defaults.lua: support scalable mp.add_key_binding()

For complex key bindings, the table now contains a new member
of the current key scale. mp.add_key_binding() now accepts the
scalable flag to make the binding scalable.

DOCS/man/lua.rst

@@ -323,6 +323,13 @@ The ``mp`` module is preloaded, although it can be loaded manually with
             If set to ``true``, enables key repeat for this specific binding.
             This option only makes sense when ``complex`` is not set to ``true``.
 
+        ``scalable``
+            If set to ``true``, enables key scaling for this specific binding.
+            This option only makes sense when ``complex`` is set to ``true``.
+            Note that this has no effect if the key binding is invoked by
+            ``script-binding`` command, where the scalability of the command
+            takes precedence.
+
         ``complex``
             If set to ``true``, then ``fn`` is called on key down, repeat and up
             events, with the first argument being a table. This table has the
@@ -350,6 +357,10 @@ The ``mp`` module is preloaded, although it can be loaded manually with
                     description of ``script-binding`` command for details (this
                     field is equivalent to the 5th argument).
 
+                ``scale``
+                    The scale of the key, such as the ones produced by ``WHEEL_*``
+                    keys. The scale is 1 if the key is nonscalable.
+
     Internally, key bindings are dispatched via the ``script-message-to`` or
     ``script-binding`` input commands and ``mp.register_script_message``.
 

player/lua/defaults.lua

@@ -60,10 +60,10 @@ local function reserve_binding()
     return "__keybinding" .. tostring(message_id)
 end
 
-local function dispatch_key_binding(name, state, key_name, key_text)
+local function dispatch_key_binding(name, state, key_name, key_text, scale)
     local fn = dispatch_key_bindings[name]
     if fn then
-        fn(name, state, key_name, key_text)
+        fn(name, state, key_name, key_text, scale)
     end
 end
 
@@ -186,6 +186,7 @@ local function add_binding(attrs, key, name, fn, rp)
         name = reserve_binding()
     end
     local repeatable = rp == "repeatable" or rp["repeatable"]
+    local scalable = rp == "scalable" or rp["scalable"]
     if rp["forced"] then
         attrs.forced = true
     end
@@ -200,7 +201,7 @@ local function add_binding(attrs, key, name, fn, rp)
             ["r"] = "repeat",
             ["p"] = "press",
         }
-        key_cb = function(_, state, key_name, key_text)
+        key_cb = function(_, state, key_name, key_text, scale)
             if key_text == "" then
                 key_text = nil
             end
@@ -210,6 +211,7 @@ local function add_binding(attrs, key, name, fn, rp)
                 canceled = state:sub(3, 3) == "c",
                 key_name = key_name,
                 key_text = key_text,
+                scale = tonumber(scale),
             })
         end
         msg_cb = function()
@@ -235,8 +237,9 @@ local function add_binding(attrs, key, name, fn, rp)
         end
         msg_cb = fn
     end
+    local prefix = scalable and "" or " nonscalable"
     if key and #key > 0 then
-        attrs.bind = key .. " script-binding " .. mp.script_name .. "/" .. name
+        attrs.bind = key .. prefix .. " script-binding " .. mp.script_name .. "/" .. name
     end
     attrs.name = name
     -- new bindings override old ones (but do not overwrite them)