From c535968128f929e73182c72f52ac1d44879e1aea Mon Sep 17 00:00:00 2001
From: Kotomine Shiki <126475460+Touma-Kazusa2@users.noreply.github.com>
Date: Sun, 1 Mar 2026 21:08:45 +0800
Subject: [PATCH] win32: fix ime setcontext lparam

Fixes #3893.
---
 winit-win32/src/event_loop.rs     | 6 +++---
 winit/src/changelog/unreleased.md | 1 +
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/winit-win32/src/event_loop.rs b/winit-win32/src/event_loop.rs
index 925f01f56..8f1008f98 100644
--- a/winit-win32/src/event_loop.rs
+++ b/winit-win32/src/event_loop.rs
@@ -1503,9 +1503,9 @@ unsafe fn public_window_callback_inner(
         },
 
         WM_IME_SETCONTEXT => {
-            // Hide composing text drawn by IME.
-            let wparam = wparam & (!ISC_SHOWUICOMPOSITIONWINDOW as usize);
-            result = ProcResult::DefWindowProc(wparam);
+            // IME UI visibility flags are in lparam.
+            let lparam = lparam & !(ISC_SHOWUICOMPOSITIONWINDOW as isize);
+            result = ProcResult::Value(unsafe { DefWindowProcW(window, msg, wparam, lparam) });
         },
 
         // this is necessary for us to maintain minimize/restore state
diff --git a/winit/src/changelog/unreleased.md b/winit/src/changelog/unreleased.md
index ceab7e091..1a4158644 100644
--- a/winit/src/changelog/unreleased.md
+++ b/winit/src/changelog/unreleased.md
@@ -55,5 +55,6 @@ changelog entry.
 - On Redox, handle `EINTR` when reading from `event_socket` instead of panicking.
 - On Wayland, switch from using the `ahash` hashing algorithm to `foldhash`.
 - On macOS, fix borderless game presentation options not sticking after switching spaces.
+- On Windows, fix `WM_IME_SETCONTEXT` IME UI flag masking on `lParam`.
 - On macOS, fix crash in `set_marked_text` when native Pinyin IME sends out-of-bounds `selected_range`.
 - On X11, fix debug mode overflow panic in `set_timestamp`.