It is useful to be able to edit text, e.g. to allow the user to edit the
environment or the command-line arguments for the OS.

Add the beginnings of an implementation. Future work is needed to finish
this: keypress handling and scrolling. For now it just displays the
text.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add support for left, right and centred alignment for text, in the
horizontal dimension.

Also support top, bottom and centred in the vertical dimension, for the
text object as a whole.

Alignment is not yet implemented for images. It has no meaning for
menus. A textline object uses a text object internally, so alignment
is supported there.

Provide some documentation to explain how objects are positioned.

Signed-off-by: Simon Glass <sjg@chromium.org>

It is useful to be able to draw a box around elements in the menu. Add
support for an unfilled box with a selectable thickness.

Note that there is no support for selecting the colour for any expo
objects yet.

Signed-off-by: Simon Glass <sjg@chromium.org>

At present menu items are stored according to their sequence number in
the menu. In some cases we may want to have holes in that sequence, or
not use a sequence at all.

Add a new 'value' property for menu items. This will be used for
reading and writing, if present. If there is no 'value' property, then
the normal sequence number will be used instead.

Signed-off-by: Simon Glass <sjg@chromium.org>

Set aside some expo IDs for 'save' and 'discard' buttons. This avoids
needing to store the IDs for these. Adjust the documentation and expo
tool for the new EXPOID_BASE_ID value.

Ignore these objects when saving and loading the cedit, since they do
not contain real data.

Adjust 'cedit run' to return failure when the user exits the expo
without saving. Update the test for this change as well.

Signed-off-by: Simon Glass <sjg@chromium.org>

At present a fixed position is used for menu items, 200 pixels to the
right of the left side of the labels. This means that a menu item with
a very long label may overlap the items.

It seems better to calculate the maximum label width and then place the
items to the right of all of them.

To implement this, add a new struct to containing arrangement
information. Calculate it before doing the actual arrangement. Add a
new style item which sets the amount of space from the right side of
the labels to left side of the items.

Signed-off-by: Simon Glass <sjg@chromium.org>

Update the expo documentation to include mention of this new object
type.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add mention of persistent settings in the documentation.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add a command to write cedit settings to CMOS RAM so that it can be
preserved across a reboot. This uses a simple bit-encoding, where each
field has a 'bit position' and a 'bit length' in the schema.

Signed-off-by: Simon Glass <sjg@chromium.org>

This is mentioned in passing in the 'cedit' command. Its file format is
described under `expo`. But it would be better if it had its own entry
in the documentation.

Add a new 'cedit' entry with a few details about this feature.

Signed-off-by: Simon Glass <sjg@chromium.org>