Merge branch '2023-10-12-expo-add-support-for-edting-lines-of-text'

To quote the author:
So far expo only supports menus. These are quite flexible for various
kinds of settings, but cannot deal with free-form input, such as a
serial number or a machine name.

This series adds support for a textline object, which is a single line
of text. It has a maximum length and its value is stored within the expo
structure.

U-Boot already has a command-line editor which provides most of the
features needed by expo. But the code runs in its own loop and only
returns when the line is finished. This is not suitable for expo, which
must handle a keypress at a time, returning to its caller after each
one.

In order to use the CLI code, some significant refactoring is included
here. This mostly involves moving the internal loop of the CLI to a
separate function and recording its state in a struct, just as was done
for single keypresses some time back. A minor addition is support for
Ctrl-W to delete a word, since strangely this is currently only present
in the simple version.

The video-console system provides most of the features needed by
testline, but a few things are missing. This series provides:

- primitive cursor support so the user can see where he is typing
- saving and restoring of the text-entry context, so that expo can allow
  the user to continue where he left off, including deleting previously
  entered characters correctly (for Truetype)
- obtaining the nominal width of a string of n characters, so that a
  suitable width can be chosen for the textline object

Note that no support is provided for clearing the cursor. This was
addressed in a previous series[1] which could perhaps be rebased. For
this implementation, the cursor is therefore not enabled for the normal
command line, only for expo.

Reading and writing textline objects is supported for FDT and
environment, but not for CMOS RAM, since it would likely use too much
RAM to store a string.

In terms of code size, the overall size increase is 180 bytes for
Thumb02 boards, 160 of whcih is the addition of Ctrl-W to delete a word.

[1] https://patchwork.ozlabs.org/project/uboot/list/?series=280178&state=*

2 files changed, 45 insertions, 6 deletions

diff --git a/doc/develop/cedit.rst b/doc/develop/cedit.rst
index 63dff9d3f14..82305b921f0 100644
--- a/doc/develop/cedit.rst
+++ b/doc/develop/cedit.rst
@@ -162,7 +162,8 @@ Cedit provides several options for persistent settings:
 - Writing an FDT file to a filesystem
 - Writing to U-Boot's environment variables, which are then typically stored in
   a persistent manner
-- Writing to CMOS RAM registers (common on x86 machines)
+- Writing to CMOS RAM registers (common on x86 machines). Note that textline
+  objects do not appear in CMOS RAM registers
 
 For now, reading and writing settings is not automatic. See the
 :doc:`../usage/cmd/cedit` for how to do this on the command line or in a
diff --git a/doc/develop/expo.rst b/doc/develop/expo.rst
index f13761995d3..c87b6ec8128 100644
--- a/doc/develop/expo.rst
+++ b/doc/develop/expo.rst
@@ -63,9 +63,12 @@ select the item), label and description. All three are shown in a single line
 within the menu. Items can also have a preview image, which is shown when the
 item is highlighted.
 
-All components have a name. This is purely for debugging, so it is easy to see
-what object is referred to. Of course the ID numbers can help as well, but they
-are less easy to distinguish.
+A `textline object` contains a label and an editable string.
+
+All components have a name. This is mostly for debugging, so it is easy to see
+what object is referred to, although the name is also used for saving values.
+Of course the ID numbers can help as well, but they are less easy to
+distinguish.
 
 While the expo implementation provides support for handling keypresses and
 rendering on the display or serial port, it does not actually deal with reading
@@ -136,7 +139,9 @@ this is to use `cli_ch_process()`, since it handles conversion of escape
 sequences into keys. However, expo has some special menu-key codes for
 navigating the interface. These are defined in `enum bootmenu_key` and include
 `BKEY_UP` for moving up and `BKEY_SELECT` for selecting an item. You can use
-`bootmenu_conv_key()` to convert an ASCII key into one of these.
+`bootmenu_conv_key()` to convert an ASCII key into one of these, but if it
+returns a value >= `BKEY_FIRST_EXTRA` then you should pass the unmodified ASCII
+key to the expo, since it may be used by textline objects.
 
 Once a keypress is decoded, call `expo_send_key()` to send it to the expo. This
 may cause an update to the expo state and may produce an action.
@@ -312,6 +317,9 @@ type
     "menu"
         Menu containing items which can be selected by the user
 
+    "textline"
+        A line of text which can be edited
+
 id
     type: u32, required
 
@@ -362,6 +370,26 @@ desc-label / desc-label-id
     Specifies the description for each item in the menu. These are currently
     only intended for use in simple mode.
 
+Textline nodes have the following additional properties:
+
+label / label-id
+    type: string / u32, required
+
+    Specifies the label of the textline. This is shown to the left of the area
+    for this textline.
+
+edit-id
+    type: u32, required
+
+    Specifies the ID of the of the editable text object. This can be used to
+    obtain the text from the textline
+
+max-chars:
+    type: u32, required
+
+    Specifies the maximum number of characters permitted to be in the textline.
+    The user will be prevented from adding more.
+
 
 Expo layout
 ~~~~~~~~~~~
@@ -401,6 +429,9 @@ strings are provided inline in the nodes where they are used.
         ID_AC_ON,
         ID_AC_MEMORY,
 
+        ID_MACHINE_NAME,
+        ID_MACHINE_NAME_EDIT,
+
         ID_DYNAMIC_START,
     */
 
@@ -447,6 +478,13 @@ strings are provided inline in the nodes where they are used.
 
                     item-id = <ID_AC_OFF ID_AC_ON ID_AC_MEMORY>;
                 };
+
+            machine-name {
+                id = <ID_MACHINE_NAME>;
+                type = "textline";
+                max-chars = <20>;
+                title = "Machine name";
+                edit-id = <ID_MACHINE_NAME_EDIT>;
             };
         };
 
@@ -474,7 +512,7 @@ Some ideas for future work:
 - Image formats other than BMP
 - Use of ANSI sequences to control a serial terminal
 - Colour selection
-- Support for more widgets, e.g. text, numeric, radio/option
+- Support for more widgets, e.g. numeric, radio/option
 - Mouse support
 - Integrate Nuklear, NxWidgets or some other library for a richer UI
 - Optimise rendering by only updating the display with changes since last render