From f1bc9c07df167722f1bacbda1e95cae998cad86f Mon Sep 17 00:00:00 2001
From: Tongfei Chen <tongfei@protonmail.com>
Date: Thu, 25 Feb 2021 22:56:31 -0500
Subject: [PATCH] fixes #91: only update when progress is made

---
 CHANGELOG.md                                           |  3 +++
 docs/builder.md                                        |  1 +
 .../me/tongfei/progressbar/ProgressUpdateAction.java   | 10 ++++++++--
 src/test/java/me/tongfei/progressbar/Slf4jTest.java    |  2 +-
 4 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b06fe15..1f0f130 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,9 @@
 # Changelog
 
  * `0.9.1`:
+     - Improvements:
+        - Only renders the progress bar when progress is made (#91). This improves the performance of progress bars. Thanks @elanzini !
+        - Added `setMaxRenderedLength` method to builders (#71). Thanks @koppor !
      - Misc:
         - Updates JUnit 4 to JUnit 5 (PR #93). Thanks @michaelsiepmann !
         - Dependency version bump.
diff --git a/docs/builder.md b/docs/builder.md
index 2958f98..37f4922 100644
--- a/docs/builder.md
+++ b/docs/builder.md
@@ -11,6 +11,7 @@ ProgressBarBuilder pbb = new ProgressBarBuilder()
     .setTaskName(<taskName name>)
     .setUnit(<unit name>, <unit size>)
     .setUpdateIntervalMillis(<update interval>)
+    .setMaxRenderedLength(<max rendered length in terminal>)
     .showSpeed();
   // or .showSpeed(new DecimalFormat("#.##")) to customize speed display
 
diff --git a/src/main/java/me/tongfei/progressbar/ProgressUpdateAction.java b/src/main/java/me/tongfei/progressbar/ProgressUpdateAction.java
index 9748886..ec71d74 100644
--- a/src/main/java/me/tongfei/progressbar/ProgressUpdateAction.java
+++ b/src/main/java/me/tongfei/progressbar/ProgressUpdateAction.java
@@ -8,6 +8,7 @@ class ProgressUpdateAction implements Runnable {
     ProgressState progress;
     private ProgressBarRenderer renderer;
     private ProgressBarConsumer consumer;
+    private long last;
 
     ProgressUpdateAction(
             ProgressState progress,
@@ -17,11 +18,16 @@ class ProgressUpdateAction implements Runnable {
         this.progress = progress;
         this.renderer = renderer;
         this.consumer = consumer;
+        this.last = progress.start;
     }
 
     private void refresh() {
-        String rendered = renderer.render(progress, consumer.getMaxRenderedLength());
-        consumer.accept(rendered);
+        if (progress.current > last) {
+            String rendered = renderer.render(progress, consumer.getMaxRenderedLength());
+            consumer.accept(rendered);
+            last = progress.current;
+        }
+        // else do nothing: only print when actual progress is made (#91).
     }
 
     public void run() {
diff --git a/src/test/java/me/tongfei/progressbar/Slf4jTest.java b/src/test/java/me/tongfei/progressbar/Slf4jTest.java
index d9c6207..5e9fd89 100644
--- a/src/test/java/me/tongfei/progressbar/Slf4jTest.java
+++ b/src/test/java/me/tongfei/progressbar/Slf4jTest.java
@@ -17,7 +17,7 @@ void printLoggerTest() throws InterruptedException {
                 .setInitialMax(100)
                 .setTaskName("log.test")
                 .setConsumer(new DelegatingProgressBarConsumer(logger::info))
-                .setUpdateIntervalMillis(100)
+                .setUpdateIntervalMillis(1)
                 .build()) {
             for (int i = 0; i < 100; i++) {
                 pb.step();