Modal is closed when doing an Alt-Tab to another window not in its hierarchy

[arnaud-neny]

Version/Branch of Dear ImGui:

Version: 1.89.5
Branch: docking

Back-end/Renderer/Compiler/OS

Back-ends: imgui_impl_win32.cpp + imgui_impl_dx12.cpp
Compiler: VS 2022
Operating System: Windows 10

My Issue/Question:

When having a popup modal opened in a separate window, and it has not having the focus, doing a alt-tab to another window not in its hierarchy is getting it closed.
(Open the demo, open a "Delete..." modal, make all windows popped out, click on the main window, Alt-Tab to "Dear ImGui Window", and the modal get closed).

[ocornut]

Seems like a regression caused by #6299 (comment)
Working on it!

[ocornut]

I have pushed a fix for this, it comes a series of commits, mainly 30eceaf, 01ca196, 4d42450, ending with d76699b d2291df .

There was a much needed refactor of whose responsibility it is to check for the presence of blocking modal before a focus change and this allowed me to start doing this refactor. I think there's more to do on that topic (other than your specific issue) but I will need to wait until we have a more serious battery of regression tests around this.

Specifically, my general plan is:

• The newly added ImGuiFocusRequestFlags_UnlessBelowModal flag should probably be made opposite to be opt-out instead of opt-in. But we'll need to double check and add regression tests for as many FocusWindow() calling paths as possible before.
• This should eventually be exposed into public facing API such as SetNextWindowFocus().