Introduction to shinyjqui

The ui mode and server mode

The interaction functions can be used in the ui definition (ui mode) or the server function (server mode)

In ui definition, you can wrap any shiny ui object (tag, tagList, input or output) with the interaction function like this:

# create a draggable textInput in shiny ui
ui <- fluidPage(
  jqui_draggable(textInput("foo", "Input"))
)

The function returns a modified shiny ui with the corresponding interaction effect attached.

You can use interaction functions inside the server function too. In this case, depends on the operation parameter, the functions add, modify or remove the interaction effect of an existing (pre-defined in ui) ui element:

# create a textInput in shiny ui without mouse interaction
ui <- fluidPage(
  textInput("foo", "Input")
)

# make the ui element with id "foo" draggable
server <- function(input, output) {
  jqui_draggable(ui = "#foo", operation = "enable")
}

The ui mode is the most straightforward way to create an ui element with mouse interactions, however, the server mode is more flexible. 1) You can reactively control element’s interaction effect through observe() or observEvent(); 2) You can use a jQuery_selector or even a JavaScript expression to locate multiple target elements; 3) You can control the interaction effects with the operation parameter. (see the operation parameter section below).

The ui parameter

The first parameter of interaction functions is ui. It determines the target element(s) to manipulate. Based on the working mode, it accepts different object types.

In ui mode, as mentioned above, you can pass a shiny ui object with class shiny.tag or shiny.tag.list. For example:

# shiny input
jqui_draggable(ui = textInput("foo", "Caption", "Data Summary"))

# shiny output
jqui_resizable(ui = plotOutput("myplot"))

# HTML list
jqui_sortable(
  ui = tags$ul(
    tags$li("Coffice"), 
    tags$li("Tea"), 
    tags$li("Milk")
  )
)

In server mode, you can pass a string of jQuery_selector. For example:

# target multiple HTML elements by passing a set of ids
jqui_draggable(ui = "#id1,#id2,#id3")

# target all the shiny `plotOuput`s by passing the class `shiny-plot-output`
jqui_resizable(ui = ".shiny-plot-output")

# target all <p> elements where the parent is a <div> element
jqui_draggable(ui = "div > p")

Or even more flexible, you can use the htmlwidgets::JS() function to wrap a custom javascript expression that returns a jQuery object. For example:

# target all the child elements whose parent has the id `foo`
jqui_draggable(ui = JS("$('#foo').children()"))

From shinyjqui v0.4.0, the interaction functions can work on static htmlwidgets. For example, you can pass a plotly htmlwidget object:

# render a resizable plotly htmlwidget in RStudio Viewer or RMarkdown
jqui_resizable(ui = plot_ly(z = ~volcano, type = "surface"))

The operation parameter

The parameter is for server mode only. It determines how to manipulate the interaction. The following five options are supported:

• enable: Initiate the corresponding mouse interaction to the target(s) (the default option).
• disable: Initiate the interaction if not and temporarily disable it (by only setting the JS options).
• destroy: Completely remove the interaction.
• save: Initiate the interaction if not and save the current interaction state.
• load: Initiate the interaction if not and restore the target(s) to an user defined interaction state or the last saved state.

The save and load options were included from v0.3.0. They can be used to save and restore the state (e.g. size, position, order) of an element. You can find more details in the Vignette Save and restore.

The options parameter

The options parameter can be used to further specify the behavior of interaction. A complete list of the available options for each interaction can be found in jQuery UI’s API Documentation page. Here are some examples:

# drag only horizontally
jqui_draggable('#foo', options = list(axis = 'x'))
# make movement snapping to a 80 x 80 grid
jqui_draggable('#foo', options = list(grid = c(80, 80)))

jqui_droppable('#foo', options = list(
  accept = '#bar', # jQuery selector to define which draggable element to monitor. Accept anything if not set.
  classes = list(
    `ui-droppable-active` = 'ui-state-focus', # change class when draggable element is dragging
    `ui-droppable-hover` = 'ui-state-highlight' # change class when draggable element is dragging over
  ),
  drop = JS(
    'function(event, ui){$(this).addClass("ui-state-active");}'
  ) # a javascrip callback to change class when draggable element is dropped in
))

# keep aspect ratio when resizing
jqui_resizable('#foo', options = list(aspectRatio = TRUE))

# Limit the resizable element to a maximum or minimum height or width
jqui_resizable('#foo', options = list(minHeight = 100, maxHeight = 300,
                                      minWidth = 200, maxWidth = 400))

# make the two plotOutputs resize synchronously
jqui_resizable(plotOutput('plot1', width = '400px', height = '400px'), 
                  options = list(alsoResize = '#plot2')),
plotOutput('plot2', width = '400px', height = '400px')

# highlight the selected plotOutput
jqui_selectable(
  div(
    plotOutput('plot1', width = '400px', height = '400px'),
    plotOutput('plot2', width = '400px', height = '400px')
  ),
  options = list(classes = list(`ui-selected` = 'ui-state-highlight'))
)

# change opacity while sorting
jqui_sortable('#foo', options = list(opacity = 0.5))

# only items with class "items" inside the element become sortable
jqui_sortable('#foo', options = list(items = '> .items'))

# connect two sortable elements, so that items in one element can be dragged to another
jqui_sortable('#foo1', options = list(connectWith = '#foo2'))
jqui_sortable('#foo2', options = list(connectWith = '#foo1'))

The input values and shiny options

In shiny, the user input values are sent back to the server in the form of input$<id>. Similarly, the interaction functions can send back interaction-specific state values in the form of input$<id>_<suffix>, where the id is the element id (id attribute for shiny tag, inputId for shiny inputs, outputId for shiny outputs) and the suffix depends on the type of interaction enabled. The table below shows the currently deployed interaction state values:

You can even customize the returned values by including a shiny option in the options parameter. The shiny option should be created in the following format:

shiny_opt = list(
  
  # define shiny input value input$id_suffix1
  suffix1 = list(
    # on event_type1 run callback1 and send the returned value to input$id_suffix1
    event_type1 = JS(callback1),
    # on event_type2 or event_type3 run callback2 and send the returned value to input$id_suffix1
    `event_type2 event_type3` = JS(callback2),
    ...
  ),
  
  # define another shiny input value input$id_suffix2
  suffix2 = list(
    ...
  ),
  
  # define more shiny input values
  
)

# pass the shiny option to an interaction function
jqui_draggable('#foo', options = list(
  shiny = shiny_opt, 
  #other draggable-specific options
))

The shiny option is defined by a list of event-callback pairs named with suffix.The valid event types for each interactions can be found in the API Documentation of jQuery UI.The callback should be wrapped with JS(). The JS callback functions take two parameters, event and ui. The definition of the ui parameter can also be found in the API document too. Here is an example:

# server
jqui_draggable('#foo', options = list(
  shiny = list(
    # By default, draggable element has a shiny input value showing the
    # element's position (relative to the parent element). Here, another shiny
    # input value (input$foo_offset) is added. It returns the element's offset
    # (position relative to the document).
    offset = list(
      # return the updated offset value when the draggable is created or dragging
      `dragcreate drag` = JS('function(event, ui) {return $(event.target).offset();}'),
    )
  )
))

When using the shiny option and callbacks, you may want to get the id of a certain element in JavaScript. For simple shiny tags (e.g. tags$div), element.attr("id") just works fine, however, things become more complicated for shiny inputs (e.g. textInput). The id attribute of most shiny inputs is hidden inside a div container. You may use the jQuery function .find() to locate it. The shinyjqui package comes with an internal JavaScript function shinyjqui.getId() which will take care of this. You can just simply pass in any shiny element, either simple tag, shiny input or shiny output. It will use the appropriate way to find out the id.