Within tests it is useful to be able to control rendering of the expo.
Drop the automatic call to expo_render() within expo_poll() and adjust
its callers to handle this instead.

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

If the user does not quickly provide some input, exit so that other
things can be done, such as searching for the next OS.

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

Allow this setting to be controlled from the theme.

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

In some cases dynamic text is needed, e.g. for a menu countdown. Add a
function which handles this, allowing the caller to take control of the
text that is shown on each render.

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

It is more convenient to put strings in an abuf so they can easily be
resized. Adjust the struct accordingly.

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

Both bootflow_menu and cedit use similar logic to poll an expo. Move
this into the expo library so the code can be shared.

Update bootflow_menu_run() to return -EPIPE when the user quits without
choosing anything, since -EAGAIN is ambiguous and elsewhere means that
there is no input yet.

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

An expo generally needs to keep track of the keyboard state while it is
running, so move the context into struct expo

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

The CONFIG_WHITE_ON_BLACK setting is hard-coded at build-time. It is
useful to be able to control this when showing menus.

Create a property to hold this information, using the CONFIG as the
initial value.

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>

If expo_set_dynamic_start() is never called, the first scene created
will have an ID of 0, which is invalid. Correct this by setting a
default value.

Add a test to check this.

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