boolean", "break", "byte",
    "case", "catch", "char", "class", "const",
    "continue", "default", "double", "else",
    "enum", "extends", "final", "finally", "float",
    "goto", "if", "implements", "import",
    "instanceof", "int", "interface", "long", "native",
    "new", "package", "private", "protected", "public",
    "return", "short", "static", "strictfp", "super",
    "switch", "synchronized", "this", "throw", "throws",
    "transient", "try", "void", "volatile",};

private static final String[] GREEN = new String[]{
    "for", "while", "do"
};

private static final Pattern GOlD_PATTERN = Pattern.compile("\\b(" + String.join("|", GOLD) + ")\\b");
private static final Pattern GREEN_PATTERN = Pattern.compile("\\b(" + String.join("|", GREEN) + ")\\b");

private static final String sampleCode = String.join("\n", new String[]{
    "package com.example;",
    "",
    "import java.util.*;",
    "",
    "public class Foo extends Bar implements Baz {",
    "",
    "   public static void main(String[] args) {",
    "       for(String arg: args) {",
    "           if(arg.length() != 0)",
    "               System.out.println(arg);",
    "           else",
    "               System.err.println(\"Warning: empty string as argument\");",
    "       }",
    "   }",
    "",
    "}"
});

public static void main(String[] args) {
    launch(args);
}

@Override
public void start(Stage primaryStage) {
    CodeArea codeArea = new CodeArea();
    codeArea.textProperty().addListener((obs, oldText, newText) -> {
        codeArea.setStyleSpans(0, computeHighlighting(newText));
    });
    codeArea.replaceText(0, 0, sampleCode);

    Scene scene = new Scene(new StackPane(codeArea), 600, 400);
    scene.getStylesheets().add(Keywords.class.getResource("java-keywords.css").toExternalForm());
    primaryStage.setScene(scene);
    primaryStage.show();
}

private static StyleSpans<Collection<String>> computeHighlighting(String text) {
    Matcher goldMatcher = GOlD_PATTERN.matcher(text);
    Matcher greenMatcher = GREEN_PATTERN.matcher(text);

    int lastKwEnd = 0;
    StyleSpansBuilder<Collection<String>> spansBuilder = new StyleSpansBuilder<>();
    while (goldMatcher.find()) {
        spansBuilder.add(Collections.emptyList(), goldMatcher.start() - lastKwEnd);
        spansBuilder.add(Collections.singleton("gold"), goldMatcher.end() - goldMatcher.start());
        lastKwEnd = goldMatcher.end();
    }

    while (greenMatcher.find()) {
        spansBuilder.add(Collections.emptyList(), greenMatcher.start() - lastKwEnd);
        spansBuilder.add(Collections.singleton("green"), greenMatcher.end() - greenMatcher.start());
        lastKwEnd = greenMatcher.end();
    }
    spansBuilder.add(Collections.emptyList(), text.length() - lastKwEnd);
    return spansBuilder.create();
}

but this of course is giving me an error at the copmuteHighlighting method. My understanding is that you build a collection of styleSpans based on the matches founds. so I just went and made another loop to look for words that match another pattern. What is the right way to get it to work? I must be extremely wrong somewhere :) Thanks!

this is the css
.green {
-fx-fill: green;
-fx-font-weight: bold;
}

.gold {
-fx-fill: gold;
-fx-font-weight: bold;
}

[TomasMikula]

You are probably getting an error because you didn't reset lastKwEnd to 0 before the second loop. But anyway, even after that you would get an error at setStyleSpans, because you are attempting to build StyleSpans that are (roughly) twice as long as the text in the area.

You need a little work with regular expressions:

private static final String[] GOLD = new String[] {
    "abstract", "assert", "boolean", "break", "byte",
    "case", "catch", "char", "class", "const",
    "continue", "default", "double", "else",
    "enum", "extends", "final", "finally", "float",
    "goto", "if", "implements", "import",
    "instanceof", "int", "interface", "long", "native",
    "new", "package", "private", "protected", "public",
    "return", "short", "static", "strictfp", "super",
    "switch", "synchronized", "this", "throw", "throws",
    "transient", "try", "void", "volatile",};

private static final String[] GREEN = new String[] {
    "for", "while", "do"
};

private static final String GOLD_PATTERN = "\\b(" + String.join("|", GOLD) + ")\\b";
private static final String GREEN_PATTERN = "\\b(" + String.join("|", GREEN) + ")\\b";

private static final Pattern PATTERN = Pattern.compile(
        "(?<GOLD>" + GOLD_PATTERN + ")" +
        "|" +
        "(?<GREEN>" + GREEN_PATTERN + ")");



private static StyleSpans<Collection<String>> computeHighlighting(String text) {
    Matcher matcher = PATTERN.matcher(text);
    int lastKwEnd = 0;
    StyleSpansBuilder<Collection<String>> spansBuilder
            = new StyleSpansBuilder<>();
    while(matcher.find()) {
        String styleClass = matcher.group("GOLD") != null ? "gold" : "green";
        spansBuilder.add(Collections.emptyList(), matcher.start() - lastKwEnd);
        spansBuilder.add(Collections.singleton(styleClass), matcher.end() - matcher.start());
        lastKwEnd = matcher.end();
    }
    spansBuilder.add(Collections.emptyList(), text.length() - lastKwEnd);
    return spansBuilder.create();
}

Thanks! that did it. I will take it from here.

Tomas, I am really sorry my questions might be really simple, but I can't figure out how to set multiple colors. How do you do that?

how do I make this function sort multiple colors?

while(matcher.find()) {
    String styleClass = matcher.group("GOLD") != null ? "gold" : "green";
    spansBuilder.add(Collections.emptyList(), matcher.start() - lastKwEnd);
    spansBuilder.add(Collections.singleton(styleClass), matcher.end() - matcher.start());
    lastKwEnd = matcher.end();
}

[TomasMikula]

You mean more than two colors? Any number of colors?

I mean a finite set if colours. In my case it's probably 5 or 6.
On Jun 13, 2014 8:07 AM, "TomasMikula" notifications@github.com wrote:

You mean more than two colors? Any number of colors?

—
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#62 (comment)
.

[TomasMikula]

If you have a fixed set of colors, then extending my sample is really simple.

    String styleClass =
            matcher.group("GOLD") != null ? "gold" :
            matcher.group("GREEN") != null ? "green" :
            matcher.group("BLUE") != null ? "brown" :
            matcher.group("RED") != null ? "red" :
            "purple";

The last colour, purple, is basically the colour that gets applied when no
match have is found correct?
On Jun 13, 2014 8:22 AM, "TomasMikula" notifications@github.com wrote:

If you have a fixed set of colors, then extending my sample is really
simple.

String styleClass =
        matcher.group("GOLD") != null ? "gold" :
        matcher.group("GREEN") != null ? "green" :
        matcher.group("BLUE") != null ? "brown" :
        matcher.group("RED") != null ? "red" :
        "purple";

—
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#62 (comment)
.

[TomasMikula]

No, everything inside the while(matcher.find()) loop is applied when a match is found. As the match is either of "GOLD", "GREEN", "BLUE", "RED" and "PURPLE", once you rule out "GOLD", "GREEN", "BLUE", "RED", the only possibility is it being "PURPLE", so you don't test it. If you want, you can rewrite the above as

String styleClass;
if(matcher.group("GOLD") != null) {
    styleClass = "gold";
} else if(matcher.group("GREEN") != null) {
    styleClass = "green";
} else if(matcher.group("BLUE") != null) {
    styleClass = "blue";
} else if(matcher.group("RED") != null) {
    styleClass = "red";
} else if(matcher.group("PURPLE") != null) {
    styleClass = "purple";
} else {
    throw new AssertionError("Unreachable code");
}

Thanks! I am still in the verbose code writing skill level. :)
On Jun 13, 2014 8:32 AM, "TomasMikula" notifications@github.com wrote:

No, everything inside the while(matcher.find()) loop is applied when a
match is found. As the match is either of "GOLD", "GREEN", "BLUE",
"RED" and "PURPLE", once you rule out "GOLD", "GREEN", "BLUE", "RED", the
only possibility is it being "PURPLE", so you don't test it. If you want,
you can rewrite the above as

String styleClass;if(matcher.group("GOLD") != null) {
styleClass = "gold";} else if(matcher.group("GREEN") != null) {
styleClass = "green";} else if(matcher.group("BLUE") != null) {
styleClass = "blue";} else if(matcher.group("RED") != null) {
styleClass = "red";} else if(matcher.group("PURPLE") != null) {
styleClass = "purple";} else {
throw new AssertionError("Unreachable code");}

—
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#62 (comment)
.

[deepsidhu1313]

From above example i tried modifying my CodeArea code, but it didn't worked for me. Here is the url to my code https://github.com/deepsidhu1313/java-example/ . Am i doing something wrong ??

[TomasMikula]

Brackets, semicolons, etc. are not words for the purposes of regular expressions, so you shouldn't delimit them by word boundaries (\\b). Change the corresponding lines to

private static final Pattern SEMICOL_PATTERN = Pattern.compile("(" + String.join("|", SEMICOL) + ")");

i.e. omitting \\b, and let me know if it resolved your problem.