No way to intercept `MdDialog` close events

[benelliott]

Bug, feature request, or proposal:

There doesn't seem to be any way to intercept clicks outside a dialog that are intended to dismiss it. This can be desirable if, for example, the user has made some changes but has chosen to click outside the modal instead of clicking the "confirm" button.

The only way to intercept dialog close requests currently is to set disableClose: true in the dialog config and then to wire up the dialog action buttons to perform this logic when clicked.

What is the expected behavior?

There should be some way to intercept and cancel close events that come from the user clicking outside the dialog.

What is the current behavior?

There are only two possible scenarios - either

1. the user cannot click outside the dialog at all, or
2. clicking outside the dialog will always dismiss the modal

I suppose one workaround would be to allow the modal to be dismissed, but check and reopen it afterwards if necessary, but this would be clunky.

What are the steps to reproduce?

Create a modal without setting disableClose: true and try to intercept these close events.

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

I feel that it is detrimental to the UX of the dialog not to allow the user to click outside of it to close it, however there should be some way to cancel these events if they were performed by mistake. Otherwise this could lead to an anti-pattern where the behaviour of dialogs are consistent across an app: some are dismissible, as they don't involve editing valuable data, while some are not as the developer doesn't want to take the risk that the user might accidentally dismiss them.

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

Angular 4/Material 2 beta 2/Windows 7/Chrome 57

Is there anything else we should know?

This might issue might be a more general discussion about dialog dismissal behaviour than a simple bug.

[willshowell]

@fxck has been pushing for this for a while and has a PR for it here #3460

[remillc]

@benelliott, you can disable click outside the dialog, more exactly clicks on the backdrop, using the css property pointer-events:

.mdc-dialog__backdrop {
	pointer-events: none;
}

[willshowell]

This should be solved by #6682. The gist of it is that, if you want to intercept closing of the dialog,

1. set disableClose: true
2. subscribe to backdropClick() and keydownEvents() to detect backdrop clicks or potential ESCAPE keydowns
3. do whatever
4. close manually when you're ready

[emilio-martinez]

@benelliott it looks like this is resolved as per @willshowell's PR, correct?

[jelbourn]

Going to close this since I believe the idea of "preventing dialog from closing" works today based on the aforementioned work.

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