From c61e397658371a2c43bc633918e946ca8c15a779 Mon Sep 17 00:00:00 2001
From: Kaz Wesley <kaz@lambdaverse.org>
Date: Tue, 12 Mar 2024 12:44:29 -0400
Subject: [PATCH] Scrollbars (#9310)

Scrollbars
---
 app/gui2/mock/providers.ts                    |   1 +
 app/gui2/src/components/GraphEditor.vue       |  22 +--
 .../src/components/GraphEditor/GraphEdge.vue  |   2 +-
 app/gui2/src/components/SceneScroller.vue     |  65 +++++++
 app/gui2/src/components/ScrollBar.vue         | 163 ++++++++++++++++++
 app/gui2/src/composables/navigator.ts         |  12 +-
 app/gui2/src/util/data/__tests__/rect.test.ts |   2 +-
 app/gui2/src/util/data/rect.ts                |  16 +-
 app/gui2/src/util/data/vec2.ts                |  26 ++-
 9 files changed, 284 insertions(+), 25 deletions(-)
 create mode 100644 app/gui2/src/components/SceneScroller.vue
 create mode 100644 app/gui2/src/components/ScrollBar.vue

diff --git a/app/gui2/mock/providers.ts b/app/gui2/mock/providers.ts
index 3614d7835ae0..e8667ce2d6ea 100644
--- a/app/gui2/mock/providers.ts
+++ b/app/gui2/mock/providers.ts
@@ -9,6 +9,7 @@ export const graphNavigator: GraphNavigator = {
   clientToSceneRect: () => Rect.Zero,
   panAndZoomTo: () => {},
   panTo: () => {},
+  scrollTo: () => {},
   stepZoom: () => {},
   transform: '',
   prescaledTransform: '',
diff --git a/app/gui2/src/components/GraphEditor.vue b/app/gui2/src/components/GraphEditor.vue
index 6c1dfbcc9084..aedfc5a7ef33 100644
--- a/app/gui2/src/components/GraphEditor.vue
+++ b/app/gui2/src/components/GraphEditor.vue
@@ -15,6 +15,7 @@ import { performCollapse, prepareCollapsedInfo } from '@/components/GraphEditor/
 import { Uploader, uploadedExpression } from '@/components/GraphEditor/upload'
 import GraphMouse from '@/components/GraphMouse.vue'
 import PlusButton from '@/components/PlusButton.vue'
+import SceneScroller from '@/components/SceneScroller.vue'
 import TopBar from '@/components/TopBar.vue'
 import { useDoubleClick } from '@/composables/doubleClick'
 import { keyboardBusy, keyboardBusyExceptIn, useEvent } from '@/composables/events'
@@ -190,25 +191,14 @@ onMounted(() => viewportNode.value?.focus())
 
 function zoomToSelected() {
   if (!viewportNode.value) return
-  let left = Infinity
-  let top = Infinity
-  let right = -Infinity
-  let bottom = -Infinity
   const nodesToCenter =
     nodeSelection.selected.size === 0 ? graphStore.db.nodeIdToNode.keys() : nodeSelection.selected
+  let bounds = Rect.Bounding()
   for (const id of nodesToCenter) {
     const rect = graphStore.vizRects.get(id) ?? graphStore.nodeRects.get(id)
-    if (!rect) continue
-    left = Math.min(left, rect.left)
-    right = Math.max(right, rect.right)
-    top = Math.min(top, rect.top)
-    bottom = Math.max(bottom, rect.bottom)
+    if (rect) bounds = Rect.Bounding(bounds, rect)
   }
-  graphNavigator.panAndZoomTo(
-    Rect.FromBounds(left, top, right, bottom),
-    0.1,
-    Math.max(1, graphNavigator.scale),
-  )
+  graphNavigator.panAndZoomTo(bounds, 0.1, Math.max(1, graphNavigator.scale))
 }
 
 const graphBindingsHandler = graphBindings.handler({
@@ -651,6 +641,10 @@ function handleEdgeDrop(source: AstId, position: Vec2) {
         <CodeEditor v-if="showCodeEditor" />
       </Suspense>
     </Transition>
+    <SceneScroller
+      :navigator="graphNavigator"
+      :scrollableArea="Rect.Bounding(...graphStore.visibleNodeAreas)"
+    />
     <GraphMouse />
   </div>
 </template>
diff --git a/app/gui2/src/components/GraphEditor/GraphEdge.vue b/app/gui2/src/components/GraphEditor/GraphEdge.vue
index 30aea5d6f800..3859e5adf1e8 100644
--- a/app/gui2/src/components/GraphEditor/GraphEdge.vue
+++ b/app/gui2/src/components/GraphEditor/GraphEdge.vue
@@ -354,7 +354,7 @@ function lengthTo(path: SVGPathElement, pos: Vec2): number {
   let best: number | undefined
   let bestDist: number | undefined
   const tryPos = (len: number) => {
-    const dist = pos.distanceSquared(Vec2.FromDomPoint(path.getPointAtLength(len)))
+    const dist = pos.distanceSquared(Vec2.FromXY(path.getPointAtLength(len)))
     if (bestDist == null || dist < bestDist) {
       best = len
       bestDist = dist
diff --git a/app/gui2/src/components/SceneScroller.vue b/app/gui2/src/components/SceneScroller.vue
new file mode 100644
index 000000000000..962723215087
--- /dev/null
+++ b/app/gui2/src/components/SceneScroller.vue
@@ -0,0 +1,65 @@
+<script setup lang="ts">
+import ScrollControl, { type ScrollbarEvent } from '@/components/ScrollBar.vue'
+import type { GraphNavigator } from '@/providers/graphNavigator'
+import { Rect } from '@/util/data/rect'
+import { Vec2 } from '@/util/data/vec2'
+import { computed, ref } from 'vue'
+
+const props = defineProps<{
+  navigator: GraphNavigator
+  scrollableArea: Rect
+}>()
+
+const scrollbarState = computed(() => scrollingState.value ?? scrollInputs.value)
+const scrollInputs = computed(() => ({
+  scale: props.navigator.scale,
+  range: props.scrollableArea.size.scale(props.navigator.scale),
+  pos: props.navigator.viewport.pos.sub(props.scrollableArea.pos).scale(props.navigator.scale),
+}))
+const scrollingState = ref<{
+  /** Current scrollbar position, as offset in client units from the origin of the scrollable area. */
+  pos: Vec2
+  /** Zoom factor when scrolling started. */
+  readonly scale: number
+  /** Scrollbar range, in client units, when scrolling started. */
+  readonly range: Vec2
+  /** `pos` when scrolling started. */
+  readonly scrollStartPos: Vec2
+  /** Viewport center, in scene coordinates, when scrolling started. */
+  readonly scrollOrigin: Vec2
+}>()
+
+function scroll(event: ScrollbarEvent) {
+  switch (event.type) {
+    case 'start': {
+      const scrollStartPos = scrollInputs.value.pos
+      const scrollOrigin = props.navigator.viewport.center()
+      scrollingState.value = { ...scrollInputs.value, scrollStartPos, scrollOrigin }
+      break
+    }
+    case 'move': {
+      if (!scrollingState.value) return
+      scrollingState.value.pos = scrollingState.value.scrollStartPos.add(event.startOffset)
+      props.navigator.scrollTo(
+        scrollingState.value.scrollOrigin.addScaled(
+          event.startOffset,
+          1 / scrollingState.value.scale,
+        ),
+      )
+      break
+    }
+    case 'stop': {
+      scrollingState.value = undefined
+      break
+    }
+  }
+}
+</script>
+
+<template>
+  <ScrollControl
+    :size="scrollbarState.range"
+    :position="scrollbarState.pos"
+    @scroll="scroll($event)"
+  />
+</template>
diff --git a/app/gui2/src/components/ScrollBar.vue b/app/gui2/src/components/ScrollBar.vue
new file mode 100644
index 000000000000..3862925c6cc4
--- /dev/null
+++ b/app/gui2/src/components/ScrollBar.vue
@@ -0,0 +1,163 @@
+<script setup lang="ts">
+import { usePointer, useResizeObserver } from '@/composables/events'
+import { Rect } from '@/util/data/rect'
+import { Vec2 } from '@/util/data/vec2'
+import { computed, ref, watchEffect } from 'vue'
+
+const element = ref<HTMLElement>()
+
+const props = defineProps<{
+  /** The size of the scrollable area, in client pixels. */
+  size: Vec2
+  /** The scrollbar's offset from the top-left of the scrollable area, in client pixels. */
+  position: Vec2
+}>()
+
+const emit = defineEmits<{
+  scroll: [event: ScrollbarEvent]
+}>()
+
+const BAR_END_MARGIN = 2
+const BAR_WIDTH = 6
+
+const viewportSize = useResizeObserver(element)
+
+const range = computed(
+  () =>
+    Rect.Bounding(new Rect(Vec2.Zero, props.size), new Rect(props.position, viewportSize.value))
+      .size,
+)
+
+const xStart = ref('')
+const yStart = ref('')
+const xLength = ref('')
+const yLength = ref('')
+const xFull = ref(false)
+const yFull = ref(false)
+
+watchEffect(() => {
+  const viewportFraction = Vec2.ElementwiseProduct(viewportSize.value, range.value.reciprocal())
+  const barStartFraction = Vec2.ElementwiseProduct(props.position, range.value.reciprocal())
+  const trackLength = viewportSize.value.sub(
+    new Vec2(BAR_END_MARGIN * 2 + BAR_WIDTH, BAR_END_MARGIN * 2 + BAR_WIDTH),
+  )
+  const barStart = Vec2.ElementwiseProduct(trackLength, barStartFraction).max(Vec2.Zero)
+  const barLength = Vec2.ElementwiseProduct(trackLength, viewportFraction)
+  const barEnd = barStart.add(barLength).min(trackLength)
+  xStart.value = `${barStart.x}px`
+  xLength.value = `${barEnd.x - barStart.x}px`
+  yStart.value = `${barStart.y}px`
+  yLength.value = `${barEnd.y - barStart.y}px`
+  xFull.value = range.value.x === viewportSize.value.x
+  yFull.value = range.value.y === viewportSize.value.y
+})
+
+const dragging = ref<Vec2>()
+
+function dragEventsHandler(axis: 'x' | 'y') {
+  return usePointer((pos, _event, eventType) => {
+    switch (eventType) {
+      case 'start': {
+        const factor = Vec2.ElementwiseProduct(range.value, viewportSize.value.reciprocal())
+        const speed = new Vec2(axis === 'x' ? factor.x : 0, axis === 'y' ? factor.y : 0)
+        if (speed.isZero()) return
+        dragging.value = speed
+        emit('scroll', { type: 'start' })
+        break
+      }
+      case 'move': {
+        if (!dragging.value) return
+        const startOffset = Vec2.ElementwiseProduct(pos.relative, dragging.value)
+        emit('scroll', { type: 'move', startOffset })
+        break
+      }
+      case 'stop': {
+        if (!dragging.value) return
+        dragging.value = undefined
+        emit('scroll', { type: 'stop' })
+        break
+      }
+    }
+  })
+}
+
+const xDrag = dragEventsHandler('x')
+const yDrag = dragEventsHandler('y')
+</script>
+<script lang="ts">
+export type ScrollbarEvent =
+  | {
+      type: 'start'
+    }
+  | {
+      type: 'move'
+      startOffset: Vec2
+    }
+  | {
+      type: 'stop'
+    }
+</script>
+
+<template>
+  <div ref="element" class="ScrollBar" @click.stop @pointerdown.stop @pointerup.stop>
+    <div class="bar vertical" :class="{ full: yFull }" v-on="yDrag.events" />
+    <div class="bar horizontal" :class="{ full: xFull }" v-on="xDrag.events" />
+  </div>
+</template>
+
+<style scoped>
+.ScrollBar {
+  position: absolute;
+  width: 100%;
+  height: 100%;
+  pointer-events: none;
+}
+
+.vertical {
+  position: absolute;
+  top: v-bind('yStart');
+  height: v-bind('yLength');
+  width: v-bind('`${BAR_WIDTH}px`');
+  right: 2px;
+  margin-top: v-bind('`${BAR_END_MARGIN}px`');
+  margin-bottom: v-bind('`${BAR_WIDTH + BAR_END_MARGIN}px`');
+}
+
+.horizontal {
+  position: absolute;
+  left: v-bind('xStart');
+  width: v-bind('xLength');
+  height: v-bind('`${BAR_WIDTH}px`');
+  bottom: 2px;
+  margin-left: v-bind('`${BAR_END_MARGIN}px`');
+  margin-right: v-bind('`${BAR_WIDTH + BAR_END_MARGIN}px`');
+}
+
+.bar {
+  border-radius: v-bind('`${BAR_WIDTH / 2}px`');
+  pointer-events: all;
+  background-color: rgba(170 170 170 / 50%);
+  transition: background-color 0.2s ease-in;
+  &:hover {
+    transition: background-color 0.2s ease-in;
+    background-color: rgba(150 150 150 / 75%);
+  }
+  &:active {
+    transition: none;
+    background-color: rgba(130 130 130 / 100%);
+  }
+}
+
+.full {
+  transition: opacity 0.2s ease-in;
+  opacity: 0;
+  &:hover {
+    transition: opacity 0.2s ease-in;
+    opacity: 1;
+  }
+  &:active {
+    transition: none;
+    opacity: 1;
+  }
+}
+</style>
diff --git a/app/gui2/src/composables/navigator.ts b/app/gui2/src/composables/navigator.ts
index 1af695c70d72..b09e330d6630 100644
--- a/app/gui2/src/composables/navigator.ts
+++ b/app/gui2/src/composables/navigator.ts
@@ -13,10 +13,8 @@ const PAN_AND_ZOOM_DEFAULT_SCALE_RANGE: ScaleRange = [0.1, 1]
 const ZOOM_STEP_DEFAULT_SCALE_RANGE: ScaleRange = [0.1, 10]
 
 function elemRect(target: Element | undefined): Rect {
-  if (target != null && target instanceof Element) {
-    const domRect = target.getBoundingClientRect()
-    return new Rect(new Vec2(domRect.x, domRect.y), new Vec2(domRect.width, domRect.height))
-  }
+  if (target != null && target instanceof Element)
+    return Rect.FromDomRect(target.getBoundingClientRect())
   return Rect.Zero
 }
 
@@ -118,6 +116,11 @@ export function useNavigator(viewportNode: Ref<Element | undefined>) {
     targetCenter.value = target.center()
   }
 
+  /** Pan immediately to center the viewport at the given point, in scene coordinates. */
+  function scrollTo(newCenter: Vec2) {
+    center.value = newCenter
+  }
+
   let zoomPivot = Vec2.Zero
   const zoomPointer = usePointer((pos, _event, ty) => {
     if (ty === 'start') {
@@ -329,5 +332,6 @@ export function useNavigator(viewportNode: Ref<Element | undefined>) {
     panTo,
     viewport,
     stepZoom,
+    scrollTo,
   })
 }
diff --git a/app/gui2/src/util/data/__tests__/rect.test.ts b/app/gui2/src/util/data/__tests__/rect.test.ts
index e5baf46d6473..8877653634cf 100644
--- a/app/gui2/src/util/data/__tests__/rect.test.ts
+++ b/app/gui2/src/util/data/__tests__/rect.test.ts
@@ -11,7 +11,7 @@ test.prop({
   x: fc.nat(),
   y: fc.nat(),
 })('offsetToInclude', ({ rectX, rectY, width, height, x, y }) => {
-  const rect = new Rect(new Vec2(rectX, rectY), new Vec2(width, height))
+  const rect = Rect.XYWH(rectX, rectY, width, height)
   const point = new Vec2(x, y)
   const offsetRect = rect.offsetToInclude(point)
   expect(
diff --git a/app/gui2/src/util/data/rect.ts b/app/gui2/src/util/data/rect.ts
index 66e79b1fb8d5..7094ca5a07a6 100644
--- a/app/gui2/src/util/data/rect.ts
+++ b/app/gui2/src/util/data/rect.ts
@@ -24,7 +24,21 @@ export class Rect {
   }
 
   static FromDomRect(domRect: DOMRect): Rect {
-    return new Rect(new Vec2(domRect.x, domRect.y), new Vec2(domRect.width, domRect.height))
+    return new Rect(Vec2.FromXY(domRect), Vec2.FromSize(domRect))
+  }
+
+  static Bounding(...rects: Rect[]): Rect {
+    let left = NaN
+    let top = NaN
+    let right = NaN
+    let bottom = NaN
+    for (const rect of rects) {
+      if (!(rect.left >= left)) left = rect.left
+      if (!(rect.top >= top)) top = rect.top
+      if (!(rect.right <= right)) right = rect.right
+      if (!(rect.bottom <= bottom)) bottom = rect.bottom
+    }
+    return this.FromBounds(left, top, right, bottom)
   }
 
   offsetBy(offset: Vec2): Rect {
diff --git a/app/gui2/src/util/data/vec2.ts b/app/gui2/src/util/data/vec2.ts
index d4b0353914d3..c46b143bd131 100644
--- a/app/gui2/src/util/data/vec2.ts
+++ b/app/gui2/src/util/data/vec2.ts
@@ -11,12 +11,26 @@ export class Vec2 {
 
   static Zero: Vec2
 
-  static FromArr(arr: [number, number]): Vec2 {
-    return new Vec2(arr[0], arr[1])
+  static FromXY(point: Readonly<{ x: number; y: number }>): Vec2 {
+    return new Vec2(point.x, point.y)
   }
 
-  static FromDomPoint(point: DOMPoint): Vec2 {
-    return new Vec2(point.x, point.y)
+  static FromSize(point: Readonly<{ width: number; height: number }>): Vec2 {
+    return new Vec2(point.width, point.height)
+  }
+
+  static FromClientSize(point: Readonly<{ clientWidth: number; clientHeight: number }>): Vec2 {
+    return new Vec2(point.clientWidth, point.clientHeight)
+  }
+
+  static ElementwiseProduct(...values: Vec2[]): Vec2 {
+    let x = 1
+    let y = 1
+    for (const value of values) {
+      x *= value.x
+      y *= value.y
+    }
+    return new Vec2(x, y)
   }
 
   equals(other: Vec2): boolean {
@@ -41,6 +55,10 @@ export class Vec2 {
     return new Vec2(-this.x, -this.y)
   }
 
+  reciprocal(): Vec2 {
+    return new Vec2(1 / this.x, 1 / this.y)
+  }
+
   add(other: Vec2): Vec2 {
     return new Vec2(this.x + other.x, this.y + other.y)
   }