diff: do not require init() call on DiffRequestProcessor

* avoid potentially dangerous non-EDT calls
* we require explicit call for updateRequest() anyway

platform/diff-api/src/com/intellij/diff/requests/MessageDiffRequest.java

@@ -49,4 +49,8 @@ public abstract class MessageDiffRequest extends DiffRequest {
   public void setMessage(@NotNull String message) {
     myMessage = message;
   }
+
+  @Override
+  public final void onAssigned(boolean isAssigned) {
+  }
 }

platform/diff-impl/src/com/intellij/diff/impl/DiffRequestPanelImpl.java

@@ -35,7 +35,6 @@ public class DiffRequestPanelImpl implements DiffRequestPanel {
 
   public DiffRequestPanelImpl(@Nullable Project project, @Nullable Window window) {
     myProcessor = new MyCacheDiffRequestChainProcessor(project, window);
-    myProcessor.init();
 
     myPanel = new JPanel(new BorderLayout()) {
       @Override

platform/diff-impl/src/com/intellij/diff/impl/DiffRequestProcessor.java

@@ -93,7 +93,7 @@ public abstract class DiffRequestProcessor implements Disposable {
 
   @NotNull private DiffRequest myActiveRequest;
 
-  @NotNull private ViewerState myState;
+  @Nullable private ViewerState myState;
 
   public DiffRequestProcessor(@Nullable Project project) {
     this(project, new UserDataHolderBase());
@@ -106,14 +106,14 @@ public abstract class DiffRequestProcessor implements Disposable {
   public DiffRequestProcessor(@Nullable Project project, @NotNull UserDataHolder context) {
     myProject = project;
 
-    myAvailableTools = DiffManagerEx.getInstance().getDiffTools();
-    myToolOrder = new LinkedList<DiffTool>();
-
     myContext = new MyDiffContext(context);
     myActiveRequest = NoDiffRequest.INSTANCE;
 
     mySettings = DiffSettingsHolder.getInstance().getSettings(myContext.getUserData(DiffUserDataKeysEx.PLACE));
 
+    myAvailableTools = DiffManagerEx.getInstance().getDiffTools();
+    myToolOrder = new LinkedList<DiffTool>(getToolOrderFromSettings(myAvailableTools));
+
     // UI
 
     myPanel = new JPanel(new BorderLayout());
@@ -139,6 +139,8 @@ public abstract class DiffRequestProcessor implements Disposable {
     if (bottomPanel != null) myMainPanel.add(bottomPanel, BorderLayout.SOUTH);
     if (bottomPanel instanceof Disposable) Disposer.register(this, (Disposable)bottomPanel);
 
+    myState = new EmptyState();
+    myContentPanel.setContent(DiffUtil.createMessagePanel(NoDiffRequest.INSTANCE.getMessage()));
 
     myOpenInEditorAction = new OpenInEditorAction(new Runnable() {
       @Override
@@ -148,14 +150,6 @@ public abstract class DiffRequestProcessor implements Disposable {
     });
   }
 
-  public void init() {
-    myToolOrder.addAll(getToolOrderFromSettings(myAvailableTools));
-
-    myActiveRequest.onAssigned(true);
-    myState = new ErrorState((MessageDiffRequest)myActiveRequest);
-    myState.init();
-  }
-
   //
   // Update
   //
@@ -966,6 +960,7 @@ public abstract class DiffRequestProcessor implements Disposable {
   //
 
   private interface ViewerState {
+    @CalledInAwt
     void init();
 
     @CalledInAwt
@@ -981,6 +976,34 @@ public abstract class DiffRequestProcessor implements Disposable {
     DiffTool getActiveTool();
   }
 
+  private static class EmptyState implements ViewerState {
+    @Override
+    public void init() {
+    }
+
+    @Override
+    public void destroy() {
+    }
+
+    @Nullable
+    @Override
+    public JComponent getPreferredFocusedComponent() {
+      return null;
+    }
+
+    @Nullable
+    @Override
+    public Object getData(@NonNls String dataId) {
+      return null;
+    }
+
+    @NotNull
+    @Override
+    public DiffTool getActiveTool() {
+      return ErrorDiffTool.INSTANCE;
+    }
+  }
+
   private class ErrorState implements ViewerState {
     @Nullable private final DiffTool myDiffTool;
     @NotNull private final MessageDiffRequest myRequest;
@@ -999,6 +1022,7 @@ public abstract class DiffRequestProcessor implements Disposable {
     }
 
     @Override
+    @CalledInAwt
     public void init() {
       myContentPanel.setContent(myViewer.getComponent());
 
@@ -1043,6 +1067,7 @@ public abstract class DiffRequestProcessor implements Disposable {
     }
 
     @Override
+    @CalledInAwt
     public void init() {
       myContentPanel.setContent(myViewer.getComponent());
       setTitle(myActiveRequest.getTitle());
@@ -1100,6 +1125,7 @@ public abstract class DiffRequestProcessor implements Disposable {
     }
 
     @Override
+    @CalledInAwt
     public void init() {
       myContentPanel.setContent(myWrapperViewer.getComponent());
       setTitle(myActiveRequest.getTitle());

platform/diff-impl/src/com/intellij/diff/impl/DiffWindowBase.java

@@ -64,7 +64,6 @@ public abstract class DiffWindowBase {
         }
       })
       .build();
-    myProcessor.init();
     myWrapper.setImage(ImageLoader.loadFromResource("/diff/Diff.png"));
     Disposer.register(myWrapper, myProcessor);
 

platform/vcs-impl/src/com/intellij/openapi/vcs/changes/ChangesViewManager.java

@@ -121,7 +121,6 @@ public class ChangesViewManager implements ChangesViewI, JDOMExternalizable, Pro
     Disposer.register(project, myView);
     myRepaintAlarm = new Alarm(Alarm.ThreadToUse.SWING_THREAD, project);
     myDiffDetails = new MyChangeProcessor(myProject);
-    myDiffDetails.init();
     myTsl = new TreeSelectionListener() {
       @Override
       public void valueChanged(TreeSelectionEvent e) {

platform/vcs-impl/src/com/intellij/openapi/vcs/changes/ui/CommitChangeListDialog.java

@@ -321,7 +321,6 @@ public class CommitChangeListDialog extends DialogWrapper implements CheckinProj
         });
       }
     });
-    myDiffDetails.init();
 
     myBrowserExtender.addToolbarActions(this);