Update IME ESC key handling

Author: SadPencil

src/TSMapEditor/UI/IME/IMEHandler.cs

@@ -79,28 +79,6 @@ protected virtual void OnIMETextInput(char character)
 
         LastActionIMEChatInput = true;
 
-        // Handle ESC. The IME reports ESC key as a text input.
-        if (character == 27)
-        {
-            LastActionIMEChatInput = false;
-            if (HandleEscapeKey())
-            {
-                // Do not return this ESC key back to the textbox if HandleEscapeKey returns true.
-                return;
-            }
-            else
-            {
-                // handleChatInput() method rejects the ESC message. Therefore, we need to manually clear the TextBox here.
-                if (IMEFocus != null)
-                {
-                    // TODO: wrap this logic as a new action in RegisterXNATextBox(). This requires an API breaking change on XNAUI, and therefore left as a TODO.
-                    IMEFocus.Text = string.Empty;
-                }
-
-                return;
-            }
-        }
-
         if (IMEFocus != null)
         {
             TextBoxHandleChatInputCallbacks.TryGetValue(IMEFocus, out var handleChatInput);
@@ -228,21 +206,17 @@ bool IIMEHandler.HandleEnterKey(XNATextBox sender)
         => false;
 
     bool IIMEHandler.HandleEscapeKey(XNATextBox sender)
-    {
-        return HandleEscapeKey();
-    }
-
-    private bool HandleEscapeKey()
     {
         //Debug.WriteLine($"IME: HandleEscapeKey: handled: {IMEEventReceived}");
 
-        // This method disables the ESC handling of the TextBox as long as the user has used IME.
-        // This is because IME users often use ESC to cancel composition, and even if currently the composition is empty,
+        // This method disables the ESC handling of the TextBox as long as the user has ever used IME.
+        // This is because IME users often use ESC to cancel composition. Even if currently the composition is empty,
         // the user still expects ESC to cancel composition rather than deleting the whole sentence.
         // For example, the user might mistakenly hit ESC key twice to cancel composition -- deleting the whole sentence is definitely a heavy punishment for such a small mistake.
 
-        // Note: "!string.IsNullOrEmpty(Composition) =>IMEEventReceived" should hold, but just in case
-        return IMEEventReceived || !string.IsNullOrEmpty(Composition);
+        // Note: "!CompositionEmpty => IMEEventReceived" should hold, but just in case
+
+        return IMEEventReceived || !CompositionEmpty;
     }
 
     void IIMEHandler.OnTextChanged(XNATextBox sender) { }