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windows-terminal/doc/specs/#885 - Terminal Settings Model/Actions Addendum.md

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---
author: Carlos Zamora @carlos-zamora
created on: 2021-03-12
last updated: 2021-03-17
issue id: [#885]
---
# Actions in the Settings Model
## Abstract
This spec proposes a refactor of how Windows Terminal actions are stored in the settings model.
The new representation would mainly allow the serialization and deserialization of commands and keybindings.
## Inspiration
A major component that is missing from the Settings UI is the representation of keybindings and commands.
The JSON represents both of these as a combined entry as follows:
```js
{ "icon": "path/to/icon.png", "name": "Copy the selected text", "command": "copy", "keys": "ctrl+c" },
```
In the example above, the copy action is...
- bound to <kbd>ctrl+c</kbd>
- presented as "Copy the selected text" with the "path/to/icon.png" icon
However, at the time of writing this spec, the settings model represents it as...
- (key binding) a `KeyChord` to `ActionAndArgs` entry in a `KeyMapping`
- (command) a `Command` with an associated icon, name, and action (`ActionAndArgs`)
This introduces the following issues:
1. Serialization
- We have no way of knowing when a command and a key binding point to the same action. Thus, we don't
know when to write a "name" to the json.
- We also don't know if the name was auto-generated or set by the user. This can make the JSON much more bloated by
actions with names that would normally be autogenerated.
2. Handling Duplicates
- The same action can be bound to multiple key chords. The command palette combines all of these actions into one entry
because they have the same name. In reality, this same action is just being referenced in different ways.
## Solution Design
I propose that the issues stated above be handled via the following approach.
### Step 1: Consolidating actions
`Command` will be updated to look like the following:
```c++
runtimeclass Command
{
// The path to the icon (or icon itself, if it's an emoji)
String IconPath;
// The associated name. If none is defined, one is auto-generated.
String Name;
// The key binding that can be used to invoke this action.
// NOTE: We're actually holding the KeyChord instead of just the text.
// KeyChordText just serializes the relevant keychord
Microsoft.Terminal.Control.KeyChord Keys;
String KeyChordText;
// The action itself.
ActionAndArgs ActionAndArgs;
// NOTE: nested and iterable command logic will still be here,
// But they are omitted to make this section seem cleaner.
// Future Considerations:
// - [#6899]: Action IDs --> add an identifier here
}
```
The goal here is to consolidate key binding actions and command palette actions into a single class.
This will also require the following supplemental changes:
- `Command::LayerJson`
- This must combine the logic of `KeyMapping::LayerJson` and `Command::LayerJson`.
- Key Chord data
- Internally, store a `vector<KeyChord> _keyMappings` to keep track of all the key chords associated with this action.
- `RegisterKey` and `EraseKey` update `_keyMappings`, and ensure that the latest key registered is at the end of the list.
- `Keys()` simply returns the last entry of `_keyMappings`, which is the latest key chord this action is bound to.
- `KeyChordText())` is exposed to pass the text directly to the command palette.
This depends on `Keys` and, thus, propagate changes automatically.
- Observable properties
- `Command` has observable properties today, but does not need them because `Command` will never change while the app is running.
- Nested and iterable commands
- `HasNestedCommands`, `NestedCommands{ get; }`, `IterateOn` will continue to be exposed.
- A setter for these customizations will not be exposed until we find it necessary (i.e. adding support for customizing it in the Settings UI)
- Command expansion can continue to be exposed here to reduce implementation cost.
- An additional `IsNestedCommand` is necessary to record a case where a nested command is being unbound `{ "commands": null, "name": "foo" }`.
Overall, the `Command` class is simply being promoted to include the `KeyChord` it has.
This allows the implementation cost of this step to be relatively small.
Completion of this step should only cause relatively minor changes to anything that depends on `Command`, because
it is largely the same class. However, key bindings will largely be impacted because we represent key bindings as
a map of `KeyChord`s to `ActionAndArgs`. This leads us to step 2 of this process.
### Step 2: Querying actions
Key bindings and commands are deserialized by basically storing individual actions to a map.
- `KeyMapping` is basically an `IMap<KeyChord, ActionAndArgs>` with a few extra functions. In fact, it actually
stores key binding data to a `std::map<KeyChord, ActionAndArgs>` and directly interacts with it.
- `Command::LayerJson` populates an `IMap<String, Command>` during deserialization as it iterates over every action.
Note that `Command` can be interpreted as a wrapper for `ActionAndArgs` with more stuff here.
It makes sense to store these actions as maps. So, following step 1 above, we can also store and expose actions
something like the following:
```c++
runtimeclass ActionMap
{
ActionAndArgs GetActionByKeyChord(KeyChord keys);
KeyChord GetKeyBindingForAction(ShortcutAction action);
KeyChord GetKeyBindingForAction(ShortcutAction action, IActionArgs actionArgs);
IMapView<String, Command> NameMap { get; };
// Future Considerations:
// - [#6899]: Action IDs --> GetActionByID()
}
```
The getters will return null if a matching action or key chord is not found. Since iterable commands need to be expanded at in TerminalApp, we'll just expose `NameMap`, then let TerminalApp perform the expansion as they do now. Internally, we can store the actions as follows:
```c++
std::map<KeyChord, InternalActionID> _KeyMap;
std::map<InternalActionID, Command> _ActionMap;
```
`InternalActionID` will be a hash of `ActionAndArgs` such that two `ActionAndArgs` with the same `ShortcutAction` and `IActionArgs` output the same hash value.
`GetActionByKeyChord` will use `_KeyMap` to find the `InternalActionID`, then use the `_ActionMap` to find the bound `Command`.
`GetKeyBindingForAction` will hash the provided `ActionAndArgs` (constructed by the given parameters) and check `_ActionMap` for the given `InternalActionID`.
`NameMap` will need to ensure every action in `_ActionMap` is added to the output name map if it has an associated name. This is done by simply iterating over `_ActionMap`. Nested commands must be added separately because they cannot be hashed.
`ActionMap` will have an `AddAction(Command cmd)` that will update the internal state whenever a command is registered. If the given command is valid, we will check for collisions and resolve them. Otherwise, we will consider this an "unbound" action and update the internal state normally. It is important that we don't handle "unbound" actions differently because this ensures that we are explicitly unbinding a key chord.
### Step 3: Settings UI needs
After the former two steps are completed, the new representation of actions in the settings model is now on-par with
what we have today. In order to bind these new actions to the Settings UI, we need the following:
1. Exposing the maps
- `ActionMap::KeyBindings` and `ActionMap::Commands` may need to be added to pass the full list of actions to the Settings UI.
- In doing this, we can already update the Settings UI to include a better view of our actions.
2. Creating a copy of the settings model
- The Settings UI operates by binding the XAML controls to a copy of the settings model.
- Copying the `ActionMap` is fairly simple. Just copy the internal state and ensure that `Command::Copy` is called such that no reference to the original WinRT objects persist. Since we are using `InternalActionID`, we will not have to worry about multiple `Command` references existing within the same `ActionMap`.
3. Modifying the `Command`s
- `ActionMap` must be responsible for changing `Command`s so that we can ensure `ActionMap` always has a correct internal state:
- It is important that `Command` only exposes getters (not setters) to ensure `ActionMap` is up to date.
- If a key chord is being changed, update the `_KeyMap` and the `Command` itself.
- If a key binding is being deleted, add an unbound action to the given key chord.
- This is similar to how color schemes are maintained today.
- In the event that name/key-chord is set to something that's already taken, we need to propagate those changes to
the rest of `ActionMap`. As we do with the JSON, we respect the last name/key-chord set by the user. See [Modifying Actions](#modifying-actions)
in potential issues.
- For the purposes of the key bindings page, we will introduce a `KeyBindingViewModel` to serve as an intermediator between the settings UI and the settings model. The view model will be responsible for things like...
- exposing relevant information to the UI controls
- converting UI control interactions into proper API calls to the settings model
4. Serialization
- `Command::ToJson()` and `ActionMap::ToJson()` should perform most of the work for us. Simply iterate over the `_ActionMap` and call `Command::ToJson` on each action.
- See [Unbinding actions](#unbinding-actions) in potential issues.
## UI/UX Design
N/A
## Capabilities
N/A
### Accessibility
N/A
### Security
N/A
### Reliability
N/A
### Compatibility
N/A
### Performance, Power, and Efficiency
## Potential Issues
### Layering Actions
We need a way to determine where an action came from to minimize how many actions we serialize when we
write to disk. This is a two part approach that happens as we're loading the settings
1. Load defaults.json
- For each of the actions in the JSON...
- Construct the `Command` (basically the `Command::LayerJson` we have today)
- Add it to the `ActionMap`
- this should update the internal state of `ActionMap` appropriately
- if the newly added key chord conflicts with a preexisting one,
redirect `_KeyMap` to the newly added `Command` instead,
and update the conflicting one.
2. Load settings.json
- Create a child for the `ActionMap`
- The purpose of a parent is to continue a search when the current `ActionMap` can't find a `Command` for a query. The parent is intended to be immutable.
- Load the actions array like normal into the child (see step 1)
Introducing a parent mechanism to `ActionMap` allows it to understand where a `Command` came from. This allows us to minimize the number of actions we serialize when we write to disk, as opposed to serializing the entire list of actions.
`ActionMap` queries will need to check their parent when they cannot find a matching `InternalActionID` in their `_ActionMap`.
Since `NameMap` is generated upon request, we will need to use a `std::set<InternalActionID>` as we generate the `NameMap`. This will ensure that each `Command` is only added to the `NameMap` once. The name map will be generated as follows:
1. Get an accumulated list of `Command`s from our parents
2. Iterate over the list...
- Update `NameMap` with any new `Command`s (tracked by the `std::set<InternalActionID>`)
Nested commands will be saved to their own map since they do not have an `InternalActionID`.
- During `ActionMap`'s population, we must ensure to resolve any conflicts immediately. This means that any new `Command`s that generate a name conflicting with a nested command will take priority (and we'll remove the nested command from its own map). Conversely, if a new nested command conflicts with an existing standard `Command`, we can ignore it because our generation of `NameMap` will handle it.
- When populating `NameMap`, we must first add all of the standard `Command`s. To ensure layering is accomplished correctly, we will need to start from the top-most parent and update `NameMap`. As we go down the inheritance tree, any conflicts are resolved by prioritizing the current layer (the child). This ensures that the current layer takes priority.
- After adding all of the standard `Command`s to the `NameMap`, we can then register all of the nested commands. Since nested commands have no identifier other than a name, we cannot use the `InternalActionID` heuristic. However, as mentioned earlier, we are updating our internal nested command map as we add new actions. So when we are generating the name map, we can assume that all of these nested commands now have priority. Thus, we simply add all of these nested commands to the name map. Any conflicts are resolved in favor of th nested command.
### Modifying Actions
There are several ways a command can be modified:
- change/remove the key chord
- change the name
- change the icon
- change the action
It is important that these modifications are done through `ActionMap` instead of `Command`.
This is to ensure that the `ActionMap` is always aligned with `Command`'s values. `Command` should only expose getters in the projected type to enforce this. Thus, we can add the following functions to `ActionMap`:
```c++
runtimeclass ActionMap
{
void SetKeyChord(Command cmd, KeyChord keys);
void SetName(Command cmd, String name);
void SetIcon(Command cmd, String iconPath);
void SetAction(Command cmd, ShortcutAction action, IActionArgs actionArgs);
}
```
`SetKeyChord` will need to make sure to modify the `_KeyMap` and the provided `Command`.
If the new key chord was already taken, we also need to update the conflicting `Command`
and remove its key chord.
`SetName` will need to make sure to modify the `Command` in `_ActionMap` and regenerate `NameMap`.
`SetIcon` will only need to modify the provided `Command`. We can choose to not expose this in the `ActionMap`, but doing so makes the API consistent.
`SetAction` will need to begin by updating the provided `Command`'s `ActionAndArgs`.
If the generated name is being used, the name will need to be updated. `_ActionMap` will need to be updated with a new `InternalActionID` for the new action. This is a major operation and so all views exposed will need to be regenerated.
Regarding [Layering Actions](#layering-actions), if the `Command` does not exist in the current layer,
but exists in a parent layer, we need to...
0. check if it exists
- use the hash `InternalActionID` to see if it exists in the current layer
- if it doesn't (which is the case we're trying to solve here), call `_GetActionByID(InternalActionID)` to retrieve the `Command` wherever it may be. This helper function simply checks the current layer, if none is found, it recursively checks its parents until a match is found.
1. duplicate it with `Command::Copy`
2. store the duplicate in the current layer
- `ActionMap::AddAction(duplicate)`
3. make the modification to the duplicate
This ensures that the change persists post-serialization.
TerminalApp has no reason to ever call these setters. To ensure that relationship, we will introduce an `IActionMapView` interface that will only expose `ActionMap` query functions. Conversely, `ActionMap` will be exposed to the TerminalSettingsEditor to allow for modifications.
### Unbinding actions
Removing a name is currently omitted from this spec because there
is no Settings UI use case for it at the moment. This scenario is
designed for Command Palette customization.
The only kind of unbinding currently in scope is freeing a key chord such that
no action is executed on that key stroke. To do this, simply `ActionMap::AddAction` a `Command` with...
- `ActionAndArgs`: `ShortcutAction = Invalid` and `IActionArgs = nullptr`
- `Keys` being the provided key chord
In explicitly storing an "unbound" action, we are explicitly saying that this key chord
must be passed through and this string must be removed from the command palette. `AddAction` automatically handles updating the internal state of `ActionMap` and any conflicting `Commands`.
This allows us to output something like this in the JSON:
```js
{ "command": "unbound", "keys": "ctrl+c" }
```
### Consolidated Actions
`AddAction` must be a bit smarter when it comes to the following scenario:
- Given a command that unbinds a key chord: `{ "command": "unbound", "keys": "ctrl+c" }`
- And... that key chord was set in a parent layer `{ "command": "copy", "keys": "ctrl+c" }`
- But... the action has another key chord from a parent layer `{ "command": "copy", "keys": "ctrl+shift+c" }`
`_ActionMap` does not contain any information about a parent layer; it only contains actions introduced in the current layer. Thus, in the scenario above, unbinding `ctrl+c` is what is relevant to `_ActionMap`. However, this may cause some complications for `GetKeyChordForAction`. We cannot simply check our internal `_ActionMap`, because the primary key chord in the entry may be incorrect. Again, this is because `_ActionMap` is only aware of what was bound in the current layer.
To get around this issue, we've introduced `_ConsolidatedActions`. In a way, `_ConsolidatedActions` is similar to `_ActionMap`, except that it consolidates the `Command` data into one entry constructed across the current layer and the parent layers. Specifically, in the scenario above, `_ActionMap` will say that `copy` has no key chords. In fact, `_ActionMap` has no reason to have `copy` at all, because it was not introduced in this layer. Conversely, `_ConsolidatedActions` holds `copy` with a `ctrl+shift+c` binding, which is then returned to `GetKeyChordForAction`.
To maintain `_ConsolidatedActions`, any new action added to the Action Map must also update `_ConsolidatedActions`. It is especially important to handle and propagate collisions to `_ConsolidatedActions`.
When querying Action Map for an ID, we should always check in the following order:
- `_ConsolidatedActions`
- `_ActionMap`
- repeat this process for each parent
This is to ensure that we are returning the correct and wholistic view of a `Command` on a query. Rather than acquiring a `Command` constructed in this layer, we receive one that contains all of the data acquired across the entire Action Map and its parents.
## Future considerations
There are a number of ideas regarding actions that would be fairly trivial to implement given this refactor:
- [#6899]: Action IDs
- As actions grow to become more widespread within Windows Terminal (i.e. dropdown and jumplist integration),
a formal ID system would help users reference the same action throughout the app. With the internal
ID system introduced earlier, we would simply introduce a new
`std:map<string, InternalActionID> _ExternalIDMap` that is updated like the others, and add a `String ID`
property to `Action`.
- [#8100] Source Tracking
- Identifying where a setting came from can be very beneficial in the settings model and UI. For example,
profile settings now have an `OverrideSource` getter that describes what `Profile` object the setting
came from (i.e. base layer, profile generator, etc...). A similar system can be used for `Action` in
that we record if the action was last modified in defaults.json or settings.json.
- There seems to be no desire for action inheritance (i.e. inheriting the name/key-chord from the parent).
So this should be sufficient.
## Resources
[#885]: https://github.com/microsoft/terminal/issues/885
[#6899]: https://github.com/microsoft/terminal/issues/6899
[#8100]: https://github.com/microsoft/terminal/issues/8100
[#8767]: https://github.com/microsoft/terminal/issues/8767
Other references:
[Settings UI: Actions Page]: https://github.com/microsoft/terminal/issues/6900
[Settings UI: Actions Page Design]: https://github.com/microsoft/terminal/pulls/9427
[Action ID Spec]: https://github.com/microsoft/terminal/issues/7175
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