Popups opened from another popup are immediately closed since 1.89.5

[cfillion]

Version/Branch of Dear ImGui:

Version: 1.89.5 and 54c1ac3, OK in 1.89.4
Branch: docking

Back-end/Renderer/OS

Observed on:

• macOS in example_apple_metal
• macOS in example_sdl2_opengl3
• macOS, Linux and Windows in custom backends

Not happening on:

• macOS in example_glfw_opengl3
• Windows in example_win32_directx10 (EDIT: unless disabling handling of ImGuiViewportFlags_NoFocusOnClick)

My Issue/Question:

When opening a second popup while another popup that has its own viewport is open, the new popup is closed before the user can interact with it.

There was a similar regression with modal popups however that has already been fixed in #6357. A similar issue remains for non-modal popups in some backends. I haven't found what other backends do differently focus-related to work properly.

It seems that (as expected) the OS gives focus back to the underlying window ('test') when the platform window of the first popup is destroyed and that triggers this line before the platform window of the second popup is created and shown:

imgui/imgui.cpp

Line 14022 in 2e810d5

FocusWindow(focused_viewport->Window, focus_request_flags);

[148347] [focus] SetNavWindow("test")
[148352] [popup] OpenPopup("first" -> 0xCA2DB483)
[148352] [popup] OpenPopupEx(0xCA2DB483)
[148353] [viewport] Add Viewport F94658BA '##Popup_ca2db483'
[148353] [focus] SetNavWindow("##Popup_ca2db483")
[148354] [viewport] Create Platform Window F94658BA '##Popup_ca2db483'
[148404] [popup] CloseCurrentPopup 0 -> 0
[148404] [popup] ClosePopupToLevel(0), restore_focus_to_window_under_popup=1
[148404] [focus] SetNavWindow("test")
[148404] [popup] OpenPopup("second" -> 0x37F95BFE)
[148404] [popup] OpenPopupEx(0x37F95BFE)
[148405] [viewport] Add Viewport 2322D768 '##Popup_37f95bfe'
[148405] [focus] SetNavWindow("##Popup_37f95bfe")
* Platform_DestroyWindow for "##Popup_ca2db483" (first) is called here *
[148406] [focus] SetNavWindow("test")
[148406] [popup] ClosePopupsOverWindow("test")
[148406] [popup] ClosePopupToLevel(0), restore_focus_to_window_under_popup=0
[148407] [viewport] Delete Viewport F94658BA '##Popup_ca2db483'
[148408] [viewport] Delete Viewport 2322D768 '##Popup_37f95bfe'

Screenshots/Video

Standalone, minimal, complete and verifiable example:

if(ImGui::Begin("test")) {
  if(ImGui::BeginPopup("second")) {
    ImGui::Text("success!");
    ImGui::EndPopup();
  }

  bool open_edit_popup { false };
  if(ImGui::BeginPopup("first")) {
    if(ImGui::Button("open second"))
      open_edit_popup = true;
    ImGui::EndPopup();
  }
  if(open_edit_popup)
    ImGui::OpenPopup("second");

  if(ImGui::Button("open first"))
    ImGui::OpenPopup("first");
}
ImGui::End();

[cfillion]

I found the difference between my Windows backend and imgui_impl_win32.cpp: mine wasn't handling ImGuiViewportFlags_NoFocusOnClick. (Somehow with imgui_impl_glfw.cpp on macOS GetWindowFocus for 'test' still returns false after the platform window for the first popup is destroyed so the bug doesn't trigger there.)

Issue can be duplicated with imgui_impl_win32.cpp after commenting out its handling of ImGuiViewportFlags_NoFocusOnClick.

Preventing focus isn't reliable everywhere (could be focused externally, on X11 it's only a hint to the window manager, plus I'm dealing with a parent application whose UI toolkit forces focus on click on Linux).

[ocornut]

Thank you for the investigation and repro and report. Will be looking at this now.

[ocornut]

Here is a slightly different repro which showcase how it isn't specifically a ImGuiViewportFlags_NoFocusOnClick issue. Here the first popup is replaced by a regular movable window.

The issue happens when the first window (or popup in your version) is destroyed, giving platform focus back to main viewport before the new one has a chance to appear. In my version the bug happens even if the backend handles ImGuiViewportFlags_NoFocusOnClick.

Preventing focus isn't reliable everywhere (could be focused externally

If popup B is opened over window A, focusing window A would normally close the popup.
This is essentially what we are doing.

While I think this one specific issue probably has a specific resolution, which I am looking for, we could potentially decide to make imgui-focus-on-platform-focus an operation with less side-effects by deciding to not close popups, which would be a non-confident way of reducing the scope of work done since #6299. Not entirely opposed to it as it seems like this is can of worm.

I'm certainly glad we now have this Debug Log to help. I started adding some basic platform-focus-emulation in tests for viewports (see "viewport_platform_focus" in test suite https://github.com/ocornut/imgui_test_engine/blob/main/imgui_test_suite/imgui_tests_viewports.cpp#L170) recently so the least I can do here would be to try emulating this issue in a platform agnostic way.

if (ImGui::Begin("test"))
{
    static bool open_window_1 = false;

    if (ImGui::BeginPopup("second"))
    {
        ImGui::Text("success!");
        ImGui::EndPopup();
    }

    bool open_edit_popup = false;
    if (open_window_1 && ImGui::Begin("First"))
    {
        if (ImGui::Button("open second"))
        {
            open_edit_popup = true;
            open_window_1 = false;
        }
        ImGui::End();
    }
    if (open_edit_popup)
        ImGui::OpenPopup("second");

    if (ImGui::Button("open first"))
        open_window_1 = true;
}
ImGui::End();

[ocornut]

Hello,

I have pushed 3418d50 which I think should fix this problem, as well as a test for it.
As the whole setup is rather complicated could you give it a short with your setup/backend ?

Thanks!

[cfillion]

Thank you! Fix works perfectly. I've tested with example_apple_metal & example_sdl2_opengl3 on macOS and my backend on all platforms (macOS/Linux/Windows/wine).

If popup B is opened over window A, focusing window A would normally close the popup. This is essentially what we are doing.

[...] we could potentially decide to make imgui-focus-on-platform-focus an operation with less side-effects by deciding to not close popups,

I like that popup-closing behavior, it behaves like native widget toolkits. My backend builds upon that by clearing ImGui focus when a non-imgui (or different context's) window gains it. Popups are closed, active item cleared (like #6467) and titlebar visibly unfocused.

void onFocusLossAllImGuiPlatformWindowsInContext()
{
  if(ImGui::GetTopMostPopupModal())
    ImGui::ClearActiveID();
  else
    ImGui::FocusWindow(nullptr);
}

Usecase 1: imgui popup auto-closing when focusing anything else in or outside the application:

Usecase 2: imgui window losing focus and clearing active item to mimick a native window: