UI Feature Implementation

Single entry point for sidecar UI work. All new modals must use internal/modal. For complete keyboard shortcut listings, see references/keyboard-shortcuts-reference.md.

Quick Checklist

• Modals: use internal/modal, render with ui.OverlayModal, avoid manual hit region math
• Pills/chips/tabs: use styles.RenderPillWithStyle; auto-fallback when nerdFontsEnabled is false
• Keyboard: Commands + FocusContext + bindings must match; names short; priorities set
• Mouse: rebuild hit regions on each render; add general regions first, specific last
• Rendering: keep output within View width/height to avoid header/footer overlap. Use contentHeight := height - headerLines - footerLines
• Testing: verify keyboard, mouse, hover, scrolling, and footer hints
• Plugins must NOT render their own footer -- the app renders a unified footer from Commands()

Modals (internal/modal)

All new modals must use internal/modal. See docs/guides/declarative-modal-guide.md for the full API.

Create a modal

m := modal.New("Delete Worktree?",
    modal.WithWidth(58),
    modal.WithVariant(modal.VariantDanger),
    modal.WithPrimaryAction("delete"),
).
    AddSection(modal.Text("Name: " + wt.Name)).
    AddSection(modal.Spacer()).
    AddSection(modal.Buttons(
        modal.Btn(" Delete ", "delete", modal.BtnDanger()),
        modal.Btn(" Cancel ", "cancel"),
    ))

Render in View

func (p *Plugin) renderDeleteView(width, height int) string {
    background := p.renderListView(width, height)
    rendered := p.deleteModal.Render(width, height, p.mouseHandler)
    return ui.OverlayModal(background, rendered, width, height)
}

Handle input in Update

case tea.KeyMsg:
    action, cmd := p.deleteModal.HandleKey(msg)
    if action != "" {
        return p.handleModalAction(action)
    }
    return p, cmd

case tea.MouseMsg:
    action := p.deleteModal.HandleMouse(msg, p.mouseHandler)
    if action != "" {
        return p.handleModalAction(action)
    }
    return p, nil

Modal initialization and caching (critical)

Always call ensureModal() in BOTH View and Update handlers. Create an ensure function that:

1. Returns early if required state is missing
2. Caches based on width to avoid rebuilding every frame
3. Creates the modal only when needed

func (p *Plugin) ensureMyModal() {
    if p.targetItem == nil {
        return
    }
    modalW := 50
    if modalW > p.width-4 { modalW = p.width - 4 }
    if modalW < 20 { modalW = 20 }
    if p.myModal != nil && p.myModalWidthCache == modalW {
        return
    }
    p.myModalWidthCache = modalW
    p.myModal = modal.New("Title", modal.WithWidth(modalW), ...).
        AddSection(...)
}

The key handler MUST call ensure before checking nil:

func (p *Plugin) handleMyModalKeys(msg tea.KeyMsg) tea.Cmd {
    p.ensureMyModal()  // CRITICAL: Initialize before nil check
    if p.myModal == nil { return nil }
    action, cmd := p.myModal.HandleKey(msg)
    return cmd
}

Async content invalidation

When modal content depends on async data, invalidate the cache when data arrives:

case MyDataLoadedMsg:
    p.myData = msg.Data
    p.clearMyModal()  // Force rebuild with new content
    return p, nil

Modal keyboard shortcuts and footer hints

Modals need their own focus context and commands for footer hints:

1. Return a dedicated context from FocusContext()
2. Add commands for the modal context in Commands()
3. Add bindings in internal/keymap/bindings.go
4. Intercept custom keys before modal.HandleKey (Tab/Enter/Esc are handled internally)

func (p *Plugin) FocusContext() string {
    switch p.viewMode {
    case ViewModeError:  return "git-error"
    case ViewModePushMenu: return "git-push-menu"
    default: return "git-status"
    }
}

Modal notes

• HandleKey/HandleMouse handle Tab, Shift+Tab, Enter, Esc internally
• Backdrop clicks return "cancel"; use WithCloseOnBackdropClick(false) to disable
• Use built-in sections (Text, Input, Textarea, Buttons, Checkbox, List, When) before custom layouts
• For bespoke layouts, use modal.Custom and return explicit focusable offsets
• SetFocus(id) auto-scrolls viewport to focused element
• Prefer ui.OverlayModal(background, modal, width, height) for dimmed overlays; do not pre-center with lipgloss.Place

Background colors (critical)

Lipgloss Background() does not cascade into child content. ANSI resets clear the parent background. Solution: replace ANSI resets within viewport lines with reset + background re-apply, then pad short lines. See fillBackground in internal/modal/layout.go.

Pill-Shaped Elements (internal/styles)

Controlled by nerdFontsEnabled in ~/.config/sidecar/config.json (ui.nerdFontsEnabled).

// With explicit colors
label := styles.RenderPill("Output", styles.TextPrimary, styles.Primary, "")

// With a lipgloss.Style (preferred for tabs/chips)
active := styles.RenderPillWithStyle("Output", styles.BarChipActive, "")
inactive := styles.RenderPillWithStyle("Diff", styles.BarChip, "")

Available styles: styles.BarChip (inactive), styles.BarChipActive (active), or custom lipgloss.Style.

Test with both nerdFontsEnabled: true and false to verify fallback.

Keyboard Shortcuts

For complete per-plugin shortcut listings, see references/keyboard-shortcuts-reference.md.

Three things must match

1. Command ID in Commands() (e.g., "stage-file")
2. Binding command in internal/keymap/bindings.go (e.g., "stage-file")
3. Context string in both places (e.g., "git-status")

// 1) Commands()
{ID: "stage-file", Name: "Stage", Context: "git-status", Priority: 1}

// 2) FocusContext()
func (p *Plugin) FocusContext() string { return "git-status" }

// 3) bindings.go
{Key: "s", Command: "stage-file", Context: "git-status"}

Multiple contexts (view modes)

Return different context strings from FocusContext() for different modes. Each context gets its own footer hints and key bindings.

Priority guidelines

• 1: Primary actions (Stage, Commit, Open)
• 2: Secondary actions (Diff, Search, Push)
• 3: Tertiary actions (History, Refresh)
• 4+: Palette only

Root contexts (q behavior)

In root contexts, q shows quit confirmation. In non-root, q navigates back. Root contexts: global, conversations, conversations-sidebar, git-status, git-status-commits, git-status-diff, file-browser-tree, workspace-list, td-monitor.

Update isRootContext() in internal/app/update.go when adding new contexts.

Text input contexts

When a view has text input, implement plugin.TextInputConsumer and return true while active. This prevents app-level shortcuts from intercepting typed characters.

func (p *Plugin) ConsumesTextInput() bool {
    return p.showMyModal
}

Footer rendering flow

footerHints()
    +-- pluginFooterHints() -> Commands() filtered by FocusContext(), sorted by Priority
    +-- globalFooterHints() -> App-level hints
renderHintLineTruncated(hints, availableWidth)
    -> Renders left-to-right until width exceeded

Keyboard checklist

• Command in Commands() with ID, Name, Context, Priority
• FocusContext() returns matching context
• Binding in internal/keymap/bindings.go
• Key handled in Update() if app does not intercept
• No conflicting keys in same context
• Short footer hint names, primary actions Priority 1-2
• Verify q behavior with isRootContext()

Core files

Scrollbar (internal/ui)

ui.RenderScrollbar(ui.ScrollbarParams{
    TotalItems:   len(items),
    ScrollOffset: p.scrollOffset,
    VisibleItems: visibleCount,
    TrackHeight:  height,
})

Pattern: reduce content width by 1, render content, render scrollbar, join horizontally with lipgloss.JoinHorizontal(lipgloss.Top, content, scrollbar).

For multi-line items, set TrackHeight to actual terminal rows: visibleCount * linesPerItem.

Mouse Support

Setup

type Plugin struct {
    mouseHandler *mouse.Handler
}
func New() *Plugin {
    return &Plugin{mouseHandler: mouse.NewHandler()}
}

Register hit regions during render

func (p *Plugin) View(width, height int) string {
    p.mouseHandler.Clear()
    p.mouseHandler.HitMap.AddRect("pane", 0, 0, width, height, nil)
    p.mouseHandler.HitMap.AddRect("item", 2, 5, width-4, 1, 0)
    return content
}

Region ordering (critical)

Regions tested in reverse order. Add general regions first, specific regions last.

Coordinate system

App offsets Y by 2 (header height) before forwarding to plugins. Plugins operate in local coords where Y=0 is plugin content top.

Common patterns

• Click to select/focus, scroll wheel to move, double-click to open
• Drag regions for pane resizing
• Hover for visual feedback (focus takes precedence)

Mouse troubleshooting