From 6eb70944ea0a415a1f985cd0850178e34b972b03 Mon Sep 17 00:00:00 2001
From: Kirill Likhodedov <Kirill.Likhodedov@jetbrains.com>
Date: Mon, 26 Nov 2012 19:40:53 +0400
Subject: [PATCH] [git] Fix blinking temporary notifications about
 "unregistered Git roots" IDEA-83015, IDEA-85606

PROBLEM CAUSE:
Notifications blinked because 2 events were arriving from different threads almost simultaneously: creating .git, and registering the mapping.
The first event initiated rescan => notification was shown.
The second event initiated another rescan => notification was hidden.

FIX:
Queue scan requests instead of immediate scanning, and add a delay before beginning the scan.
Use an Alarm (1s delay, pooled thread) instead of self-made state-aware handler.
Don't queue requests: only one (the latest) is needed, because consecutive scan won't add more information.
---
 .../src/git4idea/roots/GitRootScanner.java    | 58 ++++++-------------
 1 file changed, 19 insertions(+), 39 deletions(-)

diff --git a/plugins/git4idea/src/git4idea/roots/GitRootScanner.java b/plugins/git4idea/src/git4idea/roots/GitRootScanner.java
index 37e15beea9d2..b67491e2cd40 100644
--- a/plugins/git4idea/src/git4idea/roots/GitRootScanner.java
+++ b/plugins/git4idea/src/git4idea/roots/GitRootScanner.java
@@ -17,7 +17,6 @@ package git4idea.roots;
 
 import com.intellij.ProjectTopics;
 import com.intellij.openapi.Disposable;
-import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.project.DumbAwareRunnable;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.roots.ModuleRootEvent;
@@ -28,12 +27,13 @@ import com.intellij.openapi.vcs.VcsListener;
 import com.intellij.openapi.vfs.VirtualFileManager;
 import com.intellij.openapi.vfs.newvfs.BulkFileListener;
 import com.intellij.openapi.vfs.newvfs.events.VFileEvent;
+import com.intellij.util.Alarm;
 import com.intellij.util.messages.MessageBus;
 import git4idea.GitUtil;
 import org.jetbrains.annotations.NotNull;
 
-import javax.swing.*;
 import java.util.List;
+import java.util.concurrent.TimeUnit;
 
 /**
  * @author Kirill Likhodedov
@@ -45,11 +45,13 @@ public class GitRootScanner implements BulkFileListener, ModuleRootListener, Dis
 
   private volatile boolean myProjectIsInitialized;
   private volatile boolean myMappingsAreReady;
-  private volatile boolean myScanning;
-  @NotNull private final Object SCAN_LOCK = new Object();
+
+  @NotNull private final Alarm myAlarm;
+  private static final long WAIT_BEFORE_SCAN = TimeUnit.SECONDS.toMillis(1);
 
   public GitRootScanner(@NotNull Project project, @NotNull Runnable executeAfterScan) {
     myExecuteAfterScan = executeAfterScan;
+    myRootProblemNotifier = GitRootProblemNotifier.getInstance(project);
 
     StartupManager.getInstance(project).runWhenProjectIsInitialized(new DumbAwareRunnable() {
       @Override
@@ -64,7 +66,7 @@ public class GitRootScanner implements BulkFileListener, ModuleRootListener, Dis
     messageBus.connect().subscribe(VirtualFileManager.VFS_CHANGES, this);
     messageBus.connect().subscribe(ProjectTopics.PROJECT_ROOTS, this);
 
-    myRootProblemNotifier = GitRootProblemNotifier.getInstance(project);
+    myAlarm = new Alarm(Alarm.ThreadToUse.OWN_THREAD, project);
   }
 
   @Override
@@ -102,40 +104,7 @@ public class GitRootScanner implements BulkFileListener, ModuleRootListener, Dis
 
   private void scanIfReady() {
     if (readyToScan()) {
-      scan();
-    }
-  }
-
-  private void scan() {
-    if (myScanning) {
-      return;
-    }
-
-    if (SwingUtilities.isEventDispatchThread()) {
-      ApplicationManager.getApplication().executeOnPooledThread(new Runnable() {
-        public void run() {
-          scanWithLock();
-        }
-      });
-    }
-    else {
-      scanWithLock();
-    }
-  }
-
-  private void scanWithLock() {
-    synchronized (SCAN_LOCK) {
-      if (myScanning) {
-        return;
-      }
-      myScanning = true;
-      try {
-        myRootProblemNotifier.rescanAndNotifyIfNeeded();
-        myExecuteAfterScan.run();
-      }
-      finally {
-        myScanning = false;
-      }
+      scheduleScan();
     }
   }
 
@@ -143,4 +112,15 @@ public class GitRootScanner implements BulkFileListener, ModuleRootListener, Dis
     return myMappingsAreReady && myProjectIsInitialized;
   }
 
+  private void scheduleScan() {
+    myAlarm.cancelAllRequests(); // one scan is enough, no need to queue, they all do the same
+    myAlarm.addRequest(new Runnable() {
+      @Override
+      public void run() {
+        myRootProblemNotifier.rescanAndNotifyIfNeeded();
+        myExecuteAfterScan.run();
+      }
+    }, WAIT_BEFORE_SCAN);
+  }
+
 }