| E:focus-within | [CSS Selector Level 4](https://drafts.csswg.org/selectors/#focus-within-pseudo) | Set on all ancestors of the focus widget, unlike CSS |
| E:focus-visible | [CSS Selector Level 4](https://drafts.csswg.org/selectors/#focus-within-pseudo) | Set on focus widget and all ancestors, unlike CSS |
|text-decoration-color| [CSS Text Decoration Level 3](https://www.w3.org/TR/css-text-decor-3/#text-decoration-color-property) | |
|text-decoration-style| [CSS Text Decoration Level 3](https://www.w3.org/TR/css-text-decor-3/#text-decoration-style-property) | CSS allows dashed and dotted |
|text-shadow| [CSS Text Decoration Level 3](https://www.w3.org/TR/css-text-decor-3/#text-shadow-property) | |
|text-decoration| [CSS Text Decoration Level 3](https://www.w3.org/TR/css-text-decor-3/#text-decoration-property) | |
|-gtk-icon-source| [Image](https://www.w3.org/TR/css-backgrounds-3/#typedef-image), `builtin` or `none` | used for builtin icons in buttons and expanders |
|-gtk-icon-size| [Length](https://www.w3.org/TR/css3-values/#length-value) | size used for builtin icons in buttons and expanders |
|-gtk-icon-style| `requested`, `regular` or `symbolic` | preferred style for application-loaded icons |
|-gtk-icon-transform| [Transform list](https://drafts.csswg.org/css-transforms-1/#typedef-transform-list) or `none` | applied to builtin and application-loaded icons |
|-gtk-icon-palette| Color palette, as explained above | used to recolor symbolic icons |
|-gtk-icon-shadow| [Shadow](https://www.w3.org/TR/css-backgrounds-3/#typedef-shadow) or `none` | applied to builtin and application-loaded icons |
|-gtk-icon-filter| [Filter value list](https://www.w3.org/TR/filter-effects-1/#typedef-filter-value-list) or `none` | applied to builtin and application-loaded icons |
|margin| [CSS Box Model Level 3](https://www.w3.org/TR/css3-box/#margin) | a 'four sides' property |
|padding| [CSS Box Model Level 3](https://www.w3.org/TR/css3-box/#padding) | a 'four sides' property |
|border-top-width| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-width) | CSS allows other values |
|border-right-width| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-width) | CSS allows other values |
|border-bottom-width| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-width) | CSS allows other values |
|border-left-width| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-width) | CSS allows other values |
|border-top-style| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-style) | |
|border-right-style| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-style) | |
|border-bottom-style| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-style) | |
|border-left-style| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-style) | |
|border-top-right-radius| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-radius) | |
|border-bottom-right-radius| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-radius) | |
|border-bottom-left-radius| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-radius) | |
|border-top-left-radius| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-radius) | |
|border-top-color| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-color) | |
|border-right-color| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-color) | |
|border-bottom-color| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-color) | |
|border-left-color| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-color) | |
|border-image-source| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-image-source) | |
|border-image-repeat| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-image-repeat) | |
|border-image-slice| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-image-slice) | a 'four sides' property |
|border-image-width| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-image-width) | a 'four sides' property |
|border-width| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-width) | a 'four sides' property |
|border-style| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#the-border-style) | a 'four sides' property |
|border-color| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#border-color) | a 'four sides' property |
|border-top| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#border-top) | |
|border-right| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#border-right) | |
|border-bottom| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#border-bottom) | |
|border-left| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#border-left) | |
|border| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#border) | |
|border-radius| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#border-radius) | |
|border-image| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#border-image) | |
|outline-style| [CSS Basic User Interface Level 3](https://www.w3.org/TR/css3-ui/#outline-style) | initial value is none, auto is not supported |
|outline-width| [CSS Basic User Interface Level 3](https://www.w3.org/TR/css3-ui/#outline-width) | |
|outline-color| [CSS Basic User Interface Level 3](https://www.w3.org/TR/css3-ui/#outline-color) | initial value is currentColor, invert is not supported |
|outline-offset| [CSS Basic User Interface Level 3](https://www.w3.org/TR/css3-ui/#outline-offset) | |
|outline| [CSS Basic User Interface Level 3](https://www.w3.org/TR/css3-ui/#propdef-outline) | |
|background-color| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#background-color) | |
|background-clip| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#background-clip) | |
|background-origin| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#background-origin) | |
|background-size| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#background-size) | |
|background-position| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#background-position) | |
|background-repeat| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#background-repeat) | |
|background-image| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#background-image) | not supported: urls without quotes, colors in crossfades |
|box-shadow| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#box-shadow) | |
|background-blend-mode| [CSS Compositing and Blending Level 1](https://www.w3.org/TR/compositing-1/#propdef-background-blend-mode) | only affects multiple backgrounds |
|background| [CSS Backgrounds and Borders Level 3](https://www.w3.org/TR/css3-background/#background) | |