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| title | layout | root | idx | redirect_from |
|---|---|---|---|---|
| HUD | default | ../../ | 4.6 | /en/chapters/hud.html |
Introduction
Heads Up Display (HUD) elements allow you to show text, images, and other graphical elements.
The HUD doesn't accept user input. For that, you should use a Formspec.
Positioning
Position and Offset
Screens come in a variety of different physical sizes and resolutions, and the HUD needs to work well on all screen types.
Minetest's solution to this is to specify the location of an element using both a percentage position and an offset. The percentage position is relative to the screen size, so to place an element in the center of the screen you would need to provide a percentage position of half the screen, eg (50%, 50%), and an offset of (0, 0).
The offset is then used to move an element relative to the percentage position.
Alignment
Alignment is where the result of position and offset is on the element -
for example, {x = -1.0, y = 0.0} will make the result of position and offset point
to the left of the element's bounds. This is particularly useful when you want to
make a text element left, center, or right justified.
The above diagram shows 3 windows (blue), each with a single HUD element (yellow) with a different alignment each time. The arrow is the result of the position and offset calculation.
Scoreboard
For the purposes of this chapter, you will learn how to position and update a score panel like so:
In the above screenshot all of the elements have the same percentage position - (100%, 50%) - but different offsets. This allows the whole thing to be anchored to the right of the window, but to resize without breaking.
Text Elements
You can create a hud element once you have a copy of the player object:
{% highlight lua %} local player = minetest.get_player_by_name("username") local idx = player:hud_add({ hud_elem_type = "text", position = {x = 0.5, y = 0.5}, offset = {x = 0, y = 0}, text = "Hello world!", alignment = {x = 0, y = 0}, -- center aligned scale = {x = 100, y = 100}, -- covered later }) {% endhighlight %}
The hud_add function returns an element ID - this can be used later to modify
or remove a HUD element.
Parameters
The element's type is given using the hud_elem_type property in the definition
table. The meaning of other properties varies based on this type.
scale is the maximum bounds of text, text outside these bounds is cropped, eg: {x=100, y=100}.
The text's color in Hexadecimal form, eg: 0xFF0000,
and stored in
Our Example
Let's go ahead, and place all of the text in our score panel:
{% highlight lua %} player:hud_add({ hud_elem_type = "text", position = {x = 1, y = 0.5}, offset = {x = -120, y = -25}, text = "Stats", alignment = 0, scale = { x = 100, y = 30}, number = 0xFFFFFF, })
-- Get the dig and place count from storage, or default to 0 local digs = tonumber(player:get_attribute("scoreboard:digs") or 0) local digs_text = "Digs: " .. digs local places = tonumber(player:get_attribute("scoreboard:digs") or 0) local places_text = "Places: " .. places
player:hud_add({ hud_elem_type = "text", position = {x = 1, y = 0.5}, offset = {x = -180, y = 0}, text = digs_text, alignment = -1, scale = { x = 50, y = 10}, number = 0xFFFFFF, })
player:hud_add({ hud_elem_type = "text", position = {x = 1, y = 0.5}, offset = {x = -70, y = 0}, text = places_text, alignment = -1, scale = { x = 50, y = 10}, number = 0xFFFFFF, }) {% endhighlight %}
This results in the following:
Image Elements
Image elements are created in a very similar way to text elements:
{% highlight lua %} player:hud_add({ hud_elem_type = "image", position = {x = 1, y = 0.5}, offset = {x = -220, y = 0}, text = "scoreboard_background.png", scale = { x = 1, y = 1}, alignment = { x = 1, y = 0 }, }) {% endhighlight %}
You will now have this:
Parameters
The text field is used to provide the image name.
If a co-ordinate is positive, then it is a scale factor with 1 being the
original image size, and 2 being double the size, and so on.
However, if a co-ordinate is negative it is a percentage of the screensize.
For example, x=-100 is 100% of the width.
Scale
Let's make the progress bar for our score panel as an example of scale:
{% highlight lua %} local percent = tonumber(player:get_attribute("scoreboard:score") or 0.2)
player:hud_add({ hud_elem_type = "image", position = {x = 1, y = 0.5}, offset = {x = -215, y = 23}, text = "scoreboard_bar_empty.png", scale = { x = 1, y = 1}, alignment = { x = 1, y = 0 }, })
player:hud_add({ hud_elem_type = "image", position = {x = 1, y = 0.5}, offset = {x = -215, y = 23}, text = "scoreboard_bar_full.png", scale = { x = percent, y = 1}, alignment = { x = 1, y = 0 }, }) {% endhighlight %}
We now have a HUD that looks like the one in the first post! There is one problem however, it won't update when the stats change
Changing an Element
You can use the ID returned by the hud_add method to update or remove it later.
{% highlight lua %} local idx = player:hud_add({ hud_elem_type = "text", text = "Hello world!", -- parameters removed for brevity })
player:hud_change(idx, "text", "New Text") player:hud_remove(idx) {% endhighlight %}
The hud_change method takes the element ID, the property to change, and the new
value. The above call changes the text property from "Hello World" to "Test".
This means that doing the hud_change immediately after the hud_add is
functionally equivalent to the following, in a rather inefficient way:
{% highlight lua %} local idx = player:hud_add({ hud_elem_type = "text", text = "New Text", }) {% endhighlight %}
Storing IDs
{% highlight lua %} scoreboard = {} local saved_huds = {}
function scoreboard.update_hud(player) local player_name = player:get_player_name()
local digs = tonumber(player:get_attribute("scoreboard:digs") or 0)
local digs_text = "Digs: " .. digs
local places = tonumber(player:get_attribute("scoreboard:digs") or 0)
local places_text = "Places: " .. places
local percent = tonumber(player:get_attribute("scoreboard:score") or 0.2)
local ids = saved_huds[player_name]
if ids then
player:hud_change(ids["places"], "text", places_text)
player:hud_change(ids["digs"], "text", digs_text)
player:hud_change(ids["bar_foreground"],
"scale", { x = percent, y = 1 })
else
ids = {}
saved_huds[player_name] = ids
-- create HUD elements and set ids into `ids`
end
end
minetest.register_on_joinplayer(scoreboard.update_hud)
minetest.register_on_leaveplayer(function(player) saved_huds[player:get_player_name()] = nil end) {% endhighlight %}
Other Elements
Read [lua_api.txt]({{ page.root }}lua_api.html#hud-element-types) for a complete list of HUD elements.