Moves the given iter
backward by one display (wrapped) line.
A display line is different from a paragraph. Paragraphs are separated by newlines or other paragraph separator characters. Display lines are created by line-wrapping a paragraph. If wrapping is turned off, display lines and paragraphs will be the same. Display lines are divided differently for each view, since they depend on the view’s width; paragraphs are the same in all views, since they depend on the contents of the `GtkTextBuffer`.
this |
a `GtkTextView` |
iter |
a `GtkTextIter` |
true if |