5.8 KiB
Theming Documentation
Basic Architecture
A theme collection in Hydrogen is represented by a manifest.json
file and a theme.css
file.
The manifest specifies variants (eg: dark,light ...) each of which is a theme and maps to a single css file in the build output.
Each such theme is produced by changing the values of variables in the base theme.css
file with those specified in the variant section of the manifest:
More in depth explanations can be found in later sections.
Structure of manifest.json
Variables
CSS variables specific to a particular variant are specified in the variants
section of the manifest:
"variants": {
"light": {
...
"variables": {
"background-color-primary": "#fff",
"text-color": "#2E2F32",
}
},
"dark": {
...
"variables": {
"background-color-primary": "#21262b",
"text-color": "#fff",
}
}
}
These variables will appear in the css file (theme.css):
body {
background-color: var(--background-color-primary);
color: var(--text-color);
}
During the build process, this would result in the creation of two css files (one for each variant) where the variables are substitued with the corresponding values specified in the manifest:
element-light.css:
body {
background-color: #fff;
color: #2E2F32;
}
element-dark.css:
body {
background-color: #21262b;
color: #fff;
}
Derived Variables
In addition to simple substitution of variables in the stylesheet, it is also possible to instruct the build system to first produce a new value from the base variable value before the substitution.
Such derived variables have the form base_css_variable--operation-arg
and can be read as:
apply operation
to base_css_variable
with argument arg
.
Continuing with the previous example, it possible to specify:
.left-panel {
/* background color should be 20% more darker
than background-color-primary */
background-color: var(--background-color-primary--darker-20);
}
Currently supported operations are:
Operation | Argument | Operates On |
---|---|---|
darker | percentage | color |
lighter | percentage | color |
Aliases
It is possible give aliases to variables in the theme.css
file:
:root {
font-size: 10px;
/* Theme aliases */
--icon-color: var(--background-color-secondary--darker-40);
}
It is possible to further derive from these aliased variables:
div {
background: var(--icon-color--darker-20);
--my-alias: var(--icon-color--darker-20);
/* Derive from aliased variable */
color: var(--my-alias--lighter-15);
}
Colorizing svgs
Along with a change in color-scheme, it may be necessary to change the colors in the svg icons and images.
This can be done by supplying the preferred colors with query parameters:
my-awesome-logo.svg?primary=base-variable-1&secondary=base-variable-2
This instructs the build system to colorize the svg with the given primary and secondary colors.
base-variable-1
and base-variable-2
are the css-variables specified in the variables
section of the manifest.
For colorizing svgs, the source svg must use #ff00ff
as the primary color and #00ffff
as the secondary color:
original source image | transformation process |
Creating your own theme variant in Hydrogen
If you're looking to change the color-scheme of the existing Element theme, you only need to add your own variant to the existing manifest.json
.
The steps are fairly simple:
- Copy over an existing variant to the variants section of the manifest.
- Change
dark
,default
andname
fields. - Give new values to each variable in the
variables
section. - Build hydrogen.
Creating your own theme collection in Hydrogen
If a theme variant does not solve your needs, you can create a new theme collection with a different base theme.css
file.
- Create a directory for your new theme-collection under
src/platform/web/ui/css/themes/
. - Create
manifest.json
andtheme.css
files within the newly created directory. - Populate
manifest.json
with the base css variables you wish to use. - Write styles in your
theme.css
file using the base variables, derived variables and colorized svg icons. - Tell the build system where to find this theme-collection by providing the location of this directory to the
themeBuilder
plugin invite.config.js
:
...
themeBuilder({
themeConfig: {
themes: {
element: "./src/platform/web/ui/css/themes/element",
awesome: "path/to/theme-directory"
},
default: "element",
},
compiledVariables,
}),
...
- Build Hydrogen.
Changing the default theme
To change the default theme used in Hydrogen, modify the defaultTheme
field in config.json
file (which can be found in the build output):
"defaultTheme": {
"light": theme-id,
"dark": theme-id
}
Here theme-id is of the form theme-variant
where theme
is the key used when specifying the manifest location of the theme collection in vite.config.js
and variant
is the key used in variants section of the manifest.
Some examples of theme-ids are element-dark
and element-light
.
To find the theme-id of some theme, you can look at the built-asset section of the manifest in the build output.
This default theme will render as "Default" option in the theme-chooser dropdown. If the device preference is for dark theme, the dark default is selected and vice versa.
You'll need to reload twice so that Hydrogen picks up the config changes!