why text view can't mark block?

[mili <milimeter 163 com>]

Hello, every one

  I write a program to use a gtk_text_view. But I found that sometimes when I 
open chinput (chinese input method) window, then text view can't mark block, 
neither can with mouse or with hotkey "shift+arrow". Has anyone ever met such 
a circumstance? Can someone tell me how to solve it?

  Thanks,
  mili