Add IME support (#991)

src/api/system.c

@@ -249,6 +249,23 @@ top:
       lua_pushstring(L, e.text.text);
       return 2;
 
+    case SDL_TEXTEDITING:
+      lua_pushstring(L, "textediting");
+      lua_pushstring(L, e.edit.text);
+      lua_pushinteger(L, e.edit.start);
+      lua_pushinteger(L, e.edit.length);
+      return 4;
+
+#if SDL_VERSION_ATLEAST(2, 0, 22)
+    case SDL_TEXTEDITING_EXT:
+      lua_pushstring(L, "textediting");
+      lua_pushstring(L, e.editExt.text);
+      lua_pushinteger(L, e.editExt.start);
+      lua_pushinteger(L, e.editExt.length);
+      SDL_free(e.editExt.text);
+      return 4;
+#endif
+
     case SDL_MOUSEBUTTONDOWN:
       if (e.button.button == 1) { SDL_CaptureMouse(1); }
       lua_pushstring(L, "mousepressed");
@@ -425,6 +442,23 @@ static int f_get_window_mode(lua_State *L) {
   return 1;
 }
 
+static int f_set_text_input_rect(lua_State *L) {
+  SDL_Rect rect;
+  rect.x = luaL_checknumber(L, 1);
+  rect.y = luaL_checknumber(L, 2);
+  rect.w = luaL_checknumber(L, 3);
+  rect.h = luaL_checknumber(L, 4);
+  SDL_SetTextInputRect(&rect);
+  return 0;
+}
+
+static int f_clear_ime(lua_State *L) {
+#if SDL_VERSION_ATLEAST(2, 0, 22)
+  SDL_ClearComposition();
+#endif
+  return 0;
+}
+
 
 static int f_raise_window(lua_State *L) {
   /*
@@ -986,6 +1020,8 @@ static const luaL_Reg lib[] = {
   { "set_window_hit_test", f_set_window_hit_test },
   { "get_window_size",     f_get_window_size     },
   { "set_window_size",     f_set_window_size     },
+  { "set_text_input_rect", f_set_text_input_rect },
+  { "clear_ime",           f_clear_ime           },
   { "window_has_focus",    f_window_has_focus    },
   { "raise_window",        f_raise_window        },
   { "show_fatal_error",    f_show_fatal_error    },

src/main.c

@@ -133,6 +133,12 @@ int main(int argc, char **argv) {
 #if SDL_VERSION_ATLEAST(2, 0, 5)
   SDL_SetHint(SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH, "1");
 #endif
+#if SDL_VERSION_ATLEAST(2, 0, 18)
+  SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");
+#endif
+#if SDL_VERSION_ATLEAST(2, 0, 22)
+  SDL_SetHint(SDL_HINT_IME_SUPPORT_EXTENDED_TEXT, "1");
+#endif
 
 #if SDL_VERSION_ATLEAST(2, 0, 8)
   /* This hint tells SDL to respect borderless window as a normal window.