Component Interaction Patterns

Component Interaction Patterns

Detailed interaction patterns for common UI components, with attention to user goals, meaning, and error prevention.

Table of Contents

• Pattern Philosophy
• Forms & Inputs
• Modals & Dialogs
• Dropdowns & Menus
• Drag & Drop
• Lists & Tables
• Navigation
• Search
• Notifications & Toasts
• Tooltips & Popovers
• Sliders & Range Inputs
• Date & Time Pickers

Pattern Philosophy

Before implementing any pattern, ask:

1. What is the user's goal? Not "use this component" but "accomplish this task"
2. Is this component necessary? Could we eliminate it entirely?
3. What errors might occur? How do we prevent or recover from them?
4. What should the user feel? Confidence? Delight? Relief?

Components are means, not ends. The best component is often no component at all.

Forms & Inputs

User Goal Context

Users filling forms rarely want to "fill a form." They want to:

• Complete a purchase
• Submit an application
• Update their settings
• Send a message

Every field is friction. Eliminate fields that don't directly serve the goal.

Text Inputs

States & Meaning

Error Prevention

• Use input constraints (type="email", maxlength)
• Auto-format as user types (phone numbers, credit cards)
• Show format hints before errors occur
• Validate on blur, re-validate on change after error
• Never clear user input on error

Label Patterns

• Always use visible labels (not placeholder-only)
• Float label: compact, modern feel
• Static label: clearest, most accessible
• Associate labels with inputs (for/id) for screen readers

Keyboard

• Tab: next field
• Shift+Tab: previous field
• Enter: submit (single-line) or next field
• Escape: blur, optionally revert

Textareas

• Auto-grow height as content grows (with max-height)
• Character count for limited fields (shows remaining, not error at limit)
• Resize handle if appropriate

Checkboxes & Radio Buttons

Goal context: Selection is a micro-commitment. Make the commitment clear.

Checkbox States

• Unchecked → Checked → (Indeterminate for mixed children)
• Click anywhere on label to toggle
• Focus ring on control, not label

Radio Groups

• Arrow keys navigate between options
• Only one radio receives Tab focus
• Selection can follow focus (faster) or require explicit activation (safer for consequential choices)

Form Layout

Single Column (default)

• Labels above inputs for easy scanning
• Group related fields with spacing or dividers
• Primary action left-aligned (right in RTL)

Progressive Disclosure

• Show only required fields initially
• Reveal optional/advanced fields on demand
• Don't overwhelm; respect the user's attention

Error Summary

• On submit failure, summarize errors at top
• Link each error to its field
• Focus the summary or first error

Modals & Dialogs

When to Use Modals

Use modals when:

• User must make a decision before continuing
• Action is destructive and needs confirmation
• Context isolation reduces errors (complex wizards)
• System requires exclusive attention (authentication)

Avoid modals when:

• User needs to reference content behind the modal
• Trial-and-error adjustment is needed (use inline/inspector)
• Action can easily be undone (use undo, not confirmation)
• You're using a modal because it's "easy" to implement

Modal Types & User Goals

Opening

• Animate from trigger element (connection) or center (focus)
• Duration: 200-300ms ease-out
• Focus first interactive element or close button
• Prevent background scroll

Focus Management (Critical)

1. Store previous focus location
2. Move focus into modal (first focusable element)
3. Trap focus within modal (Tab cycles through)
4. On close, restore focus to trigger element

Closing

• Close button (X) always visible
• Escape key closes (unless destructive action in progress)
• Backdrop click closes (configurable—disable for critical confirmations)
• Warn on unsaved changes: "You have unsaved changes. Discard?"

Error Handling in Modals

• If form submission fails, keep modal open
• Show errors inline within the modal
• Don't close on error—user loses context

Stacking Modals

Avoid when possible. Stacking modals indicates a flow design problem.

If truly necessary:

• Each modal gets its own backdrop layer
• Escape closes topmost only
• Focus trapped in topmost
• Consider: should this be a multi-step wizard instead?

Dropdowns & Menus

User Goal Context

Dropdowns present choices. The goal is to make the right choice quickly and confidently.

Activation

• Click to open (not hover—accessibility requirement)
• Enter/Space opens when trigger focused
• Arrow Down opens and selects first item

Keyboard Navigation

Positioning

• Default: below trigger
• Flip if insufficient space
• Maintain 8px from viewport edges

Menu Item Design

Error Prevention

• Disable unavailable options (don't hide them—explain why)
• For long lists, add search/filter
• Group related items with headers
• Show selected value in trigger (never unclear state)

Nested Menus

• Open on hover with 200ms delay
• Arrow Right opens submenu
• Arrow Left closes submenu
• Safe triangle for diagonal mouse movement

Drag & Drop

User Goal Context

Drag and drop enables direct manipulation—physically moving objects. The goal is natural, intuitive rearrangement.

Signifiers (Affordances Made Visible)

• Drag handle: grip icon (⋮⋮) or entire item
• Cursor: grab on hover, grabbing during drag
• Lift effect on drag start (shadow + slight scale)

During Drag

Visual Feedback

• Ghost/preview following cursor (semi-transparent)
• Placeholder in original position
• Valid drop zones highlighted
• Invalid zones dimmed or unchanged
• Insertion indicator (line) shows where item will land

Auto-Scroll

• Scroll container when dragging near edges
• Accelerate near very edge

Drop Feedback

• Animate item into new position (200-300ms)
• Remove ghost immediately
• Brief highlight on dropped item (confirmation)

Keyboard Alternative (Required)

• Space: select item for move
• Arrow keys: navigate through positions
• Space/Enter: drop at current position
• Escape: cancel move, return to original

Multi-Item Drag

• Badge showing count ("3 items")
• Visual stack of selected items
• All items move as unit

Error Recovery

• Undo for accidental drops
• Escape cancels during drag
• Clear visual state if drop fails

Lists & Tables

User Goal Context

Lists and tables help users find, compare, and act on items. Goals include:

• Find a specific item
• Compare items to make a choice
• Perform actions on one or multiple items
• Understand patterns across data

Selection

Single Select

• Click to select
• Arrow keys move selection
• Enter activates selected item

Multi-Select

• Click toggles individual selection
• Shift+Click for range
• Cmd/Ctrl+Click for non-contiguous
• Checkbox column for explicit multi-select

Sorting

• Click column header to sort
• Click again to reverse
• Visual indicator (arrow) shows sort state
• Remember sort preference (if appropriate)

Filtering

• Filter controls above list
• Instant filtering (debounce 150-300ms)
• Show count: "23 of 156 items"
• Clear all filters button when active
• Preserve filters across sessions (if appropriate)

Empty States (Dramatic Moments)

Row Actions

• Hover actions: appear on row hover
• Context menu: right-click or overflow (⋮)
• Swipe actions: mobile (always provide undo)
• Inline edit: click cell to edit

Infinite Scroll / Virtualization

• Load more 2-3 screens before bottom
• Show loading indicator during fetch
• Maintain scroll position on data updates
• Virtualize for performance (render only visible)

Navigation

User Goal Context

Navigation helps users understand where they are and how to get where they want to go. The goal is orientation and confidence.

Tab Navigation

• Tabs as role="tablist" with role="tab" children
• Arrow keys move between tabs
• Tab/Shift+Tab exits tablist
• Active tab: aria-selected="true", clear visual indicator

Breadcrumbs

What they communicate: "You are here, and here's how you got here."

• Current page: text only (not a link)
• Separator between items (/ or >)
• Truncate middle items with "..." for long paths
• Click any ancestor to navigate up

Pagination

• Show current page and total
• Previous/Next buttons (disabled at bounds)
• Direct page input for large page counts
• Consider: is pagination better than infinite scroll for this use case?

Sidebar Navigation

• Collapsible: icon-only or full labels
• Nested items: expand/collapse with disclosure
• Current item: strong visual indicator
• Keyboard: Arrow keys navigate, Enter activates

Search

User Goal Context

Search users have a target in mind. Help them find it quickly, or learn it doesn't exist.

Search Input

• Magnifying glass icon (left, signifies purpose)
• Clear button (right, appears when filled)
• Escape clears and closes results
• Placeholder suggests what can be searched

Instant Search

• Debounce input (150-300ms)
• Show loading state in results area
• Minimum characters (2-3) before searching
• Highlight matching text in results

Search Results

• Show count: "12 results for 'widget'"
• Group by type if mixed content
• No results: helpful suggestions, check spelling
• Recent searches when input empty

Command Palette

• Open: Cmd/Ctrl+K
• Fuzzy matching on command names
• Recent commands at top
• Category headers
• Keyboard-first: arrows + Enter

Notifications & Toasts

User Goal Context

Notifications inform users of events they didn't directly trigger. The goal is awareness without disruption.

When to Notify

Notify for:

• Completion of background tasks
• Important state changes
• Errors requiring attention
• Time-sensitive information

Don't notify for:

• Every action the user just performed (use inline feedback)
• Low-importance information
• Marketing messages (unless explicitly opted in)

Positioning

• Top-right or bottom-right (most common)
• Top-center for critical alerts
• Stack vertically with 8-12px gap
• New notifications push others

Auto-Dismiss Timing

Interaction

• Hover pauses auto-dismiss
• Close button always visible
• Action button: "Undo", "View", "Retry"
• Swipe to dismiss (mobile)

Animation

• Enter: slide + fade (200-300ms)
• Exit: fade + slide (150-200ms)
• Stack reflow: animate position changes

Tooltips & Popovers

Tooltips

Purpose: Provide helpful context for ambiguous elements.

When to use:

• Icon-only buttons needing labels
• Truncated text needing full display
• Form fields needing clarification

When NOT to use:

• Critical information (use visible labels)
• Mobile-primary interfaces (hover-triggered)
• Lengthy content (use popovers)

Behavior:

• Show on hover after 300-500ms delay
• Hide immediately on mouse leave
• Show on focus for keyboard users
• Position: above by default, flip if clipped
• Content: text only, 1-2 lines max

Popovers

Purpose: Provide interactive content in context.

• Trigger: click (not hover)
• Can contain interactive elements
• Dismiss: click outside, Escape, explicit close
• Arrow pointing to trigger
• Focus trap if contains form elements

Sliders & Range Inputs

User Goal Context

Sliders let users explore a value space. The goal is finding the right value through direct manipulation.

When Sliders Excel

• Imprecise values where "about right" suffices
• Exploring a range to see effects
• Values that benefit from relative positioning

When Text Input is Better

• Precise values needed (type "24px" vs. drag to 24)
• Very large ranges
• Values with specific meaningful numbers

Single Value Slider

• Thumb: 20-24px minimum (44px for touch)
• Track: filled portion shows progress to value
• Value label: above thumb or in tooltip during drag
• Tick marks for discrete/meaningful values

Range Slider

• Two thumbs, independently draggable
• Thumbs cannot cross
• Filled track between thumbs

Keyboard (Required)

• ← / →: decrease/increase by step
• Page Up/Down: larger jumps
• Home/End: min/max values

Accessibility

• role="slider" with aria-valuemin, aria-valuemax, aria-valuenow
• aria-valuetext for human-readable: "50%" or "$500"
• Announce value changes

Date & Time Pickers

User Goal Context

Users selecting dates are usually scheduling something or filtering by time. The goal is choosing the right date quickly and confidently.

Date Picker

Input States

• Text input with format hint (MM/DD/YYYY or locale-appropriate)
• Calendar icon triggers picker
• Support manual typing for power users

Calendar View

• Month/year header with navigation
• Day grid with weekday headers
• Today: highlighted (subtle)
• Selected: filled/prominent
• Disabled: dimmed (past dates, unavailable slots)

Keyboard

• Arrow keys navigate days
• Page Up/Down: months
• Home/End: first/last of month
• Enter: select and close

Date Range Picker

• Two inputs or single with separator
• Visual range highlight in calendar
• Click start, then end
• Presets: "Last 7 days", "This month"

Time Picker

• Input with format hint
• Dropdown with intervals (15-30 min)
• Allow manual entry for precise times

Error Prevention

• Disable unavailable dates (don't let users select then show error)
• Clear format hints
• Accept multiple input formats, normalize display
• Show timezone clearly when relevant