Select Tool: Grab/drag selected layers around viewport

[Keavon]

If the user has no layers selected, this will select the layer under the cursor (see #140) and then drag (transform) it. If multiple are selected, and the drag occurs on one of the selected, it will drag (transform) all of them. If one or more are selected but the drag occurs on another layer, it deselects the current selection and selects the new layer and drags it (like in the first sentence).

After this is implemented, we can then add support for snapping: #200.

Complexity: 3
Involves: Editor (Rust), Document (Rust)

[Keavon]

@pkupper do you know if this task is blocked, or soft-blocked in some capacity, by your work on #178? Or could somebody get to work on this right now? It does require knowledge of where the user clicks because dragging should only happen if the mousedown occurred on the shapes that will be dragged.

[pkupper]

This is does require #178. I'll see how much work this is and perhaps include it in my PR. We haven't really had the need to modify existing Layer yet so it will require some new Document Operations

[Keavon]

Blocked on #243.

[Keavon]

@AyeTbk you might like this one.

Edit: I actually just remembered you expressed interest in bounding boxes rather than this one, if my memory serves me correctly (I got them mixed up since they're similar). We realized #151 is not actually blocked, and its completion will open up #207 which I believe you were interested in. Would you want to work on those two?

Meanwhile this issue (#143) relates to nudging, which @henryksloan already completed, so perhaps this would be a logical one for him to do next.

[henryksloan]

I'd like to take this one, now that Fill is merged.

[Keavon]

Some additional features for this one: Shift hotkey constraints to a 15° angle, and adding the Ctrl hotkey locks to that particular constraint angle no matter where you move your mouse after. But let's merge the basic feature before the modifier keys. Also the Ctrl hotkey on its own causes it to snap to the grid, although we don't have a grid yet so don't bother with that yet.