Filter state snapshot management.

Usage

snapshot_manager_ui(id)

snapshot_manager_srv(id, slices_global, mapping_matrix, filtered_data_list)

Arguments

id

(character(1)) shiny module id

slices_global

(reactiveVal) that contains a teal_slices object containing all teal_slices existing in the app, both active and inactive

mapping_matrix

(reactive) that contains a data.frame representation of the mapping of filter state ids (rows) to modules labels (columns); all columns are logical vectors

filtered_data_list

non-nested (named list) that contains FilteredData objects

Value

Nothing is returned.

Details

This module introduces snapshots: stored descriptions of the filter state of the entire application. Snapshots allow the user to save the current filter state of the application for later use in the session, as well as to save it to file in order to share it with an app developer or other users.

The snapshot manager is accessed through the filter manager, with the cog icon in the top right corner. At the beginning of a session it presents two icons: a camera and an circular arrow. Clicking the camera captures a snapshot and clicking the arrow resets initial application state. As snapshots are added, they will show up as rows in a table and each will have a select button and a save button.

Server logic

Snapshots are basically teal_slices objects, however, since each module is served by a separate instance of FilteredData and these objects require shared state, teal_slice is a reactiveVal so teal_slices cannot be stored as is. Therefore, teal_slices are reversibly converted to a list of lists representation (attributes are maintained).

Snapshots are stored in a reactiveVal as a named list. The first snapshot is the initial state of the application and the user can add a snapshot whenever they see fit.

For every snapshot except the initial one, a piece of UI is generated that contains the snapshot name, a select button to restore that snapshot, and a save button to save it to a file. The initial snapshot is restored by a separate "reset" button. It cannot be saved directly but a user is welcome to capture the initial state as a snapshot and save that.

Snapshot mechanics

When a snapshot is captured, the user is prompted to name it. Names are displayed as is but since they are used to create button ids, under the hood they are converted to syntactically valid strings. New snapshot names are validated so that their valid versions are unique. Leading and trailing white space is trimmed.

The module can read the global state of the application from slices_global and mapping_matrix. The former provides a list of all existing teal_slices and the latter says which slice is active in which module. Once a name has been accepted, slices_global is converted to a list of lists - a snapshot. The snapshot contains the mapping attribute of the initial application state (or one that has been restored), which may not reflect the current one, so mapping_matrix is transformed to obtain the current mapping, i.e. a list that, when passed to the mapping argument of teal_slices, would result in the current mapping. This is substituted as the snapshot's mapping attribute and the snapshot is added to the snapshot list.

To restore app state, a snapshot is retrieved from storage and rebuilt into a teal_slices object. Then state of all FilteredData objects (provided in filtered_data_list) is cleared and set anew according to the mapping attribute of the snapshot. The snapshot is then set as the current content of slices_global.

To save a snapshot, the snapshot is retrieved and reassembled just like for restoring, and then saved to file with teal.slice::slices_store.

Author

Aleksander Chlebowski