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fix(drag-drop): detect changes on custom preview/placeholder before measuring #18698

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Merged
merged 1 commit into from
Mar 12, 2020
Merged

fix(drag-drop): detect changes on custom preview/placeholder before measuring #18698

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43 changes: 40 additions & 3 deletions src/cdk/drag-drop/directives/drag.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3010,6 +3010,30 @@ describe('CdkDrag', () => {
expect(placeholder.textContent!.trim()).not.toContain('Custom placeholder');
}));

it('should measure the custom placeholder after the first change detection', fakeAsync(() => {
const fixture = createComponent(DraggableInDropZoneWithCustomPlaceholder);
fixture.componentInstance.extraPlaceholderClass = 'tall-placeholder';
fixture.detectChanges();
const dragItems = fixture.componentInstance.dragItems;
const item = dragItems.toArray()[0].element.nativeElement;

startDraggingViaMouse(fixture, item);

const thirdItem = dragItems.toArray()[2].element.nativeElement;
const thirdItemRect = thirdItem.getBoundingClientRect();

dispatchMouseEvent(document, 'mousemove', thirdItemRect.left + 1, thirdItemRect.top + 1);
fixture.detectChanges();

dispatchMouseEvent(document, 'mouseup');
fixture.detectChanges();
flush();
fixture.detectChanges();

const event = fixture.componentInstance.droppedSpy.calls.mostRecent().args[0];
expect(event.currentIndex).toBe(2);
}));

it('should not throw when custom placeholder only has text', fakeAsync(() => {
const fixture = createComponent(DraggableInDropZoneWithCustomTextOnlyPlaceholder);
fixture.detectChanges();
Expand Down Expand Up @@ -5127,21 +5151,34 @@ class DraggableInDropZoneWithCustomTextOnlyPreview {

@Component({
template: `
<div cdkDropList style="width: 100px; background: pink;">
<div
cdkDropList
(cdkDropListDropped)="droppedSpy($event)"
style="width: 100px; background: pink;">
<div *ngFor="let item of items" cdkDrag
style="width: 100%; height: ${ITEM_HEIGHT}px; background: red;">
{{item}}
<ng-container *ngIf="renderPlaceholder">
<div class="custom-placeholder" *cdkDragPlaceholder>Custom placeholder</div>
<div
class="custom-placeholder"
[ngClass]="extraPlaceholderClass"
*cdkDragPlaceholder>Custom placeholder</div>
</ng-container>
</div>
</div>
`
`,
styles: [`
.tall-placeholder {
height: ${ITEM_HEIGHT * 3}px;
}
`]
})
class DraggableInDropZoneWithCustomPlaceholder {
@ViewChildren(CdkDrag) dragItems: QueryList<CdkDrag>;
items = ['Zero', 'One', 'Two', 'Three'];
renderPlaceholder = true;
extraPlaceholderClass = '';
droppedSpy = jasmine.createSpy('dropped spy');
}

@Component({
Expand Down
2 changes: 2 additions & 0 deletions src/cdk/drag-drop/drag-ref.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -884,6 +884,7 @@ export class DragRef<T = any> {
if (previewTemplate) {
const viewRef = previewConfig!.viewContainer.createEmbeddedView(previewTemplate,
previewConfig!.context);
viewRef.detectChanges();
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Rather than directly calling detectChanges, couldn't we instead defer measuring until Angular completes the change detection it needs to do anyway?

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Almost none of the drag&drop events trigger change detection so we can't really depend on it since it can happen at any time for other reason. This only detects on a small chunk of the tree anyway.

preview = getRootNode(viewRef, this._document);
this._previewRef = viewRef;

Expand Down Expand Up @@ -984,6 +985,7 @@ export class DragRef<T = any> {
placeholderTemplate,
placeholderConfig!.context
);
this._placeholderRef.detectChanges();
placeholder = getRootNode(this._placeholderRef, this._document);
} else {
placeholder = deepCloneNode(this._rootElement);
Expand Down