a magical problem about ImGui_ImplWin32_EnableAlphaCompositing api

[iKunCai]

Version/Branch of Dear ImGui:

Branch master 1.90.9

Back-ends:

imgui_impl_dx9.cpp + imgui_impl_win32.cpp

Compiler, OS:

Windows 11 +MSVC 2022

Full config/build information:

No response

Details:

**My Issue/Question: i used intel 13980hx + 4090 laptop gpu and use ImGui_ImplWin32_EnableAlphaCompositing

I write an app use topmost and will be moving window overlay on the game. like cs2. However, i found a little strange..

when i use mix gpu mode(intel igpu +4090 both work) run game in 4090,the imgui will be 100% transparent.which means,i can't see imgui . if this game/or any app run in igpu(i guess) i can see imgui that is not transparent.

if i did not use ImGui_ImplWin32_EnableAlphaCompositing. i can see imgui normally.

and also, i don't use mix gpu mode.(which means i only use 4090 gpu) ImGui_ImplWin32_EnableAlphaCompositing or not. work everything fines...

it is nvidia bug? or windows?

Screenshots/Video:

Minimal, Complete and Verifiable Example code:

// Here's some code anyone can copy and paste to reproduce your issue
ImGui::Begin("Example Bug");
MoreCodeToExplainMyIssue();
ImGui::End();

[iKunCai]

//it's use ImGui_ImplWin32_EnableAlphaCompositing

3d93924175f533b6f827addbf618bbdd.mp4

i don't know why video can not play..

[iKunCai]

//it's NOT use ImGui_ImplWin32_EnableAlphaCompositing

fc01aefce2a4dbb3dc22bebfb6e8b8e7.mp4

[ocornut]

Sorry but #1586