server-nalc/mods/hudbars/API.md

API documentation for the HUD bars mod 1.0.2

Introduction

This API allows you to add, change, hide and unhide custom HUD bars for this mod.

Overview

To give you a very brief overview over this API, here is the basic workflow on how to add your own custom HUD bar:

• Create images for your HUD bar
• Call hb.register_hudbar to make the definition of the HUD bar known to this mod
• Call hb.init_hudbar for each player for which you want to use previously defined HUD bar
• Use hb.change_hudbar whenever you need to change the values of a HUD bar of a certain player
• If you need it: Use hb.hide_hudbar and hb.unhide_hudbar to hide or unhide HUD bars of a certain player

The basic rules

In order to use this API, you should be aware of a few basic rules in order to understand it:

• A HUD bar is an approximate graphical representation of the ratio of a current value and a maximum value, i.e. current health of 15 and maximum health of 20. A full HUD bar represents 100%, an empty HUD bar represents 0%.
• The current value must always be equal to or smaller then the maximum
• Both current value and maximum must not be smaller than 0
• Both current value and maximum must be real numbers. So no NaN, infinity, etc.
• The HUD bar will be hidden if the maximum equals 0. This is intentional.
• The health and breath HUD bars are hardcoded.

These are soft rules, the HUD bars mod will not enforce all of these. But this mod has been programmed under the assumption that these rules are followed, for integrity.

Adding a HUD bar

To make a new HUD bar known to this mod, you need …

• … an image of size 2×16 for the bar
• … an icon of size 16×16 (optional)
• … to register it with hb.register_hudbar

Bar image

The image for the bar will be repeated horizontally to denote the “value” of the HUD bar. It must be of size 2×16. If neccessary, the image will be split vertically in half, and only the left half of the image is displayed. So the final HUD bar will always be displayed on a per-pixel basis.

The default bar images are single-colored, but you can use other styles as well, for instance, a vertical gradient.

Icon

A 16×16 image shown left of the HUD bar. This is optional.

hb.register_hudbar(identifier, text_color, label, textures, default_start_value, default_start_max, default_start_hidden, format_string)

This function registers a new custom HUD bar definition to the HUD bars mod, so it can be later used to be displayed, changed, hidden and unhidden on a per-player basis. Note this does not yet display the HUD bar.

The HUD bars will be displayed in a “first come, first serve” order. This mod does not allow fow a custom order or a way to set it manually in a reliable way.

Parameters

• identifier: A globally unique internal name for the HUD bar, will be used later to refer to it. Please only rely on alphanumeric characters for now. The identifiers “health” and “breath” are used internally for the built-in health and breath bar, respectively. Please do not use these names.
• text_color: A 3-octet number defining the color of the text. The octets denote, in this order red, green and blue and range from 0x00 (complete lack of this component) to 0xFF (full intensity of this component). Example: 0xFFFFFF for white.
• label: A string which is displayed on the HUD bar itself to describe the HUD bar. Try to keep this string short.
• textures: A table with the following fields:
• bar: The file name of the bar image (as string).
• icon: The file name of the icon, as string. This field can be nil, in which case no icon will be used.
• default_start_value: If this HUD bar is added to a player, and no initial value is specified, this value will be used as initial current value
• default_max_value: If this HUD bar is added to a player, and no initial maximum value is specified, this value will be used as initial maximum value
• default_start_hidden: The HUD bar will be initially start hidden by default when added to a player. Use hb.unhide_hudbar to unhide it.
• format_string: This is optional; You can specify an alternative format string display the final text on the HUD bar. The default format string is “%s: %d/%d” (in this order: Label, current value, maximum value). See also the Lua documentation of string.format.

Return value

Always nil.

Displaying a HUD bar

After a HUD bar has been registered, they are not yet displayed yet for any player. HUD bars must be explicitly initialized on a per-player basis.

You probably want to do this in the minetest.register_on_joinplayer.

hb.init_hudbar(player, identifier, start_value, start_max, start_hidden)

This function initialzes and activates a previously registered HUD bar and assigns it to a certain client/player. This has only to be done once per player and after that, you can change the values using hb.change_hudbar.

However, if start_hidden was set to true for the HUD bar (in hb.register_hudbar), the HUD bar will initially be hidden, but the HUD elements are still sent to the client. Otherwise, the HUD bar will be initially be shown to the player.

Parameters

• player: ObjectRef of the player to which the new HUD bar should be displayed to.
• identifier: The identifier of the HUD bar type, as specified in hb.register_hudbar.
• start_value: The initial current value of the HUD bar. This is optional, default_start_value of the registration function will be used, if this is nil.
• start_max: The initial maximum value of the HUD bar. This is optional, default_start_max of the registration function will be used, if this is nil
• start_hidden: Whether the HUD bar is initially hidden. This is optional, default_start_hidden of the registration function will be used as default

Return value

Always nil.

Modifying a HUD bar

After a HUD bar has been added, you can change the current and maximum value on a per-player basis. You use the function hb.change_hudbar for this.

hb.change_hudbar(player, identifier, new_value, new_max_value)

Changes the values of an initialized HUD bar for a certain player. new_value and new_max_value can be nil; if one of them is nil, that means the value is unchanged. If both values are nil, this function is a no-op. This function also tries minimize the amount of calls to hud_change of the Minetest Lua API, and therefore, network traffic. hud_change is only called if it is actually needed, i.e. when the actual length of the bar or the displayed string changed, so you do not have to worry about it.

Parameters

• player: ObjectRef of the player to which the HUD bar belongs to
• identifier: The identifier of the HUD bar type to change, as specified in hb.register_hudbar.
• new_value: The new current value of the HUD bar
• new_max_value: The new maximum value of the HUD bar

Return value

Always nil.

Hiding and unhiding a HUD bar

You can also hide custom HUD bars, meaning they will not be displayed for a certain player. You can still use hb.change_hudbar on a hidden HUD bar, the new values will be correctly displayed after the HUD bar has been unhidden. Both functions will only call hud_change if there has been an actual change to avoid unneccessary traffic.

Note that the hidden state of a HUD bar will not be saved by this mod on server shutdown, so you may need to write your own routines for this or by setting the correct value for start_hidden when calling hb.init_hudbar.

hb.hide_hudbar(player, identifier)

Hides the specified HUD bar from the screen of the specified player.

Parameters

• player: ObjectRef of the player to which the HUD bar belongs to
• identifier: The identifier of the HUD bar type to hide, as specified in hb.register_hudbar.

Return value

Always nil.

hb.unhide_hudbar(player, identifier)

Makes a previously hidden HUD bar visible again to a player.

Parameters

• player: ObjectRef of the player to which the HUD bar belongs to
• identifier: The identifier of the HUD bar type to unhide, as specified in hb.register_hudbar.

Return value

Always nil.

Reading HUD bar information

It is also possible to read information about an active HUD bar.

hb.get_hudbar_state(player, identifier)

Returns the current state of the active player's HUD bar.

Parameters

• player: ObjectRef of the player to which the HUD bar belongs to
• identifier: The identifier of the HUD bar type to hide, as specified in hb.register_hudbar.

Return value

A table which holds information on the current state of the HUD bar. Note the table is a deep copy of the internal HUD bar state, it is not a reference; the information hold by the table is only true for the moment you called this function. The fields of this table are:

• value: Current value of HUD bar.
• max: Current maximum value of HUD bar.
• hidden: Boolean denoting whether the HUD bar is hidden.
• barlength: The length of the HUD bar in pixels. This field is meaningless if the HUD bar is currently hidden.
• text: The text shown on the HUD bar. This fiels is meaningless if the HUD bar is currently hidden.