Diving Into the Toplayer: Where Dialogs, Popovers, and Modals Live

Tim Dame's talk focuses on the top layer of web design, particularly dialogues, popovers, and models, and how they overlap content on the web.

Dialogue elements were not widely used before 2020 because they were only supported in Chrome and had numerous accessibility issues, making them an impractical choice for web developers.

A popover is an HTML attribute that creates a floating overlay for providing information or actions, appearing above the main content without blocking the user's workflow.

A popover appears above the main content without blocking the user's workflow and uses light dismiss, whereas a modal dialogue requires user interaction to proceed and uses explicit dismiss.

The dialogue element automatically adds a role of dialogue for accessibility, allows opening as a modal or non-modal, supports closing with the escape key, and manages focus trapping when used as a modal.

The top layer provides a dedicated layer above the main document for content like dialogues and popovers, eliminating the complexity and limitations of using Z-index for positioning overlays.

The maximum Z-index value is about 2 billion, which is the largest number that can be stored in a 32-bit integer, marking the limit for Z-index values in web development.

Tim Dame is a frontend chapter lead at ABN AMRO, a Dutch bank, and an advocate for web accessibility. He is also a host of the "Focus Trap" podcast, discussing digital accessibility and web development.

Using Z-index for overlay content can lead to a "Z-index mess," where complex web applications end up with conflicting Z-index values, causing issues in content layering.

The dialogue element in HTML supports automatic role assignment for screen readers, focus management by focusing the first interactable element, and trapping focus within modal dialogues for better accessibility.