How to hide the OS rendered IME window in TSF(not IMM32) for games running with exclusive fullscreen mode?

Ryan Cheung 1

For any games(like World of Warcraft Classic) running with exclusive fullscreen mode, the IME Candidate List window has to be renderer by the game manually. To interact with IME in Windows, Windows provide two framework, IMM32 and TSF. IMM32 is for Windows 7 and older. TSF is for Windows 8+.

According to the doc of IMM32(link), we can hide the os ime window like this:

The IMM sends a WM_IME_SETCONTEXT message when a window of the application is activated. The lParam parameter of this message contains a flag that indicates to the IME which windows should get drawn and which should not. Because the application is handling all of the drawing, it does not need the IME to draw any of the IME windows. Therefore, the application's message handler simply sets lParam to 0 and returns.

But for TSF(msctf.dll), how do I hide the os renderer IME window? I can't find any workable ways to do that in ITfContext and its related interface

Rita Han - MSFT 2,161 Reputation points

2020-08-03T03:32:40.517+00:00

Welcome to Microsoft Q&A! I have installed TSF and my Windows version is 1909. Setting lParam to 0 and returns to response to WM_IME_SETCONTEXT doesn't prevent IME Candidate List window from appearing for me. What's your Windows version? And does this issue happen only when your game app in exclusive fullscreen mode?
Ryan Cheung 1 Reputation point

2020-08-03T05:09:26.597+00:00

"Setting lParam to 0 and returns to response to WM_IME_SETCONTEXT doesn't prevent IME Candidate List window from appearing for me."
This only works when the active IME is IMM32-based, because WM_IME_SETCONTEXT is IMM32(imm32.dll) API, not the API in TSF(msctf.dll). And I can confirm this works for IMM32 IMEs. This code shows how it works.

But here I'm asking is HOW can I hide os rendered IME Candidate List window in TSF. TSF is different IME framework than IMM32.

My Windows version installed is Win10 2004.
Ryan Cheung 1 Reputation point

2020-08-03T10:09:20.94+00:00

BTW, "Setting lParam to 0 and returns to response to WM_IME_SETCONTEXT prevent IME Candidate List window from appearing" works fine in Windows 1909, but has bug in Windows 2004, it will apeare the first time of starting composition, and then stuck there with no nay other changes in next text compositions. This should be a bug of IMM32 in Windows 2004.
Rita Han - MSFT 2,161 Reputation points

2020-08-04T01:44:25.15+00:00

I create a simple Win32 desktop application with an edit control. Code like this:
case WM_IME_SETCONTEXT:
{
lParam = 0;
return DefWindowProc(hWnd, message, wParam, lParam);
}
It doesn't work for me on 1909 (build 18363.836). When I typing in the edit control the candidates window always opens. Is there anything I missed?
Ryan Cheung 1 Reputation point

2020-08-04T11:51:52.107+00:00

It may have two reasons: One is 1909 (build 18363.836) may have bugs here; Another is you have to use a IMM32-based IME, since WM_IME_SETCONTEXT is a IMM32 API.
You should try with an IMM32-based IME instead of the OS provided IME.
Fei Xue - MSFT 1,111 Reputation points

2020-08-07T07:31:25.497+00:00

@Ryan Cheung To create UILessMode, we need to making ui-less thread when we active it, here is an helpful document describing the flow and details for your reference:
https://video2.skills-academy.com/en-us/windows/win32/tsf/uiless-mode-overview

However, there is something inaccurate. I am trying to confirm with my college. And any update will keep post here.
Ryan Cheung 1 Reputation point

2020-08-07T09:42:27.427+00:00

Thanks, there is actually a doc link about UI less mode of TSF. And I tried with interface ITfUIElementSink to hide OS rendered Candidate List and found it works.
But there're some bugs when using UILess model in TSF:
When UIless model enable in TSF, candidate changing event IMM.ImnChangeCandidate starts to propagate (no this event in non-UILess-mode), but it has bug, the event just propagate sometime, but not all the time as it should.
Fei Xue - MSFT 1,111 Reputation points

2020-08-14T00:33:27.647+00:00

@Ryan Cheung , Thanks for this detailed info. The IMM32 still works on windows 10. Actually the TSF API and interfaces which are related to IME internally call. Does IMM32 works for you? Or would you mind sharing if there is any requirement that you want to use TSF?

And for the potential issue in the TSF, would mind sharing a mini code sample and reproduce steps to help us identify this issue?
Fei Xue - MSFT 1,111 Reputation points

2020-08-17T23:27:27.843+00:00

@Ryan Cheung , Is the issue fixed now? If not, feel free let me know. And please share a mini code sample so that we can investigate this issue and fix it as soon as possible.
Ryan Cheung 1 Reputation point

2020-09-10T23:50:59.533+00:00

Sorry for the late reply, I'd been leaving for creating a C# library that support both TSF and IMM32 for days. Here is the library: https://github.com/ryancheung/ImeSharp

After all the testing when creating the library. I found TSF has no issue it wokrs very well. But I found IMM32 has issue with Microsfot PinYin in Windows 10. If you only enables IMM32 and disables TSF, like https://github.com/ryancheung/ImeSharp#test-imm32-implementation-only , you only get IMM.ImnChangeCandidate sometimes, but not all the time. You can test it yourself.

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How to hide the OS rendered IME window in TSF(not IMM32) for games running with exclusive fullscreen mode?