adjust the position of the input method window so that it follows the caret

lib/CMakeLists.txt

@@ -348,9 +348,10 @@ if (WIN32 AND NOT MSVC)
    target_link_libraries(elements PUBLIC ws2_32)
 endif()
 
-# Replace missing Shcore library removed by WIN32_LEAN_AND_MEAN
+# 1.Replace missing Shcore library removed by WIN32_LEAN_AND_MEAN
+# 2.IME requires Imm32
 if (WIN32)
-   target_link_libraries(elements PUBLIC Shcore)
+   target_link_libraries(elements PUBLIC Shcore Imm32)
 endif()
 
 add_library(cycfi::elements ALIAS elements)

lib/host/windows/key.cpp

@@ -72,7 +72,7 @@ namespace cycfi::elements
       {
          // IME notifies that keys have been filtered by setting the virtual
          // key-code to VK_PROCESSKEY
-         return key_code::unknown;
+         return key_code::ime_process_key;
       }
 
       unsigned int key = HIWORD(lparam) & 0x1FF;
@@ -206,5 +206,6 @@ namespace cycfi::elements
          case 0x037:  return key_code::kp_multiply;
          case 0x04a:  return key_code::kp_subtract;
       }
+      return key_code::unknown;
    }
 }

lib/include/elements/base_view.hpp

@@ -144,6 +144,9 @@ namespace cycfi::elements
 
    enum class key_code : int16_t
    {
+#ifdef WIN32
+      ime_process_key   = -2,
+#endif
       unknown           = -1,
 
       // Printable keys

lib/include/elements/element/text.hpp

@@ -156,6 +156,7 @@ namespace cycfi::elements
 
       char const*             caret_position(context const& ctx, point p);
       glyph_metrics           glyph_info(context const& ctx, char const* s);
+      bool                    get_caret_position(context const& ctx, rect& caret_bounds);
 
    private:
 

lib/src/element/text.cpp

@@ -335,6 +335,34 @@ namespace cycfi::elements
          )
          return false;
 
+#ifdef WIN32
+      if(k.key == key_code::ime_process_key) {
+         rect caret_bounds;
+         if(get_caret_position(ctx, caret_bounds)) {
+            if(HIMC imc = ImmGetContext(ctx.view.host())) {
+               const auto& tl = ctx.canvas.user_to_device(caret_bounds.top_left());
+               const auto& br = ctx.canvas.user_to_device(caret_bounds.bottom_right());
+
+               COMPOSITIONFORM cf;
+               memset(&cf, 0, sizeof(COMPOSITIONFORM));
+               cf.dwStyle = CFS_FORCE_POSITION;
+               cf.ptCurrentPos.x = tl.x + 1;
+               cf.ptCurrentPos.y = tl.y;
+               ImmSetCompositionWindow(imc, &cf);
+
+               CANDIDATEFORM candf;
+               memset(&candf, 0, sizeof(CANDIDATEFORM));
+               candf.dwIndex = 0;
+               candf.dwStyle = CFS_CANDIDATEPOS;
+               candf.ptCurrentPos.x = tl.x + 1;
+               candf.ptCurrentPos.y = br.y;
+               ImmSetCandidateWindow(imc, &candf);
+
+               return true;
+            }
+         }
+      }
+#endif
       _show_caret = true;
       bool move_caret = false;
       bool save_x = false;
@@ -586,6 +614,42 @@ namespace cycfi::elements
       return true;
    }
 
+   bool basic_text_box::get_caret_position(context const& ctx, rect& caret_bounds) {
+      // Make sure _this_handle is initialized to this
+      if (!_this_handle)
+         _this_handle = std::make_shared<basic_text_box*>(this);
+
+      if (!editable() || _select_start == -1)
+         return false;
+
+      if (!_is_focus) //No caret if not focused
+         return false;
+
+      auto const& theme = get_theme();
+      // Handle the case where text is empty
+      if (_text.empty())
+      {
+         auto  size = _layout.metrics();
+         auto  line_height = size.ascent + size.descent + size.leading;
+         auto  width = theme.text_box_caret_width;
+         auto  left = ctx.bounds.left;
+         auto  top = ctx.bounds.top;
+
+         caret_bounds = rect{left, top, left + width, top + line_height};
+         return true;
+      }
+      else if (_select_start == _select_end)
+      {
+         auto  start_info = glyph_info(ctx, _text.data() + _select_start);
+         auto width = theme.text_box_caret_width;
+         rect& caret = start_info.bounds;
+
+         caret_bounds = rect{caret.left - 0.5f, caret.top, caret.left + width + 0.5f, caret.bottom};
+         return true;
+      }
+      return false;
+   }
+
    void basic_text_box::draw_caret(context const& ctx)
    {
       // Make sure _this_handle is initialized to this