T-shirt Sizing

T-shirt sizing is the way that Grommet leverages familiar clothing sizes of "small", "medium", "large", and other ranges of sizes to drive the sizing and spacing of components. Grommet maps these t-shirt sizes to specific pixel values. The mapping and pixel value derivation is explained below.

T-shirt sizing controls two aspects of a user interface:

• the height and width of layout components
• the spacing within and around components (e.g. gap, margin, padding, border, etc.)

When designing and developing with the HPE Design System, you should always use t-shirt sizes. If you find yourself specifying custom pixel values, this should be a warning signaling either:

• A need to consult with your designer about why a custom value is needed.
• Something in the implementation can and should be simplified.
• Or, there could be a gap in the Design System which should be reported and addressed.

In nearly every case, designs and development should be using t-shirt sizes for compatibility and maintenance.

T-shirt sizing delivers a more unified experience for HPE customers by creating consistent user interfaces across pages and across applications.

There are also benefits of t-shirt sizing for designers and developers!

T-shirt sizing creates a common language between designers and developers, as well as provides common, well-defined intervals which make designing and developing more efficient. Using pixel values, percentages, or other sizing methods to create layouts can result in applications that are less composable and less scalable. Instead, a container of content may just have a width of "medium", for example, and Grommet will take care of the rest.

Finally, t-shirt sizes enable content to responsively scale more easily and consistently. For example, a layout's padding may be set to "large" on desktop screen and gracefully adjust to "small" on mobile devices with minimal effort.

In order to create the range of sizes and their corresponding pixel values, a base unit of 24px is used as a scalar.

Below is a snippet from Grommet's base.js theme file where the calculations and resulting pixel values for the t-shirt sizes driving the height/width for components such as Box are defined. The base.js theme establishes many of the defaults leveraged across Grommet applications.

One of the main ways t-shirt sizing is used is to control the width/height of a component. For some components, like Box, this can be controlled with the width and height props. For other components, like Avatar, DataTable, or Text, the dimensions are controlled by the size prop. And others, like Grid, t-shirt sizes specify row and column dimensions.

The Grommet site provides documentation on the props available to any given component. If you're unsure if a component supports width, height, or size, that would be the right place to check.

Given the code snippet from the previous section and the explanation on t-shirt sizing for dimensions, if you were to implement the following code, you would have a Box with width of "384px" and height of "192px".

In addition to overall component dimensions, t-shirt sizing can also be used to define spacing and other styling such as pad, gap, margin, and border.

To create the pixel values for these styles, Grommet divides and/or multiplies the base unit of 24px by various integers.

Pad, gap, and margin are controlled by edgeSize and the corresponding pixel values also come from base.js in Grommet

Given this code snippet, if you were to implement the following code, you would have a Box with width of 384px, height of 192px, and pad of 48px.

Border sizing is controlled by borderSize.

Given this code snippet, if you were to implement the following code, you would have a Box with width of 384px, height of 192px, and a border with a width of 2px.

Sizes are intended to help give a UI a unified, harmonious experience. Therefore, there is a relationship between the pixel values that each size value maps to.

A given size (e.g., medium) is one half of the next size up (e.g., large).

For components that support a size prop, the default size is medium. This means that if you do not specify your own size, the component will render with the styling that corresponds with "medium" size.

Notice in this example of Button sizes how the "Default" button is the same size as the "Medium" button. In the code, you'll see:

Because medium is the default size, you can simplify your code by implementing a component without the size prop when medium is the desired size.