Added in mousewheel as part of this.

data/core/init.lua

@@ -928,7 +928,9 @@ function core.on_event(type, ...)
   elseif type == "mousereleased" then
     core.root_view:on_mouse_released(...)
   elseif type == "mousewheel" then
-    core.root_view:on_mouse_wheel(...)
+    if not core.root_view:on_mouse_wheel(...) then
+      did_keymap = keymap.on_mouse_wheel(...)
+    end
   elseif type == "resized" then
     core.window_mode = system.get_window_mode()
   elseif type == "minimized" or type == "maximized" or type == "restored" then

data/core/keymap.lua

@@ -85,6 +85,11 @@ function keymap.on_key_pressed(k, ...)
   return false
 end
 
+function keymap.on_mouse_wheel(delta, ...)
+  return not keymap.on_key_pressed("wheel" .. (delta > 0 and "up" or "down"), delta, ...)
+    and keymap.on_key_pressed("wheel", delta, ...)
+end
+
 local click_prefixes = { "", "d", "t" }
 function keymap.on_mouse_pressed(button, x, y, clicks)
   return keymap.on_key_pressed(click_prefixes[((clicks - 1) % 3) + 1] .. button:sub(1,1) .. "click", x, y, clicks)