Issue with Closing Open3D 3D Model Window without Closing the Entire GUI Interface

Question

I am working on an Open3D GUI interface to perform geometric cropping on 3D models. However, I am facing an issue where, when I open a 3D model and then close the 3D model viewer window using the "q" key, the entire GUI interface is also closing, which is not the behavior I desire.

Here's a simplified version of the code I'm using:

import open3d.visualization.gui as gui
import open3d.visualization.rendering as rendering

class Open3dApp:
    def __init__(self):
        self.window = gui.Application.instance.create_window("3D Full Body Human Viewer", 1400, 900)
        win = self.window
        self.current_file = None
        self.Clean3DPLY = None
        # Check if file exists
        if os.path.isfile('Clean body.ply'):
            self.Clean3DPLY = 'Clean body.ply'

        # member variables
        self.model_dir = ""
        self.model_name = ""
        self.pcd = None  # to store the loaded .ply file
        self._widget3d = None  # to store the 3D widget

        em = win.theme.font_size
        # 3D Widget
        self.test = gui.Combobox()
        self.test.add_item("First")

        self._widget3d = gui.SceneWidget()
        self._widget3d.scene = rendering.Open3DScene(w.renderer)
        self._widget3d.set_view_controls(gui.SceneWidget.Controls.ROTATE_CAMERA)
        # create a frame that encapsulates the SceneWidget
        self._widget3d.frame = gui.Rect(500, win.content_rect.y, 900, win.content_rect.height)
        mesh = o3d.geometry.TriangleMesh.create_sphere()
        mesh.compute_vertex_normals()
        material = rendering.MaterialRecord()
        material.shader = "defaultLit"
        self._widget3d.scene.add_geometry('mesh', mesh, material)
        self._widget3d.scene.set_background([200, 0, 0, 200])  # not working?!
        self._widget3d.scene.camera.look_at([0, 0, 0], [1, 1, 1], [0, 0, 1])

        # gui layout
        gui_layout = gui.Vert(0, gui.Margins(0.5 * em, 0.5 * em, 0.5 * em, 0.5 * em))
        # create frame that encapsulates the gui
        gui_layout.frame = gui.Rect(w.content_rect.x, win.content_rect.y, 500, win.content_rect.height)
        # File-chooser widget
        self._fileedit = gui.TextEdit()
        filedlgbutton = gui.Button("...")
        filedlgbutton.horizontal_padding_em = 0.5
        filedlgbutton.vertical_padding_em = 0
        filedlgbutton.set_on_clicked(self._on_filedlg_button)
        # Add a fixed height empty layout for spacing
        empty_layout = gui.Vert(0)
        empty_layout.add_fixed(1 * em)
        fileedit_layout = gui.Horiz()
        fileedit_layout.add_child(gui.Label("Model file"))
        fileedit_layout.add_child(self._fileedit)
        fileedit_layout.add_fixed(0.25 * em)
        fileedit_layout.add_child(filedlgbutton)
        # Add to the top-level (vertical) layout
        gui_layout.add_child(fileedit_layout)

        # Add a fixed height empty layout for spacing
        empty_layout = gui.Vert(0)
        empty_layout.add_fixed(1 * em)
        gui_layout.add_child(empty_layout)

        # start pre processing
        collapse = gui.CollapsableVert("Pre Processing Data", 0.33 * em,
                                       gui.Margins(em, 0, 0, 0))

        # Additional feature buttons
        feature_button1 = gui.Button("Geometry Cropping")
        feature_button1.set_on_clicked(self.demo_3d)
        feature_button2 = gui.Button("Segmentation")
        feature_button2.set_on_clicked(self.clean3d)

        geometry_button4 = gui.Button("Exit")
        geometry_button4.set_on_clicked(self._on_exit_click)

        gui_layout.add_child(geometry_button4)
        gui_layout.add_child(empty_layout)

        w.add_child(gui_layout)
        w.add_child(self._widget3d)


    def demo_3d(self):
        if not self.file_path:
            print("Error", "Please select a file")
        else:
            # Load the point cloud data from the selected file
            indi = o3d.io.read_point_cloud(self.file_path)

            # Convert point cloud data to numpy arrays for mesh and colors
            mesh_array = np.asarray(indi.points)
            colors = np.asarray(indi.colors)

            # Print mesh and color information for debugging
            print("Mesh Array:", mesh_array)
            print("Colors:", colors)

            # Call the demo_crop_geometry function with the loaded point cloud
            self.demo_crop_geometry(indi)

            # Update the label with the selected file path
            # self.label.config(text=self.path)

            # Set the current file to Clean3DPLY (assuming this is what you intended)
            self.current_file = self.Clean3DPLY


    def demo_crop_geometry(self, indi):
        print("Demo for manual geometry cropping")
        print(
            "1) Press 'Y' twice to align geometry with negative direction of y-axis"
        )
        print("2) Press 'K' to lock screen and to switch to selection mode")
        print("3) Drag for rectangle selection,")
        print("   or use ctrl + left click for polygon selection")
        print("4) Press 'C' to get a selected geometry and to save it")
        print("5) Press 'F' to switch to freeview mode")
        o3d.visualization.draw_geometries_with_editing([indi], width=800, height=900, left=1050, top=100)

In this code, I have a GUI interface that allows me to load a 3D model and perform geometric cropping on it. When I press "q" to close the 3D model viewer, it closes the entire interface, which is not the expected behavior.

I would like to know how to modify my code to ensure that when I close the 3D model viewer window, it only closes the 3D model viewer window and not the entire GUI interface.

Any suggestions or guidance on how to achieve this behavior would be greatly appreciated.

Thank you!