Angular2: progress/loading overlay directive

I'm trying to create a loading indicator/overlay in Angular2 that I can add to any container div. When a dynamic boolean property like isLoading changes, it should grey out the div and show a spinning indicator, and disappear again after the property changes back.

I got a working solution:

@Component({
  selector: 'loading-overlay',
  styleUrls: ['...'],
  template: `
        <div class="bg-loading" *ngIf="isLoading">
          <h3><span class="glyphicon glyphicon-refresh spinning"></span></h3>
        </div>`
})
export class LoadingOverlay {
  @Input()    
  isLoading: boolean;
}

And usage:

<div> <!-- container for whatever -->
  <loading-overlay [isLoading]="dynamicProp"></loading-overlay>
  <!-- ... other content -->
</div>

So far so good, but this is hard to get right with styling for different use cases, mostly to make the margins/paddings look good in different containers.

So I want to make this whole thing into an attribute directive like so:

<div loading-overlay="dynamicProp"> <!-- container for whatever -->
  <!-- content ... -->
</div>

I'm pretty sure this should be easy, but I can't find anything useful in the docs or via googling. It feels like I should dynamically add/remove the overlay div, but I'm not sure if this is the right approach, or even how to do it.

Answers:

Answer

We created a similar thing in a project, however we stuck to the element-directive approach. Not sure if/what benefits you would get by converting it to a directive. I think it would even make it harder.

Our solution was for sure no the cleanest approach, here's roughly what we did which worked well for us so far:

When the components state toggles to "is showing" the component will inspect its parent element for size information (height/width) and apply these values to itself.

for positioning we use the simple: container-element with 0x0px positionioned at pos 0/0 of the parent (relative), inside that there is the real overlay (positioned fixed, size set dynamically as described above).

For padding/margin i'm currently not sure if we had to do lots of fixes, i think it shouldn't be too difficult to get around that by querying the parent element.

We even re-called our "calculate size" method a few times after the component is shown: the reason is that the element which we wanted to overlay sometimes changed its size during the loading process. Imagine for example a table (has 3 lines), gets reloaded, expands to 6 lines but for some reason we aren't done loading so the overlay should still be shown, but we want the overlay to automatically cover these newly added lines as well.

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