[feature] add erase line (#708)

* Add erase line

* Fix erasing small dots

* bump perfect-freehand

examples/core-example-advanced/package.json

@@ -32,7 +32,7 @@
     "immer": "^9.0.12",
     "lodash": "^4.17.21",
     "nanoid": "^3.1.31",
-    "perfect-freehand": "^1.0.16",
+    "perfect-freehand": "^1.1.0",
     "react": "^17.0.2",
     "react-dom": "^17.0.2",
     "react-feather": "^2.0.9",

packages/core/package.json

@@ -41,6 +41,7 @@
     "@tldraw/vec": "^1.7.0",
     "@use-gesture/react": "^10.2.14",
     "mobx-react-lite": "^3.2.3",
+    "perfect-freehand": "^1.1.0",
     "resize-observer-polyfill": "^1.5.1"
   },
   "peerDependencies": {

packages/core/src/components/Canvas/Canvas.tsx

@@ -30,12 +30,14 @@ import { UsersIndicators } from '~components/UsersIndicators'
 import { SnapLines } from '~components/SnapLines/SnapLines'
 import { Grid } from '~components/Grid'
 import { Overlay } from '~components/Overlay'
+import { EraseLine } from '~components/EraseLine'
 
 interface CanvasProps<T extends TLShape, M extends Record<string, unknown>> {
   page: TLPage<T, TLBinding>
   pageState: TLPageState
   assets: TLAssets
   snapLines?: TLSnapLine[]
+  eraseLine?: number[][]
   grid?: number
   users?: TLUsers<T>
   userId?: string
@@ -64,6 +66,7 @@ export const Canvas = observer(function _Canvas<
   pageState,
   assets,
   snapLines,
+  eraseLine,
   grid,
   users,
   userId,
@@ -134,6 +137,7 @@ export const Canvas = observer(function _Canvas<
           {users && <Users userId={userId} users={users} />}
         </div>
         <Overlay camera={pageState.camera}>
+          {eraseLine && <EraseLine points={eraseLine} />}
           {snapLines && <SnapLines snapLines={snapLines} />}
         </Overlay>
       </div>

packages/core/src/components/EraseLine/EraseLine.tsx

@@ -0,0 +1,18 @@
+import * as React from 'react'
+import { observer } from 'mobx-react-lite'
+import getStroke from 'perfect-freehand'
+import Utils from '~utils'
+
+export interface UiEraseLintProps {
+  points: number[][]
+}
+
+export type UiEraseLineComponent = (props: UiEraseLintProps) => any | null
+
+export const EraseLine = observer(function EraserLine({ points }: UiEraseLintProps) {
+  if (points.length === 0) return null
+
+  const d = Utils.getSvgPathFromStroke(getStroke(points, { size: 16, start: { taper: true } }))
+
+  return <path d={d} className="tl-erase-line" />
+})

packages/core/src/components/EraseLine/index.ts

@@ -0,0 +1 @@
+export * from './EraseLine'

packages/core/src/components/Renderer/Renderer.tsx

@@ -56,6 +56,10 @@ export interface RendererProps<T extends TLShape, M = any> extends Partial<TLCal
    * (optional) The current snap lines to render.
    */
   snapLines?: TLSnapLine[]
+  /**
+   * (optional) The current erase line to render.
+   */
+  eraseLine?: number[][]
   /**
    * (optional) The current user's id, used to identify the user.
    */
@@ -141,6 +145,7 @@ export const Renderer = observer(function _Renderer<
   theme,
   meta,
   snapLines,
+  eraseLine,
   grid,
   containerRef,
   performanceMode,
@@ -196,6 +201,7 @@ export const Renderer = observer(function _Renderer<
         pageState={pageState}
         assets={assets}
         snapLines={snapLines}
+        eraseLine={eraseLine}
         grid={grid}
         users={users}
         userId={userId}

packages/core/src/hooks/useStyle.tsx

@@ -367,6 +367,13 @@ export const TLCSS = css`
   .tl-grid-dot {
     fill: var(--tl-grid);
   }
+  .tl-erase-line {
+    stroke-linejoin: round;
+    stroke-linecap: round;
+    pointer-events: none;
+    fill: var(--tl-grid);
+    opacity: 0.32;
+  }
 `
 
 export function useTLTheme(theme?: Partial<TLTheme>, selector?: string) {

packages/tldraw/package.json

@@ -55,7 +55,7 @@
     "@types/lz-string": "^1.3.34",
     "idb-keyval": "^6.1.0",
     "lz-string": "^1.4.4",
-    "perfect-freehand": "^1.0.16",
+    "perfect-freehand": "^1.1.0",
     "react-error-boundary": "^3.1.4",
     "react-hotkey-hook": "^1.0.2",
     "react-hotkeys-hook": "^3.4.4",

packages/tldraw/src/Tldraw.tsx

@@ -431,6 +431,7 @@ const InnerTldraw = React.memo(function InnerTldraw({
             pageState={pageState}
             assets={assets}
             snapLines={appState.snapLines}
+            eraseLine={appState.eraseLine}
             grid={GRID_SIZE}
             users={room?.users}
             userId={room?.userId}

packages/tldraw/src/state/StateManager/StateManager.ts

@@ -198,7 +198,7 @@ export class StateManager<T extends Record<string, any>> {
    * @param patch The patch to apply.
    * @param id (optional) An id for this patch.
    */
-  protected patchState = (patch: Patch<T>, id?: string): this => {
+  patchState = (patch: Patch<T>, id?: string): this => {
     this.applyPatch(patch, id)
     if (this.onPatch) {
       this.onPatch(this._state, id)

packages/tldraw/src/state/TldrawApp.ts

@@ -4103,6 +4103,7 @@ export class TldrawApp extends StateManager<TDSnapshot> {
       isToolLocked: false,
       isMenuOpen: false,
       isEmptyCanvas: false,
+      eraseLine: [],
       snapLines: [],
       isLoading: false,
       disableAssets: false,

packages/tldraw/src/state/sessions/EraseSession/EraseSession.ts

@@ -22,12 +22,56 @@ export class EraseSession extends BaseSession {
   initialSelectedShapes: TDShape[]
   erasableShapes: Set<TDShape>
   prevPoint: number[]
+  prevEraseShapesSize = 0
 
   constructor(app: TldrawApp) {
     super(app)
     this.prevPoint = [...app.originPoint]
     this.initialSelectedShapes = this.app.selectedIds.map((id) => this.app.getShape(id))
     this.erasableShapes = new Set(this.app.shapes.filter((shape) => !shape.isLocked))
+    this.interval = this.loop()
+  }
+
+  interval: any
+  timestamp1 = 0
+  timestamp2 = 0
+  prevErasePoint: number[] = []
+
+  loop = () => {
+    const now = Date.now()
+    const elapsed1 = now - this.timestamp1
+    const elapsed2 = now - this.timestamp2
+    const { eraseLine } = this.app.appState
+
+    let next = [...eraseLine]
+    let didUpdate = false
+
+    if (elapsed1 > 16 && this.prevErasePoint !== this.prevPoint) {
+      didUpdate = true
+      next = [...eraseLine, this.prevPoint]
+      this.prevErasePoint = this.prevPoint
+    }
+
+    if (elapsed2 > 32) {
+      if (next.length > 1) {
+        didUpdate = true
+        next.splice(0, Math.ceil(next.length * 0.1))
+        this.timestamp2 = now
+      }
+    }
+
+    if (didUpdate) {
+      this.app.patchState(
+        {
+          appState: {
+            eraseLine: next,
+          },
+        },
+        'eraseline'
+      )
+    }
+
+    this.interval = requestAnimationFrame(this.loop)
   }
 
   start = (): TldrawPatch | undefined => void null
@@ -100,6 +144,12 @@ export class EraseSession extends BaseSession {
 
     this.prevPoint = newPoint
 
+    if (erasedShapes.length === this.prevEraseShapesSize) {
+      return
+    }
+
+    this.prevEraseShapesSize = erasedShapes.length
+
     return {
       document: {
         pages: {
@@ -114,6 +164,8 @@ export class EraseSession extends BaseSession {
   cancel = (): TldrawPatch | undefined => {
     const { page } = this.app
 
+    cancelAnimationFrame(this.interval)
+
     this.erasedShapes.forEach((shape) => {
       if (!this.app.getShape(shape.id)) {
         this.erasedShapes.delete(shape)
@@ -136,12 +188,17 @@ export class EraseSession extends BaseSession {
           },
         },
       },
+      appState: {
+        eraseLine: [],
+      },
     }
   }
 
   complete = (): TldrawPatch | TldrawCommand | undefined => {
     const { page } = this.app
 
+    cancelAnimationFrame(this.interval)
+
     this.erasedShapes.forEach((shape) => {
       if (!this.app.getShape(shape.id)) {
         this.erasedShapes.delete(shape)
@@ -217,6 +274,9 @@ export class EraseSession extends BaseSession {
             },
           },
         },
+        appState: {
+          eraseLine: [],
+        },
       },
       after: {
         document: {
@@ -232,6 +292,9 @@ export class EraseSession extends BaseSession {
             },
           },
         },
+        appState: {
+          eraseLine: [],
+        },
       },
     }
   }

packages/tldraw/src/state/shapes/DrawUtil/DrawUtil.tsx

@@ -276,8 +276,8 @@ export class DrawUtil extends TDShapeUtil<T, E> {
     const ptB = Vec.sub(B, point)
     const bounds = this.getBounds(shape)
 
-    if (points.length <= 2) {
-      return Vec.distanceToLineSegment(A, B, shape.point) < 4
+    if (bounds.width < 8 && bounds.height < 8) {
+      return Vec.distanceToLineSegment(A, B, Utils.getBoundsCenter(bounds)) < 5
     }
 
     if (intersectLineSegmentBounds(ptA, ptB, bounds)) {

packages/tldraw/src/types.ts

@@ -105,6 +105,7 @@ export interface TDSnapshot {
     isMenuOpen: boolean
     status: string
     snapLines: TLSnapLine[]
+    eraseLine: number[][]
     isLoading: boolean
     disableAssets: boolean
     selectByContain?: boolean

yarn.lock

@@ -9029,6 +9029,11 @@ perfect-freehand@^1.0.16:
   resolved "https://registry.yarnpkg.com/perfect-freehand/-/perfect-freehand-1.0.16.tgz#38575ef946ff513b9c94057c763cac003b504020"
   integrity sha512-D4+avUeR8CHSl2vaPbPYX/dNpSMRYO3VOFp7qSSc+LRkSgzQbLATVnXosy7VxtsSHEh1C5t8K8sfmo0zCVnfWQ==
 
+perfect-freehand@^1.1.0:
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/perfect-freehand/-/perfect-freehand-1.1.0.tgz#65b459f4d6ccceb873e9ac06e07c924761649b32"
+  integrity sha512-nVWukMN9qlii1dQsQHVvfaNpeOAWVLgTZP6e/tFcU6cWlLo+6YdvfRGBL2u5pU11APlPbHeB0SpMcGA8ZjPgcQ==
+
 picocolors@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/picocolors/-/picocolors-1.0.0.tgz#cb5bdc74ff3f51892236eaf79d68bc44564ab81c"