Viewmodels

When implementing frontend components, you’ll sooner or later want to define your own KnockoutJS view models in order to provide custom functionality.

Registering custom viewmodels

Register your view model with OctoPrint’s web app by pushing a config object unto the global array OCTOPRINT_VIEWMODELS.

Possible properties in this config object are:

construct
Function to use for constructing the view model instance. Usually that will be the view model class, which acts as a constructor. This property is mandatory.
name
Name to register the view model under. If not provided, the name of the construct function will be used, turning the first letter lower case. If a view model under the same name already exists at time of construction, an error will be logged and the view model will not be instantiated.
additionalNames
A list of additional names to also register the view model under. Only those that do not already exist will be registered.
dependencies
List of dependencies the view model needs injected. If any of the view models in this list cannot be found, initialization of the view model will fail. The parameters injected on instantiation will consist of first the dependencies, then the optional list concatenated.
optional
A list of optional dependencies the view model needs injected. If any of the view models in this list cannot be found, they will be null in the parameter list injected to the constructor on instantiation. The parameters injected on instantiation will consist of first the dependencies, then the optional list concatenated.
elements
A list of UI elements to bind to. Each binding target can be either a string which will then be passed to jQuery’s $(...) method to resolve the target, or alternatively directly a jQuery element

Example:

$(function() {
    function MyCustomViewModel(parameters) {
        var self = this;

        self.loginState = parameters[0]; // requested as first dependency below
        self.settings = parameters[1]; // requested as second dependency below
        self.someOtherViewModel = parameters[2]; // requested as first optional dependency below

        // more of your view model's implementation
    }

    // we don't explicitely declare a name property here
    // our view model will be registered under "myCustomViewModel" (implicit
    // name derived from contructor name) and "yourCustomViewModel" (explicitely
    // provided as additional name)
    OCTOPRINT_VIEWMODELS.push({
        construct: MyCustomViewModel,
        additionalNames: ["yourCustomViewModel"],
        dependencies: ["loginStateViewModel", "settingsViewModel"],
        optional: ["someOtherViewModel"],
        elements: ["#some_div", "#some_other_div"]
    });
})

You might also come across a different approach to view model declaration, providing not a config object but instead a 3-tuple of constructor, dependencies and elements to bind to. Additional names, different names than the default name and optional dependencies cannot be specified with this format. It should be considered deprecated. Still, an example of how that would look in practice is provided here as well:

Listing 27 Old tuple-based configuration format, consider this deprecated
$(function() {
    function MyCustomViewModel(parameters) {
        var self = this;

        self.loginState = parameters[0]; // requested as first constructor parameter below
        self.settingsViewModel = parameters[1] // requested as second constructor parameter below

        // more of your view model's implementation
    }

    // construct, dependencies, elements
    OCTOPRINT_VIEWMODELS.push([
        MyCustomViewModel,
        ["loginStateViewModel", "settingsViewModel"],
        ["#some_div", "#some_other_div"]
    ]);
})

Dependencies

OctoPrint will try to inject all view model dependencies requested by your view model. In order to do this it will perform multiple passes iterating over all registered view models and collecting the necessary dependencies prior to construction. Circular dependencies (A depends on B, B on C, C on A) naturally cannot be resolved and will cause an error to be logged to the JavaScript console.

OctoPrint’s core currently comes with the following view models that your plugin can request for injection:

appearanceViewModel
View model that holds the appearance settings (name, color and transparency flag).
connectionViewModel
View model for the connection sidebar entry.
controlViewModel
View model for the control tab.
filesViewModel
View model for the files sidebar entry. Also available under the deprecated name gcodeFilesViewModel.
firstRunViewModel
View model for the first run dialog.
gcodeViewModel
View model for the gcode viewer tab.
gcodeFilesViewModel
Deprecated in favor of filesViewModel.
logViewModel
View model for the logfile settings dialog.
loginStateViewModel
View model for the current loginstate of the user, very interesting for plugins that need to evaluate the current login state or information about the current user, e.g. associated roles.
navigationViewModel
View model for the navigation bar.
printerProfilesViewModel
View model for the printer profiles settings dialog.
printerStateViewModel
View model for the current printer state, very interesting for plugins that need to know information about the current print job, if the printer is connected, operational etc.
settingsViewModel
View model for the settings dialog, also holds all settings to be used by other view models, hence very interesting for plugins as well.
slicingViewModel
View model for the slicing dialog.
temperatureViewModel
View model for the temperature tab, also holds current temperature information which might be interesting for plugins.
terminalViewModel
View model for the terminal tab, also holds terminal log entries.
timelapseViewModel
View model for the timelapse tab.
usersViewModel
View model for the user management in the settings dialog.
userSettingsViewModel
View model for settings associated with the currently logged in user, used for the user settings dialog.
wizardViewModel
View model for the wizard dialog.

Each plugin’s view model will be added to the view model map used for resolving dependencies as well, using the view model’s class name with a lower case first character as identifier (so “MyCustomViewModel” will be registered for dependency injection as “myCustomViewModel”) or an alternative name provided in the name property of the config object, plus any configured additionalNames.

Callbacks

OctoPrint’s web application will call several callbacks on all registered view models, provided they implement them. Those are listed below:

onStartup()
Called when the first initialization has been done: All view models are constructed and hence their dependencies resolved, no bindings have been done yet.
onBeforeBinding()
Called per view model before attempting to bind it to its binding targets.
onAfterBinding()
Called per view model after binding it to its binding targets.
onAllBound(allViewModels)
Called after all view models have been bound, with the list of all view models as the single parameter.
onStartupComplete()
Called after the startup of the web app has been completed.
onServerDisconnect()
Called if a disconnect from the server is detected.
onDataUpdaterReconnect()
Called when the connection to the server has been reestablished after a disconnect.
fromHistoryData(data)
Called when history data is received from the server. Usually that happens only after initial connect in order to transmit the temperature and terminal log history to the connecting client. Called with the data as single parameter.
fromCurrentData(data)
Called when current printer status data is received from the server with the data as single parameter.
onSlicingProgress(slicer, modelPath, machineCodePath, progress)
Called on slicing progress, call rate is once per percentage point of the progress at maximum.
onEvent<EventName>(payload)
Called on firing of an event of type EventName, e.g. onEventPrintDone. See the list of available events for the possible events and their payloads.
fromTimelapseData(data)
Called when timelapse configuration data is received from the server. Usually that happens after initial connect.
onDataUpdaterPluginMessage(plugin, message)
Called when a plugin message is pushed from the server with the identifier of the calling plugin as first and the actual message as the second parameter. Note that the latter might be a full fledged object, depending on the plugin sending the message. You can use this method to asynchronously push data from your plugin’s server component to it’s frontend component.
onUserLoggedIn(user)
Called when a user gets logged into the web app, either passively (upon initial load of the page due to a valid “Remember Me” cookie) or due to an active completion of the login dialog. The user data of the just logged in user will be provided as only parameter.
onUserLoggedOut()
Called when a user gets logged out of the web app.
onTabChange(next, current)
Called before the main tab view switches to a new tab, so before the new tab becomes visible. Called with the next (changed to) and current (still visible) tab’s hash (e.g. #control). Note that current might be undefined on the very first call.
onAfterTabChange(current, previous)
Called after the main tab view switches to a new tab, so after the new tab becomes visible. Called with the current and previous tab’s hash (e.g. #control).
getAdditionalControls()
Your view model may return additional custom control definitions for inclusion on the “Control” tab of OctoPrint’s interface. See the custom control feature.
onSettingsShown()
Called when the settings dialog is shown.
onSettingsHidden()
Called when the settings dialog is hidden.
onSettingsBeforeSave()
Called just before the settings view model is sent to the server. This is useful, for example, if your plugin needs to compute persisted settings from a custom view model.
onUserSettingsShown()
Called when the user settings dialog is shown.
onUserSettingsHidden()
Called when the user settings dialog is hidden.
onWizardDetails(response)
Called with the response from the wizard detail API call initiated before opening the wizard dialog. Will contain the data from all WizardPlugin implementations returned by their get_wizard_details() method, mapped by the plugin identifier.
onBeforeWizardTabChange(next, current)
Called before the wizard tab/step is changed, with the ids of the next (changed to) and the current (still visible) tab as parameters. Return false in order to prevent the tab change, e.g. if the wizard step is mandatory and not yet completed by the user. Take a look at the “Core Wizard” plugin bundled with OctoPrint and the ACL wizard step in particular for an example on how to use this.
onAfterWizardTabChange(current)
Called after the wizard tab/step is changed, with the id of the current tab as parameter. The id of the previous tab is sadly not available currently.
onBeforeWizardFinish()
Called before executing the finishing of the wizard. Return false here to stop the actual finish, e.g. if some step is still incomplete.
onWizardFinish()
Called after executing the finishing of the wizard and before closing the dialog. Return reload here in order to instruct OctoPrint to reload the UI after the wizard closes.

In order to hook into any of those callbacks, just have your view model define a function named accordingly, e.g. to get called after all view models have been bound during application startup, implement a function onAllBound on your view model, taking a list of all bound view models:

$(function() {
    function MyCustomViewModel(parameters) {
        var self = this;

        // ...

        self.onAllBound = function(allViewModels) {
            // do something with them
        }

        // ...
    }

    OCTOPRINT_VIEWMODELS.push({
        construct: MyCustomViewModel,
        dependencies: ["loginStateViewModel"],
        elements: ["#some_div", "#some_other_div"]
    });
})

Lifecycle diagrams

Web interface startup

sequenceDiagram participant Main participant onServerConnect participant fetchSettings participant bindViewModels participant DataUpdater participant LoginStateViewModel Note right of DataUpdater: connectCallback = undefined activate Main Main->>+DataUpdater: connect Note right of DataUpdater: initialized = false DataUpdater-->>Main: ok deactivate Main DataUpdater->>DataUpdater: asynchronous connect to server... activate DataUpdater Note right of DataUpdater: store any callbacks instead of triggering (e.g. onServerConnect, fromHistoryData, fromCurrentData, ...) DataUpdater-X+Main: done deactivate DataUpdater deactivate DataUpdater Main->>+DataUpdater: connectCallback = onServerConnect Note right of DataUpdater: connectCallback = onServerConnect DataUpdater-->>-Main: ok Main->>+onServerConnect: call onServerConnect->>+LoginStateViewModel: passiveLogin LoginStateViewModel-->>onServerConnect: ok onServerConnect-->>Main: ok deactivate onServerConnect deactivate Main LoginStateViewModel->>+LoginStateViewModel: asynchronous passive login Note over Main,LoginStateViewModel: Session available! LoginStateViewModel-X+onServerConnect: done deactivate LoginStateViewModel deactivate LoginStateViewModel onServerConnect->>+DataUpdater: initialized Note right of DataUpdater: initialized = true DataUpdater->DataUpdater: trigger stored callbacks DataUpdater-->>-onServerConnect: ok onServerConnect-X+Main: done deactivate onServerConnect Main->>+fetchSettings: call Note right of fetchSettings: trigger onStartup fetchSettings-->>Main: ok deactivate Main fetchSettings->>+fetchSettings: asynchronous settings fetch fetchSettings->>+bindViewModels: call loop for each view model bindViewModels->bindViewModels: trigger onBeforeBinding bindViewModels->bindViewModels: trigger onBoundTo bindViewModels->bindViewModels: trigger onAfterBinding end bindViewModels->bindViewModels: trigger onAllBound opt User is logged in bindViewModels->>+LoginStateViewModel: onAllBound LoginStateViewModel->LoginStateViewModel: trigger onUserLoggedIn LoginStateViewModel-->>-bindViewModels: ok end bindViewModels->bindViewModels: trigger onStartupComplete bindViewModels-->>-fetchSettings: ok deactivate fetchSettings deactivate fetchSettings

Web interface reconnect

sequenceDiagram participant onServerConnect participant DataUpdater participant LoginStateViewModel activate DataUpdater DataUpdater->>DataUpdater: call connectCallback DataUpdater->>+onServerConnect: call onServerConnect-->>DataUpdater: ok deactivate DataUpdater onServerConnect->>+LoginStateViewModel: passiveLogin LoginStateViewModel-->>onServerConnect: ok deactivate onServerConnect LoginStateViewModel->>+LoginStateViewModel: asynchronous passive login Note over onServerConnect,LoginStateViewModel: Session available! opt User is logged in LoginStateViewModel->LoginStateViewModel: trigger onUserLoggedIn end activate onServerConnect LoginStateViewModel-XonServerConnect: done deactivate LoginStateViewModel deactivate LoginStateViewModel onServerConnect->>+DataUpdater: initialized DataUpdater->DataUpdater: trigger stored callbacks DataUpdater-->>onServerConnect: ok deactivate DataUpdater deactivate onServerConnect

See also

OctoPrint’s core viewmodels
OctoPrint’s own view models use the same mechanisms for interacting with each other and the web application as plugins. Their source code is therefore a good point of reference on how to achieve certain things.
KnockoutJS documentation
OctoPrint makes heavy use of KnockoutJS for building up its web app.