Add AddInputCharacterUTF16 for windows backend to handle WM_CHAR

imgui.cpp

@@ -1254,6 +1254,28 @@ void ImGuiIO::AddInputCharacter(ImWchar c)
     InputQueueCharacters.push_back(c);
 }
 
+// UTF16 string use Surrogate to encode unicode > 0x10000, so we should save the Surrogate.
+void ImGuiIO::AddInputCharacterUTF16(ImWchar c)
+{
+    if (c >= 0xD800 && c <= 0xDBFF)
+    {
+        Surrogate = c;
+    }
+    else
+    {
+        ImWchar cp = c;
+        if (c >= 0xDC00 && c <= 0xDFFF)
+        {
+            if (sizeof(ImWchar) == 2)
+                cp = 0xFFFD;
+            else
+                cp = ((ImWchar)(Surrogate - 0xD800) << 10) + (c - 0xDC00) + 0x10000;
+            Surrogate = 0;
+        }
+        InputQueueCharacters.push_back(cp);
+    }
+}
+
 void ImGuiIO::AddInputCharactersUTF8(const char* utf8_chars)
 {
     while (*utf8_chars != 0)

imgui.h

@@ -1403,6 +1403,7 @@ struct ImGuiIO
 
     // Functions
     IMGUI_API void  AddInputCharacter(ImWchar c);               // Queue new character input
+    IMGUI_API void  AddInputCharacterUTF16(ImWchar c);          // Queue new character input from an UTF-16 character, it can be a surrogate
     IMGUI_API void  AddInputCharactersUTF8(const char* str);    // Queue new characters input from an UTF-8 string
     IMGUI_API void  ClearInputCharacters();                     // Clear the text input buffer manually
 
@@ -1445,6 +1446,7 @@ struct ImGuiIO
     float       KeysDownDurationPrev[512];      // Previous duration the key has been down
     float       NavInputsDownDuration[ImGuiNavInput_COUNT];
     float       NavInputsDownDurationPrev[ImGuiNavInput_COUNT];
+    ImWchar     Surrogate;                      // For AddInputCharacterUTF16
     ImVector<ImWchar> InputQueueCharacters;     // Queue of _characters_ input (obtained by platform back-end). Fill using AddInputCharacter() helper.
 
     IMGUI_API   ImGuiIO();