Expo menu

U-Boot provides a menu implementation for use with selecting bootflows and changing U-Boot settings. This is in early stages of development.

Motivation

U-Boot already has a text-based menu system accessed via the bootmenu command. This works using environment variables, or via some EFI-specific hacks.

The command makes use of a lower-level menu implementation, which is quite flexible and can be used to make menu hierarchies.

However this system is not flexible enough for use with standard boot. It does not support a graphical user interface and cannot currently support anything more than a very simple list of items. While it does support multiple menus in hierarchies, these are implemented by the caller. See for example eficonfig.c.

Another challenge with the current menu implementation is that it controls the event loop, such that bootmenu_loop() does not return until a key is pressed. This makes it difficult to implement dynamic displays or to do other things while the menu is running, such as searching for more bootflows.

For these reasons an attempt has been made to develop a more flexible system which can handle menus as well as other elements. This is called ‘expo’, short for exposition, in an attempt to avoid common words like display, screen, menu and the like. The primary goal is to support Verified Boot for Embedded (VBE), although it is available to any boot method, using the ‘bootflow menu’ command.

Efforts have been made to use common code with the existing menu, including key processing in particular.

Previous work looked at integrating Nuklear into U-Boot. This works fine and could provide a way to provide a more flexible UI, perhaps with expo dealing with the interface to Nuklear. But this is quite a big step and it may be years before this becomes desirable, if at all. For now, U-Boot only needs a fairly simple set of menus and options, so rendering them directly is fairly straightforward.

Concepts

The creator of the expo is here called a controller and it controls most aspects of the expo. This is the code that you must write to use expo.

An expo is a set of scenes which can be presented to the user one at a time, to show information and obtain input from the user.

A scene is a collection of objects which are displayed together on the screen. Only one scene is visible at a time and scenes do not share objects.

A scene object is something that appears in the scene, such as some text, an image or a menu. Objects can be positioned and hidden.

A menu object contains a title, a set of menu items and a pointer to the current item. Menu items consist of a keypress (indicating what to press to 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.

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 input from the user, nor what should be done when a particular menu item is selected. This is deliberate since having the event loop outside the expo is more flexible, particularly in a single-threaded environment like U-Boot.

Everything within an expo has a unique ID number. This is done so that it is easy to refer to things after the expo has been created. The expectation is that the controller declares an enum containing all of the elements in the expo, passing the ID of each object as it is created. When a menu item is selected, its ID is returned. When a object’s font or position needs to change, the ID is passed to expo functions to indicate which object it is. It is possible for expo to auto-allocate IDs, but this is not recommended. The use of IDs is a convenience, removing the need for the controller to store pointers to objects, or even the IDs of objects. Programmatic creation of many items in a loop can be handled by allocating space in the enum for a maximum number of items, then adding the loop count to the enum values to obtain unique IDs.

Where dynamic IDs are need, use expo_set_dynamic_start() to set the start value, so that they are allocated above the starting (enum) IDs.

All text strings are stored in a structure attached to the expo, referenced by a text ID. This makes it easier at some point to implement multiple languages or to support Unicode strings.

Menu objects do not have their own text and image objects. Instead they simply refer to objects which have been created. So a menu item is just a collection of IDs of text and image objects. When adding a menu item you must create these objects first, then create the menu item, passing in the relevant IDs.

Creating an expo

To create an expo programmatically, use expo_new() followed by scene_new() to create a scene. Then add objects to the scene, using functions like scene_txt_str() and scene_menu(). For every menu item, add text and image objects, then create the menu item with scene_menuitem(), referring to those objects.

To create an expo using a description file, see Expo Format below.

Layout

Individual objects can be positioned using scene_obj_set_pos(). Menu items cannot be positioned manually: this is done by scene_arrange() which is called automatically when something changes. The menu itself determines the position of its items.

Rendering

Rendering is performed by calling expo_render(). This uses either the vidconsole, if present, or the serial console in text mode. Expo handles presentation automatically in either case, without any change in how the expo is created.

For the vidconsole, Truetype fonts can be used if enabled, to enhance the quality of the display. For text mode, each menu item is shown in a single line, allowing easy selection using arrow keys.

Input

The controller is responsible for collecting keyboard input. A good way to do 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, 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.

Actions

Call expo_action_get() in the event loop to check for any actions that the expo wants to report. These can include selecting a particular menu item, or quitting the menu. Processing of these is the responsibility of your controller.

Event loop

Expo is intended to be used in an event loop. For an example loop, see bootflow_menu_run(). It is possible to perform other work in your event loop, such as scanning devices for more bootflows.

Themes

Expo supports simple themes, for setting the font size, for example. Use the expo_apply_theme() function to load a theme, passing a node with the required properties:

font-size: Font size to use for all text (type: u32)
menu-inset: Number of pixels to inset the menu on the sides and top (type: u32)
menuitem-gap-y: Number of pixels between menu items

Pop-up mode

Expos support two modes. The simple mode is used for selecting from a single menu, e.g. when choosing with OS to boot. In this mode the menu items are shown in a list (label, > pointer, key and description) and can be chosen using arrow keys and enter:

U-Boot Boot Menu

UP and DOWN to choose, ENTER to select

mmc1           > 0  Fedora-Workstation-armhfp-31-1.9
mmc3             1  Armbian

The popup mode allows multiple menus to be present in a scene. Each is shown just as its title and label, as with the CPU Speed and AC Power menus here:

           Test Configuration

CPU Speed        <2 GHz>  (highlighted)

AC Power         Always Off

  UP and DOWN to choose, ENTER to select

Expo Format

It can be tedious to create a complex expo using code. Expo supports a data-driven approach, where the expo description is in a devicetree file. This makes it easier and faster to create and edit the description. An expo builder is provided to convert this format into an expo structure.

Layout of the expo scenes is handled automatically, based on a set of simple rules. The cedit command can be used to load a configuration and create an expo from it.

Top-level node

The top-level node has the following properties:

dynamic-start

type: u32, optional

Specifies the start of the dynamically allocated objects. This results in a call to expo_set_dynamic_start().

The top-level node has the following subnodes:

scenes: Specifies the scenes in the expo, each one being a subnode
strings: Specifies the strings in the expo, each one being a subnode

scenes node

Contains a list of scene subnodes. The name of each subnode is passed as the name to scene_new().

strings node

Contains a list of string subnodes. The name of each subnode is ignored.

strings subnodes

Each subnode defines a string which can be used by scenes and objects. Each string has an ID number which is used to refer to it.

The strings subnodes have the following properties:

id

type: u32, required

Specifies the ID number for the string.

value:

type: string, required

Specifies the string text. For now only a single value is supported. Future work may add support for multiple languages by using a value for each language.

Scene nodes (scenes subnodes)

Each subnode of the scenes node contains a scene description.

Most properties can use either a string or a string ID. For example, a title property can be used to provide the title for a menu; alternatively a title-id property can provide the string ID of the title. If both are present, the ID takes preference, except that if a string with that ID does not exist, it falls back to using the string from the property (title in this example). The description below shows these are alternative properties with the same description.

The scene nodes have the following properties:

id

type: u32, required

Specifies the ID number for the string.

title / title-id

type: string / u32, required

Specifies the title of the scene. This is shown at the top of the scene.

prompt / prompt-id

type: string / u32, required

Specifies a prompt for the scene. This is shown at the bottom of the scene.

The scene nodes have a subnode for each object in the scene.

Object nodes

The object-node name is used as the name of the object, e.g. when calling scene_menu() to create a menu.

Object nodes have the following common properties:

type

type: string, required

Specifies the type of the object. Valid types are:

“menu”: Menu containing items which can be selected by the user
“textline”: A line of text which can be edited

id

type: u32, required

Specifies the ID of the object. This is used when referring to the object.

Where CMOS RAM is used for reading and writing settings, the following additional properties are required:

start-bit: Specifies the first bit in the CMOS RAM to use for this setting. For a RAM with 0x100 bytes, there are 0x800 bit locations. For example, register 0x80 holds bits 0x400 to 0x407.
bit-length: Specifies the number of CMOS RAM bits to use for this setting. The bits extend from start-bit to start-bit + bit-length - 1. Note that the bits must be contiguous.

Menu nodes have the following additional properties:

title / title-id

type: string / u32, required

Specifies the title of the menu. This is shown to the left of the area for this menu.

item-id

type: u32 list, required

Specifies the ID for each menu item. These are used for checking which item has been selected.

item-label / item-label-id

type: string list / u32 list, required

Specifies the label for each item in the menu. These are shown to the user. In ‘popup’ mode these form the items in the menu.

key-label / key-label-id

type: string list / u32 list, optional

Specifies the key for each item in the menu. These are currently only intended for use in simple mode.

desc-label / desc-label-id

type: string list / u32 list, optional

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

The expo_arrange() function can be called to arrange the expo objects in a suitable manner. For each scene it puts the title at the top, the prompt at the bottom and the objects in order from top to bottom.

Expo format example

This example shows an expo with a single scene consisting of two menus. The scene title is specified using a string from the strings table, but all other strings are provided inline in the nodes where they are used.

/* this comment is parsed by the expo.py tool to insert the values below

enum {
    ZERO,
    ID_PROMPT,
    ID_SCENE1,
    ID_SCENE1_TITLE,

    ID_CPU_SPEED,
    ID_CPU_SPEED_TITLE,
    ID_CPU_SPEED_1,
    ID_CPU_SPEED_2,
    ID_CPU_SPEED_3,

    ID_POWER_LOSS,
    ID_AC_OFF,
    ID_AC_ON,
    ID_AC_MEMORY,

    ID_MACHINE_NAME,
    ID_MACHINE_NAME_EDIT,

    ID_DYNAMIC_START,
*/

&cedit {
    dynamic-start = <ID_DYNAMIC_START>;

    scenes {
        main {
            id = <ID_SCENE1>;

            /* value refers to the matching id in /strings */
            title-id = <ID_SCENE1_TITLE>;

            /* simple string is used as it is */
            prompt = "UP and DOWN to choose, ENTER to select";

            /* defines a menu within the scene */
            cpu-speed {
                type = "menu";
                id = <ID_CPU_SPEED>;

                /*
                 * has both string and ID. The string is ignored
                 * if the ID is present and points to a string
                 */
                title = "CPU speed";
                title-id = <ID_CPU_SPEED_TITLE>;

                /* menu items as simple strings */
                item-label = "2 GHz", "2.5 GHz", "3 GHz";

                /* IDs for the menu items */
                item-id = <ID_CPU_SPEED_1 ID_CPU_SPEED_2
                    ID_CPU_SPEED_3>;
            };

            power-loss {
                type = "menu";
                id = <ID_POWER_LOSS>;

                title = "AC Power";
                item-label = "Always Off", "Always On",
                    "Memory";

                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>;
        };
    };

    strings {
        title {
            id = <ID_SCENE1_TITLE>;
            value = "Test Configuration";
            value-es = "configuración de prueba";
        };
    };
};

API documentation

enum expoact_type: types of actions reported by the expo

Constants

EXPOACT_NONE: no action
EXPOACT_POINT_OBJ: object was highlighted (id indicates which)
EXPOACT_POINT_ITEM: menu item was highlighted (id indicates which)
EXPOACT_SELECT: menu item was selected (id indicates which)
EXPOACT_OPEN: menu was opened, so an item can be selected (id indicates which menu object)
EXPOACT_CLOSE: menu was closed (id indicates which menu object)
EXPOACT_QUIT: request to exit the menu

struct expo_action: an action report by the expo

Definition

struct expo_action {
  enum expoact_type type;
  union {
    struct {
      int id;
    } select;
  };
};

Members

type: Action type (EXPOACT_NONE if there is no action)
{unnamed_union}: anonymous
select: Used for EXPOACT_POINT_ITEM and EXPOACT_SELECT

struct expo_theme: theme for the expo

Definition

struct expo_theme {
  u32 font_size;
  u32 menu_inset;
  u32 menuitem_gap_y;
};

Members

font_size: Default font size for all text
menu_inset: Inset width (on each side and top/bottom) for menu items
menuitem_gap_y: Gap between menu items in pixels

struct expo: information about an expo

Definition

struct expo {
  char *name;
  struct udevice *display;
  struct udevice *cons;
  uint scene_id;
  uint next_id;
  struct expo_action action;
  bool text_mode;
  bool popup;
  void *priv;
  struct expo_theme theme;
  struct list_head scene_head;
  struct list_head str_head;
};

Members

name: Name of the expo (allocated)
display: Display to use (UCLASS_VIDEO), or NULL to use text mode
cons: Console to use (UCLASS_VIDEO_CONSOLE), or NULL to use text mode
scene_id: Current scene ID (0 if none)
next_id: Next ID number to use, for automatic allocation
action: Action selected by user. At present only one is supported, with the type set to EXPOACT_NONE if there is no action
text_mode: true to use text mode for the menu (no vidconsole)
popup: true to use popup menus, instead of showing all items
priv: Private data for the controller
theme: Information about fonts styles, etc.
scene_head: List of scenes
str_head: list of strings

Description

A group of scenes which can be presented to the user, typically to obtain input or to make a selection.

struct expo_string: a string that can be used in an expo

Definition

struct expo_string {
  uint id;
  const char *str;
  struct list_head sibling;
};

Members

id: ID number of the string
str: String
sibling: Node to link this object to its siblings

struct scene: information about a scene in an expo

Definition

struct scene {
  struct expo *expo;
  char *name;
  uint id;
  uint title_id;
  uint highlight_id;
  struct cli_line_state cls;
  struct abuf buf;
  struct abuf entry_save;
  struct list_head sibling;
  struct list_head obj_head;
};

Members

expo: Expo this scene is part of
name: Name of the scene (allocated)
id: ID number of the scene
title_id: String ID of title of the scene (allocated)
highlight_id: ID of highlighted object, if any
cls: cread state to use for input
buf: Buffer for input
entry_save: Buffer to hold vidconsole text-entry information
sibling: Node to link this scene to its siblings
obj_head: List of objects in the scene

Description

A collection of text/image/menu items in an expo

enum scene_obj_t: type of a scene object

Constants

SCENEOBJT_NONE: Used to indicate that the type does not matter
SCENEOBJT_IMAGE: Image data to render
SCENEOBJT_TEXT: Text line to render
SCENEOBJT_MENU: Menu containing items the user can select
SCENEOBJT_TEXTLINE: Line of text the user can edit

struct scene_dim: Dimensions of an object

Definition

struct scene_dim {
  int x;
  int y;
  int w;
  int h;
};

Members

x: x position, in pixels from left side
y: y position, in pixels from top
w: width, in pixels
h: height, in pixels

enum scene_obj_flags_t: flags for objects

Constants

SCENEOF_HIDE: object should be hidden
SCENEOF_POINT: object should be highlighted
SCENEOF_OPEN: object should be opened (e.g. menu is opened so that an option can be selected)

struct scene_obj: information about an object in a scene

Definition

struct scene_obj {
  struct scene *scene;
  char *name;
  uint id;
  enum scene_obj_t type;
  struct scene_dim dim;
  u8 flags;
  u8 bit_length;
  u16 start_bit;
  struct list_head sibling;
};

Members

scene: Scene that this object relates to
name: Name of the object (allocated)
id: ID number of the object
type: Type of this object
dim: Dimensions for this object
flags: Flags for this object
bit_length: Number of bits used for this object in CMOS RAM
start_bit: Start bit to use for this object in CMOS RAM
sibling: Node to link this object to its siblings

struct scene_obj_img: information about an image object in a scene

Definition

struct scene_obj_img {
  struct scene_obj obj;
  char *data;
};

Members

obj: Basic object information
data: Image data in BMP format

Description

This is a rectangular image which is blitted onto the display

struct scene_obj_txt: information about a text object in a scene

Definition

struct scene_obj_txt {
  struct scene_obj obj;
  uint str_id;
  const char *font_name;
  uint font_size;
};

Members

obj: Basic object information
str_id: ID of the text string to display
font_name: Name of font (allocated by caller)
font_size: Nominal size of font in pixels

Description

This is a single-line text object

struct scene_obj_menu: information about a menu object in a scene

Definition

struct scene_obj_menu {
  struct scene_obj obj;
  uint title_id;
  uint cur_item_id;
  uint pointer_id;
  struct list_head item_head;
};

Members

obj: Basic object information
title_id: ID of the title text, or 0 if none
cur_item_id: ID of the current menu item, or 0 if none
pointer_id: ID of the object pointing to the current selection
item_head: List of items in the menu

Description

A menu has a number of items which can be selected by the user

It also has:

a text/image object (pointer_id) which points to the current item (cur_item_id)
a preview object which shows an image related to the current item

enum scene_menuitem_flags_t: flags for menu items

Constants

SCENEMIF_GAP_BEFORE: Add a gap before this item

struct scene_menitem: a menu item in a menu

Definition

struct scene_menitem {
  char *name;
  uint id;
  uint key_id;
  uint label_id;
  uint desc_id;
  uint preview_id;
  uint flags;
  struct list_head sibling;
};

Members

name: Name of the item (this is allocated by this call)
id: ID number of the object
key_id: ID of text object to use as the keypress to show
label_id: ID of text object to use as the label text
desc_id: ID of text object to use as the description text
preview_id: ID of the preview object, or 0 if none
flags: Flags for this item
sibling: Node to link this item to its siblings

Description

A menu item has:

text object holding the name (short) and description (can be longer)
a text object holding the keypress

struct scene_obj_textline: information about a textline in a scene

Definition

struct scene_obj_textline {
  struct scene_obj obj;
  uint label_id;
  uint edit_id;
  uint max_chars;
  struct abuf buf;
  uint pos;
};

Members

obj: Basic object information
label_id: ID of the label text, or 0 if none
edit_id: ID of the editable text
max_chars: Maximum number of characters allowed
buf: Text buffer containing current text
pos: Cursor position

Description

A textline has a prompt and a line of editable text

int expo_new(const char *name, void *priv, struct expo **expp): create a new expo

Parameters

const char *name: Name of expo (this is allocated by this call)
void *priv: Private data for the controller
struct expo **expp: Returns a pointer to the new expo on success

Description

Allocates a new expo

Return

0 if OK, -ENOMEM if out of memory

void expo_destroy(struct expo *exp): Destroy an expo and free all its memory

Parameters

struct expo *exp: Expo to destroy

void expo_set_dynamic_start(struct expo *exp, uint dyn_start): Set the start of the ‘dynamic’ IDs

Parameters

struct expo *exp: Expo to update
uint dyn_start: Start ID that expo should use for dynamic allocation

Description

It is common for a set of ‘static’ IDs to be used to refer to objects in the expo. These typically use an enum so that they are defined in sequential order.

Dynamic IDs (for objects not in the enum) are intended to be used for objects to which the code does not need to refer. These are ideally located above the static IDs.

Use this function to set the start of the dynamic range, making sure that the value is higher than all the statically allocated IDs.

int expo_str(struct expo *exp, const char *name, uint id, const char *str): add a new string to an expo

Parameters

struct expo *exp: Expo to update
const char *name: Name to use (this is allocated by this call)
uint id: ID to use for the new object (0 to allocate one)
const char *str: Pointer to text to display (allocated by caller)

Return

ID number for the object (typically id), or -ve on error

const char *expo_get_str(struct expo *exp, uint id): Get a string by ID

Parameters

struct expo *exp: Expo to use
uint id: String ID to look up returns string, or NULL if not found

int expo_set_display(struct expo *exp, struct udevice *dev): set the display to use for a expo

Parameters

struct expo *exp: Expo to update
struct udevice *dev: Display to use (UCLASS_VIDEO), NULL to use text mode

Return

0 (always)

int expo_calc_dims(struct expo *exp): Calculate the dimensions of the objects

Parameters

struct expo *exp: Expo to update Returns 0 if OK, -ENOTSUPP if there is no graphical console

Description

Updates the width and height of all objects based on their contents

int expo_set_scene_id(struct expo *exp, uint scene_id): Set the current scene ID

Parameters

struct expo *exp: Expo to update
uint scene_id: New scene ID to use (0 to select no scene)

Return

0 if OK, -ENOENT if there is no scene with that ID

int expo_first_scene_id(struct expo *exp): Get the ID of the first scene

Parameters

struct expo *exp: Expo to check

Return

Scene ID of first scene, or -ENOENT if there are no scenes

int expo_render(struct expo *exp): render the expo on the display / console

Parameters

struct expo *exp: Expo to render

Return

0 if OK, -ECHILD if there is no current scene, -ENOENT if the current scene is not found, other error if something else goes wrong

void expo_set_text_mode(struct expo *exp, bool text_mode): Controls whether the expo renders in text mode

Parameters

struct expo *exp: Expo to update
bool text_mode: true to use text mode, false to use the console

int scene_new(struct expo *exp, const char *name, uint id, struct scene **scnp): create a new scene in a expo

Parameters

struct expo *exp: Expo to update
const char *name: Name to use (this is allocated by this call)
uint id: ID to use for the new scene (0 to allocate one)
struct scene **scnp: Returns a pointer to the new scene on success

Description

The scene is given the ID id which must be unique across all scenes, objects and items. The expo’s next_id is updated to at least id + 1

Return

ID number for the scene (typically id), or -ve on error

struct scene *expo_lookup_scene_id(struct expo *exp, uint scene_id): Look up a scene by ID

Parameters

struct expo *exp: Expo to check
uint scene_id: Scene ID to look up returns pointer to scene if found, else NULL

void scene_highlight_first(struct scene *scn): Highlight the first item in a scene

Parameters

struct scene *scn: Scene to update

Description

This highlights the first item, so that the user can see that it is pointed to

void scene_set_highlight_id(struct scene *scn, uint id): Set the object which is highlighted

Parameters

struct scene *scn: Scene to update
uint id: ID of object to highlight

Description

Sets a new object to highlight in the scene

int scene_set_open(struct scene *scn, uint id, bool open): Set whether an item is open or not

Parameters

struct scene *scn: Scene to update
uint id: ID of object to update
bool open: true to open the object, false to close it

Return

0 if OK, -ENOENT if id is invalid

int scene_title_set(struct scene *scn, uint title_id): set the scene title

Parameters

struct scene *scn: Scene to update
uint title_id: Title ID to set

Return

0 if OK

int scene_obj_count(struct scene *scn): Count the number of objects in a scene

Parameters

struct scene *scn: Scene to check

Return

number of objects in the scene, 0 if none

int scene_img(struct scene *scn, const char *name, uint id, char *data, struct scene_obj_img **imgp): add a new image to a scene

Parameters

struct scene *scn: Scene to update
const char *name: Name to use (this is allocated by this call)
uint id: ID to use for the new object (0 to allocate one)
char *data: Pointer to image data
struct scene_obj_img **imgp: If non-NULL, returns the new object

Return

ID number for the object (typically id), or -ve on error

int scene_txt(struct scene *scn, const char *name, uint id, uint str_id, struct scene_obj_txt **txtp): add a new text object to a scene

Parameters

struct scene *scn: Scene to update
const char *name: Name to use (this is allocated by this call)
uint id: ID to use for the new object (0 to allocate one)
uint str_id: ID of the string to use
struct scene_obj_txt **txtp: If non-NULL, returns the new object

Return

ID number for the object (typically id), or -ve on error

int scene_txt_str(struct scene *scn, const char *name, uint id, uint str_id, const char *str, struct scene_obj_txt **txtp): add a new string to expo and text object to a scene

Parameters

struct scene *scn: Scene to update
const char *name: Name to use (this is allocated by this call)
uint id: ID to use for the new object (0 to allocate one)
uint str_id: ID of the string to use
const char *str: Pointer to text to display (allocated by caller)
struct scene_obj_txt **txtp: If non-NULL, returns the new object

Return

ID number for the object (typically id), or -ve on error

int scene_menu(struct scene *scn, const char *name, uint id, struct scene_obj_menu **menup): create a menu

Parameters

struct scene *scn: Scene to update
const char *name: Name to use (this is allocated by this call)
uint id: ID to use for the new object (0 to allocate one)
struct scene_obj_menu **menup: If non-NULL, returns the new object

Return

ID number for the object (typically id), or -ve on error

int scene_textline(struct scene *scn, const char *name, uint id, uint max_chars, struct scene_obj_textline **tlinep): create a textline

Parameters

struct scene *scn: Scene to update
const char *name: Name to use (this is allocated by this call)
uint id: ID to use for the new object (0 to allocate one)
uint max_chars: Maximum length of the textline in characters
struct scene_obj_textline **tlinep: If non-NULL, returns the new object

Return

ID number for the object (typically id), or -ve on error

int scene_txt_set_font(struct scene *scn, uint id, const char *font_name, uint font_size): Set the font for an object

Parameters

struct scene *scn: Scene to update
uint id: ID of object to update
const char *font_name: Font name to use (allocated by caller)
uint font_size: Font size to use (nominal height in pixels)

int scene_obj_set_pos(struct scene *scn, uint id, int x, int y): Set the postion of an object

Parameters

struct scene *scn: Scene to update
uint id: ID of object to update
int x: x position, in pixels from left side
int y: y position, in pixels from top

Return

0 if OK, -ENOENT if id is invalid

int scene_obj_set_size(struct scene *scn, uint id, int w, int h): Set the size of an object

Parameters

struct scene *scn: Scene to update
uint id: ID of object to update
int w: width in pixels
int h: height in pixels

Return

0 if OK, -ENOENT if id is invalid

int scene_obj_set_hide(struct scene *scn, uint id, bool hide): Set whether an object is hidden

Parameters

struct scene *scn: Scene to update
uint id: ID of object to update
bool hide: true to hide the object, false to show it

Description

The update happens when the expo is next rendered.

Return

0 if OK, -ENOENT if id is invalid

int scene_menu_set_title(struct scene *scn, uint id, uint title_id): Set the title of a menu

Parameters

struct scene *scn: Scene to update
uint id: ID of menu object to update
uint title_id: ID of text object to use as the title

Return

0 if OK, -ENOENT if id is invalid, -EINVAL if title_id is invalid

int scene_menu_set_pointer(struct scene *scn, uint id, uint cur_item_id): Set the item pointer for a menu

Parameters

struct scene *scn: Scene to update
uint id: ID of menu object to update
uint cur_item_id: ID of text or image object to use as a pointer to the current item

Description

This is a visual indicator of the current item, typically a “>” character which sits next to the current item and moves when the user presses the up/down arrow keys

Return

0 if OK, -ENOENT if id is invalid, -EINVAL if cur_item_id is invalid

int scene_obj_get_hw(struct scene *scn, uint id, int *widthp): Get width and height of an object in a scene

Parameters

struct scene *scn: Scene to check
uint id: ID of menu object to check
int *widthp: If non-NULL, returns width of object in pixels

Return

Height of object in pixels

int scene_menuitem(struct scene *scn, uint menu_id, const char *name, uint id, uint key_id, uint label_id, uint desc_id, uint preview_id, uint flags, struct scene_menitem **itemp): Add an item to a menu

Parameters

struct scene *scn: Scene to update
uint menu_id: ID of menu object to update
const char *name: Name to use (this is allocated by this call)
uint id: ID to use for the new object (0 to allocate one)
uint key_id: ID of text object to use as the keypress to show
uint label_id: ID of text object to use as the label text
uint desc_id: ID of text object to use as the description text
uint preview_id: ID of object to use as the preview (text or image)
uint flags: Flags for this item (enum scene_menuitem_flags_t)
struct scene_menitem **itemp: If non-NULL, returns the new object

Return

ID number for the item (typically id), or -ve on error

int scene_arrange(struct scene *scn): Arrange the scene to deal with object sizes

Parameters

struct scene *scn: Scene to arrange

Description

Updates any menus in the scene so that their objects are in the right place.

Return

0 if OK, -ve on error

int expo_send_key(struct expo *exp, int key): set a keypress to the expo

Parameters

struct expo *exp: Expo to receive the key
int key: Key to send (ASCII or enum bootmenu_key)

Return

0 if OK, -ECHILD if there is no current scene

int expo_action_get(struct expo *exp, struct expo_action *act): read user input from the expo

Parameters

struct expo *exp: Expo to check
struct expo_action *act: Returns action

Return

0 if OK, -EAGAIN if there was no action to return

int expo_apply_theme(struct expo *exp, ofnode node): Apply a theme to an expo

Parameters

struct expo *exp: Expo to update
ofnode node: Node containing the theme

int expo_build(ofnode root, struct expo **expp): Build an expo from an FDT description

Parameters

ofnode root: Root node for expo description
struct expo **expp: Returns the new expo

Description

Build a complete expo from a description in the provided devicetree.

See doc/develop/expo.rst for a description of the format

Return

0 if OK, -ENOMEM if out of memory, -EINVAL if there is a format error, -ENOENT if there is a references to a non-existent string

Future ideas

Some ideas for future work:

Default menu item and a timeout
Image formats other than BMP
Use of ANSI sequences to control a serial terminal
Colour selection
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
Use expo to replace the existing menu implementation
Add a Kconfig option to drop the names to save code / data space
Add a Kconfig option to disable vidconsole support to save code / data space
Support both graphical and text menus at the same time on different devices
Support unicode
Support curses for proper serial-terminal menus
Add support for large menus which need to scroll
Update expo.py tool to check for overlapping names and CMOS locations