hope this solves #362

Added a job so the codde is not triggered directly from the event.

Author: jantje

it.baeyens.arduino.core/src/it/baeyens/arduino/listeners/IndexerListener.java

@@ -1,7 +1,7 @@
 package it.baeyens.arduino.listeners;
 
 /**
- * his index listener makes ity possible to detect missing libraries
+ * this index listener makes it possible to detect missing libraries
  * if configured to do so libraries are added automatically to the project
  */
 import java.util.HashSet;
@@ -12,12 +12,17 @@
 import org.eclipse.cdt.core.index.IIndexerStateEvent;
 import org.eclipse.cdt.core.index.IIndexerStateListener;
 import org.eclipse.core.resources.IProject;
+import org.eclipse.core.runtime.IProgressMonitor;
+import org.eclipse.core.runtime.IStatus;
+import org.eclipse.core.runtime.Status;
+import org.eclipse.core.runtime.jobs.Job;
 
 import it.baeyens.arduino.common.InstancePreferences;
 import it.baeyens.arduino.tools.Libraries;
 
 public class IndexerListener implements IIndexChangeListener, IIndexerStateListener {
-    Set<IProject> ChangedProjects = new HashSet<>();
+    protected Set<IProject> ChangedProjects = new HashSet<>();
+    Job installLibJob = null;
 
     @Override
     public void indexChanged(IIndexChangeEvent event) {
@@ -30,11 +35,27 @@ public void indexChanged(IIndexerStateEvent event) {
 
 	if (event.indexerIsIdle()) {
 	    if (InstancePreferences.getAutomaticallyIncludeLibraries()) {
-		for (IProject curProject : this.ChangedProjects) {
-		    Libraries.checkLibraries(curProject);
+		if (this.installLibJob == null) {
+		    this.installLibJob = new Job("Adding Arduino libs...") { //$NON-NLS-1$
+
+			@Override
+			protected IStatus run(IProgressMonitor monitor) {
+			    for (IProject curProject : IndexerListener.this.ChangedProjects) {
+				Libraries.checkLibraries(curProject);
+			    }
+			    IndexerListener.this.ChangedProjects.clear();
+			    IndexerListener.this.installLibJob = null;
+			    return Status.OK_STATUS;
+			}
+
+		    };
+
+		    this.installLibJob.setPriority(Job.DECORATE);
+		    this.installLibJob.schedule();
 		}
+
 	    }
-	    this.ChangedProjects.clear();
+
 	}
     }
 

it.baeyens.arduino.core/src/it/baeyens/arduino/tools/Libraries.java

@@ -233,21 +233,25 @@ public static void removeLibrariesFromProject(IProject project, Set<String> sele
     private static Set<String> getUnresolvedProjectIncludes(IProject iProject) {
 	Set<String> ret = new TreeSet<>();
 	ICProject tt = CoreModel.getDefault().create(iProject);
+	IIndex index = null;
 
 	try {
-	    IIndex index = CCorePlugin.getIndexManager().getIndex(tt);
+	    index = CCorePlugin.getIndexManager().getIndex(tt);
 	    index.acquireReadLock();
+	    try {
 
-	    IIndexFile allFiles[] = index.getFilesWithUnresolvedIncludes();
-	    for (IIndexFile curUnesolvedIncludeFile : allFiles) {
-		IIndexInclude includes[] = curUnesolvedIncludeFile.getIncludes();
-		for (IIndexInclude curinclude : includes) {
-		    if (curinclude.isActive() && !curinclude.isResolved()) {
-			ret.add(new Path(curinclude.getName()).removeFileExtension().toString());
+		IIndexFile allFiles[] = index.getFilesWithUnresolvedIncludes();
+		for (IIndexFile curUnesolvedIncludeFile : allFiles) {
+		    IIndexInclude includes[] = curUnesolvedIncludeFile.getIncludes();
+		    for (IIndexInclude curinclude : includes) {
+			if (curinclude.isActive() && !curinclude.isResolved()) {
+			    ret.add(new Path(curinclude.getName()).removeFileExtension().toString());
+			}
 		    }
 		}
+	    } finally {
+		index.releaseReadLock();
 	    }
-	    index.releaseReadLock();
 	} catch (CoreException e1) {
 	    // TODO Auto-generated catch block
 	    e1.printStackTrace();

it.baeyens.arduino.core/src/it/baeyens/arduino/ui/ExplorerLabelDecorator.java

@@ -46,10 +46,12 @@ public String decorateText(String text, Object element) {
 	// TODO Auto-generated method stub
 	IProject proj = (IProject) element;
 	try {
-	    if (proj.hasNature(Const.ArduinoNatureID)) {
-		String boardName = Common.getBuildEnvironmentVariable(proj, Const.ENV_KEY_JANTJE_BOARD_NAME, "Board Error"); //$NON-NLS-1$
-		String portName = Common.getBuildEnvironmentVariable(proj, Const.ENV_KEY_JANTJE_COM_PORT, "no port"); //$NON-NLS-1$
-		return text + ' ' + boardName + ' ' + ':' + portName;
+	    if (proj.isOpen()) {
+		if (proj.hasNature(Const.ArduinoNatureID)) {
+		    String boardName = Common.getBuildEnvironmentVariable(proj, Const.ENV_KEY_JANTJE_BOARD_NAME, "Board Error"); //$NON-NLS-1$
+		    String portName = Common.getBuildEnvironmentVariable(proj, Const.ENV_KEY_JANTJE_COM_PORT, "no port"); //$NON-NLS-1$
+		    return text + ' ' + boardName + ' ' + ':' + portName;
+		}
 	    }
 	} catch (CoreException e) {
 	    // TODO Auto-generated catch block