GtkPreview::draw_row
void draw_row(string data, int start, int row, int pixels);
Replaces pixels pixels of data on row
row of the preview starting at
start with data.
If the preview is of type GTK_PREVIEW_GREYSCALE,
data must be pixels bytes
of data. If the preview is of type GTK_PREVIEW_COLOR,
data must be 3*pixels
bytes of data.
