Add initial API documentation

API.md

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+API documentation for the HUD bars mod 0.1.0
+============================================
+
+**Warning**: This API is still experimental, everything may change at any time,
+and backwards compability will not be ensured until the 1.0.0 release of the
+HUD bars mod.
+
+## 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 `hud.register_hudbar` to make the definition of the HUD bar known to this mod
+* Call `hud.hudbars[identifier].add_all` for each player for which you want to use previously defined HUD bar
+* 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.
+
+### `hud.register_hudbar(identifier, text_color, label, textures, default_start_value, default_start_max, start_hide, format_string)`
+This function adds a new custom HUD
+Note this does not yet display the HUD bar.
+
+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`.
+
+### `hud.hudtables[identifier].add_all(player, start_value, start_max)`
+This function activates and displays
+
+However, if `start_hide` was set to `true` for the HUD bar, the HUD bar will initially be hidden, but
+the HUD elements are still sent to the client.
+
+You have to replace `identifier` with the identifier string you have specified previously, i.e. use
+`hud.hudtables["example"].add_all` if your identifier string is `"example"`. The identifier
+specifies the type of HUD bar you want to display.
+
+This is admittedly a rather odd function call and will likely to be changed.
+
+#### Parameters
+* `player`: `ObjectRef` of the player to which the new HUD bar should be displayed to.
+* `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.
+
+### `hud.change_hudbar(player, hudtable, new_value, new_max_value)`
+Changes the values of. If
+
+#### Parameters
+* `player`: `ObjectRef` of the player to which the HUD bar belongs to
+* `hudtable`: The table containing the HUD bar definition. Specify as `hud.hudtables[identifier]`, i.e. if your identifier was `example`, then you use `hud.hudtables["example"]`.
+* `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 `hud.change_hudbar` on a hidden HUD bar, the new values will be correctly displayed after the HUD bar
+has been unhidden.
+
+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.
+
+### `hud.hide_hudbar(player, hudtable)`
+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
+* `hudtable`: The table containing the HUD bar definition, see `hud.change_hudbar`.
+
+#### Return value
+Always `nil`.
+
+
+### `hud.hide_hudbar(player, hudtable)`
+Makes a previously hidden HUD bar visible again to a player
+
+#### Parameters
+* `player`: `ObjectRef` of the player to which the HUD bar belongs to
+* `hudtable`: The table containing the HUD bar definition, see `hud.change_hudbar`.
+
+#### Return value
+Always `nil`.
+

README.txt

@@ -25,6 +25,11 @@ You can create a “hud.conf” file to customize the positions of the health an
 IMPORTANT:
 Keep in mind if running a server with this mod, that the custom position should be displayed correct on every screen size!
 
+API:
+----
+The API is used to add your own custom HUD bars.
+Documentation for the API of this mod can be found in API.md.
+
 
 License of textures:
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