Brief summary of issue / Description of requested feature:

When you try to select text in the text area while using wide character encoding (like Big5), the text selection/highlighting seems to treat wide characters as narrow characters.

For example, if a line contains 12 chinese characters, and you move your mouse to the beginning of the sentence and start click-and-dragging, you'll notice that the text highlighting move twice as far as your mouse movement, so you only need to move your mouse 6 characters to the right to select the entire sentence.

Steps to reproduce the issue / Reasons for adding feature:

1. Connect to a MUD with traditional chinese encoding (I use wfmud.org:7788)
2. Change character encoding to Big5.
3. Try to select any text in the welcome message to notice the behavior.

Error output / Expected result of feature

Text highlight should follow where the mouse is, just like in normal GUI.

Extra information, such as Mudlet version, operating system and ideas for how to solve / implement:

I think it's pretty clear that somewhere someone made an assumption about character width. If someone wants to give me some pointers I'm happy to investigate this myself.