When a selection box is dragged, holding Ctrl while pressing the arrow
keys will shift the mosaics one sixel at a time.
If a shifting sixel encounters a non-mosaic cell it will pass through to
the other side of it.
For cut and copy sixels are converted to a monochrome image; unset sixels
are black and set sixels are white. Alphanumerics and control codes are
ignored. Held mosaics are not considered.
For paste a clipboard with only an image is converted to black and white
for unset and set sixels. This only works reliably with fully-black and
fully-white pixels.
When the clipboard has plain text data copied from a plain text or ASCII
text editor, pasting the text will perform word wrapping.
The text will originate from the cursor position and subsequent lines will
by default start from column 1 to provide room for alphanumeric colour
control codes in column 0.
If the cursor is at column 0 then all lines will start at column 0.
If a box selection is dragged before pasting the text will originate at
the top left of the selection box and be confined to the box. This can be
used if the second and subsequent lines need to start at a different
column, or if the pasted text must not overwrite an existing feature at
the right side of the page.
Note that cutting or copying text from within QTeletextMaker itself will
not be word wrapped on paste.
This does not word-wrap single lines of text at all, it assumes the
plain text is in a neat block with newlines at the end of each line.
We can't yet handle non-ASCII Unicode characters as that will need
further work on the keymapping tables.
