GUI Application Crashing Without Error During Combobox Interaction

[Timezyxdev]

Checklist

• [X] I have searched for similar issues.
• [X] For Python issues, I have tested with the latest development wheel.
• [X] I have checked the release documentation and the latest documentation (for master branch).

Describe the issue

I have been developing an application working of of the vis_gui.py example provided in the documentation. I have added additional panels with buttons and comboboxes and allowed users to load multiple point clouds. Unfortunately I cannot share my full code but I was able to replicate my issue just using the vis_gui.py example on multiple computers.

After I load in data, even if it's a very dense point cloud, Open3d seems to be able to handle rotations, transformations, and other manipulations of the 3D point cloud without slowdown. However, as soon as I interact with any Combobox in my panels, if there is any slowdown the application will close without any error message. The most extreme example is when I load a dense (41126103 point) cloud into the vis_gui.py example and it becomes very slow. As soon as I begin interacting with a Combobox the app freezes and quickly crashes.

This is more frustrating in my own use case, where the point clouds are a little bit smaller (downsampled from the cloud mentioned above). I load multiple at once and store them in global variables, allowing the user to switch between them, and don't see any slow down. Sometimes interacting with Comboboxes doesn't crash the app, and I can begin selecting from them. However, other times as soon as I begin running my mouse over the items in the Combobox the loading wheel appears and then the app crashes. It's very inconsistent and I don't know if it can even be fixed since the issue seems to appear in the base GUI example as well. This bug occurs in my version of the GUI even when no data has been loaded sometimes. If I just hover my mouse across many options in a Combobox quickly then which option is highlighted will lag and the app will crash. I have not been able to replicate this crash with no data loaded in the vis_gui.py example yet. I'm not sure what about the state of my machine causes this but when it happens once it seems to occur very frequently and is easy to trigger, however after waiting a while it can be very hard to replicate until suddenly it crops up again hours or days later.

The only workaround I have thought of so far is simply not using Comboboxes. However using Comboboxes would be much more convenient as I'm populating them with an unknown number of items, and it's important for me to know which item is selected when the Combobox is used.

Steps to reproduce the bug

# Below is the vis_gui.py code with an added button at the top of the right panel to generate a random 
# point cloud large enough to quickly cause the crash.

# ----------------------------------------------------------------------------
# -                        Open3D: www.open3d.org                            -
# ----------------------------------------------------------------------------
# Copyright (c) 2018-2023 www.open3d.org
# SPDX-License-Identifier: MIT
# ----------------------------------------------------------------------------

import glob
import numpy as np
import open3d as o3d
import open3d.visualization.gui as gui
import open3d.visualization.rendering as rendering
import os
import platform
import sys

isMacOS = (platform.system() == "Darwin")

class Settings:
    UNLIT = "defaultUnlit"
    LIT = "defaultLit"
    NORMALS = "normals"
    DEPTH = "depth"

    DEFAULT_PROFILE_NAME = "Bright day with sun at +Y [default]"
    POINT_CLOUD_PROFILE_NAME = "Cloudy day (no direct sun)"
    CUSTOM_PROFILE_NAME = "Custom"
    LIGHTING_PROFILES = {
        DEFAULT_PROFILE_NAME: {
            "ibl_intensity": 45000,
            "sun_intensity": 45000,
            "sun_dir": [0.577, -0.577, -0.577],
            # "ibl_rotation":
            "use_ibl": True,
            "use_sun": True,
        },
        "Bright day with sun at -Y": {
            "ibl_intensity": 45000,
            "sun_intensity": 45000,
            "sun_dir": [0.577, 0.577, 0.577],
            # "ibl_rotation":
            "use_ibl": True,
            "use_sun": True,
        },
        "Bright day with sun at +Z": {
            "ibl_intensity": 45000,
            "sun_intensity": 45000,
            "sun_dir": [0.577, 0.577, -0.577],
            # "ibl_rotation":
            "use_ibl": True,
            "use_sun": True,
        },
        "Less Bright day with sun at +Y": {
            "ibl_intensity": 35000,
            "sun_intensity": 50000,
            "sun_dir": [0.577, -0.577, -0.577],
            # "ibl_rotation":
            "use_ibl": True,
            "use_sun": True,
        },
        "Less Bright day with sun at -Y": {
            "ibl_intensity": 35000,
            "sun_intensity": 50000,
            "sun_dir": [0.577, 0.577, 0.577],
            # "ibl_rotation":
            "use_ibl": True,
            "use_sun": True,
        },
        "Less Bright day with sun at +Z": {
            "ibl_intensity": 35000,
            "sun_intensity": 50000,
            "sun_dir": [0.577, 0.577, -0.577],
            # "ibl_rotation":
            "use_ibl": True,
            "use_sun": True,
        },
        POINT_CLOUD_PROFILE_NAME: {
            "ibl_intensity": 60000,
            "sun_intensity": 50000,
            "use_ibl": True,
            "use_sun": False,
            # "ibl_rotation":
        },
    }

    DEFAULT_MATERIAL_NAME = "Polished ceramic [default]"
    PREFAB = {
        DEFAULT_MATERIAL_NAME: {
            "metallic": 0.0,
            "roughness": 0.7,
            "reflectance": 0.5,
            "clearcoat": 0.2,
            "clearcoat_roughness": 0.2,
            "anisotropy": 0.0
        },
        "Metal (rougher)": {
            "metallic": 1.0,
            "roughness": 0.5,
            "reflectance": 0.9,
            "clearcoat": 0.0,
            "clearcoat_roughness": 0.0,
            "anisotropy": 0.0
        },
        "Metal (smoother)": {
            "metallic": 1.0,
            "roughness": 0.3,
            "reflectance": 0.9,
            "clearcoat": 0.0,
            "clearcoat_roughness": 0.0,
            "anisotropy": 0.0
        },
        "Plastic": {
            "metallic": 0.0,
            "roughness": 0.5,
            "reflectance": 0.5,
            "clearcoat": 0.5,
            "clearcoat_roughness": 0.2,
            "anisotropy": 0.0
        },
        "Glazed ceramic": {
            "metallic": 0.0,
            "roughness": 0.5,
            "reflectance": 0.9,
            "clearcoat": 1.0,
            "clearcoat_roughness": 0.1,
            "anisotropy": 0.0
        },
        "Clay": {
            "metallic": 0.0,
            "roughness": 1.0,
            "reflectance": 0.5,
            "clearcoat": 0.1,
            "clearcoat_roughness": 0.287,
            "anisotropy": 0.0
        },
    }

    def __init__(self):
        self.mouse_model = gui.SceneWidget.Controls.ROTATE_CAMERA
        self.bg_color = gui.Color(1, 1, 1)
        self.show_skybox = False
        self.show_axes = False
        self.use_ibl = True
        self.use_sun = True
        self.new_ibl_name = None  # clear to None after loading
        self.ibl_intensity = 45000
        self.sun_intensity = 45000
        self.sun_dir = [0.577, -0.577, -0.577]
        self.sun_color = gui.Color(1, 1, 1)

        self.apply_material = True  # clear to False after processing
        self._materials = {
            Settings.LIT: rendering.MaterialRecord(),
            Settings.UNLIT: rendering.MaterialRecord(),
            Settings.NORMALS: rendering.MaterialRecord(),
            Settings.DEPTH: rendering.MaterialRecord()
        }
        self._materials[Settings.LIT].base_color = [0.9, 0.9, 0.9, 1.0]
        self._materials[Settings.LIT].shader = Settings.LIT
        self._materials[Settings.UNLIT].base_color = [0.9, 0.9, 0.9, 1.0]
        self._materials[Settings.UNLIT].shader = Settings.UNLIT
        self._materials[Settings.NORMALS].shader = Settings.NORMALS
        self._materials[Settings.DEPTH].shader = Settings.DEPTH

        # Conveniently, assigning from self._materials[...] assigns a reference,
        # not a copy, so if we change the property of a material, then switch
        # to another one, then come back, the old setting will still be there.
        self.material = self._materials[Settings.LIT]

    def set_material(self, name):
        self.material = self._materials[name]
        self.apply_material = True

    def apply_material_prefab(self, name):
        assert (self.material.shader == Settings.LIT)
        prefab = Settings.PREFAB[name]
        for key, val in prefab.items():
            setattr(self.material, "base_" + key, val)

    def apply_lighting_profile(self, name):
        profile = Settings.LIGHTING_PROFILES[name]
        for key, val in profile.items():
            setattr(self, key, val)

class AppWindow:
    MENU_OPEN = 1
    MENU_EXPORT = 2
    MENU_QUIT = 3
    MENU_SHOW_SETTINGS = 11
    MENU_ABOUT = 21

    DEFAULT_IBL = "default"

    MATERIAL_NAMES = ["Lit", "Unlit", "Normals", "Depth"]
    MATERIAL_SHADERS = [
        Settings.LIT, Settings.UNLIT, Settings.NORMALS, Settings.DEPTH
    ]

    def __init__(self, width, height):
        self.settings = Settings()
        resource_path = gui.Application.instance.resource_path
        self.settings.new_ibl_name = resource_path + "/" + AppWindow.DEFAULT_IBL

        self.window = gui.Application.instance.create_window(
            "Open3D", width, height)
        w = self.window  # to make the code more concise

        # 3D widget
        self._scene = gui.SceneWidget()
        self._scene.scene = rendering.Open3DScene(w.renderer)
        self._scene.set_on_sun_direction_changed(self._on_sun_dir)

        # ---- Settings panel ----
        # Rather than specifying sizes in pixels, which may vary in size based
        # on the monitor, especially on macOS which has 220 dpi monitors, use
        # the em-size. This way sizings will be proportional to the font size,
        # which will create a more visually consistent size across platforms.
        em = w.theme.font_size
        separation_height = int(round(0.5 * em))

        # Widgets are laid out in layouts: gui.Horiz, gui.Vert,
        # gui.CollapsableVert, and gui.VGrid. By nesting the layouts we can
        # achieve complex designs. Usually we use a vertical layout as the
        # topmost widget, since widgets tend to be organized from top to bottom.
        # Within that, we usually have a series of horizontal layouts for each
        # row. All layouts take a spacing parameter, which is the spacing
        # between items in the widget, and a margins parameter, which specifies
        # the spacing of the left, top, right, bottom margins. (This acts like
        # the 'padding' property in CSS.)
        self._settings_panel = gui.Vert(
            0, gui.Margins(0.25 * em, 0.25 * em, 0.25 * em, 0.25 * em))

        # Pcd button:
        pcd_button = gui.Button("View Dense Point Cloud")
        pcd_button.set_on_clicked(self._on_pcd_click)
        self._settings_panel.add_child(pcd_button)

        # Create a collapsible vertical widget, which takes up enough vertical
        # space for all its children when open, but only enough for text when
        # closed. This is useful for property pages, so the user can hide sets
        # of properties they rarely use.
        view_ctrls = gui.CollapsableVert("View controls", 0.25 * em,
                                         gui.Margins(em, 0, 0, 0))

        self._arcball_button = gui.Button("Arcball")
        self._arcball_button.horizontal_padding_em = 0.5
        self._arcball_button.vertical_padding_em = 0
        self._arcball_button.set_on_clicked(self._set_mouse_mode_rotate)
        self._fly_button = gui.Button("Fly")
        self._fly_button.horizontal_padding_em = 0.5
        self._fly_button.vertical_padding_em = 0
        self._fly_button.set_on_clicked(self._set_mouse_mode_fly)
        self._model_button = gui.Button("Model")
        self._model_button.horizontal_padding_em = 0.5
        self._model_button.vertical_padding_em = 0
        self._model_button.set_on_clicked(self._set_mouse_mode_model)
        self._sun_button = gui.Button("Sun")
        self._sun_button.horizontal_padding_em = 0.5
        self._sun_button.vertical_padding_em = 0
        self._sun_button.set_on_clicked(self._set_mouse_mode_sun)
        self._ibl_button = gui.Button("Environment")
        self._ibl_button.horizontal_padding_em = 0.5
        self._ibl_button.vertical_padding_em = 0
        self._ibl_button.set_on_clicked(self._set_mouse_mode_ibl)
        view_ctrls.add_child(gui.Label("Mouse controls"))
        # We want two rows of buttons, so make two horizontal layouts. We also
        # want the buttons centered, which we can do be putting a stretch item
        # as the first and last item. Stretch items take up as much space as
        # possible, and since there are two, they will each take half the extra
        # space, thus centering the buttons.
        h = gui.Horiz(0.25 * em)  # row 1
        h.add_stretch()
        h.add_child(self._arcball_button)
        h.add_child(self._fly_button)
        h.add_child(self._model_button)
        h.add_stretch()
        view_ctrls.add_child(h)
        h = gui.Horiz(0.25 * em)  # row 2
        h.add_stretch()
        h.add_child(self._sun_button)
        h.add_child(self._ibl_button)
        h.add_stretch()
        view_ctrls.add_child(h)

        self._show_skybox = gui.Checkbox("Show skymap")
        self._show_skybox.set_on_checked(self._on_show_skybox)
        view_ctrls.add_fixed(separation_height)
        view_ctrls.add_child(self._show_skybox)

        self._bg_color = gui.ColorEdit()
        self._bg_color.set_on_value_changed(self._on_bg_color)

        grid = gui.VGrid(2, 0.25 * em)
        grid.add_child(gui.Label("BG Color"))
        grid.add_child(self._bg_color)
        view_ctrls.add_child(grid)

        self._show_axes = gui.Checkbox("Show axes")
        self._show_axes.set_on_checked(self._on_show_axes)
        view_ctrls.add_fixed(separation_height)
        view_ctrls.add_child(self._show_axes)

        self._profiles = gui.Combobox()
        for name in sorted(Settings.LIGHTING_PROFILES.keys()):
            self._profiles.add_item(name)
        self._profiles.add_item(Settings.CUSTOM_PROFILE_NAME)
        self._profiles.set_on_selection_changed(self._on_lighting_profile)
        view_ctrls.add_fixed(separation_height)
        view_ctrls.add_child(gui.Label("Lighting profiles"))
        view_ctrls.add_child(self._profiles)
        self._settings_panel.add_fixed(separation_height)
        self._settings_panel.add_child(view_ctrls)

        advanced = gui.CollapsableVert("Advanced lighting", 0,
                                       gui.Margins(em, 0, 0, 0))
        advanced.set_is_open(False)

        self._use_ibl = gui.Checkbox("HDR map")
        self._use_ibl.set_on_checked(self._on_use_ibl)
        self._use_sun = gui.Checkbox("Sun")
        self._use_sun.set_on_checked(self._on_use_sun)
        advanced.add_child(gui.Label("Light sources"))
        h = gui.Horiz(em)
        h.add_child(self._use_ibl)
        h.add_child(self._use_sun)
        advanced.add_child(h)

        self._ibl_map = gui.Combobox()
        for ibl in glob.glob(gui.Application.instance.resource_path +
                             "/*_ibl.ktx"):

            self._ibl_map.add_item(os.path.basename(ibl[:-8]))
        self._ibl_map.selected_text = AppWindow.DEFAULT_IBL
        self._ibl_map.set_on_selection_changed(self._on_new_ibl)
        self._ibl_intensity = gui.Slider(gui.Slider.INT)
        self._ibl_intensity.set_limits(0, 200000)
        self._ibl_intensity.set_on_value_changed(self._on_ibl_intensity)
        grid = gui.VGrid(2, 0.25 * em)
        grid.add_child(gui.Label("HDR map"))
        grid.add_child(self._ibl_map)
        grid.add_child(gui.Label("Intensity"))
        grid.add_child(self._ibl_intensity)
        advanced.add_fixed(separation_height)
        advanced.add_child(gui.Label("Environment"))
        advanced.add_child(grid)

        self._sun_intensity = gui.Slider(gui.Slider.INT)
        self._sun_intensity.set_limits(0, 200000)
        self._sun_intensity.set_on_value_changed(self._on_sun_intensity)
        self._sun_dir = gui.VectorEdit()
        self._sun_dir.set_on_value_changed(self._on_sun_dir)
        self._sun_color = gui.ColorEdit()
        self._sun_color.set_on_value_changed(self._on_sun_color)
        grid = gui.VGrid(2, 0.25 * em)
        grid.add_child(gui.Label("Intensity"))
        grid.add_child(self._sun_intensity)
        grid.add_child(gui.Label("Direction"))
        grid.add_child(self._sun_dir)
        grid.add_child(gui.Label("Color"))
        grid.add_child(self._sun_color)
        advanced.add_fixed(separation_height)
        advanced.add_child(gui.Label("Sun (Directional light)"))
        advanced.add_child(grid)

        self._settings_panel.add_fixed(separation_height)
        self._settings_panel.add_child(advanced)

        material_settings = gui.CollapsableVert("Material settings", 0,
                                                gui.Margins(em, 0, 0, 0))

        self._shader = gui.Combobox()
        self._shader.add_item(AppWindow.MATERIAL_NAMES[0])
        self._shader.add_item(AppWindow.MATERIAL_NAMES[1])
        self._shader.add_item(AppWindow.MATERIAL_NAMES[2])
        self._shader.add_item(AppWindow.MATERIAL_NAMES[3])
        self._shader.set_on_selection_changed(self._on_shader)
        self._material_prefab = gui.Combobox()
        for prefab_name in sorted(Settings.PREFAB.keys()):
            self._material_prefab.add_item(prefab_name)
        self._material_prefab.selected_text = Settings.DEFAULT_MATERIAL_NAME
        self._material_prefab.set_on_selection_changed(self._on_material_prefab)
        self._material_color = gui.ColorEdit()
        self._material_color.set_on_value_changed(self._on_material_color)
        self._point_size = gui.Slider(gui.Slider.INT)
        self._point_size.set_limits(1, 10)
        self._point_size.set_on_value_changed(self._on_point_size)

        grid = gui.VGrid(2, 0.25 * em)
        grid.add_child(gui.Label("Type"))
        grid.add_child(self._shader)
        grid.add_child(gui.Label("Material"))
        grid.add_child(self._material_prefab)
        grid.add_child(gui.Label("Color"))
        grid.add_child(self._material_color)
        grid.add_child(gui.Label("Point size"))
        grid.add_child(self._point_size)
        material_settings.add_child(grid)

        self._settings_panel.add_fixed(separation_height)
        self._settings_panel.add_child(material_settings)
        # ----

        # Normally our user interface can be children of all one layout (usually
        # a vertical layout), which is then the only child of the window. In our
        # case we want the scene to take up all the space and the settings panel
        # to go above it. We can do this custom layout by providing an on_layout
        # callback. The on_layout callback should set the frame
        # (position + size) of every child correctly. After the callback is
        # done the window will layout the grandchildren.
        w.set_on_layout(self._on_layout)
        w.add_child(self._scene)
        w.add_child(self._settings_panel)

        # ---- Menu ----
        # The menu is global (because the macOS menu is global), so only create
        # it once, no matter how many windows are created
        if gui.Application.instance.menubar is None:
            if isMacOS:
                app_menu = gui.Menu()
                app_menu.add_item("About", AppWindow.MENU_ABOUT)
                app_menu.add_separator()
                app_menu.add_item("Quit", AppWindow.MENU_QUIT)
            file_menu = gui.Menu()
            file_menu.add_item("Open...", AppWindow.MENU_OPEN)
            file_menu.add_item("Export Current Image...", AppWindow.MENU_EXPORT)
            if not isMacOS:
                file_menu.add_separator()
                file_menu.add_item("Quit", AppWindow.MENU_QUIT)
            settings_menu = gui.Menu()
            settings_menu.add_item("Lighting & Materials",
                                   AppWindow.MENU_SHOW_SETTINGS)
            settings_menu.set_checked(AppWindow.MENU_SHOW_SETTINGS, True)
            help_menu = gui.Menu()
            help_menu.add_item("About", AppWindow.MENU_ABOUT)

            menu = gui.Menu()
            if isMacOS:
                # macOS will name the first menu item for the running application
                # (in our case, probably "Python"), regardless of what we call
                # it. This is the application menu, and it is where the
                # About..., Preferences..., and Quit menu items typically go.
                menu.add_menu("Example", app_menu)
                menu.add_menu("File", file_menu)
                menu.add_menu("Settings", settings_menu)
                # Don't include help menu unless it has something more than
                # About...
            else:
                menu.add_menu("File", file_menu)
                menu.add_menu("Settings", settings_menu)
                menu.add_menu("Help", help_menu)
            gui.Application.instance.menubar = menu

        # The menubar is global, but we need to connect the menu items to the
        # window, so that the window can call the appropriate function when the
        # menu item is activated.
        w.set_on_menu_item_activated(AppWindow.MENU_OPEN, self._on_menu_open)
        w.set_on_menu_item_activated(AppWindow.MENU_EXPORT,
                                     self._on_menu_export)
        w.set_on_menu_item_activated(AppWindow.MENU_QUIT, self._on_menu_quit)
        w.set_on_menu_item_activated(AppWindow.MENU_SHOW_SETTINGS,
                                     self._on_menu_toggle_settings_panel)
        w.set_on_menu_item_activated(AppWindow.MENU_ABOUT, self._on_menu_about)
        # ----

        self._apply_settings()

    def _apply_settings(self):
        bg_color = [
            self.settings.bg_color.red, self.settings.bg_color.green,
            self.settings.bg_color.blue, self.settings.bg_color.alpha
        ]
        self._scene.scene.set_background(bg_color)
        self._scene.scene.show_skybox(self.settings.show_skybox)
        self._scene.scene.show_axes(self.settings.show_axes)
        if self.settings.new_ibl_name is not None:
            self._scene.scene.scene.set_indirect_light(
                self.settings.new_ibl_name)
            # Clear new_ibl_name, so we don't keep reloading this image every
            # time the settings are applied.
            self.settings.new_ibl_name = None
        self._scene.scene.scene.enable_indirect_light(self.settings.use_ibl)
        self._scene.scene.scene.set_indirect_light_intensity(
            self.settings.ibl_intensity)
        sun_color = [
            self.settings.sun_color.red, self.settings.sun_color.green,
            self.settings.sun_color.blue
        ]
        self._scene.scene.scene.set_sun_light(self.settings.sun_dir, sun_color,
                                              self.settings.sun_intensity)
        self._scene.scene.scene.enable_sun_light(self.settings.use_sun)

        if self.settings.apply_material:
            self._scene.scene.update_material(self.settings.material)
            self.settings.apply_material = False

        self._bg_color.color_value = self.settings.bg_color
        self._show_skybox.checked = self.settings.show_skybox
        self._show_axes.checked = self.settings.show_axes
        self._use_ibl.checked = self.settings.use_ibl
        self._use_sun.checked = self.settings.use_sun
        self._ibl_intensity.int_value = self.settings.ibl_intensity
        self._sun_intensity.int_value = self.settings.sun_intensity
        self._sun_dir.vector_value = self.settings.sun_dir
        self._sun_color.color_value = self.settings.sun_color
        self._material_prefab.enabled = (
            self.settings.material.shader == Settings.LIT)
        c = gui.Color(self.settings.material.base_color[0],
                      self.settings.material.base_color[1],
                      self.settings.material.base_color[2],
                      self.settings.material.base_color[3])
        self._material_color.color_value = c
        self._point_size.double_value = self.settings.material.point_size

    def _on_layout(self, layout_context):
        # The on_layout callback should set the frame (position + size) of every
        # child correctly. After the callback is done the window will layout
        # the grandchildren.
        r = self.window.content_rect
        self._scene.frame = r
        width = 17 * layout_context.theme.font_size
        height = min(
            r.height,
            self._settings_panel.calc_preferred_size(
                layout_context, gui.Widget.Constraints()).height)
        self._settings_panel.frame = gui.Rect(r.get_right() - width, r.y, width,
                                              height)

    def _on_pcd_click(self):
        try:
            self._scene.scene.clear_geometry()
            pcd_array = np.random.rand(41126103, 3)*20 #random array with xyz coords between 0 and 20
            color_array = np.random.rand(41126103, 3)
            pcd = o3d.geometry.PointCloud()
            pcd.points = o3d.utility.Vector3dVector(pcd_array)
            pcd.colors = o3d.utility.Vector3dVector(color_array)
            self._scene.scene.add_geometry("__model__", pcd,
                                                    self.settings.material)
            bounds = self._scene.scene.bounding_box
            self._scene.setup_camera(60, bounds, bounds.get_center())
        except Exception as e:
            print(e)

    def _set_mouse_mode_rotate(self):
        self._scene.set_view_controls(gui.SceneWidget.Controls.ROTATE_CAMERA)

    def _set_mouse_mode_fly(self):
        self._scene.set_view_controls(gui.SceneWidget.Controls.FLY)

    def _set_mouse_mode_sun(self):
        self._scene.set_view_controls(gui.SceneWidget.Controls.ROTATE_SUN)

    def _set_mouse_mode_ibl(self):
        self._scene.set_view_controls(gui.SceneWidget.Controls.ROTATE_IBL)

    def _set_mouse_mode_model(self):
        self._scene.set_view_controls(gui.SceneWidget.Controls.ROTATE_MODEL)

    def _on_bg_color(self, new_color):
        self.settings.bg_color = new_color
        self._apply_settings()

    def _on_show_skybox(self, show):
        self.settings.show_skybox = show
        self._apply_settings()

    def _on_show_axes(self, show):
        self.settings.show_axes = show
        self._apply_settings()

    def _on_use_ibl(self, use):
        self.settings.use_ibl = use
        self._profiles.selected_text = Settings.CUSTOM_PROFILE_NAME
        self._apply_settings()

    def _on_use_sun(self, use):
        self.settings.use_sun = use
        self._profiles.selected_text = Settings.CUSTOM_PROFILE_NAME
        self._apply_settings()

    def _on_lighting_profile(self, name, index):
        if name != Settings.CUSTOM_PROFILE_NAME:
            self.settings.apply_lighting_profile(name)
            self._apply_settings()

    def _on_new_ibl(self, name, index):
        self.settings.new_ibl_name = gui.Application.instance.resource_path + "/" + name
        self._profiles.selected_text = Settings.CUSTOM_PROFILE_NAME
        self._apply_settings()

    def _on_ibl_intensity(self, intensity):
        self.settings.ibl_intensity = int(intensity)
        self._profiles.selected_text = Settings.CUSTOM_PROFILE_NAME
        self._apply_settings()

    def _on_sun_intensity(self, intensity):
        self.settings.sun_intensity = int(intensity)
        self._profiles.selected_text = Settings.CUSTOM_PROFILE_NAME
        self._apply_settings()

    def _on_sun_dir(self, sun_dir):
        self.settings.sun_dir = sun_dir
        self._profiles.selected_text = Settings.CUSTOM_PROFILE_NAME
        self._apply_settings()

    def _on_sun_color(self, color):
        self.settings.sun_color = color
        self._apply_settings()

    def _on_shader(self, name, index):
        self.settings.set_material(AppWindow.MATERIAL_SHADERS[index])
        self._apply_settings()

    def _on_material_prefab(self, name, index):
        self.settings.apply_material_prefab(name)
        self.settings.apply_material = True
        self._apply_settings()

    def _on_material_color(self, color):
        self.settings.material.base_color = [
            color.red, color.green, color.blue, color.alpha
        ]
        self.settings.apply_material = True
        self._apply_settings()

    def _on_point_size(self, size):
        self.settings.material.point_size = int(size)
        self.settings.apply_material = True
        self._apply_settings()

    def _on_menu_open(self):
        dlg = gui.FileDialog(gui.FileDialog.OPEN, "Choose file to load",
                             self.window.theme)
        dlg.add_filter(
            ".ply .stl .fbx .obj .off .gltf .glb",
            "Triangle mesh files (.ply, .stl, .fbx, .obj, .off, "
            ".gltf, .glb)")
        dlg.add_filter(
            ".xyz .xyzn .xyzrgb .ply .pcd .pts",
            "Point cloud files (.xyz, .xyzn, .xyzrgb, .ply, "
            ".pcd, .pts)")
        dlg.add_filter(".ply", "Polygon files (.ply)")
        dlg.add_filter(".stl", "Stereolithography files (.stl)")
        dlg.add_filter(".fbx", "Autodesk Filmbox files (.fbx)")
        dlg.add_filter(".obj", "Wavefront OBJ files (.obj)")
        dlg.add_filter(".off", "Object file format (.off)")
        dlg.add_filter(".gltf", "OpenGL transfer files (.gltf)")
        dlg.add_filter(".glb", "OpenGL binary transfer files (.glb)")
        dlg.add_filter(".xyz", "ASCII point cloud files (.xyz)")
        dlg.add_filter(".xyzn", "ASCII point cloud with normals (.xyzn)")
        dlg.add_filter(".xyzrgb",
                       "ASCII point cloud files with colors (.xyzrgb)")
        dlg.add_filter(".pcd", "Point Cloud Data files (.pcd)")
        dlg.add_filter(".pts", "3D Points files (.pts)")
        dlg.add_filter("", "All files")

        # A file dialog MUST define on_cancel and on_done functions
        dlg.set_on_cancel(self._on_file_dialog_cancel)
        dlg.set_on_done(self._on_load_dialog_done)
        self.window.show_dialog(dlg)

    def _on_file_dialog_cancel(self):
        self.window.close_dialog()

    def _on_load_dialog_done(self, filename):
        self.window.close_dialog()
        self.load(filename)

    def _on_menu_export(self):
        dlg = gui.FileDialog(gui.FileDialog.SAVE, "Choose file to save",
                             self.window.theme)
        dlg.add_filter(".png", "PNG files (.png)")
        dlg.set_on_cancel(self._on_file_dialog_cancel)
        dlg.set_on_done(self._on_export_dialog_done)
        self.window.show_dialog(dlg)

    def _on_export_dialog_done(self, filename):
        self.window.close_dialog()
        frame = self._scene.frame
        self.export_image(filename, frame.width, frame.height)

    def _on_menu_quit(self):
        gui.Application.instance.quit()

    def _on_menu_toggle_settings_panel(self):
        self._settings_panel.visible = not self._settings_panel.visible
        gui.Application.instance.menubar.set_checked(
            AppWindow.MENU_SHOW_SETTINGS, self._settings_panel.visible)

    def _on_menu_about(self):
        # Show a simple dialog. Although the Dialog is actually a widget, you can
        # treat it similar to a Window for layout and put all the widgets in a
        # layout which you make the only child of the Dialog.
        em = self.window.theme.font_size
        dlg = gui.Dialog("About")

        # Add the text
        dlg_layout = gui.Vert(em, gui.Margins(em, em, em, em))
        dlg_layout.add_child(gui.Label("Open3D GUI Example"))

        # Add the Ok button. We need to define a callback function to handle
        # the click.
        ok = gui.Button("OK")
        ok.set_on_clicked(self._on_about_ok)

        # We want the Ok button to be an the right side, so we need to add
        # a stretch item to the layout, otherwise the button will be the size
        # of the entire row. A stretch item takes up as much space as it can,
        # which forces the button to be its minimum size.
        h = gui.Horiz()
        h.add_stretch()
        h.add_child(ok)
        h.add_stretch()
        dlg_layout.add_child(h)

        dlg.add_child(dlg_layout)
        self.window.show_dialog(dlg)

    def _on_about_ok(self):
        self.window.close_dialog()

    def load(self, path):
        self._scene.scene.clear_geometry()

        geometry = None
        geometry_type = o3d.io.read_file_geometry_type(path)

        mesh = None
        if geometry_type & o3d.io.CONTAINS_TRIANGLES:
            mesh = o3d.io.read_triangle_model(path)
        if mesh is None:
            print("[Info]", path, "appears to be a point cloud")
            cloud = None
            try:
                cloud = o3d.io.read_point_cloud(path)
            except Exception:
                pass
            if cloud is not None:
                print("[Info] Successfully read", path)
                if not cloud.has_normals():
                    cloud.estimate_normals()
                cloud.normalize_normals()
                geometry = cloud
            else:
                print("[WARNING] Failed to read points", path)

        if geometry is not None or mesh is not None:
            try:
                if mesh is not None:
                    # Triangle model
                    self._scene.scene.add_model("__model__", mesh)
                else:
                    # Point cloud
                    self._scene.scene.add_geometry("__model__", geometry,
                                                   self.settings.material)
                bounds = self._scene.scene.bounding_box
                self._scene.setup_camera(60, bounds, bounds.get_center())
            except Exception as e:
                print(e)

    def export_image(self, path, width, height):

        def on_image(image):
            img = image

            quality = 9  # png
            if path.endswith(".jpg"):
                quality = 100
            o3d.io.write_image(path, img, quality)

        self._scene.scene.scene.render_to_image(on_image)

def main():
    # We need to initialize the application, which finds the necessary shaders
    # for rendering and prepares the cross-platform window abstraction.
    gui.Application.instance.initialize()

    w = AppWindow(1024, 768)

    if len(sys.argv) > 1:
        path = sys.argv[1]
        if os.path.exists(path):
            w.load(path)
        else:
            w.window.show_message_box("Error",
                                      "Could not open file '" + path + "'")

    # Run the event loop. This will not return until the last window is closed.
    gui.Application.instance.run()

if __name__ == "__main__":
    main()

Error message

No error message in my Anaconda Prompt window (this is a major part of the problem. I don't know why Open3d is crashing).

Expected behavior

I am expecting the Combobox elements to have slowdown but not to crash the whole application every time they do. This is understandable for the large point cloud example above because the app slows down to the point of not responding, but in my own version with smaller point clouds there's only a little slowdown and the app still crashes.

Open3D, Python and System information

Operating system: Windows 10 64-bit / Windows 11 64 bit (I've seen the crash on both)
Open3d Version: 0.17.0
System architecture: x64
Remote: no
Open3d installed with 'pip install open3d'

Additional information

No response

[Chuanlong-Zang]

I have the same issue (Combobox crash). The platform I'm using is Macbook M2 Pro. Installed open3d 0.16.1 using pip

[Timezyxdev]

Let me know if you find a good UI structure to use in place of dropdowns. I'll do the same. Might as well find a workaround until the bug itself is resolved.

[Timezyxdev]

Using gui.ListView() instead seems to be a decent workaround. It functions basically the same but I haven't experienced any crashes using it so far. For example you can replace something like:

self.profiles = gui.Combobox()
for name in sorted(Settings.LIGHTING_PROFILES.keys()):
   self.profiles.add_item(name)
self.profiles.add_item(Settings.CUSTOM_PROFILE_NAME)
self.profiles.set_on_selection_changed(self._on_lighting_profile)

with

self.profiles = gui.ListView()
list = []
for name in sorted(Settings.LIGHTING_PROFILES.keys()):
   list.append[name]
self.profiles.set_items(list)
self.profiles.set_on_selection_changed(self._on_lighting_profile)

You just have to change your function _on_lighting_profile to accomodate the fact that ListView passes the item name and whether it was a double click or not instead of the item name and index. Also useful is listview.set_max_visible_items() which lets you choose how many items the ListView shows before it adds a scrollbar. Otherwise it seems that the listview will just grow to accommodate all the items in the list.

[Timezyxdev]

The only issue I'm still having with this is that the default FileDialog menu includes two dropdown menus which can still cause my application to crash. Does anybody know how this default FileDialog menu could be edited to remove these elements? I know it removes some functionality for the user but I'd rather that then have the possibility of a sudden crash.

[Timezyxdev]

Alright, the solution for the above is to go to the file Open3D\cpp\open3d\visualization\gui\FileDialog.cpp and remove or comment out lines 238 and 258 which are the lines that add the Combo Boxes to the file dialog layout. Then you need to build from source to install your custom version of open3d, instructions for which can be found here