Add nullOnKeyRelease option

DESCRIPTION

@@ -11,11 +11,12 @@ License: Apache License (>= 2)
 Encoding: UTF-8
 LazyData: true
 Roxygen: list(markdown = TRUE)
-RoxygenNote: 7.1.1
+RoxygenNote: 7.2.3
 Imports: 
     htmltools,
     shiny,
-    jsonlite
+    jsonlite,
+    glue
 URL: https://github.com/r4fun/keys
 BugReports: https://github.com/r4fun/keys/issues
 Suggests: 

R/add_key.R

@@ -7,6 +7,7 @@
 addKeys <- function(
   inputId,
   keys,
+  nullOnKeyRelease = FALSE,
   session = shiny::getDefaultReactiveDomain()
 ){
   if (is.null(session)) alert_null_session()
@@ -17,7 +18,8 @@ addKeys <- function(
         "add_mousetrap_binding",
         list(
           id = inputId,
-          keys = x
+          keys = x,
+          nullOnKeyRelease = nullOnKeyRelease
         )
       )
     }

R/keys.R

@@ -6,8 +6,10 @@
 #' @param inputId The input slot that will be used to access the value.
 #' @param keys A character vector of keys to bind. Examples include, `command`,
 #' `command+shift+a`, `up down left right`, and more.
-#' @param global Should keys work anywhere? If TRUE, keys are triggered when
+#' @param global Should keys work anywhere? If [TRUE], keys are triggered when
 #' inside a textInput.
+#' @param nullOnKeyRelease If [TRUE], input will be set to [NULL] after keys were
+#' released.
 #'
 #' @examples
 #' \dontrun{
@@ -31,8 +33,8 @@
 #' }
 #'
 #' @export
-keysInput <- function(inputId, keys, global = FALSE) {
+keysInput <- function(inputId, keys, global = FALSE, nullOnKeyRelease = FALSE) {
   htmltools::tagList(
-    keys_js(inputId, keys, global)
+    keys_js(inputId, keys, global, nullOnKeyRelease)
   )
 }

R/utils.R

@@ -4,15 +4,37 @@ minify <- function(x) {
 
 #' @importFrom htmltools tags
 #' @importFrom jsonlite toJSON
-keys_js <- function(id, keys, global = FALSE) {
-  if (global) global <- "Global"
-  else global <- ""
-
-  x <- sprintf("$(document).on('shiny:sessioninitialized', function() {
-    Mousetrap.bind%s(%s, function(e, combo) {
-      Shiny.setInputValue('%s', combo, {priority: 'event'});
-    });
-  });", global, toJSON(keys), id)
+keys_js <- function(id, keys, global = FALSE, nullOnKeyRelease = FALSE) {
+  x <- if (!nullOnKeyRelease) {
+    glue::glue(
+      "$(document).on('shiny:sessioninitialized', function() {",
+      "  Mousetrap.{{bindFunc}}({{keys}}, function(e, combo) {",
+      "    Shiny.setInputValue('{{id}}', combo, {priority: 'event'});",
+      "  });",
+      "});",
+      bindFunc = if (global) "bindGlobal" else "bind",
+      keys = jsonlite::toJSON(keys),
+      id = id,
+      .open = "{{",
+      .close = "}}"
+    )
+  } else {
+    glue::glue(
+      "$(document).on('shiny:sessioninitialized', function() {",
+      "  Mousetrap.{{bindFunc}}({{keys}}, function(e, combo) {",
+      "    Shiny.setInputValue('{{id}}', combo, {priority: 'event'});",
+      "  }, 'keydown');",
+      "  Mousetrap.{{bindFunc}}({{keys}}, function(e, combo) {",
+      "    Shiny.setInputValue('{{id}}', null, {priority: 'event'});",
+      "  }, 'keyup');",
+      "});",
+      bindFunc = if (global) "bindGlobal" else "bind",
+      keys = jsonlite::toJSON(keys),
+      id = id,
+      .open = "{{",
+      .close = "}}"
+    )
+  }
 
   tags$head(
     tags$script(

inst/js/handlers.js

@@ -1,8 +1,17 @@
 $( document ).ready(function() {
   Shiny.addCustomMessageHandler('add_mousetrap_binding', function(arg) {
-    Mousetrap.bind(arg.keys, function() {
-      Shiny.setInputValue(arg.id, arg.keys, {priority: 'event'});
-    });
+    if (arg.nullOnKeyRelease) {
+      Mousetrap.bind(arg.keys, function() {
+        Shiny.setInputValue(arg.id, arg.keys, {priority: 'event'});
+      }, 'keydown');
+      Mousetrap.bind(arg.keys, function() {
+        Shiny.setInputValue(arg.id, null, {priority: 'event'});
+      }, 'keyup');
+    } else {
+      Mousetrap.bind(arg.keys, function() {
+        Shiny.setInputValue(arg.id, arg.keys, {priority: 'event'});
+      });
+    }
   })
   Shiny.addCustomMessageHandler('remove_mousetrap_binding', function(arg) {
     Mousetrap.unbind(arg.keys);