USS data types define typical values, including keywords and units, that USS properties and functions accept.
USS properties use the same syntax as W3C CSS documents:
auto
, baseline
.<
and >
). For example: <length>
and <color>
.<'
and '>
). For example, <'width'>
.If a property value has more than one option, the following applies:
|
) separates two or more options. One of them must occur.|
|`) separate two or more options. One or more of them must occur in any order.&
&`) separate two or more options. All options must occur.[
]
) denote grouping.Every type, keyword, or angle-bracketed group might be followed by modifiers. The following table lists the possible modifiers:
Modifier | The preceding type, keyword, or group |
---|---|
An asterisk (* ) |
Occurs zero or more times |
A plus sign (+ ) |
Occurs one or more times |
A question mark (? ) |
Is optional |
A pair of numbers in curly braces ({A,B} ) |
Occurs at least A and at most B times |
UI Toolkit supports pixelsThe smallest unit in a computer image. Pixel size depends on your screen resolution. Pixel lighting is calculated at every screen pixel. More info
See in Glossary (px
) and percentages (%
) as units of measurement for length. Pixel values are absolute, while percentages are relative to the element’s parent.
Examples:
width:200px;
expresses a width of 200 pixels.width:50%;
expresses a width of half of the parent element’s width.It’s important to specify the unit of measurement. If you don’t specify a unit of measurement, UI(User Interface) Allows a user to interact with your application. Unity currently supports three UI systems. More info
See in Glossary Toolkit assumes that the property value is expressed in pixels.
Note: 0
is a special value that doesn’t require a unit of measurement.
Numeric values are expressed as either floating points or integer literals. For example, flex:1.0
.
Specific keywords are supported for some built-in properties. Keywords give a descriptive name instead of a number. For example: position:absolute
.
All properties support the initial
global keyword which resets the default value of a property to an element.
In the following example, although you set the color of all the labels to red, the initial
keyword of color
restores the color of label1
to its default value:
/* Set the color of all the labels to red. */ Label { color: red; } /* label1 is the name of a specific label. */ #label1{ color: initial; }
UI Toolkit supports the following literal color values and functions:
#FFFF00
, #0F0
rgb(255, 255, 0)
rgba(255, 255, 0, 1.0)
You can reference project assets such as fonts and textures from your USS files. For example, you might reference a texture to use as the background image for an element.
To reference an asset, you can use either the url()
function or the resource()
function:
resource()
: Represents an asset in a Resources
folder.url()
: Represents an asset specified by a path. You can express it as either a relative path or an absolute path.Use the url()
function in most cases. However, the resource()
function supports automatically loading different versions of image assets for different screen densities.
When you reference an asset with the url()
function, the path you specify can be relative or absolute:
The path must include the file extension.
For example, if your project has a USS
folder that contains all your style sheets, and a Resources
folder that contains all your image assets.
Assets └─ Editor └─ Resources └─ USS
To reference an image named thumb.png
, you can use one of the following paths:
Relative path | Absolute path |
---|---|
url("../Resources/thumb.png") |
url("/Assets/Editor/Resources/thumb.png") url("project:/Assets/Editor/Resources/thumb.png") url("project:///Assets/Editor/Resources/thumb.png")
|
To reference an image in a package, use the Packages
folder in the path:
Relative path | Absolute path |
---|---|
url("../Packages/com.my.example.package/Editor/Resources/thumb.png") |
url("Project:///Packages/com.my.example.package/Editor/Resources/thumb.png") |
The resource()
function can reference assets in Unity’s resource folders (Resources
and Editor Default Resources
). You reference an asset by name.
Editor Default Resources
folder, you must include the file extension.Resources
folder, you must not include the file extension.For example:
Path to file | Reference syntax |
---|---|
Assets/Resources/Images/my-image.png |
resource("Images/my-image") |
Assets/Editor Default Resources/Images/my-image.png |
resource("Images/default-image.png") |
To support screens with different screen densities (DPI), do the following:
@2x
suffix in their file names. For example the high DPI version of myimage.png
should be myimage@2x.png
When Unity loads the asset, it automatically chooses the correct version for the current screen DPI.
For example, if you use resource("myimage")
in USS, Unity loads either Resources/myimage.png
or Resources/myimage@2x.png
.
Use quotes to specify a string value. For example: --my-property: "foo"
.
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