Preserve active part while switching parts layout (#8783)

Signed-off-by: Artem Zatsarynnyi <azatsary@redhat.com>

ide/che-core-ide-app/src/main/java/org/eclipse/che/ide/command/toolbar/selector/PanelSelectorPresenter.java

@@ -14,28 +14,35 @@
 
 import com.google.gwt.user.client.ui.AcceptsOneWidget;
 import com.google.inject.Inject;
+import com.google.inject.Provider;
 import com.google.web.bindery.event.shared.EventBus;
 import javax.inject.Singleton;
 import org.eclipse.che.ide.api.mvp.Presenter;
+import org.eclipse.che.ide.api.parts.PartPresenter;
 import org.eclipse.che.ide.api.parts.PartStack;
 import org.eclipse.che.ide.api.parts.PartStackStateChangedEvent;
 import org.eclipse.che.ide.api.parts.PartStackType;
 import org.eclipse.che.ide.api.parts.Perspective;
 import org.eclipse.che.ide.api.parts.PerspectiveManager;
+import org.eclipse.che.ide.api.parts.WorkspaceAgent;
 
 /** Presenter to manage Panel selector widget and perspective layout. */
 @Singleton
 public class PanelSelectorPresenter implements Presenter, PanelSelectorView.ActionDelegate {
 
+  private final Provider<WorkspaceAgent> workspaceAgentProvider;
   private PanelSelectorView view;
-
   private PerspectiveManager perspectiveManager;
 
   @Inject
   public PanelSelectorPresenter(
-      PanelSelectorView view, PerspectiveManager perspectiveManager, EventBus eventBus) {
+      PanelSelectorView view,
+      PerspectiveManager perspectiveManager,
+      EventBus eventBus,
+      Provider<WorkspaceAgent> workspaceAgentProvider) {
     this.view = view;
     this.perspectiveManager = perspectiveManager;
+    this.workspaceAgentProvider = workspaceAgentProvider;
 
     view.setDelegate(this);
 
@@ -102,6 +109,8 @@ private void showPanels(boolean left, boolean bottom, boolean right) {
       return;
     }
 
+    PartPresenter activePart = workspaceAgentProvider.get().getActivePart();
+
     PartStack editorPartStack = perspective.getPartStack(PartStackType.EDITING);
     editorPartStack.restore();
 
@@ -140,6 +149,8 @@ private void showPanels(boolean left, boolean bottom, boolean right) {
     }
 
     updateButtonState();
+
+    workspaceAgentProvider.get().setActivePart(activePart);
   }
 
   /** Updates icon for panel selector button displaying the current state of panels. */