feat(cdk/drag-drop): added dropPoint to dropped event

[timonkrebs]

I need to be able to determine the exact point where the mouse pointer was when the Item was dropped. This is not possible to calculate from the distance, because it depends on the position where the item was grabbed at drag start.

CdkDragDrop.item.getFreeDragPosition(); does also not work because it gives the position of the element top/left corner at drag start.

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[timonkrebs]

@googlebot I signed it!

[binerdy]

Ah yes, this has been confusing me. It would be nice if the drop position is decided based on the mouse pointer position. Is there an easy way to do this?

[crisbeto]

LGTM

[wagnermaciel]

@crisbeto Adding dropPoint causes ts errors. Here's an example:

error TS2741: Property 'dropPoint' is missing in type '{ container: CdkDropList<string[]>; previousContainer: CdkDropList<string[]>; currentIndex: number; previousIndex: number; item: CdkDrag<string>; isPointerOverContainer: true; distance: { ...; }; }' but required in type 'CdkDragDrop<string[], string[]>'

Should this be target: major?

[crisbeto]

It's hard to tell why it's breaking from the error. Does the app try to type an event using our interface? I don't think that this includes any changes that would be considered breaking.

[wagnermaciel]

@crisbeto It breaks in cases like this:

function createDragDropEvent(...): CdkDragDrop<string[], string[]> {

    ...
  
    return {
        container,
        previousContainer,
        currentIndex,
        previousIndex,
        item,
        isPointerOverContainer,
        distance,
    };
}

CdkDragDrop<string[], string[]> is missing 'dropPoint' so people will start seeing errors

[crisbeto]

I don't think that's something we cover with our breaking change policy. For g3 it could be patched as dropPoint: {x: 0, y: 0} and a TODO.

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