Button: Features

With click handler

Disabled button

Minimum click area

Usage with native form

Supports the following use cases:

• Submit on button click
• Reset native form fields when using type="reset"
• Submit on button enter or space keypress
• Submit on enter keypress inside an input

Important notes:

• A (lion)-button of type submit is mandatory for the last use case, if you have multiple inputs. This is native behavior.
• @click on <lion-button> and @submit on <form> are triggered by these use cases. We strongly encourage you to listen to the submit handler if your goal is to do something on form-submit.
• To prevent form submission full page reloads, add a submit handler on the form @submit with event.preventDefault(). Adding it on the <lion-button> is not enough.

Considerations

Why a Web Component?

There are multiple reasons why we used a Web Component as opposed to a CSS component.

• Target size: The minimum target size is 40 pixels, which makes even the small buttons easy to activate. A container element was needed to make this size possible.
• Advanced styling: There are advanced styling options regarding icons in buttons, where it is a lot more maintainable to handle icons in our button using slots. An example is that a sticky icon-only buttons may looks different from buttons which have both icons and text.
• Native form integration: The lion button works with native <form> submission, and even implicit form submission on-enter. A lot of delegation logic had to be created for this to work.

Event target

We want to ensure that the event target returned to the user is <lion-button>, not button. Therefore, simply delegating the click to the native button immediately, is not desired. Instead, we catch the click event in the <lion-button>, and ensure delegation inside of there.

Flashing a native button click as a direct child of form

By delegating the click() to the native button, it will bubble back up to <lion-button> which would cause duplicate actions. We have to simulate the full .click() however, otherwise form submission is not triggered. So this bubbling cannot be prevented. Therefore, on click, we flash a <button> to the form as a direct child and fire the click on that button. We then immediately remove that button. This is a fully synchronous process; users or developers will not notice this, it should not cause problems.

Native button & implicit form submission

Flashing the button in the way we do solves almost all issues except for one. One of the specs of W3C is that when you have a form with multiple inputs, pressing enter while inside one of the inputs only triggers a form submit if that form has a button of type submit.

To get this particular implicit form submission to work, having a native button in our <lion-button> is a hard requirement. Therefore, not only do we flash a native button on the form to delegate <lion-button> trigger to <button> and thereby trigger form submission, we also add a native button inside the <lion-button> whose type property is synchronized with the type of the <lion-button>.