CSS Properties

Supported CSS Properties

GTK supports CSS properties and shorthands as far as they can be applied in the context of widgets, and adds its own properties only when needed. All GTK-specific properties have a -gtk prefix.

All properties support the following keywords: inherit, initial, unset, with the same meaning as in CSS.

The following basic datatypes are used throughout:

〈length〉 = 〈number〉 [ px | pt | em | ex |rem | pc | in | cm | mm ] | 〈calc expression〉
〈percentage〉 = 〈number〉 % | 〈calc expression〉
〈angle〉 = 〈number〉 [ deg | grad | turn ] | 〈calc expression〉
〈time〉 = 〈number〉 [ s | ms ] | 〈calc expression〉

Length values with the em or ex units are resolved using the font size value, unless they occur in setting the font-size itself, in which case they are resolved using the inherited font size value.

The rem unit is resolved using the initial font size value, which is not quite the same as the CSS definition of rem.

Whereever a number is allowed, GTK also accepts a Windows-specific theme size:

〈win32 theme size〉 = 〈win32 size〉 | 〈win32 part size〉
〈win32 size〉 = -gtk-win32-size ( 〈theme name〉, 〈metric id〉 )
〈win32 part size〉 = [ -gtk-win32-part-width | -gtk-win32-part-height |
                      -gtk-win32-part-border-top | -gtk-win32-part-border-right |
                      -gtk-win32-part-border-bottom | -gtk-win32-part-border-left ]
                    ( 〈theme name〉 , 〈integer〉 , 〈integer〉 )

〈calc expression〉 = calc( 〈calc sum〉 )
〈calc sum〉 = 〈calc product〉 [ [ + | - ] 〈calc product〉 ]*
〈calc product〉 = 〈calc value〉 [ * 〈calc value〉 | / 〈number〉 ]*
〈calc value〉 = 〈number〉 | 〈length〉 | 〈percentage〉 | 〈angle〉 | 〈time〉 | ( 〈calc sum〉 )

The calc() notation adds considerable expressive power. There are limits on what types can be combined in such an expression (e.g. it does not make sense to add a number and a time). For the full details, see the CSS3 Values and Units spec.

A common pattern among shorthand properties (called ‘four sides’) is one where one to four values can be specified, to determine a value for each side of an area. In this case, the specified values are interpreted as follows:

4 values
top right bottom left
3 values
top horizontal bottom
2 values
vertical horizontal
1 value
all

Color properties

Name Value Initial Inh. Ani. Reference
color 〈color〉 rgba(1,1,1,1) ✓ ✓ CSS2, CSS3
opacity 〈alpha value〉 1 ✓ CSS3

The color property specifies the color to use for text, icons and other foreground rendering. The opacity property specifies the opacity that is used to composite the widget onto its parent widget.

Font properties

Name Value Initial Inh. Ani. Reference Notes
font-family 〈family name〉 [ , 〈family name〉 ]* gtk-font-name setting ✓ CSS2, CSS3
font-size 〈absolute size〉 | 〈relative size〉 | 〈length〉 | 〈percentage〉 gtk-font-name setting ✓ ✓ CSS2, CSS3
font-style normal | oblique | italic normal ✓ CSS2, CSS3
font-variant normal | small-caps normal ✓ CSS2, CSS3 only CSS2 values supported
font-weight normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900 normal ✓ ✓ CSS2, CSS3 normal is synonymous with 400, bold with 700
font-stretch ultra-condensed | extra-condensed | condensed | semi-condensed | normal | semi-expanded | expanded | extra-expanded | ultra-expanded normal ✓ CSS3
-gtk-dpi 〈number〉 screen resolution ✓ ✓
font-feature-settings 〈feature-tag-value〉# “” ✓ > CSS3
Shorthand Value Initial Reference Notes
font [ 〈font-style〉 || 〈font-variant〉 || 〈font-weight〉 || 〈font-stretch〉 ]? 〈font-size〉 〈font-family〉 see individual properties CSS2, CSS3 CSS allows line-height, etc 
〈absolute size〉 = xx-small | x-small | small | medium | large | x-large | xx-large
〈relative size〉 = larger | smaller

The font properties determine the font to use for rendering text. Relative font sizes and weights are resolved relative to the inherited value for these properties.

Text caret properties

Name Value Initial Inh. Ani. Reference Notes
caret-color 〈color〉 currentColor ✓ ✓ CSS3 CSS allows an auto value
-gtk-secondary-caret-color 〈color〉 currentColor ✓ ✓ Used for the secondary caret in bidirectional text

The caret properties provide a way to change the appearance of the insertion caret in editable text.

Text decoration properties

Name Value Initial Inh. Ani. Reference Notes
letter-spacing 〈length〉 0px ✓ ✓ CSS3
text-decoration-line none | underline | line-through none CSS2, CSS3 CSS allows overline
text-decoration-color 〈color〉 currentColor ✓ CSS3
text-decoration-style solid | double | wavy solid CSS3 CSS allows dashed and dotted
text-shadow none | 〈shadow〉 none ✓ ✓ CSS3
Shorthand Value Initial Reference Notes
text-decoration 〈text-decoration-line〉 || 〈text-decoration-style〉 || 〈text-decoration-color〉 see individual properties CSS3 
〈shadow〉 = 〈length〉 〈length〉 〈color〉?

The text decoration properties determine whether to apply extra decorations when rendering text.

Icon Properties

Name Value Initial Inh. Ani. Reference Notes
-gtk-icon-source builtin | 〈image〉 | none builtin ✓
-gtk-icon-transform none | 〈transform〉+ none ✓
-gtk-icon-style requested | regular | symbolic requested ✓ Determines the preferred style for application-loaded icons
-gtk-icon-theme 〈name〉 current icon theme ✓ The icon theme to use with -gtk-icontheme. Since 3.20
-gtk-icon-palette 〈color palette〉 default ✓ ✓ Used to recolor symbolic icons (both application-loaded and from -gtk-icontheme). Since 3.20
-gtk-icon-shadow none | 〈shadow〉 none ✓ ✓
-gtk-icon-effect none | highlight | dim none ✓ 
〈transform〉 = matrix( 〈number〉 [ , 〈number〉 ]{5} ) | translate( 〈length〉, 〈length〉 ) | translateX( 〈length〉 ) | translateY( 〈length〉 ) |
                scale( 〈number〉 [ , 〈number〉 ]? ) | scaleX( 〈number〉 ) | scaleY( 〈number〉 ) | rotate( 〈angle〉 ) | skew( 〈angle〉 [ , 〈angle〉 ]? ) |
                skewX( 〈angle〉 ) |  skewY( 〈angle〉 )
〈color palette〉 = default | 〈name〉 〈color〉 [ , 〈name〉 〈color〉 ]*

The -gtk-icon-source property is used by widgets that are rendering ‘built-in’ icons, such as arrows, expanders, spinners, checks or radios.

The -gtk-icon-style property determines the preferred style for application-provided icons.

The -gtk-icon-transform and -gtk-icon-shadow properties affect the rendering of both built-in and application-provided icons.

-gtk-icon-palette defines a color palette for recoloring symbolic icons. The recognized names for colors in symbolic icons are error, warning and success. The default palette maps these three names to symbolic colors with the names error_color, warning_color and success_color respectively.

Box properties

Name Value Initial Inh. Ani. Reference Notes
min-width 〈length〉 0px ✓ CSS2, CSS3 CSS allows percentages
min-height 〈length〉 0px ✓ CSS2, CSS3 CSS allows percentages
margin-top 〈length〉 0px ✓ CSS2, CSS3 CSS allows percentages or auto
margin-right 〈length〉 0px ✓ CSS2, CSS3 CSS allows percentages or auto
margin-bottom 〈length〉 0px ✓ CSS2, CSS3 CSS allows percentages or auto
margin-left 〈length〉 0px ✓ CSS2, CSS3 CSS allows percentages or auto
padding-top 〈length〉 0px ✓ CSS2, CSS3 CSS allows percentages
padding-right 〈length〉 0px ✓ CSS2, CSS3 CSS allows percentages
padding-bottom 〈length〉 0px ✓ CSS2, CSS3 CSS allows percentages
padding-left 〈length〉 0px ✓ CSS2, CSS3 CSS allows percentages
Shorthand Value Initial Reference Notes
margin 〈length〉{1,4} see individual properties CSS2, CSS3 a ‘four sides’ shorthand
padding 〈length〉{1,4} see individual properties CSS2, CSS3 a ‘four sides’ shorthand

Border properties

Name Value Initial Inh. Ani. Reference Notes
border-top-width 〈length〉 0px ✓ CSS2, CSS3 CSS allows other values
border-right-width 〈length〉 0px ✓ CSS2, CSS3 CSS allows other values
border-bottom-width 〈length〉 0px ✓ CSS2, CSS3 CSS allows other values
border-left-width 〈length〉 0px ✓ CSS2, CSS3 CSS allows other values
border-top-style 〈border style〉 none CSS2, CSS3
border-right-style 〈border style〉 none CSS2, CSS3
border-bottom-style 〈border style〉 none CSS2, CSS3
border-left-style 〈border style〉 none CSS2, CSS3
border-top-right-radius 〈corner radius〉 0 ✓ CSS2, CSS3
border-bottom-right-radius 〈corner radius〉 0 ✓ CSS2, CSS3
border-bottom-left-radius 〈corner radius〉 0 ✓ CSS2, CSS3
border-top-left-radius 〈corner radius〉 0 ✓ CSS2, CSS3
border-top-color 〈color〉 currentColor ✓ CSS2, CSS3
border-right-color 〈color〉 currentColor ✓ CSS2, CSS3
border-bottom-color 〈color〉 currentColor ✓ CSS2, CSS3
border-left-color 〈color〉 currentColor ✓ CSS2, CSS3
border-image-source 〈image〉 | none none ✓ CSS3
border-image-repeat 〈border repeat〉{1,2} stretch CSS3
border-image-slice [ 〈number〉 | 〈percentage〉 ]{1,4} && fill? 100% CSS3 a ‘four sides’ shorthand
border-image-width [ 〈length〉 | 〈number〉 | 〈percentage〉 | auto ]{1,4} 1 CSS3 a ‘four sides’ shorthand
Shorthand Value Initial Reference Notes
border-width 〈length〉{1,4} see individual properties CSS2, CSS3 a ‘four sides’ shorthand
border-style 〈border style〉{1,4} see individual properties CSS2, CSS3 a ‘four sides’ shorthand
border-color 〈color〉{1,4} see individual properties CSS3 a ‘four sides’ shorthand
border-top 〈length〉 || 〈border style〉 || 〈color〉 see individual properties CSS2, CSS3
border-right 〈length〉 || 〈border style〉 || 〈color〉 see individual properties CSS2, CSS3
border-bottom 〈length〉 || 〈border style〉 || 〈color〉 see individual properties CSS2, CSS3
border-left 〈length〉 || 〈border style〉 || 〈color〉 see individual properties CSS2, CSS3
border 〈length〉 || 〈border style〉 || 〈color〉 see individual properties CSS2, CSS3
border-radius [ 〈length〉 | 〈percentage〉 ]{1,4} [ / [ 〈length〉 | 〈percentage〉 ]{1,4} ]? see individual properties CSS3
border-image 〈border-image-source〉 || 〈border-image-slice〉 [ / 〈border-image-width〉 | / 〈border-image-width〉? / 〈border-image-outset〉 ]? || 〈border-image-repeat〉 see individual properties CSS3 
〈border style〉 = none | solid | inset | outset | hidden | dotted | dashed | double | groove | ridge
〈corner radius〉 = [ 〈length〉 | 〈percentage〉 ]{1,2}

Outline properties

Name Value Initial Inh. Ani. Reference Notes
outline-style none | solid | inset | outset | hidden | dotted | dashed | double | groove | ridge none CSS2, CSS3
outline-width 〈length〉 0px ✓ CSS2, CSS3
outline-color 〈color〉 currentColor ✓ CSS2, CSS3
outline-offset 〈length〉 0px CSS3
-gtk-outline-top-left-radius 〈corner radius〉 0 ✓
-gtk-outline-top-right-radius 〈corner radius〉 0 ✓
-gtk-outline-bottom-right-radius 〈corner radius〉 0 ✓
-gtk-outline-bottom-left-radius 〈corner radius〉 0 ✓
Shorthand Value Initial Reference Notes
outline 〈outline-color〉 || 〈outline-style〉 || 〈outline-width〉 see individual properties CSS2, CSS3
-gtk-outline-radius [ 〈length〉 | 〈percentage〉 ]{1,4} [ / [ 〈length〉 | 〈percentage〉 ]{1,4} ]? see individual properties

GTK uses the CSS outline properties to render the ‘focus rectangle’.

Background properties

Name Value Initial Inh. Ani. Reference Notes
background-color 〈color〉 rgba(0,0,0,0) ✓ CSS2, CSS3
background-clip 〈box〉 [ , 〈box〉 ]* border-box CSS3
background-origin 〈box〉 [ , 〈box〉 ]* padding-box CSS3
background-size 〈bg-size〉 [ , 〈bg-size〉 ]* auto ✓ CSS3
background-position 〈position〉 [ , 〈position〉 ]* 0 ✓ CSS2, CSS3
background-repeat 〈bg-repeat〉 [ , 〈bg-repeat〉 ]* repeat CSS2, CSS3
background-image 〈bg-image〉 [ , 〈bg-image〉 ]* none ✓ CSS2, CSS3 not supported: urls without quotes, CSS radial gradients, colors in crossfades
background-blend-mode 〈blend-mode〉 [ , 〈blend-mode〉 ]* normal only affects multiple backgrounds
box-shadow none | 〈box shadow〉 [ , 〈box shadow〉 ]* none ✓ CSS3
Shorthand Value Initial Reference Notes
background [ 〈bg-layer〉 , ]* 〈final-bg-layer〉 see individual properties CSS2, CSS3 
〈box〉 = border-box | padding-box | content-box
〈bg-size〉 = [ 〈length〉 | 〈percentage〉 | auto ]{1,2} | cover | contain
〈position〉 = [ left | right | center | top | bottom | 〈percentage〉 | 〈length〉 ]{1,2,3,4}
〈bg-repeat〉 = repeat-x | repeat-y | [ no-repeat | repeat | round | space ]{1,2}
〈bg-image〉 = 〈image〉 | none
〈bg-layer〉 = 〈bg-image〉 || 〈position〉 [ / 〈bg-size〉 ]? || 〈bg-repeat〉 || 〈box〉 || 〈box〉
〈final-bg-layer〉 = 〈bg-image〉 || 〈position〉 [ / 〈bg-size〉 ]? || 〈bg-repeat〉 || 〈box〉 || 〈box〉 || 〈color〉
〈blend-mode〉 = color || color-burn || color-dodge || darken || difference || exclusion ||
               hard-light || hue || lighten || luminosity || multiply || normal || overlay ||
               saturate || screen || soft-light
〈box shadow〉 = inset? && 〈length〉{2,4}? && 〈color〉?

As in CSS, the background color is rendered underneath all the background image layers, so it will only be visible if background images are absent or have transparency.

Alternatively, multiple backgrounds can be blended using the background-blend-mode property.

Transition properties

Name Value Initial Inh. Ani. Reference Notes
transition-property none | all | 〈property name〉 [ , 〈property name〉 ]* all CSS3
transition-duration 〈time〉 [ , 〈time〉 ]* 0s CSS3
transition-timing-function 〈single-timing-function〉 [ , 〈single-timing-function〉 ]* ease CSS3
transition-delay 〈time〉 [ , 〈time〉 ]* 0s CSS3
Shorthand Value Initial Reference Notes
transition 〈single-transition〉 [ , 〈single-transition〉 ]* see individual properties CSS3 
〈single-timing-function〉 = ease | linear | ease-in | ease-out | ease-in-out |
                           step-start | step-end | steps( 〈integer〉 [ , [ start | end ] ]? ) |
                           cubic-bezier( 〈number〉, 〈number〉, 〈number〉, 〈number〉 )
〈single-transition〉 = [ none | 〈property name〉 ] || 〈time〉 || 〈single-transition-timing-function〉 || 〈time〉

Animation properties

Name Value Initial Inh. Ani. Reference Notes
animation-name 〈single-animation-name〉 [ , 〈single-animation-name〉 ]* none CSS3
animation-duration 〈time〉 [ , 〈time〉 ]* 0s CSS3
animation-timing-function 〈single-timing-function〉 [ , 〈single-timing-function〉 ]* ease CSS3
animation-iteration-count 〈single-animation-iteration-count〉 [ , 〈single-animation-iteration-count〉 ]* 1 CSS3
animation-direction 〈single-animation-direction〉 [ , 〈single-animation-direction〉 ]* normal CSS3
animation-play-state 〈single-animation-play-state〉 [ , 〈single-animation-play-state〉 ]* running CSS3
animation-delay 〈time〉 [ , 〈time〉 ]* 0s CSS3
animation-fill-mode 〈single-animation-fill-mode〉 [ , 〈single-animation-fill-mode〉 ]* none CSS3
Shorthand Value Initial Reference Notes
animation 〈single-animation〉 [ , 〈single-animation〉 ]* see individual properties CSS3 
〈single-animation-name〉 = none | 〈property name〉
〈single-animation-iteration-count〉 = infinite | 〈number〉
〈single-animation-direction〉 = normal | reverse | alternate | alternate-reverse
〈single-animation-play-state〉 = running | paused
〈single-animation-fill-mode〉 = none | forwards | backwards | both
〈single-animation〉 = 〈single-animation-name〉 || 〈time〉 || 〈single-timing-function〉 || 〈time〉 ||
                     〈single-animation-iteration-count〉 || 〈single-animation-direction〉 ||
                     〈single-animation-play-state〉 || 〈single-animation-fill-mode〉

Key binding properties

Name Value Initial Inh. Ani. Reference Notes
-gtk-key-bindings none | 〈binding name〉 [ , 〈binding name〉 ]* none

〈binding name〉 must have been assigned to a binding set with a binding-set rule.