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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.
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 priority, are:
device
- The current user's deviceroom-device
- The current user's device, but only when in a specific roomroom-account
- The current user's account, but only when in a specific roomaccount
- The current user's accountroom
- A specific room (setting for all members of the room)config
- Values are defined by thesettingDefaults
key (usually) inconfig.tson
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.
Settings
Settings are the different options a user may set or experience in the application. These are pre-defined in
src/settings/Settings.ts
under the SETTINGS
constant, and match the ISetting
interface as defined there.
Settings that support the config level can be set in the config file under the settingDefaults
key (note that some
settings, like the "theme" setting, are special cased in the config file):
{
...
"settingDefaults": {
"settingName": true
},
...
}
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.
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:
const isSupported = SettingsStore.isLevelSupported(SettingLevel.ROOM);
if (isSupported) {
const canSetValue = SettingsStore.canSetValue("mySetting", "!curbf:matrix.org", SettingLevel.ROOM);
if (canSetValue) {
SettingsStore.setValue("mySetting", "!curbf:matrix.org", SettingLevel.ROOM, newValue);
}
}
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.
<SettingsFlag name="theSettingId"
level={SettingsLevel.ROOM}
roomId="!curbf:matrix.org"
label={_td("Your label here")} // optional, if falsey then the `SettingsStore` will be used
onChange={function(newValue) { }} // optional, called after saving
isExplicit={false} // this is passed along to `SettingsStore.getValueAt`, defaulting to false
manualSave={false} // if true, saving is delayed. You will need to call .save() on this component
// Options for radio buttons
group="your-radio-group" // this enables radio button support
value="yourValueHere" // the value for this particular option
/>
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
.
Features
Feature flags are just like regular settings with some underlying semantics for how they are meant to be used. Usually
a feature flag is used when a portion of the application is under development or not ready for full release yet, such
as new functionality or experimental ideas. In these cases, the feature name should be named with the feature_*
convention and must be tagged with isFeature: true
in the setting definition. By doing so, the feature will automatically
appear in the "labs" section of the user's settings.
Features can be controlled at the config level using the following structure:
"features": {
"feature_lazyloading": true
}
When true
, the user will see the feature as enabled. Similarly, when false
the user will see the feature as disabled.
The user will only be able to change/see these states if showLabsSettings: true
is in the config.
Determining if a feature is enabled
Call SettingsStore.getValue()
as you would for any other setting.
Enabling a feature
Call SettingsStore.setValue("feature_name", null, SettingLevel.DEVICE, true)
.
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.
For more information, see src/settings/controllers/SettingController.ts
.
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.setValue(...).then(() => {
// The value has actually been stored at this point.
});
SettingsStore.getValue(...); // this will return the value set in `setValue` above.
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.
An example of a watcher in action would be:
class MyComponent extends React.Component {
settingWatcherRef = null;
componentWillMount() {
const callback = (settingName, roomId, level, newValAtLevel, newVal) => {
this.setState({color: newVal});
};
this.settingWatcherRef = SettingsStore.watchSetting("roomColor", "!example:matrix.org", callback);
}
componentWillUnmount() {
SettingsStore.unwatchSetting(this.settingWatcherRef);
}
}
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.
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
.
Handlers (src/settings/handlers/SettingsHandler.ts
) 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.ts
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.
Features
See above for feature reference.
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.
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'.