fix: Factor out workspace drag methods into utils.

core/bubbles/textinput_bubble.ts

@@ -9,6 +9,7 @@ import * as touch from '../touch.js';
 import {browserEvents} from '../utils.js';
 import {Coordinate} from '../utils/coordinate.js';
 import * as dom from '../utils/dom.js';
+import * as drag from '../utils/drag.js';
 import {Rect} from '../utils/rect.js';
 import {Size} from '../utils/size.js';
 import {Svg} from '../utils/svg.js';
@@ -224,7 +225,8 @@ export class TextInputBubble extends Bubble {
       return;
     }
 
-    this.workspace.startDrag(
+    drag.start(
+      this.workspace,
       e,
       new Coordinate(
         this.workspace.RTL ? -this.getSize().width : this.getSize().width,
@@ -264,7 +266,7 @@ export class TextInputBubble extends Bubble {
 
   /** Handles pointer move events on the resize target. */
   private onResizePointerMove(e: PointerEvent) {
-    const delta = this.workspace.moveDrag(e);
+    const delta = drag.move(this.workspace, e);
     this.setSize(
       new Size(this.workspace.RTL ? -delta.x : delta.x, delta.y),
       false,

core/comments/comment_view.ts

@@ -11,6 +11,7 @@ import * as layers from '../layers.js';
 import * as touch from '../touch.js';
 import {Coordinate} from '../utils/coordinate.js';
 import * as dom from '../utils/dom.js';
+import * as drag from '../utils/drag.js';
 import {Size} from '../utils/size.js';
 import {Svg} from '../utils/svg.js';
 import {WorkspaceSvg} from '../workspace_svg.js';
@@ -524,8 +525,8 @@ export class CommentView implements IRenderedElement {
 
     this.preResizeSize = this.getSize();
 
-    // TODO(#7926): Move this into a utils file.
-    this.workspace.startDrag(
+    drag.start(
+      this.workspace,
       e,
       new Coordinate(
         this.workspace.RTL ? -this.getSize().width : this.getSize().width,
@@ -569,8 +570,7 @@ export class CommentView implements IRenderedElement {
 
   /** Resizes the comment in response to a drag on the resize handle. */
   private onResizePointerMove(e: PointerEvent) {
-    // TODO(#7926): Move this into a utils file.
-    const size = this.workspace.moveDrag(e);
+    const size = drag.move(this.workspace, e);
     this.setSizeWithoutFiringEvents(
       new Size(this.workspace.RTL ? -size.x : size.x, size.y),
     );

core/utils/drag.ts

@@ -0,0 +1,74 @@
+/**
+ * @license
+ * Copyright 2024 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import * as browserEvents from '../browser_events.js';
+import type {WorkspaceSvg} from '../workspace_svg.js';
+import {Coordinate} from './coordinate.js';
+
+const workspaceToDragDelta: WeakMap<WorkspaceSvg, Coordinate> = new WeakMap();
+
+/**
+ * Convert from mouse coordinates to workspace coordinates.
+ *
+ * @param workspace The workspace where the pointer event is occurring.
+ * @param e The pointer event with the source coordinates.
+ */
+function mouseToWorkspacePoint(
+  workspace: WorkspaceSvg,
+  e: PointerEvent,
+): SVGPoint {
+  const point = browserEvents.mouseToSvg(
+    e,
+    workspace.getParentSvg(),
+    workspace.getInverseScreenCTM(),
+  );
+  // Fix scale of mouse event.
+  point.x /= workspace.scale;
+  point.y /= workspace.scale;
+  return point;
+}
+
+/**
+ * Start tracking a drag of an object on this workspace by recording the offset
+ * between the pointer's current location and the object's starting location.
+ *
+ * Used for resizing block comments and workspace comments.
+ *
+ * @param workspace The workspace where the drag is occurring.
+ * @param e Pointer down event.
+ * @param xy Starting location of object.
+ */
+export function start(
+  workspace: WorkspaceSvg,
+  e: PointerEvent,
+  xy: Coordinate,
+) {
+  const point = mouseToWorkspacePoint(workspace, e);
+  // Record the starting offset between the bubble's location and the mouse.
+  workspaceToDragDelta.set(workspace, Coordinate.difference(xy, point));
+}
+
+/**
+ * Compute the new position of a dragged object in this workspace based on the
+ * current pointer position and the offset between the pointer's starting
+ * location and the object's starting location.
+ *
+ * The start function should have be called previously, when the drag started.
+ *
+ * Used for resizing block comments and workspace comments.
+ *
+ * @param workspace The workspace where the drag is occurring.
+ * @param e Pointer move event.
+ * @returns New location of object.
+ */
+export function move(workspace: WorkspaceSvg, e: PointerEvent): Coordinate {
+  const point = mouseToWorkspacePoint(workspace, e);
+  const dragDelta = workspaceToDragDelta.get(workspace);
+  if (!dragDelta) {
+    throw new Error('Drag not initialized');
+  }
+  return Coordinate.sum(dragDelta, point);
+}

core/workspace_svg.ts

@@ -63,6 +63,7 @@ import type {Trashcan} from './trashcan.js';
 import * as arrayUtils from './utils/array.js';
 import {Coordinate} from './utils/coordinate.js';
 import * as dom from './utils/dom.js';
+import * as drag from './utils/drag.js';
 import type {Metrics} from './utils/metrics.js';
 import {Rect} from './utils/rect.js';
 import {Size} from './utils/size.js';
@@ -181,9 +182,6 @@ export class WorkspaceSvg extends Workspace implements IASTNodeLocationSvg {
   /** Vertical scroll value when scrolling started in pixel units. */
   startScrollY = 0;
 
-  /** Distance from mouse to object being dragged. */
-  private dragDeltaXY: Coordinate | null = null;
-
   /** Current scale. */
   scale = 1;
 
@@ -1447,16 +1445,7 @@ export class WorkspaceSvg extends Workspace implements IASTNodeLocationSvg {
    * @param xy Starting location of object.
    */
   startDrag(e: PointerEvent, xy: Coordinate) {
-    // Record the starting offset between the bubble's location and the mouse.
-    const point = browserEvents.mouseToSvg(
-      e,
-      this.getParentSvg(),
-      this.getInverseScreenCTM(),
-    );
-    // Fix scale of mouse event.
-    point.x /= this.scale;
-    point.y /= this.scale;
-    this.dragDeltaXY = Coordinate.difference(xy, point);
+    drag.start(this, e, xy);
   }
 
   /**
@@ -1466,15 +1455,7 @@ export class WorkspaceSvg extends Workspace implements IASTNodeLocationSvg {
    * @returns New location of object.
    */
   moveDrag(e: PointerEvent): Coordinate {
-    const point = browserEvents.mouseToSvg(
-      e,
-      this.getParentSvg(),
-      this.getInverseScreenCTM(),
-    );
-    // Fix scale of mouse event.
-    point.x /= this.scale;
-    point.y /= this.scale;
-    return Coordinate.sum(this.dragDeltaXY!, point);
+    return drag.move(this, e);
   }
 
   /**