Add a condition (and expression) to check if an external layout is being previewed (and which one)

Extensions/SystemInfo/Extension.cpp

@@ -78,6 +78,28 @@ void DeclareSystemInfoExtension(gd::PlatformExtension& extension) {
 
       .AddCodeOnlyParameter("currentScene", "");
 
+  extension
+      .AddCondition(
+          "IsPreviewingAnExternalLayout",
+          _("Is the game running an external layout as a preview"),
+          _("Check if the game is currently being previewed in the editor, "
+            "and this preview was launched for an external layout."),
+          _("An external layout of the game is being previewed in the editor"),
+          "",
+          "CppPlatform/Extensions/systeminfoicon.png",
+          "CppPlatform/Extensions/systeminfoicon.png")
+
+      .AddCodeOnlyParameter("currentScene", "");
+
+  extension
+      .AddExpression("PreviewedExternalLayoutName",
+                     _("Name of the previewed external layout"),
+                     _("Returns the name of the external layout being "
+                       "previewed from the editor"),
+                     "",
+                     "CppPlatform/Extensions/systeminfoicon.png")
+      .AddCodeOnlyParameter("currentScene", "");
+
   extension
       .AddCondition(
           "HasTouchScreen",

Extensions/SystemInfo/JsExtension.cpp

@@ -39,6 +39,12 @@ class SystemInfoJsExtension : public gd::PlatformExtension {
     GetAllConditions()["SystemInfo::IsPreview"]
         .SetIncludeFile("Extensions/SystemInfo/systeminfotools.js")
         .SetFunctionName("gdjs.evtTools.systemInfo.isPreview");
+    GetAllConditions()["SystemInfo::IsPreviewingAnExternalLayout"]
+        .SetIncludeFile("Extensions/SystemInfo/systeminfotools.js")
+        .SetFunctionName("gdjs.evtTools.systemInfo.isPreviewingAnExternalLayout");
+    GetAllExpressions()["SystemInfo::PreviewedExternalLayoutName"]
+        .SetIncludeFile("Extensions/SystemInfo/systeminfotools.js")
+        .SetFunctionName("gdjs.evtTools.systemInfo.getPreviewedExternalLayoutName");
     GetAllConditions()["SystemInfo::HasTouchScreen"]
         .SetIncludeFile("Extensions/SystemInfo/systeminfotools.js")
         .SetFunctionName("gdjs.evtTools.systemInfo.hasTouchScreen");

Extensions/SystemInfo/systeminfotools.ts

@@ -81,6 +81,34 @@ namespace gdjs {
       ): boolean => {
         return instanceContainer.getGame().isPreview();
       };
+
+      /**
+       * Check if the game is running as a preview, launched from an editor,
+       * for an external layout.
+       * @param instanceContainer The current container.
+       * @returns true if the game is running as a preview for an external layout.
+       */
+      export const isPreviewingAnExternalLayout = (
+        instanceContainer: gdjs.RuntimeInstanceContainer
+      ): boolean => {
+        const game = instanceContainer.getGame();
+        return game.isPreview() && !!game.getPreviewedExternalLayoutName();
+      };
+
+      /**
+       * If the game is running as a preview, launched from an editor,
+       * this returns the name of the external layout being previewed - if any.
+       * Otherwise, returns an empty string.
+       *
+       * @param instanceContainer The current container.
+       * @returns the name of the previewed external layout.
+       */
+      export const getPreviewedExternalLayoutName = (
+        instanceContainer: gdjs.RuntimeInstanceContainer
+      ): string => {
+        const game = instanceContainer.getGame();
+        return game.getPreviewedExternalLayoutName();
+      };
     }
   }
 }

GDJS/Runtime/runtimegame.ts

@@ -186,7 +186,7 @@ namespace gdjs {
     /**
      * Allow to specify an external layout to insert in the first scene.
      */
-    _injectExternalLayout: any;
+    _injectExternalLayout: string;
     _options: RuntimeGameOptions;
 
     /**
@@ -1078,6 +1078,15 @@ namespace gdjs {
       return this._isPreview;
     }
 
+    /**
+     * Return the name of the external layout that was automatically created at position 0;0
+     * for this preview, if any.
+     * @returns the name of the external layout, or an empty string if none was injected.
+     */
+    getPreviewedExternalLayoutName(): string {
+      return this._injectExternalLayout;
+    }
+
     /**
      * Check if the game should call GDevelop development APIs or not.
      *