Add 'drag and drop' examples

[davesmith00000]

I think there's two to do:

1. Fully manual
2. Using UI Buttons

Maybe it should go in the as yet non-existent 'how to' section? #36

[bilki]

Could you explain a bit further what's the meaning of using UI buttons?

Also, maybe you're talking about this exact same thing with UI buttons, but I feel like there are two types of drag and drop:

1. Click down on element, don't release mouse button, move the element across the screen, then drop on release
2. Click down on element, release mouse button (or mouse down + mouse up in terms of events), move the element across the screen simply moving the cursor, then drop it wherever a new click happens (again mouse down + up)

Differences are subtle but I think the second one has better accessibility for everyone, and some specific use cases 🤔

Using a mouse is a simplification ofc, it should work the same for any other pointing device.

[davesmith00000]

Quite right about the two modes, and to my eternal shame my long standing habit of neglecting accessibility continues... (@hobnob usually keeps me in check there. 🙂)

Those two modes of drag and drop are easy enough to create manually, but UI buttons only support mode (1) currently.

UI Buttons are part of the new UI component system that was recently released. They come with support for drag (BUT NOT DROP) functionality built in. You can enable one of two drag modes:

1. Drag and follow
2. Drag and 'report' - which means reporting the drag information but not automatically moving the button.

In both cases you need to do something to implement the 'drop' side of things. It's possible we could add drop functionality into the UI system but I'm not sure what that would look like right now.

The use cases for those two modes are:

1. The usual, expected drag behaviour.
2. The button is part of something bigger and you want to render / update many things without a perceived frame delay where the button is 'detached' from the group. The original use case was for window controls, used to resize the window or drag it from the title bar.

(Help is welcome with any and all of this)

Does that help?