The IBus platform input context does not support surrounding text yet

Surrounding text is a feature that allows input methods to query the text and cursor position in the current text input field and also to delete part of that surrounding text.

IBus docs: http://ibus.googlecode.com/svn/docs/ibus-1.5/IBusInputContext.html#IBusInputContext-delete-surrounding-text

We can delete surrounding text by using QInputMethodEvent::commitString() with an empty string and non-zero replaceLength. On the other hand, getting surrounding text can be done with a QWidget::inputMethodQuery(Qt::ImSurroundingText).