Added: Support for showing the IME Candidate Window on Windows

include/SDL_hints.h

@@ -557,6 +557,15 @@ extern "C" {
  */
 #define SDL_HINT_IME_INTERNAL_EDITING "SDL_IME_INTERNAL_EDITING"
 
+/**
+ * \brief A variable to control whether certain IMEs should show native UI components (such as the Candidate List) instead of suppressing them.
+ *
+ * The variable can be set to the following values:
+ *   "0"       - Native UI components are not display. (default)
+ *   "1"       - Native UI components are displayed.
+ */
+#define SDL_HINT_IME_SHOW_UI "SDL_IME_SHOW_UI"
+
 /**
  * \brief  A variable controlling whether the home indicator bar on iPhone X
  *         should be hidden.

src/video/windows/SDL_windowskeyboard.c

@@ -23,6 +23,7 @@
 #if SDL_VIDEO_DRIVER_WINDOWS
 
 #include "SDL_windowsvideo.h"
+#include "SDL_hints.h"
 
 #include "../../events/SDL_keyboard_c.h"
 #include "../../events/scancodes_windows.h"
@@ -245,15 +246,23 @@ WIN_SetTextInputRect(_THIS, SDL_Rect *rect)
     himc = ImmGetContext(videodata->ime_hwnd_current);
     if (himc)
     {
-        COMPOSITIONFORM cf;
+        CANDIDATEFORM cf;
+        cf.dwIndex = 0;
+        cf.dwStyle = CFS_POINT;
         cf.ptCurrentPos.x = videodata->ime_rect.x;
         cf.ptCurrentPos.y = videodata->ime_rect.y;
-        cf.dwStyle = CFS_FORCE_POSITION;
-        ImmSetCompositionWindow(himc, &cf);
+
+        ImmSetCandidateWindow(himc, &cf);
         ImmReleaseContext(videodata->ime_hwnd_current, himc);
     }
 }
 
+static SDL_bool
+WIN_ShouldShowNativeUI()
+{
+    return SDL_GetHintBoolean(SDL_HINT_IME_SHOW_UI, SDL_FALSE);
+}
+
 #ifdef SDL_DISABLE_WINDOWS_IME
 
 
@@ -371,7 +380,10 @@ IME_Init(SDL_VideoData *videodata, HWND hwnd)
     videodata->ime_available = SDL_TRUE;
     IME_UpdateInputLocale(videodata);
     IME_SetupAPI(videodata);
-    videodata->ime_uiless = UILess_SetupSinks(videodata);
+    if (WIN_ShouldShowNativeUI())
+        videodata->ime_uiless = SDL_FALSE;
+    else
+        videodata->ime_uiless = UILess_SetupSinks(videodata);
     IME_UpdateInputLocale(videodata);
     IME_Disable(videodata, hwnd);
 }