An independent implementation informed by the supplied screen recording and BoardUI’s public preview. No paid component, source code, font, or service is used.
01 / Setup
Copy and mount
Copy the HTML, CSS, and JavaScript from the Code tab, then call mountComposer(document.querySelector('[data-composer-demo]')). The Full page tab includes everything needed to run locally.
02 / Motion
One file, three small transitions
- A 56 × 56 px tile enters over 420 ms with a slight scale, lift, and blur.
- An SVG path with
pathLength="100"maps progress directly to a clockwise rounded outline. - After reaching 100%, the percentage blurs out while the remove button resolves in the same corner.
03 / Transport
Connect actual progress in your application
This page simulates each file over 950 ms, holds 100% briefly, and leaves a 140 ms gap before the next file. It makes no upload or message requests. In a production uploader, replace the animation clock with actual progress events, and only mark a tile ready when the server confirms success. Unknown progress should remain indeterminate.
04 / Behavior
Try the complete interaction
Use the + button or drop files onto the composer. Image previews use temporary local object URLs; other formats show file icons. Remove a prepared attachment, clear the queue mid-animation, or send a local demo message. Enter sends; Shift + Enter inserts a new line. Files are capped at 8 items and 20 MB each.
05 / Accessibility
Motion is optional
Reduced-motion preferences skip the simulated animation and prepare the files immediately. Every icon button has a name, ready attachments can be removed with the keyboard, and completion and validation feedback are announced without announcing every frame. Call the returned destroy() method when unmounting to stop frames, timers, listeners, and release previews.
06 / Reference
Visual reference
Inspired by BoardUI Composer Attachments and the supplied 6-second recording. The queue controller, markup, icons, and styles here are independently authored.