[Tooltip] Change detection runs after showing tooltip

Bug, feature request, or proposal:

Bug

What is the expected behavior?

Hovering an element with a matTooltip should not trigger change detection on this element if it is an OnPush element and its @Input()s does not change.

What is the current behavior?

Hovering an element with a matTooltip triggers change detection on this element.

This only happens if matTooltip is defined using [matTooltip]="..." and not when it is defined using matTooltip="..."

What are the steps to reproduce?

See https://stackblitz.com/edit/angular-material2-issue-ocg9sj

• pass the mouse on the red div
• you get logs everytime the function needed to draw the component are called
• you don’t get any log from ngOnChanges
• I would expect that since the @Input() didn’t change, the component shouldn’t be redraw!

What is the use-case or motivation for changing an existing behavior?

Prevent useless redraws

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

cf stackblitz

Is there anything else we should know?

[Need-To-Learn]

Hi, I’m having this issue too with matTooltip directive. The component’s changeDetection is set to ChangeDetectionStrategy.OnPush. On hover / leave, the component’s change detection is triggered multiple times.

Thx !

[klinki]

I agree, this is a problem for bigger applications with slow change detection cycle. It brings us a lot of problems 😦