Introduce new APIs for managing focus and using focus to inform delivery of keyboard events.
Use new APIs to implement the following behavior:
Focus:
- If the component browser is opened, its initial state is *focused*.
- If the node input area's text component is clicked, the component browser's state becomes *blurred*.
- If a click occurs anywhere in the component browser, the component browser's state becomes *focused*.
Event dispatch:
- When the component browser is in the *focused* state, it handles certain keyboard events (chiefly, arrow keys).
- If the component browser handles an event, the event is not received by other components.
- If an event occurs that the component browser doesn't handle, the node input area's text component receives the event.
[vokoscreenNG-2023-06-29_10-55-00.webm](https://github.com/enso-org/enso/assets/1047859/f1d9d07c-8c32-4482-ba32-15b6e4e20ae7)
# Important Notes
Changes to display object interface:
- **`display::Object` can now be derived.**
- Introduce display object *focus receiver* concept. Many components, when receiving focus, should actually be focused indirectly by focusing a descendant.
- For example, when the CB Panel receives focus, its descendant at `self.model().grid.model().grid` should be focused, because that's the underlying Grid View, which has its own event handlers. By allowing each level of the hierarchy to define a `focus_receiver`, focus can reach the right object without the CB panel having to know structural details of its descendants.
- When delegating to a field's `display::Object` implementation, the derived implementation uses the child's `focus_receiver`, which will normally be the correct behavior.
**Changes to `shortcut` API**:
- New `View::focused_shortcuts()` is a focus-aware alternative to `View::default_shortcuts()` (which should now only be used for global shortcuts, i.e. shortcuts that don't depend on whether the component is focused). It's based on the *Keyboard Event* API (see below), so events propagate up the focus hierarchy until a shortcut is executed and `stop_propagation()` is called; this allows sensible resolution of event targets when more than one component is capable of handling the same keypress.
Keypress dataflow overview:
DOM -> KeyboardManager -> FrpKeyboard -> KeyboardEvents -> Shortcut.
Low-level keyboard changes to support Focus:
- New `KeyboardManager`: Attaches DOM event handlers the same way as `MouseManager`.
- New *Keyboard Event* API: `on_event::<KeyDown>()`. Events propagate up the focus hierarchy. This API is used for low-level keyboard listeners such a `Text`, which may need complex logic to determine whether a key is handled (rather than having a closed set of bindings, which can be handled by `shortcut`).
- FRP keyboard: Now attaches to the `KeyboardManager` API. It now serves primarily to produce Keyboard Events (it still performs the role of making `KeyUp` events saner in a couple different ways). The FRP keyboard can also be used directly as a global keyboard, for such things as reacting to modifier state.
Misc:
- Updated the workspace `syn` to version 2. Crates still depending on legacy `syn` now do so through the workspace-level `syn_1` alias.
This PR changes build script's `ide watch` and `ide start` commands, so they don't use `electron-builder` to package. Instead, they invoke `electron` directly, significantly reducing time overhead.
`ide watch` will now start Electron process, while continuously rebuilding gui and the client in the background. Changes can be puilled by reloading within the electron, or closing the electron and letting it start once again. To stop, the script should be interrupted with `Ctrl+C`.
