mapdeck_view() doesn't use current viewState properties

[hdmm3]

I've been trying to use mapdeck_view() to individually update some map parameters, like the bearing or zoom level. However, after manually zooming, dragging, tilting, if I call something like mapdeck_view(pitch = 45) the rest of the viewState parameters will be reset to the latest values programmatically defined for the viewState, instead of the current values.

After a quick inspection, I noticed that the underlying function here is getting the current lon, lat, pitch, bearing, zoom, etc, directly from the viewState whose values don't seem to change when interacting with the map. The current values seem to be nested inside viewState.map instead. So for instance retrieving the current pitch could be done through:

currentPitch = pitch === null ? window[ map_id + 'map'].viewState.map.pitch : pitch;

I'll submit a PR for this issue.

[dcooley]

Thanks for the PR - now merged

[dcooley]

Something in this commit causes the map to freeze, so I've reverted to the commit before this.

[dcooley]

something else was wrong so I've fully reverted this

[hdmm3]

Hi @dcooley, first of all apologies for those half-baked PRs. This time I'll share my thoughts first. I've been digging about the intended behaviour of deck.gl when using either initialViewState or viewState props. Here are some of my interpretations of what's going on when using the initialViewState prop:

• At creation the viewState object will simply be set to the input initialViewState prop.
• When using initialViewState, the onViewStateChange callback called during controller interaction, is internally followed by an update to the internal viewState here. This update will track changes to the viewState in a nested object viewState[viewId]. That way multiple views can save their own viewState independently. Most importantly, the current view state will be located in that nested object, instead of at the root viewState. Also the viewManager will be updated.
• Currently, md_change_location overwrites the internal viewState through setProps({initialViewState}) effectively destroying the nested object created during onViewStateChange.
• If a call to md_change_location is made after controller interaction, reading the values of the viewState object will pick stale values of the view instead of the most current ones.

In order to avoid fully overwriting the viewState, the initialViewState prop could be set in md_change_location as follows:

window[map_id + 'map'].setProps({
      initialViewState: {
        ...window[map_id + 'map'].viewState,
        [map_id]: {
          longitude: currentLon,
          latitude: currentLat,
          zoom: currentZoom,
          maxZoom: currentMaxZoom,
          minZoom: currentMinZoom,
          maxPitch: currentMaxPitch,
          minPitch: currentMinPitch,
          pitch: currentPitch,
          bearing: currentBearing,
          transitionInterpolator: transition === "fly" ? new deck.FlyToInterpolator() : new deck.LinearInterpolator(),
          transitionDuration: duration,
          controller: true}        
      }
    });

As such, the current viewState for the map_id could be retrieved using viewManager.getViewState(), as follows:

currentViewState = window[map_id + 'map'].viewManager?.getViewState(map_id) || window[map_id + 'map'].viewState;

getViewState() seems to be the safest approach. I'm not sure if after deck.gl 8+ the "default-view" viewId will even occur when the DeckGL views prop defines views with id as it's done with mapdeck.

I hope this helps!

[dcooley]

Thanks for the extra detail. And I've been meaining to revisit the viewState logic / code so thanks for bringing this up. When I first implemented it I had a lot of issues getting it to work in both a shiny & non-shiny environment, and getting the map & layers to update correctly.

I'll try and set some time aside next week to look at this in more detail.

[dcooley]

reprex for this:

library(shiny)
library(sinydashboard)

set_token(secret::get_secret("MAPBOX"))

ui <- shinydashboard::dashboardPage(
    header = shinydashboard::dashboardHeader()
    , sidebar = shinydashboard::dashboardSidebar(
        shiny::actionButton(inputId = "viewState", label = "Pitch")
    )
    , body = shinydashboard::dashboardBody(
        mapdeck::mapdeckOutput(
            outputId = "map"
        )
    )
)

server <- function(input, output, session) {

    observeEvent({input$viewState},{
        mapdeck::mapdeck_update(map_id = "map") %>%
            mapdeck::mapdeck_view(pitch = 45)
    })

    output$map <- mapdeck::renderMapdeck({
        mapdeck::mapdeck() %>%
            mapdeck::add_scatterplot(
                data = capitals
            )
    })
}

shiny::shinyApp(ui, server)

[dcooley]

@hdmm3 I've finally managed to look at this again and added a potential solution to the branch issue382. If you get a chance can you test it and see if it works for you?

Notes:

• initialViewState documentation - https://deck.gl/docs/api-reference/core/deck#initialviewstate
• onViewStateChange({}) is provided
• added window[ map_id + 'viewState'] to keep track of view changes inside onViewStateChange()
• these values in window[ map_id + 'viewState'] are kept / used in md_change_location