feat(MatTooltip): Mimic native tooltip behaviour

[tuhinkarmakar]

Feature Description

If nested elements have MatTooltips applied on them, show the innermost tooltip.

Suppose we have a button with a span inside it.

<button mat-raised-button matTooltip="Button tooltip">
  <span matTooltip="Span tooltip">Mat Tooltip</span>
</button>

<button mat-raised-button title="Button tooltip">
  <span title="Span tooltip">Native Tooltip</span>
</button>

If both of these elements have the title attribute applied to them and we hover the span, the browser shows title text of the span.
However, if we use the MatTooltip directive, both tooltips are shown to the user.

Minimal Reproduction on StackBlitz

Use Case

Whenever you need to show different tooltips for parent and child elements.

[crisbeto]

It should be doable by injecting parent instances of MatTooltip and going up the tree to close all of them when a new one is opened. That being said, it would probably have to be configurable since somebody might want tooltips to trigger as they do now.

[tuhinkarmakar]

Yes, you're right. This should be configurable. I had a different idea on how we could implement this feature. We can use @ContentChildren(MatTooltip) to see if there are any child MatTooltips. If yes, then don't show the tooltip. If no, then show the tooltip.

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[Anton2478]

How can it be considered a feature? Showing several tooltips at once doesn't make any sense, taking into account these tooltips don't know anything about each other and may intersect. For my application it's a bug preventing from using matTooltip at all.