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# Settings Reference
This document serves as developer documentation for using "Granular Settings". Granular Settings allow users to specify different values for a setting at particular levels of interest. For example, a user may say that in a particular room they want URL previews off, but in all other rooms they want them enabled. The `SettingsStore` helps mask the complexity of dealing with the different levels and exposes easy to use getters and setters.
This document serves as developer documentation for using "Granular Settings". Granular Settings allow users to specify
different values for a setting at particular levels of interest. For example, a user may say that in a particular room
they want URL previews off, but in all other rooms they want them enabled. The `SettingsStore` helps mask the complexity
of dealing with the different levels and exposes easy to use getters and setters.
## Levels
Granular Settings rely on a series of known levels in order to use the correct value for the scenario. These levels, in order of prioirty, are:
Granular Settings rely on a series of known levels in order to use the correct value for the scenario. These levels, in
order of prioirty, are:
* `device` - The current user's device
* `room-device` - The current user's device, but only when in a specific room
* `room-account` - The current user's account, but only when in a specific room
@ -14,12 +18,14 @@ Granular Settings rely on a series of known levels in order to use the correct v
* `config` - Values are defined by `config.json`
* `default` - The hardcoded default for the settings
Individual settings may control which levels are appropriate for them as part of the defaults. This is often to ensure that room administrators cannot force account-only settings upon participants.
Individual settings may control which levels are appropriate for them as part of the defaults. This is often to ensure
that room administrators cannot force account-only settings upon participants.
## Settings
Settings are the different options a user may set or experience in the application. These are pre-defined in `src/settings/Settings.js` under the `SETTINGS` constant and have the following minimum requirements:
Settings are the different options a user may set or experience in the application. These are pre-defined in
`src/settings/Settings.js` under the `SETTINGS` constant and have the following minimum requirements:
```
// The ID is used to reference the setting throughout the application. This must be unique.
"theSettingId": {
@ -47,13 +53,21 @@ Settings are the different options a user may set or experience in the applicati
### Getting values for a setting
After importing `SettingsStore`, simply make a call to `SettingsStore.getValue`. The `roomId` parameter should always be supplied where possible, even if the setting does not have a per-room level value. This is to ensure that the value returned is best represented in the room, particularly if the setting ever gets a per-room level in the future.
After importing `SettingsStore`, simply make a call to `SettingsStore.getValue`. The `roomId` parameter should always
be supplied where possible, even if the setting does not have a per-room level value. This is to ensure that the value
returned is best represented in the room, particularly if the setting ever gets a per-room level in the future.
In settings pages it is often desired to have the value at a particular level instead of getting the calculated value. Call `SettingsStore.getValueAt` to get the value of a setting at a particular level, and optionally make it explicitly at that level. By default `getValueAt` will traverse the tree starting at the provided level; making it explicit means it will not go beyond the provided level. When using `getValueAt`, please be sure to use `SettingLevel` to represent the target level.
In settings pages it is often desired to have the value at a particular level instead of getting the calculated value.
Call `SettingsStore.getValueAt` to get the value of a setting at a particular level, and optionally make it explicitly
at that level. By default `getValueAt` will traverse the tree starting at the provided level; making it explicit means
it will not go beyond the provided level. When using `getValueAt`, please be sure to use `SettingLevel` to represent the
target level.
### Setting values for a setting
Values are defined at particular levels and should be done in a safe manner. There are two checks to perform to ensure a clean save: is the level supported and can the user actually set the value. In most cases, neither should be an issue although there are circumstances where this changes. An example of a safe call is:
Values are defined at particular levels and should be done in a safe manner. There are two checks to perform to ensure a
clean save: is the level supported and can the user actually set the value. In most cases, neither should be an issue
although there are circumstances where this changes. An example of a safe call is:
```javascript
const isSupported = SettingsStore.isLevelSupported(SettingLevel.ROOM);
if (isSupported) {
@ -64,11 +78,13 @@ if (isSupported) {
}
```
These checks may also be performed in different areas of the application to avoid the verbose example above. For instance, the component which allows changing the setting may be hidden conditionally on the above conditions.
These checks may also be performed in different areas of the application to avoid the verbose example above. For
instance, the component which allows changing the setting may be hidden conditionally on the above conditions.
##### `SettingsFlag` component
Where possible, the `SettingsFlag` component should be used to set simple "flip-a-bit" (true/false) settings. The `SettingsFlag` also supports simple radio button options, such as the theme the user would like to use.
Where possible, the `SettingsFlag` component should be used to set simple "flip-a-bit" (true/false) settings. The
`SettingsFlag` also supports simple radio button options, such as the theme the user would like to use.
```html
<SettingsFlag name="theSettingId"
level={SettingsLevel.ROOM}
@ -86,42 +102,65 @@ Where possible, the `SettingsFlag` component should be used to set simple "flip-
### Getting the display name for a setting
Simply call `SettingsStore.getDisplayName`. The appropriate display name will be returned and automatically translated for you. If a display name cannot be found, it will return `null`.
Simply call `SettingsStore.getDisplayName`. The appropriate display name will be returned and automatically translated
for you. If a display name cannot be found, it will return `null`.
## Features
Occasionally some parts of the application may be undergoing testing and are not quite production ready. These are commonly known to be behind a "labs flag". Features behind lab flags must go through the granular settings system, and look and act very much normal settings. The exception is that they must supply `isFeature: true` as part of the setting definition and should go through the helper functions on `SettingsStore`.
Occasionally some parts of the application may be undergoing testing and are not quite production ready. These are
commonly known to be behind a "labs flag". Features behind lab flags must go through the granular settings system, and
look and act very much normal settings. The exception is that they must supply `isFeature: true` as part of the setting
definition and should go through the helper functions on `SettingsStore`.
Although features have levels and a default value, the calculation of those options is blocked by the feature's state. A feature's state is determined from the `SdkConfig` and is a little complex. If `enableLabs` (a legacy flag) is `true` then the feature's state is `labs`, if it is `false`, the state is `disable`. If `enableLabs` is not set then the state is determined from the `features` config, such as in the following:
Although features have levels and a default value, the calculation of those options is blocked by the feature's state.
A feature's state is determined from the `SdkConfig` and is a little complex. If `enableLabs` (a legacy flag) is `true`
then the feature's state is `labs`, if it is `false`, the state is `disable`. If `enableLabs` is not set then the state
is determined from the `features` config, such as in the following:
```json
"features": {
"feature_lazyloading": "labs"
}
```
In this example, `feature_lazyloading` is in the `labs` state. It may also be in the `enable` or `disable` state with a similar approach. If the state is invalid, the feature is in the `disable` state. A feature's levels are only calculated if it is in the `labs` state, therefore the default only applies in that scenario. If the state is `enable`, the feature is always-on.
In this example, `feature_lazyloading` is in the `labs` state. It may also be in the `enable` or `disable` state with a
similar approach. If the state is invalid, the feature is in the `disable` state. A feature's levels are only calculated
if it is in the `labs` state, therefore the default only applies in that scenario. If the state is `enable`, the feature
is always-on.
Once a feature flag has served its purpose, it is generally recommended to remove it and the associated feature flag checks. This would enable the feature implicitly as it is part of the application now.
Once a feature flag has served its purpose, it is generally recommended to remove it and the associated feature flag
checks. This would enable the feature implicitly as it is part of the application now.
### Determining if a feature is enabled
A simple call to `SettingsStore.isFeatureEnabled` will tell you if the feature is enabled. This will perform all the required calculations to determine if the feature is enabled based upon the configuration and user selection.
A simple call to `SettingsStore.isFeatureEnabled` will tell you if the feature is enabled. This will perform all the
required calculations to determine if the feature is enabled based upon the configuration and user selection.
### Enabling a feature
Features can only be enabled if the feature is in the `labs` state, otherwise this is a no-op. To find the current set of features in the `labs` state, call `SettingsStore.getLabsFeatures`. To set the value, call `SettingsStore.setFeatureEnabled`.
Features can only be enabled if the feature is in the `labs` state, otherwise this is a no-op. To find the current set
of features in the `labs` state, call `SettingsStore.getLabsFeatures`. To set the value, call
`SettingsStore.setFeatureEnabled`.
## Setting controllers
Settings may have environmental factors that affect their value or need additional code to be called when they are modified. A setting controller is able to override the calculated value for a setting and react to changes in that setting. Controllers are not a replacement for the level handlers and should only be used to ensure the environment is kept up to date with the setting where it is otherwise not possible. An example of this is the notification settings: they can only be considered enabled if the platform supports notifications, and enabling notifications requires additional steps to actually enable notifications.
Settings may have environmental factors that affect their value or need additional code to be called when they are
modified. A setting controller is able to override the calculated value for a setting and react to changes in that
setting. Controllers are not a replacement for the level handlers and should only be used to ensure the environment is
kept up to date with the setting where it is otherwise not possible. An example of this is the notification settings:
they can only be considered enabled if the platform supports notifications, and enabling notifications requires
additional steps to actually enable notifications.
For more information, see `src/settings/controllers/SettingController.js`.
## Local echo
`SettingsStore` will perform local echo on all settings to ensure that immediately getting values does not cause a split-brain scenario. As mentioned in the "Setting values for a setting" section, the appropriate checks should be done to ensure that the user is allowed to set the value. The local echo system assumes that the user has permission and that the request will go through successfully. The local echo only takes effect until the request to save a setting has completed (either successfully or otherwise).
`SettingsStore` will perform local echo on all settings to ensure that immediately getting values does not cause a
split-brain scenario. As mentioned in the "Setting values for a setting" section, the appropriate checks should be done
to ensure that the user is allowed to set the value. The local echo system assumes that the user has permission and that
the request will go through successfully. The local echo only takes effect until the request to save a setting has
completed (either successfully or otherwise).
```javascript
SettingsStore.setValue(...).then(() => {
@ -133,7 +172,12 @@ SettingsStore.getValue(...); // this will return the value set in `setValue` abo
## Watching for changes
Most use cases do not need to set up a watcher because they are able to react to changes as they are made, or the changes which are made are not significant enough for it to matter. Watchers are intended to be used in scenarios where it is important to react to changes made by other logged in devices. Typically, this would be done within the component itself, however the component should not be aware of the intricacies of setting inversion or remapping to particular data structures. Instead, a generic watcher interface is provided on `SettingsStore` to watch (and subsequently unwatch) for changes in a setting.
Most use cases do not need to set up a watcher because they are able to react to changes as they are made, or the
changes which are made are not significant enough for it to matter. Watchers are intended to be used in scenarios where
it is important to react to changes made by other logged in devices. Typically, this would be done within the component
itself, however the component should not be aware of the intricacies of setting inversion or remapping to particular
data structures. Instead, a generic watcher interface is provided on `SettingsStore` to watch (and subsequently unwatch)
for changes in a setting.
An example of a watcher in action would be:
@ -143,9 +187,10 @@ class MyComponent extends React.Component {
settingWatcherRef = null;
componentWillMount() {
this.settingWatcherRef = SettingsStore.watchSetting("roomColor", "!example:matrix.org", (settingName, roomId, level, newValAtLevel, newVal) => {
this.setState({color: newVal});
});
const callback = (settingName, roomId, level, newValAtLevel, newVal) => {
this.setState({color: newVal});
};
this.settingWatcherRef = SettingsStore.watchSetting("roomColor", "!example:matrix.org", callback);
}
componentWillUnmount() {
@ -157,21 +202,37 @@ class MyComponent extends React.Component {
# Maintainers Reference
The granular settings system has a few complex parts to power it. This section is to document how the `SettingsStore` is supposed to work.
The granular settings system has a few complex parts to power it. This section is to document how the `SettingsStore` is
supposed to work.
### General information
The `SettingsStore` uses the hardcoded `LEVEL_ORDER` constant to ensure that it is using the correct override procedure. The array is checked from left to right, simulating the behaviour of overriding values from the higher levels. Each level should be defined in this array, including `default`.
The `SettingsStore` uses the hardcoded `LEVEL_ORDER` constant to ensure that it is using the correct override procedure.
The array is checked from left to right, simulating the behaviour of overriding values from the higher levels. Each
level should be defined in this array, including `default`.
Handlers (`src/settings/handlers/SettingsHandler.js`) represent a single level and are responsible for getting and setting values at that level. Handlers also provide additional information to the `SettingsStore` such as if the level is supported or if the current user may set values at the level. The `SettingsStore` will use the handler to enforce checks and manipulate settings. Handlers are also responsible for dealing with migration patterns or legacy settings for their level (for example, a setting being renamed or using a different key from other settings in the underlying store). Handlers are provided to the `SettingsStore` via the `LEVEL_HANDLERS` constant. `SettingsStore` will optimize lookups by only considering handlers that are supported on the platform.
Handlers (`src/settings/handlers/SettingsHandler.js`) represent a single level and are responsible for getting and
setting values at that level. Handlers also provide additional information to the `SettingsStore` such as if the level
is supported or if the current user may set values at the level. The `SettingsStore` will use the handler to enforce
checks and manipulate settings. Handlers are also responsible for dealing with migration patterns or legacy settings for
their level (for example, a setting being renamed or using a different key from other settings in the underlying store).
Handlers are provided to the `SettingsStore` via the `LEVEL_HANDLERS` constant. `SettingsStore` will optimize lookups by
only considering handlers that are supported on the platform.
Local echo is achieved through `src/settings/handlers/LocalEchoWrapper.js` which acts as a wrapper around a given handler. This is automatically applied to all defined `LEVEL_HANDLERS` and proxies the calls to the wrapped handler where possible. The echo is achieved by a simple object cache stored within the class itself. The cache is invalidated immediately upon the proxied save call succeeding or failing.
Local echo is achieved through `src/settings/handlers/LocalEchoWrapper.js` which acts as a wrapper around a given
handler. This is automatically applied to all defined `LEVEL_HANDLERS` and proxies the calls to the wrapped handler
where possible. The echo is achieved by a simple object cache stored within the class itself. The cache is invalidated
immediately upon the proxied save call succeeding or failing.
Controllers are notified of changes by the `SettingsStore`, and are given the opportunity to override values after the `SettingsStore` has deemed the value calculated. Controllers are invoked as the last possible step in the code.
Controllers are notified of changes by the `SettingsStore`, and are given the opportunity to override values after the
`SettingsStore` has deemed the value calculated. Controllers are invoked as the last possible step in the code.
### Features
Features automatically get considered as `disabled` if they are not listed in the `SdkConfig` or `enable_labs` is false/not set. Features are always checked against the configuration before going through the level order as they have the option of being forced-on or forced-off for the application. This is done by the `features` section and looks something like this:
Features automatically get considered as `disabled` if they are not listed in the `SdkConfig` or `enable_labs` is
false/not set. Features are always checked against the configuration before going through the level order as they have
the option of being forced-on or forced-off for the application. This is done by the `features` section and looks
something like this:
```
"features": {
@ -185,9 +246,18 @@ If `enableLabs` is true in the configuration, the default for features becomes `
### Watchers
Watchers can appear complicated under the hood: there is a central `WatchManager` which handles the actual invocation of callbacks, and callbacks are managed by the SettingsStore by redirecting the caller's callback to a dedicated callback. This is done so that the caller can reuse the same function as their callback without worrying about whether or not it'll unsubscribe all watchers.
Watchers can appear complicated under the hood: there is a central `WatchManager` which handles the actual invocation
of callbacks, and callbacks are managed by the SettingsStore by redirecting the caller's callback to a dedicated
callback. This is done so that the caller can reuse the same function as their callback without worrying about whether
or not it'll unsubscribe all watchers.
Setting changes are emitted into the default `WatchManager`, which calculates the new value for the setting. Ideally, we'd also try and suppress updates which don't have a consequence on this value, however there's not an easy way to do this. Instead, we just dispatch an update for all changes and leave it up to the consumer to deduplicate.
Setting changes are emitted into the default `WatchManager`, which calculates the new value for the setting. Ideally,
we'd also try and suppress updates which don't have a consequence on this value, however there's not an easy way to do
this. Instead, we just dispatch an update for all changes and leave it up to the consumer to deduplicate.
In practice, handlers which rely on remote changes (account data, room events, etc) will always attach a listener to the `MatrixClient`. They then watch for changes to events they care about and send off appropriate updates to the generalized `WatchManager` - a class specifically designed to deduplicate the logic of managing watchers. The handlers which are localized to the local client (device) generally just trigger the `WatchManager` when they manipulate the setting themselves as there's nothing to really 'watch'.
In practice, handlers which rely on remote changes (account data, room events, etc) will always attach a listener to the
`MatrixClient`. They then watch for changes to events they care about and send off appropriate updates to the
generalized `WatchManager` - a class specifically designed to deduplicate the logic of managing watchers. The handlers
which are localized to the local client (device) generally just trigger the `WatchManager` when they manipulate the
setting themselves as there's nothing to really 'watch'.