* Use `hud.change_hudbar` whenever you need to change the values of a HUD bar of a certain player
* If you need it: Use `hud.hide_hudbar` and `hud.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 and can not be changed with this API.
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 add a HUD bar, you need …
* … an image of size 2×16 for the bar
* … an icon of size 16×16 (optional)
* … to register it wiith hud.
* … to activate it for each player for which you want the HUD
### 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.
There is currently no reliable way to force a certain order at which the custom HUD bars will be placed.
#### 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.
*`text_color`: A 3-byte number defining the color of the text. The bytes 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
*`start_hide`: The HUD bar will be initially start hidden when added to a player. Use `hud.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 enabled on a per-player basis.
You probably want to do this in the `minetest.register_on_joinplayer`.
*`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`
#### 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 `hud.change_hudbar` for this.
