feat(drag-drop): add the ability to disable dragging

Adds inputs to `cdkDrag`, `cdkDropList` and `cdkDragHandle` that allows for dragging to be disabled through those specific elements.

Fixes #13651.

Author: crisbeto

src/cdk/drag-drop/drag-drop.md

@@ -133,3 +133,11 @@ the element that is moved as the user is dragging. This is useful for cases like
 draggable.
 
 <!-- example(cdk-drag-drop-root-element) -->
+
+### Disable dragging
+If you want to disable dragging for a particular drag item, you can do so by setting the
+`cdkDragDisabled` input on a `cdkDrag` item. Furthermore, you can disable an entire list
+using the `cdkDropListDisabled` input on a `cdkDropList` or a particular handle via
+`cdkDragHandleDisabled` on `cdkDragHandle`.
+
+<!-- example(cdk-drag-drop-disabled) -->

src/cdk/drag-drop/drag-handle.ts

@@ -6,7 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Directive, ElementRef, Inject, Optional} from '@angular/core';
+import {Directive, ElementRef, Inject, Optional, Input} from '@angular/core';
+import {coerceBooleanProperty} from '@angular/cdk/coercion';
 import {CDK_DRAG_PARENT} from './drag-parent';
 import {toggleNativeDragInteractions} from './drag-styling';
 
@@ -21,6 +22,14 @@ export class CdkDragHandle {
   /** Closest parent draggable instance. */
   _parentDrag: {} | undefined;
 
+  /** Whether starting to drag through this handle is disabled. */
+  @Input('cdkDragHandleDisabled')
+  get disabled(): boolean { return this._disabled; }
+  set disabled(value: boolean) {
+    this._disabled = coerceBooleanProperty(value);
+  }
+  private _disabled = false;
+
   constructor(
     public element: ElementRef<HTMLElement>,
     @Inject(CDK_DRAG_PARENT) @Optional() parentDrag?: any) {

src/cdk/drag-drop/drag.spec.ts

@@ -412,6 +412,18 @@ describe('CdkDrag', () => {
       expect(dragElement.style.transform).toBeFalsy();
     }));
 
+    it('should not be able to drag the element if dragging is disabled', fakeAsync(() => {
+      const fixture = createComponent(StandaloneDraggable);
+      fixture.detectChanges();
+      const dragElement = fixture.componentInstance.dragElement.nativeElement;
+
+      fixture.componentInstance.dragInstance.disabled = true;
+
+      expect(dragElement.style.transform).toBeFalsy();
+      dragElementViaMouse(fixture, dragElement, 50, 100);
+      expect(dragElement.style.transform).toBeFalsy();
+    }));
+
     it('should stop propagation for the drag sequence start event', fakeAsync(() => {
       const fixture = createComponent(StandaloneDraggable);
       fixture.detectChanges();
@@ -450,6 +462,32 @@ describe('CdkDrag', () => {
       expect(dragElement.style.transform).toBe('translate3d(50px, 100px, 0px)');
     }));
 
+    it('should not be able to drag the element if the handle is disabled', fakeAsync(() => {
+      const fixture = createComponent(StandaloneDraggableWithHandle);
+      fixture.detectChanges();
+      const dragElement = fixture.componentInstance.dragElement.nativeElement;
+      const handle = fixture.componentInstance.handleElement.nativeElement;
+
+      fixture.componentInstance.handleInstance.disabled = true;
+
+      expect(dragElement.style.transform).toBeFalsy();
+      dragElementViaMouse(fixture, handle, 50, 100);
+      expect(dragElement.style.transform).toBeFalsy();
+    }));
+
+    it('should not be able to drag using the handle if the element is disabled', fakeAsync(() => {
+      const fixture = createComponent(StandaloneDraggableWithHandle);
+      fixture.detectChanges();
+      const dragElement = fixture.componentInstance.dragElement.nativeElement;
+      const handle = fixture.componentInstance.handleElement.nativeElement;
+
+      fixture.componentInstance.dragInstance.disabled = true;
+
+      expect(dragElement.style.transform).toBeFalsy();
+      dragElementViaMouse(fixture, handle, 50, 100);
+      expect(dragElement.style.transform).toBeFalsy();
+    }));
+
     it('should be able to use a handle that was added after init', fakeAsync(() => {
       const fixture = createComponent(StandaloneDraggableWithDelayedHandle);
 
@@ -1513,6 +1551,30 @@ describe('CdkDrag', () => {
       expect(thirdItem.style.transform).toBeFalsy();
     }));
 
+    it('should not move the item if the list is disabled', fakeAsync(() => {
+      const fixture = createComponent(DraggableInDropZone);
+      fixture.detectChanges();
+      const dragItems = fixture.componentInstance.dragItems;
+
+      fixture.componentInstance.dropInstance.disabled = true;
+
+      expect(dragItems.map(drag => drag.element.nativeElement.textContent!.trim()))
+          .toEqual(['Zero', 'One', 'Two', 'Three']);
+
+      const firstItem = dragItems.first;
+      const thirdItemRect = dragItems.toArray()[2].element.nativeElement.getBoundingClientRect();
+
+      dragElementViaMouse(fixture, firstItem.element.nativeElement,
+          thirdItemRect.right + 1, thirdItemRect.top + 1);
+      flush();
+      fixture.detectChanges();
+
+      expect(fixture.componentInstance.droppedSpy).not.toHaveBeenCalled();
+
+      expect(dragItems.map(drag => drag.element.nativeElement.textContent!.trim()))
+          .toEqual(['Zero', 'One', 'Two', 'Three']);
+    }));
+
   });
 
   describe('in a connected drop container', () => {
@@ -1928,6 +1990,8 @@ class StandaloneDraggable {
 class StandaloneDraggableWithHandle {
   @ViewChild('dragElement') dragElement: ElementRef<HTMLElement>;
   @ViewChild('handleElement') handleElement: ElementRef<HTMLElement>;
+  @ViewChild(CdkDrag) dragInstance: CdkDrag;
+  @ViewChild(CdkDragHandle) handleInstance: CdkDragHandle;
 }
 
 @Component({

src/cdk/drag-drop/drag.ts

@@ -29,6 +29,7 @@ import {
   ViewContainerRef,
 } from '@angular/core';
 import {supportsPassiveEventListeners} from '@angular/cdk/platform';
+import {coerceBooleanProperty} from '@angular/cdk/coercion';
 import {Observable, Subject, Subscription, Observer} from 'rxjs';
 import {take} from 'rxjs/operators';
 import {DragDropRegistry} from './drag-drop-registry';
@@ -198,6 +199,16 @@ export class CdkDrag<T = any> implements AfterViewInit, OnDestroy {
    */
   @Input('cdkDragRootElement') rootElementSelector: string;
 
+  /** Whether starting to drag this element is disabled. */
+  @Input('cdkDragDisabled')
+  get disabled(): boolean {
+    return this._disabled || (this.dropContainer && this.dropContainer.disabled);
+  }
+  set disabled(value: boolean) {
+    this._disabled = coerceBooleanProperty(value);
+  }
+  private _disabled = false;
+
   /** Emits when the user starts dragging the item. */
   @Output('cdkDragStarted') started: EventEmitter<CdkDragStart> = new EventEmitter<CdkDragStart>();
 
@@ -314,10 +325,10 @@ export class CdkDrag<T = any> implements AfterViewInit, OnDestroy {
         return !!target && (target === element || element.contains(target as HTMLElement));
       });
 
-      if (targetHandle) {
+      if (targetHandle && !targetHandle.disabled && !this.disabled) {
         this._initializeDragSequence(targetHandle.element.nativeElement, event);
       }
-    } else {
+    } else if (!this.disabled) {
       this._initializeDragSequence(this._rootElement, event);
     }
   }

src/cdk/drag-drop/drop-list-container.ts

@@ -26,6 +26,9 @@ export interface CdkDropListContainer<T = any> {
   /** Locks the position of the draggable elements inside the container along the specified axis. */
   lockAxis: 'x' | 'y';
 
+  /** Whether starting a dragging sequence from this container is disabled. */
+  disabled: boolean;
+
   /** Starts dragging an item. */
   start(): void;
 

src/cdk/drag-drop/drop-list.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {coerceArray} from '@angular/cdk/coercion';
+import {coerceArray, coerceBooleanProperty} from '@angular/cdk/coercion';
 import {
   ContentChildren,
   ElementRef,
@@ -114,6 +114,14 @@ export class CdkDropList<T = any> implements OnInit, OnDestroy {
   /** Locks the position of the draggable elements inside the container along the specified axis. */
   @Input('cdkDropListLockAxis') lockAxis: 'x' | 'y';
 
+  /** Whether starting a dragging sequence from this container is disabled. */
+  @Input('cdkDropListDisabled')
+  get disabled(): boolean { return this._disabled; }
+  set disabled(value: boolean) {
+    this._disabled = coerceBooleanProperty(value);
+  }
+  private _disabled = false;
+
   /**
    * Function that is used to determine whether an item
    * is allowed to be moved into a drop container.

src/material-examples/cdk-drag-drop-disabled/cdk-drag-drop-disabled-example.css

@@ -0,0 +1,48 @@
+.example-list {
+  width: 500px;
+  max-width: 100%;
+  border: solid 1px #ccc;
+  min-height: 60px;
+  display: block;
+  background: white;
+  border-radius: 4px;
+  overflow: hidden;
+}
+
+.example-box {
+  padding: 20px 10px;
+  border-bottom: solid 1px #ccc;
+  color: rgba(0, 0, 0, 0.87);
+  display: flex;
+  flex-direction: row;
+  align-items: center;
+  justify-content: space-between;
+  box-sizing: border-box;
+  cursor: move;
+  background: white;
+  font-size: 14px;
+}
+
+.cdk-drag-preview {
+  box-sizing: border-box;
+  border-radius: 4px;
+  box-shadow: 0 5px 5px -3px rgba(0, 0, 0, 0.2),
+              0 8px 10px 1px rgba(0, 0, 0, 0.14),
+              0 3px 14px 2px rgba(0, 0, 0, 0.12);
+}
+
+.cdk-drag-placeholder {
+  opacity: 0;
+}
+
+.cdk-drag-animating {
+  transition: transform 250ms cubic-bezier(0, 0, 0.2, 1);
+}
+
+.example-box:last-child {
+  border: none;
+}
+
+.example-list.cdk-drop-list-dragging .example-box:not(.cdk-drag-placeholder) {
+  transition: transform 250ms cubic-bezier(0, 0, 0.2, 1);
+}

src/material-examples/cdk-drag-drop-disabled/cdk-drag-drop-disabled-example.html

@@ -0,0 +1,7 @@
+<div cdkDropList class="example-list" (cdkDropListDropped)="drop($event)">
+  <div
+    class="example-box"
+    *ngFor="let item of items"
+    cdkDrag
+    [cdkDragDisabled]="item.disabled">{{item.value}}</div>
+</div>

src/material-examples/cdk-drag-drop-disabled/cdk-drag-drop-disabled-example.ts

@@ -0,0 +1,22 @@
+import {Component} from '@angular/core';
+import {CdkDragDrop, moveItemInArray} from '@angular/cdk/drag-drop';
+
+/**
+ * @title Drag&Drop disabled
+ */
+@Component({
+  selector: 'cdk-drag-drop-disabled-example',
+  templateUrl: 'cdk-drag-drop-disabled-example.html',
+  styleUrls: ['cdk-drag-drop-disabled-example.css'],
+})
+export class CdkDragDropDisabledExample {
+  items = [
+    {value: 'I can be dragged', disabled: false},
+    {value: 'I cannot be dragged', disabled: true},
+    {value: 'I can also be dragged', disabled: false}
+  ];
+
+  drop(event: CdkDragDrop<string[]>) {
+    moveItemInArray(this.items, event.previousIndex, event.currentIndex);
+  }
+}