feat(material): Allow focus origin to be an optional input to focus() methods.

[jesscxu]

Feature Description

WHAT: For Angular Material components that have a focus() method, allow for the origin param to be optional and remove the default origin value.

WHY: For cases where the focus() method is called and the origin is already defined, we don’t want to override the origin using focusVia to always be some default value. In many cases, we want to leave the origin unchanged, but if there are cases that need the origin to be updated, allow for this with an optional origin param.

Use Case

If the focus origin value is keyboard, and some interaction happens where we want to set focus to another element somewhere on the page by explicitly calling focus(), then in cases where the focus origin should remain the same, the current implementation causes the origin to change and the interaction to be weird. This is also due to the fact that we use a single, global focus monitor attached to the document body in eventual detection mode.

Here are the components to update:
-button
-checkbox
-menu item
-menu trigger
-radio
-expansion panel header
-slide toggle
-step header

[jelbourn]

Would it work for your use case if the FocusMonitor publicly exposed lastFocusOrigin so you could just read that and pass it through to the focus method manually?

Changing the default behavior if no origin was specific would be a breaking change that would potentially be difficult to land in Google, so doing it manually would be an easier change to make, especially since we seem to already track the last focus origin.

[crisbeto]

Another problem with adding origin parameters everywhere is that we'd have to inject and use FocusMonitor in components that don't use it at the moment which will be a breaking constructor change.

[jesscxu]

Interesting thought, yes that would work for components where we call focus and could pass lastFocusOrigin in. However, this wouldn't work for Angular Material components that call focus on another Angular Material component.

My main concern is that when calling focus one would need to know to access the lastFocusOrigin from the global focusMonitor and pass that through the focus call vs. just using .focus() which is more intuitive.

I am curious how "bad" the breaking change would be? I attempted to look through the history of some of these focus methods and couldn't exactly understand the reason why the default focus origin (and the chosen value that is different for different components) was necessary? Do you have more background knowledge on that?

[jesscxu]

@crisbeto I believe all the components I want to add an origin param to (the focus methods of radio, slide toggle, etc.) already inject FocusMonitor, though I may have misunderstood something!

[jesscxu]

@jelbourn I am currently trying to see how many issues my change would cause in Google with button.

@crisbeto Here is an example PR: #20898 for the change I am proposing for button (and other components as well).

Let me know if this information helps!

[mmalerba]

I think this seems fine as long as it doesn't turn out to be too breaking (which it seems not to be). The proposal isn't to add origin parameters everywhere, its just to stop defaulting the parameter to 'program' in places where it has already been added. Instead we will allow the origin to be set according to whatever the FocusMonitor decides it should be.

[jesscxu]

Closing this since it has been resolved and the changes have been made.

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