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Context <- R6Class(
'Context',
portable = FALSE,
class = FALSE,
public = list(
id = character(0),
.label = character(0), # For debug purposes
.invalidated = FALSE,
.invalidateCallbacks = list(),
.flushCallbacks = list(),
.domain = NULL,
initialize = function(domain, label='', type='other', prevId='') {
id <<- .getReactiveEnvironment()$nextId()
.label <<- label
.domain <<- domain
.graphCreateContext(id, label, type, prevId, domain)
},
run = function(func) {
"Run the provided function under this context."
withReactiveDomain(.domain, {
env <- .getReactiveEnvironment()
.graphEnterContext(id)
on.exit(.graphExitContext(id), add = TRUE)
env$runWith(self, func)
})
},
invalidate = function() {
"Invalidate this context. It will immediately call the callbacks
that have been registered with onInvalidate()."
if (.invalidated)
return()
.invalidated <<- TRUE
.graphInvalidate(id, .domain)
lapply(.invalidateCallbacks, function(func) {
func()
})
.invalidateCallbacks <<- list()
NULL
},
onInvalidate = function(func) {
"Register a function to be called when this context is invalidated.
If this context is already invalidated, the function is called
immediately."
if (.invalidated)
func()
else
.invalidateCallbacks <<- c(.invalidateCallbacks, func)
NULL
},
addPendingFlush = function(priority) {
"Tell the reactive environment that this context should be flushed the
next time flushReact() called."
if (!is.null(.domain)) {
.domain$incrementBusyCount()
}
.getReactiveEnvironment()$addPendingFlush(self, priority)
},
onFlush = function(func) {
"Register a function to be called when this context is flushed."
.flushCallbacks <<- c(.flushCallbacks, func)
},
executeFlushCallbacks = function() {
"For internal use only."
on.exit({
if (!is.null(.domain)) {
.domain$decrementBusyCount()
}
}, add = TRUE)
lapply(.flushCallbacks, function(flushCallback) {
flushCallback()
})
}
)
)
ReactiveEnvironment <- R6Class(
'ReactiveEnvironment',
portable = FALSE,
class = FALSE,
public = list(
.currentContext = NULL,
.nextId = 0L,
.pendingFlush = 'PriorityQueue',
.inFlush = FALSE,
initialize = function() {
.pendingFlush <<- PriorityQueue$new()
},
nextId = function() {
.nextId <<- .nextId + 1L
return(as.character(.nextId))
},
currentContext = function() {
if (is.null(.currentContext)) {
if (isTRUE(getOption('shiny.suppressMissingContextError'))) {
return(getDummyContext())
} else {
stop('Operation not allowed without an active reactive context. ',
'(You tried to do something that can only be done from inside a ',
'reactive expression or observer.)')
}
}
return(.currentContext)
},
runWith = function(ctx, contextFunc) {
old.ctx <- .currentContext
.currentContext <<- ctx
on.exit(.currentContext <<- old.ctx)
contextFunc()
},
addPendingFlush = function(ctx, priority) {
.pendingFlush$enqueue(ctx, priority)
},
hasPendingFlush = function() {
return(!.pendingFlush$isEmpty())
},
flush = function() {
# If already in a flush, don't start another one
if (.inFlush) return()
.inFlush <<- TRUE
on.exit(.inFlush <<- FALSE)
while (hasPendingFlush()) {
ctx <- .pendingFlush$dequeue()
ctx$executeFlushCallbacks()
}
}
)
)
.getReactiveEnvironment <- local({
reactiveEnvironment <- NULL
function() {
if (is.null(reactiveEnvironment))
reactiveEnvironment <<- ReactiveEnvironment$new()
return(reactiveEnvironment)
}
})
# Causes any pending invalidations to run.
flushReact <- function() {
.getReactiveEnvironment()$flush()
}
# Retrieves the current reactive context, or errors if there is no reactive
# context active at the moment.
getCurrentContext <- function() {
.getReactiveEnvironment()$currentContext()
}
getDummyContext <- function() {}
local({
dummyContext <- NULL
getDummyContext <<- function() {
if (is.null(dummyContext)) {
dummyContext <<- Context$new(getDefaultReactiveDomain(), '[none]',
type='isolate')
}
return(dummyContext)
}
})
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