Components: Add readme for CustomSelectControl.

docs/manifest-devhub.json

@@ -647,6 +647,12 @@
 		"markdown_source": "../packages/components/src/color-picker/README.md",
 		"parent": "components"
 	},
+	{
+		"title": "CustomSelectControl",
+		"slug": "custom-select-control",
+		"markdown_source": "../packages/components/src/custom-select-control/README.md",
+		"parent": "components"
+	},
 	{
 		"title": "Dashicon",
 		"slug": "dashicon",

packages/components/src/custom-select-control/README.md

@@ -0,0 +1,117 @@
+# CustomSelectControl
+
+`CustomSelectControl` allows users to select an item from a single-option menu just like [`SelectControl`](/packages/components/src/select-control/readme.md), with the addition of being able to provide custom styles for each item in the menu. This means it does not use a native `<select>`, so should only be used if the custom styling is necessary.
+
+## Table of contents
+
+1. [Design guidelines](#design-guidelines)
+2. [Development guidelines](#development-guidelines)
+3. [Related components](#related-components)
+
+## Design guidelines
+
+These are the same as [the ones for `SelectControl`s](/packages/components/src/select-control/readme.md#design-guidelines).
+
+## Development guidelines
+
+### Usage
+
+```jsx
+/**
+ * WordPress dependencies
+ */
+import { CustomSelectControl } from "@wordpress/components";
+import { useState } from "@wordpress/compose";
+
+const options = [
+	{
+		key: 'small',
+		name: 'Small',
+		style: { fontSize: '50%' },
+	},
+	{
+		key: 'normal',
+		name: 'Normal',
+		style: { fontSize: '100%' },
+	},
+	{
+		key: 'large',
+		name: 'Large',
+		style: { fontSize: '200%' },
+	},
+	{
+		key: 'huge',
+		name: 'Huge',
+		style: { fontSize: '300%' },
+	},
+];
+
+function MyCustomSelectControl() {
+	const [ , setFontSize ] = useState();
+	return (
+		<CustomSelectControl
+			label="Font Size"
+			options={ options }
+			onChange={ ( { selectedItem } ) => setFontSize( selectedItem ) }
+		/>
+	);
+}
+
+function MyControlledCustomSelectControl() {
+	const [ fontSize, setFontSize ] = useState( options[ 0 ] );
+	return (
+		<CustomSelectControl
+			label="Font Size"
+			options={ options }
+			onChange={ ( { selectedItem } ) => setFontSize( selectedItem ) }
+			value={ options.find( ( option ) => option.key === fontSize.key ) }
+		/>
+	);
+}
+```
+
+### Props
+
+#### className
+
+A custom class name to append to the outer `<div>`.
+- Type: `String`
+- Required: No
+
+#### hideLabelFromVision
+
+Used to visually hide the label. It will always be visible to screen readers.
+- Type: `Boolean`
+- Required: No
+
+#### label
+
+The label for the control.
+- Type: `String`
+- Required: Yes
+
+#### options
+
+The options that can be chosen from.
+- Type: `Array<{ key: String, name: String, style: ?{}, ...rest }>`
+- Required: Yes
+
+#### onChange
+
+Function called with the control's internal state changes. The `selectedItem` property contains the next selected item.
+- Type: `Function`
+- Required: No
+
+#### value
+
+Can be used to externally control the value of the control, like in the `MyControlledCustomSelectControl` example above.
+- Type: `Object`
+- Required: No
+
+## Related components
+
+- Like this component, but implemented using a native `<select>` for when custom styling is not necessary, the `SelectControl` component.
+
+- To select one option from a set, when you want to show all the available options at once, use the `Radio` component.
+- To select one or more items from a set, use the `CheckboxControl` component.
+- To toggle a single setting on or off, use the `ToggleControl` component.