codex-added logging helper

pom.xml

@@ -97,6 +97,24 @@
 				<groupId>ome</groupId>
 				<artifactId>loci_tools</artifactId>
 				<version>6.1.0</version>
+				<exclusions>
+					<exclusion>
+						<groupId>ch.qos.logback</groupId>
+						<artifactId>logback-classic</artifactId>
+					</exclusion>
+					<exclusion>
+						<groupId>ch.qos.logback</groupId>
+						<artifactId>logback-core</artifactId>
+					</exclusion>
+					<exclusion>
+						<groupId>org.slf4j</groupId>
+						<artifactId>slf4j-log4j12</artifactId>
+					</exclusion>
+					<exclusion>
+						<groupId>log4j</groupId>
+						<artifactId>log4j</artifactId>
+					</exclusion>
+				</exclusions>
 			</dependency>
 			<!-- https://mvnrepository.com/artifact/ome/pom-bio-formats -->
 			<!-- Was source in attic for development -->
@@ -133,6 +151,12 @@
 			    <artifactId>jcl-over-slf4j</artifactId>
 			    <version>1.7.5</version>
 			</dependency>
+			<!-- SLF4J backend (single binding) -->
+			<dependency>
+				<groupId>ch.qos.logback</groupId>
+				<artifactId>logback-classic</artifactId>
+				<version>1.1.1</version>
+			</dependency>
 			
 			<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-numbers-quaternion -->
 			<!-- 

src/main/java/com/elphel/imagej/common/LogTee.java

+package com.elphel.imagej.common;
+
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.PrintStream;
+import java.nio.file.Path;
+
+/**
+ * Tee System.out/System.err to a per-scene log file while preserving console output.
+ * Usage:
+ *   LogTee.install(); // once at startup
+ *   LogTee.setSceneLog(path); // enable per-scene logging (append)
+ *   LogTee.clearSceneLog();   // stop file logging
+ */
+public final class LogTee {
+    private static final Object LOCK = new Object();
+    private static final PrintStream ORIGINAL_OUT = System.out;
+    private static final PrintStream ORIGINAL_ERR = System.err;
+    private static volatile PrintStream fileStream = null;
+    private static volatile boolean installed = false;
+
+    private LogTee() {
+    }
+
+    public static void install() {
+        synchronized (LOCK) {
+            if (installed) return;
+            System.setOut(new PrintStream(new TeeStream(ORIGINAL_OUT), true));
+            System.setErr(new PrintStream(new TeeStream(ORIGINAL_ERR), true));
+            installed = true;
+        }
+    }
+
+    public static void setSceneLog(Path path) throws IOException {
+        if (path == null) {
+            clearSceneLog();
+            return;
+        }
+        synchronized (LOCK) {
+            closeFileStream();
+            fileStream = new PrintStream(new FileOutputStream(path.toFile(), true), true);
+        }
+    }
+
+    public static void clearSceneLog() {
+        synchronized (LOCK) {
+            closeFileStream();
+            fileStream = null;
+        }
+    }
+
+    private static void closeFileStream() {
+        if (fileStream != null) {
+            fileStream.flush();
+            fileStream.close();
+        }
+    }
+
+    private static final class TeeStream extends OutputStream {
+        private final PrintStream console;
+
+        private TeeStream(PrintStream console) {
+            this.console = console;
+        }
+
+        @Override
+        public void write(int b) throws IOException {
+            console.write(b);
+            PrintStream fs = fileStream;
+            if (fs != null) fs.write(b);
+        }
+
+        @Override
+        public void write(byte[] b, int off, int len) throws IOException {
+            console.write(b, off, len);
+            PrintStream fs = fileStream;
+            if (fs != null) fs.write(b, off, len);
+        }
+
+        @Override
+        public void flush() throws IOException {
+            console.flush();
+            PrintStream fs = fileStream;
+            if (fs != null) fs.flush();
+        }
+    }
+}