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Theme Select
Colour-theme switcher: click to step to the next mode, hover for the full menu.
Attributes
Name
Type
Default
Description
modes
Array<string | ThemeSelectMode>
['system', 'light', 'dark']
The states to cycle through: "system,light,dark", a JSON array, or objects from script.
value
string
—
The mode in effect. Assigning it selects that mode silently; select() and next() report the change.
menu
'auto' | 'always' | 'never'
auto
When to offer the dropdown: auto (three or more modes), always, or never.
placement
Placement
bottom
Preferred placement of the menu (floating-ui names).
show-label
boolean
false
Show the current mode's label beside its icon.
disabled
boolean
false
Blocks interaction and dims the control.
manual
boolean
false
Do not touch the document or storage; the host applies the theme itself from theme-change.
target
string | HTMLElement | undefined
undefined
Element the scheme is written to, or the id of one. Defaults to <html>.
theme-attribute
string
data-theme
Attribute written on the target, data-theme by default.
storage-key
string
c2n-theme
localStorage key the chosen mode is remembered under. Empty disables persistence.
open-delay
number
150
Milliseconds the pointer must rest on the trigger before the menu opens.
close-delay
number
200
Milliseconds the menu stays open after the pointer leaves, so it can be crossed into.
aria-label
string
—
Accessible name of the trigger. Defaults to Theme: <current label>.
Slots
Name
Description
system-icon
Replaces the built-in monitor icon of the system mode, in the trigger and in its menu row. Every mode takes its icon from <value>-icon, so a custom mode brings its own.
light-icon
Replaces the built-in sun icon of the light mode.
dark-icon
Replaces the built-in moon icon of the dark mode.
check
Mark shown beside the selected row in the menu. Defaults to a check.
Events
Name
Type
Description
theme-change
CustomEvent<ThemeSelectChangeDetail>
The scheme in effect changed: a mode was picked, or the OS preference moved while system was selected. detail.value is the mode, detail.theme the scheme it resolves to. Does not bubble; assigning value from script is silent.
CSS parts
Shadow DOM styling hooks used with ::part(name). Prefer CSS custom properties when they cover the change.
Name
Description
trigger
The button that shows the current mode and advances to the next one.
icon
The icon box inside the trigger and inside every menu row.
label
The trigger's text, rendered only with show-label.
menu
The dropdown surface.
menu-item
One row of the dropdown.
check
Marker region containing the check slot or fallback beside the selected row.
CSS custom properties
Grouped by semantic target and state from --c2-component__target__state--property. Click a group to collapse it; click a name to copy it.
Name
Type
Default
Description
c2-theme-select
--c2-theme-select--transition-duration
time
150ms
Icon cross-fade and trigger colour change.
c2-theme-select > trigger
--c2-theme-select__trigger--size
pixel
32px
Height of the trigger, and its width while icon-only.
--c2-theme-select__trigger--padding-inline
pixel
8px
Side padding, used only with show-label.
--c2-theme-select__trigger--gap
pixel
8px
Space between the icon and the label.
--c2-theme-select__trigger--border-radius
border-radius
8px
--c2-theme-select__trigger--border
border
1px solid transparent
--c2-theme-select__trigger--background
color
transparent
--c2-theme-select__trigger--color
color
#18181b
c2-theme-select > trigger > hover
--c2-theme-select__trigger__hover--background
color
#f4f4f5
--c2-theme-select__trigger__hover--color
color
—
Falls back to the resting colour.
c2-theme-select > trigger > active
--c2-theme-select__trigger__active--background
color
#e4e4e7
c2-theme-select > trigger > open
--c2-theme-select__trigger__open--background
color
—
Trigger fill while the menu is open; falls back to the hover fill.
c2-theme-select > trigger > focus
--c2-theme-select__trigger__focus--outline
outline
2px solid rgba(2, 101, 220, 0.4)
--c2-theme-select__trigger__focus--outline-offset
pixel
2px
c2-theme-select > trigger > disabled
--c2-theme-select__trigger__disabled--opacity
opacity
0.38
c2-theme-select > icon
--c2-theme-select__icon--size
pixel
16px
Side of the icon square, in the trigger and in the menu rows.
Colour-theme switcher: click to step to the next mode, hover for the full menu.
Attributes
Name
Type
Default
Description
modes
Array<string | ThemeSelectMode>
['system', 'light', 'dark']
The states to cycle through: "system,light,dark", a JSON array, or objects from script.
value
string
—
The mode in effect. Assigning it selects that mode silently; select() and next() report the change.
menu
'auto' | 'always' | 'never'
auto
When to offer the dropdown: auto (three or more modes), always, or never.
placement
Placement
bottom
Preferred placement of the menu (floating-ui names).
show-label
boolean
false
Show the current mode's label beside its icon.
disabled
boolean
false
Blocks interaction and dims the control.
manual
boolean
false
Do not touch the document or storage; the host applies the theme itself from theme-change.
target
string | HTMLElement | undefined
undefined
Element the scheme is written to, or the id of one. Defaults to <html>.
theme-attribute
string
data-theme
Attribute written on the target, data-theme by default.
storage-key
string
c2n-theme
localStorage key the chosen mode is remembered under. Empty disables persistence.
open-delay
number
150
Milliseconds the pointer must rest on the trigger before the menu opens.
close-delay
number
200
Milliseconds the menu stays open after the pointer leaves, so it can be crossed into.
aria-label
string
—
Accessible name of the trigger. Defaults to Theme: <current label>.
Slots
Name
Description
system-icon
Replaces the built-in monitor icon of the system mode, in the trigger and in its menu row. Every mode takes its icon from <value>-icon, so a custom mode brings its own.
light-icon
Replaces the built-in sun icon of the light mode.
dark-icon
Replaces the built-in moon icon of the dark mode.
check
Mark shown beside the selected row in the menu. Defaults to a check.
Events
Name
Type
Description
theme-change
CustomEvent<ThemeSelectChangeDetail>
The scheme in effect changed: a mode was picked, or the OS preference moved while system was selected. detail.value is the mode, detail.theme the scheme it resolves to. Does not bubble; assigning value from script is silent.
CSS parts
Shadow DOM styling hooks used with ::part(name). Prefer CSS custom properties when they cover the change.
Name
Description
trigger
The button that shows the current mode and advances to the next one.
icon
The icon box inside the trigger and inside every menu row.
label
The trigger's text, rendered only with show-label.
menu
The dropdown surface.
menu-item
One row of the dropdown.
check
Marker region containing the check slot or fallback beside the selected row.
CSS custom properties
Grouped by semantic target and state from --c2-component__target__state--property. Click a group to collapse it; click a name to copy it.
Name
Type
Default
Description
c2-theme-select
--c2-theme-select--transition-duration
time
150ms
Icon cross-fade and trigger colour change.
c2-theme-select > trigger
--c2-theme-select__trigger--size
pixel
32px
Height of the trigger, and its width while icon-only.
--c2-theme-select__trigger--padding-inline
pixel
8px
Side padding, used only with show-label.
--c2-theme-select__trigger--gap
pixel
8px
Space between the icon and the label.
--c2-theme-select__trigger--border-radius
border-radius
8px
--c2-theme-select__trigger--border
border
1px solid transparent
--c2-theme-select__trigger--background
color
transparent
--c2-theme-select__trigger--color
color
#18181b
c2-theme-select > trigger > hover
--c2-theme-select__trigger__hover--background
color
#f4f4f5
--c2-theme-select__trigger__hover--color
color
—
Falls back to the resting colour.
c2-theme-select > trigger > active
--c2-theme-select__trigger__active--background
color
#e4e4e7
c2-theme-select > trigger > open
--c2-theme-select__trigger__open--background
color
—
Trigger fill while the menu is open; falls back to the hover fill.
c2-theme-select > trigger > focus
--c2-theme-select__trigger__focus--outline
outline
2px solid rgba(2, 101, 220, 0.4)
--c2-theme-select__trigger__focus--outline-offset
pixel
2px
c2-theme-select > trigger > disabled
--c2-theme-select__trigger__disabled--opacity
opacity
0.38
c2-theme-select > icon
--c2-theme-select__icon--size
pixel
16px
Side of the icon square, in the trigger and in the menu rows.
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