Chords

An input chord is when two or more inputs are performed simultaneously. An example is Ctrl+C, which typically is a shortcut for Copy. The term chord is borrowed from music theory, and is when two notes performed at the same time.

An ActionContext has the CreateBindAction method, which returns a new action suitable for providing to an outer context. When the outer bind action's inputs are began (pressing control), the inner context is entered, allowing the inner actions (copy, paste) to be performed. Once released, the inner context is left, which unbinds the inner actions (and cancels them, if still being held).

local innerContext = ActionContext.new({
    -- in this context, we're holding Ctrl
    ActionContext.actionBegin("Copy", { Enum.KeyCode.C }, function () print("Copied") end),
    ActionContext.actionBegin("Paste", { Enum.KeyCode.V }, function () print("Pasted") end),
})
local outerContext = ActionContext.new({
    -- While holding either Control key, the innerContext is entered/left.
    innerContext:CreateBindAction("ControlChord", { Enum.KeyCode.LeftControl, Enum.KeyCode.RightControl }),
})
outerContext:Enter()

The above example can be shorthanded to just a few lines:

ActionContext.new({
    ActionContext.new({
        ActionContext.actionBegin("Copy", { Enum.KeyCode.C }, function () print("Copied") end),
        ActionContext.actionBegin("Paste", { Enum.KeyCode.V }, function () print("Pasted") end),
    }):CreateBindAction("ControlChord", { Enum.KeyCode.LeftControl, Enum.KeyCode.RightControl }),
}):Enter()

Input Triads

This also makes triads like Ctrl+Shift+T, a combination often assigned in browsers to re-open closed tabs, very easy. Just add one more delicious layer to your ActionContext cake:

ActionContext.new({ -- Browser opened...
    ActionContext.new({ -- Holding control...
        ActionContext.new({ -- Holding shift...
            -- Reopen your tabs!
            ActionContext.actionBegin("ReopenTabs", { Enum.KeyCode.C }, function () print("Re-opening tabs") end),
        }):CreateBindAction("ShiftChord", { Enum.KeyCode.LeftShift, Enum.KeyCode.RightShift }),
    }):CreateBindAction("ControlChord", { Enum.KeyCode.LeftControl, Enum.KeyCode.RightControl }),
}):Enter()

Ordering

Keen readers might notice this creates a strict ordering requirement which is not typically present for modifier keys (shift, ctrl, alt, super). In other words, the above example would not capture Shift+Ctrl+T. It is entirely possible to implement this by using additonal "middleware" contexts - just make sure you're re-using contexts where appropriate:

local ctrlShiftContext = ActionContext.new({
    ActionContext.actionBegin("ReopenTabs", { Enum.KeyCode.T }, function () print("Re-opening tabs") end)
})
local controlInputs = { Enum.KeyCode.LeftControl, Enum.KeyCode.RightControl }
local shiftInputs = { Enum.KeyCode.LeftShift, Enum.KeyCode.RightShift }
ActionContext.new({
    ActionContext.new({
        ctrlShiftContext:CreateBindAction("ControlShiftChord", shiftInputs),
    }):CreateBindAction("ControlChord", controlInputs),
    ActionContext.new({
        ctrlShiftContext:CreateBindAction("ShiftControlChord", controlInputs),
    }):CreateBindAction("ShiftChord", shiftInputs),
}):Enter()

The implementation of tetrads (Ctrl+Alt+Shift+T) is left up to the reader. Good luck.