Phase 6: FillPicker, GradientEditor, ExportControls headless primitives

New SDK components:
- FillPickerRoot — fill type category (solid/gradient/image), swatch
  background, category switching. Events via emit, not callback props.
- GradientEditorRoot — stop state, subtype, add/remove/drag/select stops,
  active color, bar background. All stop mutations + color updates as
  action slot props.
- ExportControlsRoot — export settings list, scale/format options,
  selected node name.

Fixed callback props passed as :on-xxx across all SDK components:
- ScrubInputRoot: :on-keydown → :keydown
- FillPickerRoot: removed :on-update (consumers use @update on the
  component itself)
- GradientEditorRoot: :on-active-color-update → :update-active-color,
  :on-stop-drag → :drag-stop

packages/vue/src/ExportControls/ExportControlsRoot.vue

@@ -0,0 +1,66 @@
+<script setup lang="ts">
+import { computed, ref } from 'vue'
+
+import { useEditor } from '../context'
+
+import type { ExportFormat } from '@open-pencil/core'
+
+interface ExportSetting {
+  scale: number
+  format: ExportFormat
+}
+
+const SCALES = [0.5, 0.75, 1, 1.5, 2, 3, 4] as const
+const FORMATS: ExportFormat[] = ['PNG', 'JPG', 'WEBP', 'SVG']
+
+const editor = useEditor()
+
+const settings = ref<ExportSetting[]>([{ scale: 1, format: 'PNG' }])
+
+const selectedIds = computed(() => {
+  void editor.state.sceneVersion
+  return [...editor.state.selectedIds]
+})
+
+const nodeName = computed(() => {
+  void editor.state.sceneVersion
+  const ids = editor.state.selectedIds
+  if (ids.size === 1) {
+    const id = [...ids][0]
+    return editor.graph.getNode(id)?.name ?? 'Export'
+  }
+  return `${ids.size} layers`
+})
+
+function addSetting() {
+  const last = settings.value[settings.value.length - 1]
+  const nextScale = SCALES.find((s) => s > (last?.scale ?? 1)) ?? 2
+  settings.value.push({ scale: nextScale, format: last?.format ?? 'PNG' })
+}
+
+function removeSetting(index: number) {
+  settings.value.splice(index, 1)
+}
+
+function updateScale(index: number, scale: number) {
+  settings.value[index] = { ...settings.value[index], scale }
+}
+
+function updateFormat(index: number, format: ExportFormat) {
+  settings.value[index] = { ...settings.value[index], format }
+}
+</script>
+
+<template>
+  <slot
+    :settings="settings"
+    :selected-ids="selectedIds"
+    :node-name="nodeName"
+    :scales="SCALES"
+    :formats="FORMATS"
+    :add-setting="addSetting"
+    :remove-setting="removeSetting"
+    :update-scale="updateScale"
+    :update-format="updateFormat"
+  />
+</template>

packages/vue/src/ExportControls/index.ts

@@ -0,0 +1 @@
+export { default as ExportControlsRoot } from './ExportControlsRoot.vue'

packages/vue/src/FillPicker/FillPickerRoot.vue

@@ -0,0 +1,71 @@
+<script setup lang="ts">
+import { computed } from 'vue'
+import { colorToCSS } from '@open-pencil/core'
+
+import type { Fill, GradientStop } from '@open-pencil/core'
+
+type FillCategory = 'SOLID' | 'GRADIENT' | 'IMAGE'
+
+const FILL_CATEGORY: Record<string, FillCategory> = {
+  SOLID: 'SOLID',
+  GRADIENT_LINEAR: 'GRADIENT',
+  GRADIENT_RADIAL: 'GRADIENT',
+  GRADIENT_ANGULAR: 'GRADIENT',
+  GRADIENT_DIAMOND: 'GRADIENT',
+  IMAGE: 'IMAGE'
+}
+
+const { fill } = defineProps<{ fill: Fill }>()
+const emit = defineEmits<{ update: [fill: Fill] }>()
+
+const category = computed(() => FILL_CATEGORY[fill.type] ?? 'SOLID')
+
+function toSolid() {
+  if (category.value === 'SOLID') return
+  const color = fill.gradientStops?.[0]?.color ?? fill.color
+  emit('update', { ...fill, type: 'SOLID', color: { ...color } })
+}
+
+function toGradient() {
+  if (category.value === 'GRADIENT') return
+  const stops: GradientStop[] = fill.gradientStops?.length
+    ? fill.gradientStops
+    : [
+        { color: { ...fill.color }, position: 0 },
+        { color: { r: 1, g: 1, b: 1, a: 1 }, position: 1 }
+      ]
+  emit('update', {
+    ...fill,
+    type: 'GRADIENT_LINEAR',
+    gradientStops: stops,
+    gradientTransform: { m00: 1, m01: 0, m02: 0, m10: 0, m11: 0, m12: 0.5 }
+  })
+}
+
+function toImage() {
+  if (category.value === 'IMAGE') return
+  emit('update', { ...fill, type: 'IMAGE' })
+}
+
+function gradientCSS(stops: GradientStop[]): string {
+  return stops.map((s) => `${colorToCSS(s.color)} ${s.position * 100}%`).join(', ')
+}
+
+const swatchBg = computed(() => {
+  if (category.value === 'GRADIENT' && fill.gradientStops?.length)
+    return `linear-gradient(to right, ${gradientCSS(fill.gradientStops)})`
+  return colorToCSS(fill.color)
+})
+
+</script>
+
+<template>
+  <slot
+    :fill="fill"
+    :category="category"
+    :swatch-bg="swatchBg"
+    :to-solid="toSolid"
+    :to-gradient="toGradient"
+    :to-image="toImage"
+  />
+</template>

packages/vue/src/FillPicker/index.ts

@@ -0,0 +1 @@
+export { default as FillPickerRoot } from './FillPickerRoot.vue'

packages/vue/src/GradientEditor/GradientEditorRoot.vue

@@ -0,0 +1,126 @@
+<script setup lang="ts">
+import { computed, ref } from 'vue'
+import { colorToCSS, parseColor } from '@open-pencil/core'
+
+import type { Fill, GradientStop, GradientTransform } from '@open-pencil/core'
+
+type GradientSubtype =
+  | 'GRADIENT_LINEAR'
+  | 'GRADIENT_RADIAL'
+  | 'GRADIENT_ANGULAR'
+  | 'GRADIENT_DIAMOND'
+
+const SUBTYPES: { value: GradientSubtype; label: string }[] = [
+  { value: 'GRADIENT_LINEAR', label: 'Linear' },
+  { value: 'GRADIENT_RADIAL', label: 'Radial' },
+  { value: 'GRADIENT_ANGULAR', label: 'Angular' },
+  { value: 'GRADIENT_DIAMOND', label: 'Diamond' }
+]
+
+const DEFAULT_TRANSFORMS: Record<GradientSubtype, GradientTransform> = {
+  GRADIENT_LINEAR: { m00: 1, m01: 0, m02: 0, m10: 0, m11: 0, m12: 0.5 },
+  GRADIENT_RADIAL: { m00: 0.5, m01: 0, m02: 0.5, m10: 0, m11: 0.5, m12: 0.5 },
+  GRADIENT_ANGULAR: { m00: 0.5, m01: 0, m02: 0.5, m10: 0, m11: 0.5, m12: 0.5 },
+  GRADIENT_DIAMOND: { m00: 0.5, m01: 0, m02: 0.5, m10: 0, m11: 0.5, m12: 0.5 }
+}
+
+const { fill } = defineProps<{ fill: Fill }>()
+const emit = defineEmits<{ update: [fill: Fill] }>()
+
+const activeStopIndex = ref(0)
+const stops = computed(() => fill.gradientStops ?? [])
+const subtype = computed(() => fill.type as GradientSubtype)
+
+const activeColor = computed(() => {
+  const s = stops.value
+  if (!s.length) return fill.color
+  return s[Math.min(activeStopIndex.value, s.length - 1)].color
+})
+
+const barBackground = computed(() =>
+  stops.value.length
+    ? `linear-gradient(to right, ${stops.value.map((s) => `${colorToCSS(s.color)} ${s.position * 100}%`).join(', ')})`
+    : ''
+)
+
+function emitStops(newStops: GradientStop[]) {
+  emit('update', { ...fill, gradientStops: newStops })
+}
+
+function setSubtype(type: GradientSubtype) {
+  if (type === fill.type) return
+  emit('update', { ...fill, type, gradientTransform: DEFAULT_TRANSFORMS[type] })
+}
+
+function selectStop(index: number) {
+  activeStopIndex.value = index
+}
+
+function addStop() {
+  const s = [...stops.value]
+  const pos = s.length >= 2 ? (s[s.length - 2].position + s[s.length - 1].position) / 2 : 0.5
+  s.push({ color: { ...activeColor.value }, position: pos })
+  s.sort((a, b) => a.position - b.position)
+  activeStopIndex.value = s.findIndex((stop) => stop.position === pos)
+  emitStops(s)
+}
+
+function removeStop(index: number) {
+  if (stops.value.length <= 2) return
+  emitStops(stops.value.filter((_, i) => i !== index))
+  activeStopIndex.value = Math.min(activeStopIndex.value, stops.value.length - 2)
+}
+
+function updateStopPosition(index: number, position: number) {
+  const s = [...stops.value]
+  s[index] = { ...s[index], position: Math.max(0, Math.min(1, position / 100)) }
+  emitStops(s)
+}
+
+function updateStopColor(index: number, hex: string) {
+  const color = parseColor(hex.startsWith('#') ? hex : `#${hex}`)
+  if (!color) return
+  const s = [...stops.value]
+  s[index] = { ...s[index], color: { ...color, a: s[index].color.a } }
+  emitStops(s)
+}
+
+function updateStopOpacity(index: number, opacity: number) {
+  const s = [...stops.value]
+  s[index] = { ...s[index], color: { ...s[index].color, a: Math.max(0, Math.min(1, opacity / 100)) } }
+  emitStops(s)
+}
+
+function onActiveColorUpdate(color: { r: number; g: number; b: number; a: number }) {
+  const s = [...stops.value]
+  const idx = Math.min(activeStopIndex.value, s.length - 1)
+  s[idx] = { ...s[idx], color }
+  emitStops(s)
+}
+
+function onStopDrag(index: number, position: number) {
+  const s = [...stops.value]
+  s[index] = { ...s[index], position }
+  emitStops(s)
+}
+</script>
+
+<template>
+  <slot
+    :stops="stops"
+    :subtype="subtype"
+    :subtypes="SUBTYPES"
+    :active-stop-index="activeStopIndex"
+    :active-color="activeColor"
+    :bar-background="barBackground"
+    :set-subtype="setSubtype"
+    :select-stop="selectStop"
+    :add-stop="addStop"
+    :remove-stop="removeStop"
+    :update-stop-position="updateStopPosition"
+    :update-stop-color="updateStopColor"
+    :update-stop-opacity="updateStopOpacity"
+    :update-active-color="onActiveColorUpdate"
+    :drag-stop="onStopDrag"
+  />
+</template>

packages/vue/src/GradientEditor/index.ts

@@ -0,0 +1 @@
+export { default as GradientEditorRoot } from './GradientEditorRoot.vue'

packages/vue/src/ScrubInput/ScrubInputRoot.vue

@@ -120,7 +120,7 @@ provideScrubInput(ctx)
     :start-scrub="startScrub"
     :start-edit="startEdit"
     :commit-edit="commitEdit"
-    :on-keydown="onKeydown"
+    :keydown="onKeydown"
     :placeholder="props.placeholder"
   />
 </template>

packages/vue/src/index.ts

@@ -36,6 +36,10 @@ export { PositionControlsRoot } from './PositionControls'
 export { LayerTreeRoot, LayerTreeItem, useLayerTree } from './LayerTree'
 
 export { EditorMenuRoot } from './EditorMenu'
+
+export { FillPickerRoot } from './FillPicker'
+export { GradientEditorRoot } from './GradientEditor'
+export { ExportControlsRoot } from './ExportControls'
 export type { LayerTreeContext, LayerNode } from './LayerTree'
 export type { CanvasContext } from './Canvas'