The image will be counted as one character in character counts,
and when obtaining the buffer contents as a string, will be
represented by the Unicode “object replacement character” 0xFFFC.
Note that the “slice” variants for obtaining portions of the buffer
as a string include this character for paintable, but the “text”
variants do not. e.g. see [method@Gtk.TextBuffer.get_slice] and
[method@Gtk.TextBuffer.get_text].
Inserts an image into the text buffer at @iter.
The image will be counted as one character in character counts, and when obtaining the buffer contents as a string, will be represented by the Unicode “object replacement character” 0xFFFC. Note that the “slice” variants for obtaining portions of the buffer as a string include this character for paintable, but the “text” variants do not. e.g. see [method@Gtk.TextBuffer.get_slice] and [method@Gtk.TextBuffer.get_text].