It is often necessary to centre objects within the display area. Add a
special position value to indicate this.

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

Expo normally uses a pointer to show the current item. Add support for
highlighting as well, since this makes it easier for the user to see the
current item.

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

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>

Use the measurement info to write each line of text separately, thus
respecting word-wrapping and newlines.

Fix up the comment for scene_obj_render() while we are here.

Since a lineedit does not support alignment, add a special case to just
display the text if there is no measurement. This happens assuming the
lineedit is initially empty.

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

Add an early return if there is no string. Move all declarations to the
top of the function.

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

The code to render text is quite long, so put it in its own function.

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

In preparation for adding more text types, refactor the common fields
into a new structure. This will allow common code to be used.

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

Add a function to allow the size of an object to be set independently
of its position.

Also add a function to permit the object's bounding box to be set
independently of its dimensions.

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