[LOGMGR-323] Add API for console feature detection

src/main/java/org/jboss/logmanager/formatters/ColorPatternFormatter.java

@@ -21,6 +21,7 @@
 
 import org.jboss.logmanager.ExtLogRecord;
 import org.jboss.logmanager.Level;
+import org.jboss.logmanager.handlers.ConsoleHandler;
 
 import java.util.logging.Formatter;
 import java.util.logging.LogRecord;
@@ -53,17 +54,6 @@ public ColorPatternFormatter(int darken, final String pattern) {
         setPattern(pattern);
     }
 
-    static final boolean trueColor = determineTrueColor();
-
-    static boolean determineTrueColor() {
-        final String colorterm = System.getenv("COLORTERM");
-        return (colorterm != null && (colorterm.contains("truecolor") || colorterm.contains("24bit")));
-    }
-
-    static boolean isTrueColor() {
-        return trueColor;
-    }
-
     public void setSteps(final FormatStep[] steps) {
         FormatStep[] colorSteps = new FormatStep[steps.length];
         for (int i = 0; i < steps.length; i++) {
@@ -146,6 +136,8 @@ public String formatMessage(final LogRecord logRecord) {
     static final class ColorStep implements FormatStep {
         private final int r, g, b;
         private final FormatStep delegate;
+        // capture current console state
+        private final boolean trueColor = ConsoleHandler.isTrueColor();
 
         ColorStep(final FormatStep delegate, final int r, final int g, final int b, final int darken) {
             this.r = r >>> darken;
@@ -155,7 +147,7 @@ static final class ColorStep implements FormatStep {
         }
 
         public void render(final Formatter formatter, final StringBuilder builder, final ExtLogRecord record) {
-            ColorUtil.startFgColor(builder, isTrueColor(), r, g, b);
+            ColorUtil.startFgColor(builder, trueColor, r, g, b);
             delegate.render(formatter, builder, record);
             ColorUtil.endFgColor(builder);
         }
@@ -183,6 +175,8 @@ static final class LevelColorStep implements FormatStep {
         private static final int SATURATION = 66;
         private final FormatStep delegate;
         private final int darken;
+        // capture current console state
+        private final boolean trueColor = ConsoleHandler.isTrueColor();
 
         LevelColorStep(final FormatStep delegate, final int darken) {
             this.delegate = delegate;
@@ -195,7 +189,7 @@ public void render(final Formatter formatter, final StringBuilder builder, final
             int r = ((level < 300 ? 0 : (level - 300) * (255 - SATURATION) / 300) + SATURATION) >>> darken;
             int g = ((300 - abs(level - 300)) * (255 - SATURATION) / 300 + SATURATION) >>> darken;
             int b = ((level > 300 ? 0 : level * (255 - SATURATION) / 300) + SATURATION) >>> darken;
-            ColorUtil.startFgColor(builder, isTrueColor(), r, g, b);
+            ColorUtil.startFgColor(builder, trueColor, r, g, b);
             delegate.render(formatter, builder, record);
             ColorUtil.endFgColor(builder);
         }
@@ -212,10 +206,4 @@ public boolean isCallerInformationRequired() {
             return false;
         }
     }
-
-    static final class TrueColorHolder {
-        private TrueColorHolder() {}
-
-        static final boolean trueColor = ColorPatternFormatter.determineTrueColor();
-    }
 }

src/main/java/org/jboss/logmanager/formatters/ColorPrintf.java

@@ -27,8 +27,11 @@
 import java.util.Locale;
 import java.util.UUID;
 
+import org.jboss.logmanager.handlers.ConsoleHandler;
+
 class ColorPrintf extends Printf {
     private final int darken;
+    private final boolean trueColor = ConsoleHandler.isTrueColor();
 
     ColorPrintf(final int darken) {
         super(Locale.getDefault());
@@ -72,11 +75,11 @@ protected void formatFormattableString(final StringBuilder target, final Formatt
 
     protected void formatPlainString(final StringBuilder target, final Object item, final GeneralFlags genFlags, final int width, final int precision) {
         if (item instanceof Class || item instanceof Executable || item instanceof Field) {
-            ColorUtil.startFgColor(target, ColorPatternFormatter.trueColor, 0xff >>> darken, 0xff >>> darken, 0xdd >>> darken);
+            ColorUtil.startFgColor(target, trueColor, 0xff >>> darken, 0xff >>> darken, 0xdd >>> darken);
         } else if (item instanceof UUID) {
-            ColorUtil.startFgColor(target, ColorPatternFormatter.trueColor, 0xdd >>> darken, 0xff >>> darken, 0xdd >>> darken);
+            ColorUtil.startFgColor(target, trueColor, 0xdd >>> darken, 0xff >>> darken, 0xdd >>> darken);
         } else {
-            ColorUtil.startFgColor(target, ColorPatternFormatter.trueColor, 0xdd >>> darken, 0xdd >>> darken, 0xdd >>> darken);
+            ColorUtil.startFgColor(target, trueColor, 0xdd >>> darken, 0xdd >>> darken, 0xdd >>> darken);
         }
         super.formatPlainString(target, item, genFlags, width, precision);
         ColorUtil.endFgColor(target);

src/main/java/org/jboss/logmanager/handlers/ConsoleHandler.java

@@ -160,4 +160,50 @@ private static Writer wrap(final Writer writer) {
     public void setOutputStream(final OutputStream outputStream) {
         super.setOutputStream(wrap(outputStream));
     }
+
+    /**
+     * Determine whether the console exists.
+     * If the console does not exist, then the standard output stream will be used when {@link Target#CONSOLE} is
+     * selected as {@linkplain #setTarget(Target) the output target}.
+     *
+     * @return {@code true} if there is a console, {@code false} otherwise
+     */
+    public static boolean hasConsole() {
+        return console != null;
+    }
+
+    /**
+     * Determine whether the console supports truecolor output.
+     * This call may be expensive, so the result should be captured for the lifetime of any formatter making use of
+     * this information.
+     *
+     * @return {@code true} if the console exists and supports truecolor output; {@code false} otherwise
+     */
+    public static boolean isTrueColor() {
+        if (! hasConsole()) {
+            return false;
+        }
+        final String colorterm = System.getenv("COLORTERM");
+        return colorterm != null && (colorterm.contains("truecolor") || colorterm.contains("24bit"));
+    }
+
+    /**
+     * Determine whether the console can be passively detected to support graphical output.
+     * This call may be expensive, so the result should be captured for the lifetime of any formatter making use of
+     * this information.
+     *
+     * @return {@code true} if the console exists and supports graphical output; {@code false} otherwise or if
+     *  graphical support cannot be passively detected
+     */
+    public static boolean isGraphicsSupportPassivelyDetected() {
+        if (! hasConsole()) {
+            return false;
+        }
+        final String term = System.getenv("TERM");
+        final String termProgram = System.getenv("TERM_PROGRAM");
+        return term != null && (term.equalsIgnoreCase("kitty")
+                || term.equalsIgnoreCase("wezterm")
+                || term.equalsIgnoreCase("konsole")
+        ) || termProgram != null && termProgram.equalsIgnoreCase("wezterm");
+    }
 }