Fix IME input bug

[minicom365]

Fixes an issue where synchronization does not work properly when entering Korean or Chinese characters in the left or right text box.

[Before fixing]

[After fixing]

[fixing]

Here's where the problem starts:

1. input_method_from is defined as a value other than -1 and then left alone.
2. In the following function, input_method_used is defined as true.
   3-1. When a complete character is entered, Korean commitString is uniquely entered as a blank space. This makes the code flow as if a string was entered but not entered.
   3-2. Since input_method_used continues to be true, even if alphabets or numbers are entered, the previous commitString is repeated.

I think that fixing this issue will also solve the input issues like #76 #313 #647 #654.
I tried using the Pinyin QQ inputter to verify, but I couldn't implement the issue.

---

Additionally, when a character is not completed, drawing strokes or shadows does not work in real time. This is because Document.toPlainText() does not include preeditString . However, I do not know how to fix this cleanly.

[dmMaze]

Thanks for your effort.
I tried 10ef9fe, the synchronization failed when I typed full-width punctuations such as ，。——？……

[dmMaze]

Besides, what did you mean by Korean or Chinese characters ? I have no trouble with Chinese characters using the system input method.

[minicom365]

I thought the problem was solved because I didn't know how to use the IME for that language and couldn't implement it. I just restored that part.

[minicom365]

Besides, what did you mean by Korean or Chinese characters ? I have no trouble with Chinese characters using the system input method.

I installed the Pinyin QQ input tool and did a quick test, and there was no problem, so I mentioned Chinese as well. It was a mistake.

[minicom365]

1. Prevent the cursor from going out of range by modifying change_added = added - removed.
2. Update the from cursor only when preedit is in progress. However, since full-width characters are input without the preedit process, modify it to always update the from cursor.

I have confirmed that full-width characters can be input with this modification. However, I could not confirm —— and … … because I do not know how to input them with the keyboard.

[dmMaze]

I could not confirm —— and … …

Looks good to me. Thanks again!