Synchronized add/rm from editor panel. Fixes #96.

META-INF/plugin.xml

@@ -1,8 +1,8 @@
 <idea-plugin version="2">
   <id>org.antlr.intellij.plugin</id>
   <name>ANTLR v4 grammar plugin</name>
-  <version>1.2</version>
-  <vendor email="[email protected]" url="http://www.antlr.org">ANTLR Project</vendor>
+  <version>1.2.1</version>
+  <vendor email="[email protected]" url="https://github.com/antlr/intellij-plugin-v4">ANTLR Project</vendor>
 
   <description><![CDATA[
       This plugin is for ANTLR v4 grammars. Features: syntax highlighting,
@@ -36,17 +36,7 @@
       ]]></description>
 
   <change-notes><![CDATA[
-	You can use the meta-key while moving the mouse and it will show you
-	token information in the preview editor box via tooltips.
-
-	Errors within the preview editor are now highlighted with tooltips
-	and underlining just like a regular editor window. The difference
-	is that this window's grammar is specified in your grammar file.
-
-	Also note that the plug-in does not pay attention to any package statements
-	and actions now. You must use the configuration dialog.
-
-	More bug fixes. See github for complete list.
+	Hush annoying error.
       ]]>
   </change-notes>
 

src/java/org/antlr/intellij/plugin/preview/PreviewPanel.java

@@ -50,6 +50,12 @@ public class PreviewPanel extends JPanel {
 	public static final int TOKEN_INFO_LAYER = HighlighterLayer.SELECTION; // Show token info over errors
 	public static final int ERROR_LAYER = HighlighterLayer.ERROR;
 
+	/** switchToGrammar() was seeing an empty slot instead of a previous
+	 *  editor or placeHolder. Figured it was an order of operations thing
+	 *  and synchronized add/remove ops. Works now w/o error.
+	 */
+	public final Object swapEditorComponentLock = new Object();
+
 	public static final JLabel placeHolder = new JLabel("");
 	public static final String missingStartRuleLabelText =
 		"Start rule: <select from navigator or grammar>";
@@ -96,10 +102,11 @@ public JPanel createEditorPanel() {
 		editorPanel = new JPanel(new BorderLayout(0,0));
 		startRuleLabel = new JLabel(missingStartRuleLabelText);
 		startRuleLabel.setForeground(JBColor.RED);
-		editorPanel.add(startRuleLabel, BorderLayout.NORTH);
-		editorPanel.add(placeHolder, BorderLayout.CENTER);
-		editorPanel.add(spane, BorderLayout.SOUTH);
-
+		synchronized ( swapEditorComponentLock ) {
+			editorPanel.add(startRuleLabel, BorderLayout.NORTH);
+			editorPanel.add(placeHolder, BorderLayout.CENTER);
+			editorPanel.add(spane, BorderLayout.SOUTH);
+		}
 		return editorPanel;
 	}
 
@@ -161,14 +168,14 @@ public void switchToGrammar(VirtualFile grammarFile) {
 		}
 
 		BorderLayout layout = (BorderLayout)editorPanel.getLayout();
-		Component editorSpotComp = layout.getLayoutComponent(BorderLayout.CENTER);
-		if ( editorSpotComp!=null ) {
-			editorPanel.remove(editorSpotComp); // remove old editor if it's there
-		}
-		else {
-			LOG.error("switchToGrammar no CENTER component in editorPanel"+" "+project.getName());
+		// atomically remove old
+		synchronized ( swapEditorComponentLock ) {
+			Component editorSpotComp = layout.getLayoutComponent(BorderLayout.CENTER);
+			if (editorSpotComp != null) {
+				editorPanel.remove(editorSpotComp); // remove old editor if it's there
+			}
+			editorPanel.add(previewState.editor.getComponent(), BorderLayout.CENTER);
 		}
-		editorPanel.add(previewState.editor.getComponent(), BorderLayout.CENTER);
 		clearParseErrors(grammarFile);
 
 		if ( previewState.startRuleName!=null ) {
@@ -205,8 +212,10 @@ public void closeGrammar(VirtualFile grammarFile) {
 		// restore the GUI
 		BorderLayout layout = (BorderLayout)editorPanel.getLayout();
 		Component editorSpotComp = layout.getLayoutComponent(BorderLayout.CENTER);
-		editorPanel.remove(editorSpotComp);
-		editorPanel.add(placeHolder, BorderLayout.CENTER); // put placeholder back after we remove the editor component.
+		synchronized ( swapEditorComponentLock ) {
+			editorPanel.remove(editorSpotComp);
+			editorPanel.add(placeHolder, BorderLayout.CENTER); // put placeholder back after we remove the editor component.
+		}
 	}
 
 	public void setParseTree(final List<String> ruleNames, final ParseTree tree) {