VizModules ships two custom Shiny inputs that go beyond standard shiny::*Input widgets: multiColorPicker and multiDynamicInput. multiColorPicker maps colors to the discrete levels of a variable using palettes or per-group hex pickers, while multiDynamicInput is a general-purpose widget that lets users dynamically add and remove rows of heterogeneous inputs.

multiColorPicker

multiColorPicker assigns a color to each level of a discrete variable. Users can apply a named palette to every group at once, or fine-tune individual groups with a native color picker and an editable hex field. The value reported to input[[inputId]] is a named character vector of hex colors keyed by group. It is used throughout the package wherever a plot maps a discrete variable to color for more granular control than just a palette selection.

Overview

The widget renders a palette selector with Apply and Reset buttons, a preview row of swatches, and one row per group. Selecting a palette and clicking Apply recolors every group in order; the per-group color picker and hex input let users override any single group afterwards.

Basic Usage

library(shiny)
library(VizModules)

ui <- fluidPage(
    br(),
    splitLayout(
        multiColorPicker(
            "dept_cols",
            label = "Plot colors",
            groups = c("Engineering", "Finance", "HR",
                       "Marketing", "Operations", "Sales"),
            selected_palette = "dittoColors"
        ),
        verbatimTextOutput("value")
    )
)

server <- function(input, output, session) {
    output$value <- renderPrint(input$dept_cols)
}

shinyApp(ui, server)

Key Arguments

Argument	Description
`inputId`	Shiny input id. The value is accessed via `input[[inputId]]`.
`label`	Optional label displayed above the control.
`groups`	Character or factor vector of group names — one color row is created per unique value.
`palette_options`	Named list of palettes (each a character vector of colors). Defaults to `default_palettes()`.
`selected_palette`	Name of the palette to preselect.
`colors`	Optional named vector of starting colors, matched to `groups` by name.
`show_text`	If `TRUE` (default), show editable hex text inputs beside the color pickers.
`compact`	If `TRUE`, render a tighter layout with smaller controls.
`panel`	If `FALSE`, remove the surrounding panel/well styling.

Reading the Value

The value in input[[inputId]] is a named character vector of hex colors keyed by group:

# With groups = c("Engineering", "Finance", "HR", ...)
input$dept_cols
#> c(
#>   Engineering = "#E69F00",
#>   Finance     = "#56B4E9",
#>   HR          = "#009E73",
#>   Marketing   = "#F0E442",
#>   Operations  = "#0072B2",
#>   Sales       = "#D55E00"
#> )

Updating from the Server

Use updateMultiColorPicker() to set specific colors, apply a palette by name, or reset the widget to its initial state:

# Set specific group colors (only named groups change)
updateMultiColorPicker(session, "dept_cols",
    colors = c(Engineering = "#1B9E77", Finance = "#D95F02"))

# Apply a named palette to all groups
updateMultiColorPicker(session, "dept_cols", palette = "ggplot2")

# Reset colors and palette back to the initial state
updateMultiColorPicker(session, "dept_cols", reset = TRUE)

Exactly one of colors, palette, or reset should be supplied per call; reset takes precedence, followed by palette, then colors.

Summary

multiColorPicker() — place in your UI, one color row per group
input[[inputId]] — read the named character vector of hex colors in your server
updateMultiColorPicker() — set colors, apply a palette, or reset from the server

multiDynamicInput

Overview

multiDynamicInput renders a “+ Add” button and a container. Each time the user clicks Add, a new row appears with whatever fields you define. An “×” button on each row deletes it. The collected value is reported to input[[inputId]] as a named list of rows.

Unlike insertUI/removeUI, rows are managed entirely client-side via DOM template cloning — no server round-trips for add/delete.

Basic Usage

library(shiny)
library(VizModules)

ui <- fluidPage(
    br(),
    splitLayout(
        multiDynamicInput(
            "layers",
            label = "Layers",
            row_spec = list(
                colour = list(
                    type = "colour",
                    args = list(value = "#000000")
                ),
                size   = list(
                    type = "numeric",
                    args = list(value = 2, min = 0.5, max = 10)
                ),
                style  = list(type = "select",
                args = list(choices = c("solid", "dashed", "dotted")))
            )
        ),
        verbatimTextOutput("value")
    )
)

server <- function(input, output, session) {
    output$value <- renderPrint(input$layers)
}

shinyApp(ui, server)

Key Arguments

Argument	Description
`inputId`	Shiny input id. The value is accessed via `input[[inputId]]`.
`label`	Label shown next to the + Add button. Also determines row naming (lowercased).
`row_spec`	Named list defining one row’s fields. Each entry has `type` (or `fn`) and `args`.
`elements`	Optional list of pre-filled rows to show on startup.
`max_per_row`	Number of fields per visual line before wrapping (default 4).
`panel`	If `FALSE`, removes the border/background styling.

Defining Fields with `row_spec`

Each field in row_spec is a named list with:

type — a shorthand alias: "select", "text", "numeric", "slider", "checkbox", "colour" / "color".
fn — alternatively, any input constructor function (e.g. shiny::dateInput). Use this for inputs without a built-in alias.
args — a list of arguments passed to the constructor (everything except inputId, which is auto-generated per row).

# Using type aliases
row_spec = list(
    name = list(type = "text", args = list(placeholder = "Enter name")),
    age  = list(type = "numeric", args = list(value = 25, min = 0, max = 120))
)

# Using fn for a custom input
row_spec = list(
    date = list(fn = shiny::dateInput, args = list(label = "Date", value = Sys.Date()))
)

Pre-filled Rows with `elements`

To show rows on startup with specific values:

multiDynamicInput(
    "models",
    label = "Models",
    row_spec = list(
        model_type = list(type = "select", args = list(choices = c("lm", "glm"))),
        formula    = list(type = "text", args = list(placeholder = "y ~ x"))
    ),
    elements = list(
        models1 = list(model_type = "lm", formula = "revenue ~ units"),
        models2 = list(model_type = "glm", formula = "revenue ~ poly(units, 2)")
    )
)

The names (models1, models2) don’t matter for input — they’re auto-generated from the label at runtime. The values inside each element must match the row_spec field names.

Reading the Value

The value in input[[inputId]] is a named list of rows:

# With label = "Models" and two rows filled in:
input$models
#> list(
#>   models1 = list(model_type = "lm", formula = "revenue ~ units"),
#>   models2 = list(model_type = "glm", formula = "revenue ~ poly(units, 2)")
#> )

Row names are derived from the label argument (lowercased) plus an index: models1, models2, etc.

Updating from the Server

Use updateMultiDynamicInput() to replace all rows or clear them:

# Replace all rows
updateMultiDynamicInput(session, "models", elements = list(
    models1 = list(model_type = "lm", formula = "y ~ x")
))

# Clear all rows
updateMultiDynamicInput(session, "models", clear = TRUE)

Backend-Specific Fields

When used with the model backend system (see vignette("custom-model-lines")), fields can be tagged with a backend attribute. These fields are hidden by default and only appear when the matching model type is selected:

row_spec = list(
    model_type = list(type = "select", args = list(choices = c("lm", "drm"))),
    formula    = list(type = "text", args = list(placeholder = "y ~ x")),
    # Only visible when model_type == "drm"
    drc_fct    = list(type = "select", backend = "drm",
                      args = list(choices = c("LL.4", "LL.3")))
)

In practice you don’t build this manually — build_model_row_spec() does it for you by collecting fields from all registered backends.

Summary

multiDynamicInput() — place in your UI
input[[inputId]] — read the named list of rows in your server
updateMultiDynamicInput() — set or clear rows from the server
build_model_row_spec() — auto-build a row_spec from registered model backends

VizModules Custom Shiny Inputs

multiColorPicker

Overview

Basic Usage

Key Arguments

Reading the Value

Updating from the Server

Summary

multiDynamicInput

Overview

Basic Usage

Key Arguments

Defining Fields with row_spec

Pre-filled Rows with elements

Reading the Value

Updating from the Server

Backend-Specific Fields

Summary

Defining Fields with `row_spec`

Pre-filled Rows with `elements`