From e7bf94483b822176d137017eb522022157d54200 Mon Sep 17 00:00:00 2001
From: "Lincoln Baxter, III" <lincolnbaxter@gmail.com>
Date: Tue, 12 May 2020 14:42:42 -0400
Subject: [PATCH] feat(cdk/drag-drop): support configurable propagation of
 mousedown and touchstart events.

Allows exposing native mousedown and touchstart events to parent elements so that listeners farther up the chain can respond before a CdkDragEvent has started. Without these events, certain gestures (swiper, etc) cannot be achieved when events are started on a DragRef element.

Fixes: https://github.com/angular/components/issues/19333
---
 src/cdk/drag-drop/directives/drag.ts |  1 +
 src/cdk/drag-drop/drag-drop.ts       |  3 ++-
 src/cdk/drag-drop/drag-ref.ts        | 11 ++++++++++-
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/cdk/drag-drop/directives/drag.ts b/src/cdk/drag-drop/directives/drag.ts
index ebd80933f645..cc4927b0d46b 100644
--- a/src/cdk/drag-drop/directives/drag.ts
+++ b/src/cdk/drag-drop/directives/drag.ts
@@ -199,6 +199,7 @@ export class CdkDrag<T = any> implements AfterViewInit, OnChanges, OnDestroy {
           config.dragStartThreshold : 5,
       pointerDirectionChangeThreshold: config && config.pointerDirectionChangeThreshold != null ?
           config.pointerDirectionChangeThreshold : 5,
+      propagateEvents: coerceBooleanProperty(config && config.propagateEvents),
       zIndex: config?.zIndex
     });
     this._dragRef.data = this;
diff --git a/src/cdk/drag-drop/drag-drop.ts b/src/cdk/drag-drop/drag-drop.ts
index a62b3a356ba0..e180d3c1068f 100644
--- a/src/cdk/drag-drop/drag-drop.ts
+++ b/src/cdk/drag-drop/drag-drop.ts
@@ -16,7 +16,8 @@ import {DragDropRegistry} from './drag-drop-registry';
 /** Default configuration to be used when creating a `DragRef`. */
 const DEFAULT_CONFIG = {
   dragStartThreshold: 5,
-  pointerDirectionChangeThreshold: 5
+  pointerDirectionChangeThreshold: 5,
+  propagateEvents: false
 };
 
 /**
diff --git a/src/cdk/drag-drop/drag-ref.ts b/src/cdk/drag-drop/drag-ref.ts
index d972c5085f42..1a99d5a86a27 100644
--- a/src/cdk/drag-drop/drag-ref.ts
+++ b/src/cdk/drag-drop/drag-ref.ts
@@ -33,6 +33,13 @@ export interface DragRefConfig {
    */
   pointerDirectionChangeThreshold: number;
 
+  /**
+   * Whether touch/mouse begin events should propagate to
+   * parent elements in the DOM when CDK initiates a drag 
+   * sequence.
+   */
+  propagateEvents: boolean;
+
   /** `z-index` for the absolutely-positioned elements that are created by the drag item. */
   zIndex?: number;
 }
@@ -744,7 +751,9 @@ export class DragRef<T = any> {
     // Always stop propagation for the event that initializes
     // the dragging sequence, in order to prevent it from potentially
     // starting another sequence for a draggable parent somewhere up the DOM tree.
-    event.stopPropagation();
+    if (!this._config.propagateEvents) {
+      event.stopPropagation();
+    }
 
     const isDragging = this.isDragging();
     const isTouchSequence = isTouchEvent(event);