mp.input: use unique event handlers for input.get requests

This makes changes to mp.input and console.lua so that every input.get
request uses a unique script-message to handle input events.

Previously, making new input.get requests shortly after the termination
of a previous request made by the same script could cause a race
condition where the input handler was closed but the new request
was still being drawn in the UI. This was caused by the `closed` event
for the previous request being received only after the new request was
registered, hence closing the event handler for the new request instead.

In addition, this commit makes the behaviour of calling input.get while
another request is active more consistent. When a new request is
received it overwrites the in-progress request, sending a `closed`
event. However, previously, the `closed` event could not be sent if both
requests came from the same script, as the new request would have
overwritten the event handler. Now, the `closed` event is called
regardless of where the new request comes from.

player/javascript/defaults.js

@@ -653,8 +653,12 @@ mp.options = { read_options: read_options };
 /**********************************************************************
 *  input
 *********************************************************************/
+var input_handle_counter = 0;
+
 function register_event_handler(t) {
-    mp.register_script_message("input-event", function (type, args) {
+    var handler_id = "input-event/" + input_handle_counter++;
+
+    mp.register_script_message(handler_id, function (type, args) {
         if (t[type]) {
             args = args ? JSON.parse(args) : [];
             var result = t[type].apply(null, args);
@@ -666,18 +670,19 @@ function register_event_handler(t) {
         }
 
         if (type == "closed")
-            mp.unregister_script_message("input-event");
+            mp.unregister_script_message(handler_id);
     })
+
+    return handler_id;
 }
 
 mp.input = {
     get: function(t) {
-        t.has_completions = t.complete !== undefined
+        t.has_completions = t.complete !== undefined;
+        t.client_name = mp.script_name;
+        t.handler_id = register_event_handler(t);
 
-        mp.commandv("script-message-to", "console", "get-input", mp.script_name,
-                    JSON.stringify(t));
-
-        register_event_handler(t)
+        mp.commandv("script-message-to", "console", "get-input", JSON.stringify(t));
     },
     terminate: function () {
         mp.commandv("script-message-to", "console", "disable");

player/lua/console.lua

@@ -96,6 +96,7 @@ local key_bindings = {}
 local dont_bind_up_down = false
 local global_margins = { t = 0, b = 0 }
 local input_caller
+local input_caller_handler
 local keep_open = false
 
 local completion_buffer = {}
@@ -949,7 +950,7 @@ end
 local function handle_edit()
     if not selectable_items then
         handle_cursor_move()
-        mp.commandv("script-message-to", input_caller, "input-event", "edited",
+        mp.commandv("script-message-to", input_caller, input_caller_handler, "edited",
                     utils.format_json({line}))
         return
     end
@@ -1070,7 +1071,7 @@ local function submit()
 
     if selectable_items then
         if #matches > 0 then
-            mp.commandv("script-message-to", input_caller, "input-event", "submit",
+            mp.commandv("script-message-to", input_caller, input_caller_handler, "submit",
                         utils.format_json({matches[focused_match].index}))
         end
     else
@@ -1079,7 +1080,7 @@ local function submit()
             cycle_through_completions()
         end
 
-        mp.commandv("script-message-to", input_caller, "input-event", "submit",
+        mp.commandv("script-message-to", input_caller, input_caller_handler, "submit",
                     utils.format_json({line}))
 
         history_add(line)
@@ -1481,7 +1482,7 @@ end
 complete = function ()
     completion_old_line = line
     completion_old_cursor = cursor
-    mp.commandv("script-message-to", input_caller, "input-event",
+    mp.commandv("script-message-to", input_caller, input_caller_handler,
                 "complete", utils.format_json({line:sub(1, cursor - 1)}))
     render()
 end
@@ -1651,7 +1652,7 @@ set_active = function (active)
         unbind_mouse()
         mp.set_property_bool("user-data/mpv/console/open", false)
         mp.set_property_bool("input-ime", ime_active)
-        mp.commandv("script-message-to", input_caller, "input-event",
+        mp.commandv("script-message-to", input_caller, input_caller_handler,
                     "closed", utils.format_json({line, cursor}))
         collectgarbage()
     end
@@ -1662,14 +1663,15 @@ mp.register_script_message("disable", function()
     set_active(false)
 end)
 
-mp.register_script_message("get-input", function (script_name, args)
-    if open and script_name ~= input_caller then
-        mp.commandv("script-message-to", input_caller, "input-event",
+mp.register_script_message("get-input", function (args)
+    if open then
+        mp.commandv("script-message-to", input_caller, input_caller_handler,
                     "closed", utils.format_json({line, cursor}))
     end
 
-    input_caller = script_name
     args = utils.parse_json(args)
+    input_caller = args.client_name
+    input_caller_handler = args.handler_id
     prompt = args.prompt or ""
     line = args.default_text or ""
     cursor = tonumber(args.cursor_position) or line:len() + 1
@@ -1704,7 +1706,7 @@ mp.register_script_message("get-input", function (script_name, args)
     else
         selectable_items = nil
         unbind_mouse()
-        id = args.id or script_name .. prompt
+        id = args.id or args.client_name .. prompt
         log_offset = 0
         completion_buffer = {}
         autoselect_completion = args.autoselect_completion
@@ -1721,11 +1723,15 @@ mp.register_script_message("get-input", function (script_name, args)
 
         if line ~= "" then
             complete()
+        elseif open then
+            -- This is needed to update the prompt if a new request is
+            -- received while another is still active.
+            render()
         end
     end
 
     set_active(true)
-    mp.commandv("script-message-to", input_caller, "input-event", "opened")
+    mp.commandv("script-message-to", input_caller, input_caller_handler, "opened")
 end)
 
 -- Add a line to the log buffer

player/lua/input.lua

@@ -18,6 +18,8 @@ License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
 local utils = require "mp.utils"
 local input = {}
 
+local handle_counter = 0
+
 local function get_non_callbacks(t)
     local non_callbacks = {}
 
@@ -31,7 +33,10 @@ local function get_non_callbacks(t)
 end
 
 local function register_event_handler(t)
-    mp.register_script_message("input-event", function (type, args)
+    local handler_id = "input-event/"..handle_counter
+    handle_counter = handle_counter + 1
+
+    mp.register_script_message(handler_id, function (type, args)
         if t[type] then
             local completions, completion_pos, completion_append =
                 t[type](unpack(utils.parse_json(args or "") or {}))
@@ -44,18 +49,20 @@ local function register_event_handler(t)
         end
 
         if type == "closed" then
-            mp.unregister_script_message("input-event")
+            mp.unregister_script_message(handler_id)
         end
     end)
+
+    return handler_id
 end
 
 function input.get(t)
     t.has_completions = t.complete ~= nil
+    t.client_name = mp.get_script_name()
+    t.handler_id = register_event_handler(t)
 
     mp.commandv("script-message-to", "console", "get-input",
-                mp.get_script_name(), utils.format_json(get_non_callbacks(t)))
-
-    register_event_handler(t)
+                utils.format_json(get_non_callbacks(t)))
 end
 
 input.select = input.get