Appendix B, Customization Guidelines

To ensure your Car UI customizations proceed as efficiently as possible, use the following values to define expectations for on-screen content visibility and functionality.

General Guidelines

Limits in this section are true regardless of layout:

Item	Guidelines
Typography	Tab text labels must be wide enough to display strings of at least 6 “W” characters. Text containers must be tall enough to fully display a single “H” character. Text sizes must appear in descending order. For example, car_ui_body_1 > car_ui_body_2 > car_ui_body_3.
Contrast	Contrast between foreground (text) and background must be at least 4.5:1. Contrast between button color and background must be at least 3:1. Tab selected state contrast with background must be at least 4.5:1. Tab selected state contrast with unselected state must be at least 3:1.
Others	All icons must be vector drawables. Touch targets must be at least 76 dp wide. Padding constants must appear in descending order. For example, car_ui_padding_0 > car_ui_padding_1 > car_ui_padding_2.

Component-Specific Guidelines

Values provided below apply to specific components:

Item	Guidelines
Toolbar	Must be wide enough to display title strings of at least 20 "W" characters.
Preference	Must be wide enough to display title strings of at least 20 "W" characters.

Layout-Based Guidelines

Limits provided in this section pertain to specific layouts and combinations of Car UI library components.

Location Dialog

A test dialog that contains the same content as the Google Play Services location dialog, constructed with Car UI library components and tested to ensure full content visibility:

Item	Guidelines
Title	Must wide enough to display strings of at least 38 “W” characters.
Body	Must be completely visible and large enough to display: Strings that may consist of at least 270 “W” characters. At least four (4) lines of text.
Call-to-Action (CTA)	CTA must be completely visible: Dialog must be wide enough to display at least two (2) CTAs. Titles must be wide enough to display strings of at least 9 “W” characters.

Settings Screen

A Test Settings screen is composed of the App Bar, Subheader, and List Items components. Each is described below:

Item	Guidelines
App Bar	Title must wide enough to display strings of at least 12 “W” characters. Must be at least 76dp tall.
Subheader	Must be wide enough to display strings of at least 12 “W” characters.
List Items	Must be: Wide enough to display strings of at least 12 “W” characters. At least 76dp tall.