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
withevent.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>
.