How to set up pop-ups with main_menu_bar

[botkero]

Hi,

Firstly, thanks for the awesome python-binding. I'm just struggling heavily getting things to work, but mostly because of the immediate model paradigm.

---

This is my current code:

from imgui_bundle import imgui, immapp, hello_imgui
from imgui_bundle import ImVec2


class Menu:
    def __init__(self) -> None:
        self.themes = [
            "imgui_colors_classic",
            "imgui_colors_dark",
            "imgui_colors_light",
        ]
        self.selected_theme = 0

    def draw_menu(self):
        self.style = imgui.get_style()

        if imgui.begin_menu("Launch"):
            imgui.separator_text("Tools")
            if imgui.menu_item("App A", "CTRL+A", False)[0]:
                pass

            if imgui.menu_item("App B", "", False)[0]:
                pass

            if imgui.menu_item("App C", "", False)[0]:
                pass

            imgui.end_menu()

        if imgui.begin_menu("Settings"):
            if imgui.begin_menu("Scaling"):
                changed, new_value = imgui.slider_float("FontScaleDpi", self.style.font_scale_dpi, 0.5, 3.0, "%.1f")  
                if changed:
                    self.style.font_scale_dpi = new_value
                imgui.end_menu()

            if imgui.begin_menu("Theme"):
                changed, self.selected_theme = imgui.combo("Select Theme", self.selected_theme, self.themes)
                if changed:
                    hello_imgui.apply_theme(hello_imgui.ImGuiTheme_(self.selected_theme))
                imgui.end_menu()
            imgui.end_menu()

            # if imgui.begin_menu("Help"):

            #     # Doesn't work
            #     if imgui.menu_item("Test", "", False)[0]:
            #         imgui.open_popup("testing")

            #     imgui.end_menu()


def main() -> None:
    class App:
        def __init__(self) -> None:
            self.menu = Menu()

        def mainloop(self):
            if imgui.begin_main_menu_bar():
                self.menu.draw_menu()

                if imgui.begin_menu("Help"):

                    # Doesn't work
                    if imgui.menu_item("Test", "", False)[0]:
                        imgui.open_popup("testing")

                    imgui.end_menu()
                imgui.end_main_menu_bar()


            # Works
            if imgui.button("Make Popup"):
                imgui.open_popup("testing")


            center = imgui.get_main_viewport().get_center()
            imgui.set_next_window_pos(center, imgui.Cond_.appearing, ImVec2(0.5, 0.5))


            if imgui.begin_popup_modal("testing", None, imgui.WindowFlags_.always_auto_resize)[0]:
                imgui.text("All those beautiful files will be deleted.\nThis operation cannot be undone!")
                imgui.separator()


                if imgui.button("OK", ImVec2(120, 0)):
                    imgui.close_current_popup()
                imgui.set_item_default_focus()
                imgui.same_line()
                if imgui.button("Cancel", ImVec2(120, 0)):
                    imgui.close_current_popup()
                imgui.end_popup()


    app = App()
    immapp.run(gui_function=app.mainloop)

if __name__ == "__main__":
    main()

I have kind of two issues:

• from the menu_bar the pop-up doesn't appear
• new widgets are drawn behind the menu_bar

There are also many different way of handling the menu_bar.

1. begin_main_menu_bar
2. begin_menu_bar + WindowFlags
3. hello_imgui and WindowParams (show_menu_bar)

I am uncertain as to which approach is the most suitable or which serves a specific purpose.

Edit: Also the changing the font_scale_dpi results in messy behaviour. So I feel like I'm doing it wrong.

[pthom]

Hi,

By default, the background window does not provide a menu bar.
To add it, replace this call:

    app = App()
    immapp.run(gui_function=app.mainloop)

By the longer version where you specify full runner params:

    app = App()
    #immapp.run(gui_function=app.mainloop)

    runner_params = hello_imgui.RunnerParams()
    runner_params.callbacks.show_gui = app.mainloop

    runner_params.imgui_window_params.show_menu_bar = True   # Show a menu bar
    runner_params.imgui_window_params.show_menu_app = False  # But remove the default menu provided by hello_imgui
    runner_params.imgui_window_params.show_menu_view = False

    immapp.run(runner_params)

[botkero]

Hmm, thanks for the quick response.

---

Sadly, even with the longer version with runner params I don't get a popup.

I also tried with imgui.begin("Test", flags=imgui.WindowFlags_.menu_bar) and removed begin_main_menu_bar. (ofc this isn't directly what I want). But I thought this would at kind of be a minimal setup that should work.

        def mainloop(self):
            imgui.begin("Test", flags=imgui.WindowFlags_.menu_bar)

            if imgui.begin_menu_bar():
                self.menu.draw_menu()

                if imgui.begin_menu("Help"):

                    # Doesn't work
                    if imgui.menu_item("Test", "", False)[0]:
                        imgui.open_popup("testing")

                    imgui.end_menu()


                if imgui.begin_popup_modal("testing", None, imgui.WindowFlags_.always_auto_resize)[0]:
                    imgui.text("All those beautiful files will be deleted.\nThis operation cannot be undone!")
                    if imgui.button("Cancel", ImVec2(120, 0)):
                        imgui.close_current_popup()

                    imgui.end_popup()
                imgui.end_menu_bar()


            # Works
            if imgui.button("Make Popup"):
                imgui.open_popup("testing")

            if imgui.begin_popup_modal("testing", None, imgui.WindowFlags_.always_auto_resize)[0]:
                imgui.text("All those beautiful files will be deleted.\nThis operation cannot be undone!")
                if imgui.button("Cancel", ImVec2(120, 0)):
                        imgui.close_current_popup()
                imgui.end_popup()

            imgui.end()

So I feel like I'm doing something fundamentally wrong. 😅

[pthom]

changing the font_scale_dpi results in messy behaviour.

Yes, with your slider the user is interacting with a slider whose size and position varies depending on the scale it sets!

Solution: place it at a know location + know size. For example this would work (but is not very user friendly):

        if imgui.begin_menu("Launch"):
            # place the slider in the left menu (known position), not in a submenu (position would vary), with a fixed size
            imgui.set_next_item_width(100)
            changed, new_value = imgui.slider_float("FontScaleDpi", self.style.font_scale_dpi, 0.5, 3.0, "%.1f")
            if changed:
                self.style.font_scale_dpi = new_value

[pthom]

Sadly, even with the longer version with runner params I don't get a popup.

You are hitting a small gotcha with popups in ImGui: "Popup identifiers are relative to the current ID stack, so OpenPopup and BeginPopup generally needs to be at the same level of the stack.".

It will get easier after these initial bumps, I'm certain of it :-)

open_popup("testing") keys the popup by GetID("testing") computed against the current ID stack. begin_menu("Help") pushes its own ID onto that stack, so the popup opened is registered under ID = hash("Help" + "testing").

Then begin_popup_modal("testing", ...) runs at the top‑level scope (the menu bar/menu has already ended), so it looks for ID = hash("testing"). This is a different ID, so the popup does not show.

With the button, both open_popup and begin_popup_modal run in the same scope, so the IDs match and it works.

Two standard fixes:

1. Defer the open to after end_main_menu_bar() (most common pattern):

  open_test_popup = False
  if imgui.begin_main_menu_bar():
      ...
      if imgui.begin_menu("Help"):
          if imgui.menu_item("Test", "", False)[0]:
              open_test_popup = True 
          imgui.end_menu()
      imgui.end_main_menu_bar()
      
  if open_test_popup:
      imgui.open_popup("testing")

2. Use push_id/pop_id so the IDs line up, but option 1 is what Dear ImGui's own FAQ recommends because it also sidesteps the related "popup gets immediately closed because a menu is still open" issue.