gtk-render-insertion-cursor (context cr x y layout index direction)

context -- a gtk-style-context object
cr -- a cairo-t context
x -- a number, coerced to a double float, with the x origin
y -- a number, coerced to a double float, with the y origin
layout -- the pango-layout object of the text
index -- an integer with the index in the Pango layout
direction -- a value of the pango-direction enumeration

Draws a text caret on the Cairo context at the specified index of the Pango layout.