Add checks to handle failure in creating entity as a child of a read-only entity in TrackView and LandscapeCanvas (#7156)

Signed-off-by: Danilo Aimini <82231674+AMZN-daimini@users.noreply.github.com>

Code/Editor/TrackView/TrackViewDialog.cpp

@@ -1046,7 +1046,12 @@ void CTrackViewDialog::OnAddSequence()
             AzToolsFramework::ScopedUndoBatch undoBatch("Create TrackView Director Node");
             sequenceManager->CreateSequence(sequenceName, sequenceType);
             CTrackViewSequence* newSequence = sequenceManager->GetSequenceByName(sequenceName);
-            AZ_Assert(newSequence, "Creating new sequence failed.");
+
+            if (!newSequence)
+            {
+                return;
+            }
+            
             undoBatch.MarkEntityDirty(newSequence->GetSequenceComponentEntityId());
 
             // make it the currently selected sequence

Gems/LandscapeCanvas/Code/Source/Editor/MainWindow.cpp

@@ -19,13 +19,16 @@
 #include <AzToolsFramework/API/ComponentEntityObjectBus.h>
 #include <AzToolsFramework/API/EntityCompositionRequestBus.h>
 #include <AzToolsFramework/Commands/EntityStateCommand.h>
+#include <AzToolsFramework/Entity/EditorEntityContextBus.h>
 #include <AzToolsFramework/Entity/EditorEntityInfoBus.h>
 #include <AzToolsFramework/Entity/EditorEntityHelpers.h>
+#include <AzToolsFramework/Entity/ReadOnly/ReadOnlyEntityInterface.h>
 #include <AzToolsFramework/Prefab/PrefabFocusPublicInterface.h>
 #include <AzToolsFramework/PropertyTreeEditor/PropertyTreeEditor.h>
 #include <AzToolsFramework/ToolsComponents/EditorDisabledCompositionBus.h>
 #include <AzToolsFramework/ToolsComponents/EditorPendingCompositionBus.h>
 #include <AzToolsFramework/UI/ComponentPalette/ComponentPaletteUtil.hxx>
+#include <AzToolsFramework/UI/UICore/WidgetHelpers.h>
 #include <AzToolsFramework/Undo/UndoSystem.h>
 #include <IEditor.h>
 
@@ -37,6 +40,7 @@
 
 // Qt
 #include <QApplication>
+#include <QMessageBox>
 #include <QStringList>
 #include <QTimer>
 #include <QVBoxLayout>
@@ -448,6 +452,8 @@ namespace LandscapeCanvasEditor
         return config;
     }
 
+    AzFramework::EntityContextId MainWindow::s_editorEntityContextId = AzFramework::EntityContextId::CreateNull();
+    
     MainWindow::MainWindow(QWidget* parent)
         : GraphModelIntegration::EditorMainWindow(GetDefaultConfig(), parent)
     {
@@ -470,9 +476,15 @@ namespace LandscapeCanvasEditor
         AZ::ComponentApplicationBus::BroadcastResult(m_serializeContext, &AZ::ComponentApplicationRequests::GetSerializeContext);
         AZ_Assert(m_serializeContext, "Failed to acquire application serialize context.");
 
+        AzToolsFramework::EditorEntityContextRequestBus::BroadcastResult(
+            s_editorEntityContextId, &AzToolsFramework::EditorEntityContextRequests::GetEditorEntityContextId);
+
         m_prefabFocusPublicInterface = AZ::Interface<AzToolsFramework::Prefab::PrefabFocusPublicInterface>::Get();
         AZ_Assert(m_prefabFocusPublicInterface, "LandscapeCanvas - could not get PrefabFocusPublicInterface on construction.");
 
+        m_readOnlyEntityPublicInterface = AZ::Interface<AzToolsFramework::ReadOnlyEntityPublicInterface>::Get();
+        AZ_Assert(m_readOnlyEntityPublicInterface, "LandscapeCanvas - could not get ReadOnlyEntityPublicInterface on construction.");
+
         const GraphCanvas::EditorId& editorId = GetEditorId();
 
         // Register unique color palettes for our connections (data types)
@@ -837,6 +849,26 @@ namespace LandscapeCanvasEditor
     {
         using namespace AzFramework::Terrain;
 
+        // Detect if it's possible to create a new entity in the current context
+        AZ::EntityId focusRootEntityId = m_prefabFocusPublicInterface->GetFocusedPrefabContainerEntityId(s_editorEntityContextId);
+        if (m_readOnlyEntityPublicInterface->IsReadOnly(focusRootEntityId))
+        {
+            // Abort
+            CloseEditor(dockWidget->GetDockWidgetId());
+
+            QWidget* activeWindow = AzToolsFramework::GetActiveWindow();
+
+            QMessageBox::warning(
+                activeWindow,
+                QString("Landscape Canvas Asset Creation Error"),
+                QString("Could not create new Landscape Canvas asset under read-only entity."),
+                QMessageBox::Ok,
+                QMessageBox::Ok
+            );
+
+            return;
+        }
+
         // Invoke the GraphCanvas base instead of the GraphModelIntegration::EditorMainWindow so that we
         // can do our own custom handling when opening an existing graph
         GraphCanvas::AssetEditorMainWindow::OnEditorOpened(dockWidget);

Gems/LandscapeCanvas/Code/Source/Editor/MainWindow.h

@@ -34,6 +34,8 @@
 
 namespace AzToolsFramework
 {
+    class ReadOnlyEntityPublicInterface;
+
     namespace Prefab
     {
         class PrefabFocusPublicInterface;
@@ -261,7 +263,9 @@ namespace LandscapeCanvasEditor
 
         AZ::SerializeContext* m_serializeContext = nullptr;
 
+        static AzFramework::EntityContextId s_editorEntityContextId;
         AzToolsFramework::Prefab::PrefabFocusPublicInterface* m_prefabFocusPublicInterface = nullptr;
+        AzToolsFramework::ReadOnlyEntityPublicInterface* m_readOnlyEntityPublicInterface = nullptr;
 
         bool m_ignoreGraphUpdates = false;
         bool m_prefabPropagationInProgress = false;