Best way to handle pressing or releasing two buttons simultaneously

SDK Development Discussion
1

On my quest to see how innovative we can all get with button input types on the Playdate, I'm looking to open a menu when both A+B are released. Currently, this way is working fine, but the way getButtonState() works, there's not a ton of room for error with how soon together someone has to release both buttons for it to register during the next update cycle.

function globalInputHandlers()
	local current, justPressed, justReleased = playdate.getButtonState()
	
	if justReleased == playdate.kButtonA|playdate.kButtonB then
		
		-- Open a menu
	end
end

For it to properly trigger, back-to-back cycles need to look like this:

-- Update cycle
current = 48,  justPressed = 0, justReleased = 0

-- Next update cycle
current = 0,  justPressed = 0, justReleased = 48

But if the user isn't relatively precise with releasing both buttons at the same time, it might look more like this:

-- Update cycle
current = 48,  justPressed = 0, justReleased = 0

-- Next update cycle
current = 32,  justPressed = 0, justReleased = 16

-- Next Next update cycle
current = 0,  justPressed = 0, justReleased = 32

... and then the original code won't get called. There's some obvious ways I can think to prevent this with a few extra conditionals and shenanigans inside of that if statement.. but just curious if this is something anyone else has encountered?

I don't find it particularly difficult to release both buttons synchronized enough to trigger it, but also I'm actively trying to do it and am aware of it. I'd hate for a user to feel frustrated that a button input works sometimes and doesn't work other times, and them not understanding why.

What's the best way to add some leeway for the input here?

2

You could store the previous frame's buttons state and do a bitwise OR operation on the that state and the current frame's state to very efficiently get a state that describes whether buttons were released in the current and/or previous frame. (untested)

2 Likes
3

I did something like this. I wouldn't claim it's the best way though! :grimacing:

local gfx = playdate.graphics
gfx.setColor(gfx.kColorBlack)

local release = {frames = 10, timer = 0, a = 0, b = 0}

function playdate.update()

    if aButtonBButton() then
        -- open menu or whatever
        spriteSquare(180, 100, 40, 40)
    end
    
    gfx.sprite.update()
    gfx.drawText("timer: " .. release.timer, 20, 20)
    
end

function aButtonBButton()
    if release.timer > 0 and playdate.buttonJustReleased('b') then release.b = 1 end
    if release.timer > 0 and playdate.buttonJustReleased('a') then release.a = 1 end
    if release.timer * release.a * release.b > 0 then
        release.timer, release.a, release.b = 0, 0, 0
        return true
    elseif playdate.buttonIsPressed('a') and playdate.buttonIsPressed('b') then
        release.timer = release.frames
    elseif release.timer > 0 then
        release.timer -= 1
    elseif release.timer == 0 then
        release.a, release.b = 0, 0
    end
    return false
end

function spriteSquare(x, y, w, h)
    local s = gfx.sprite.new(w, h)
    s.timer = 5
    local image = gfx.image.new(w, h)
    gfx.lockFocus(image)
    gfx.fillRect(0, 0, w, h)
    gfx.unlockFocus()
    s:setImage(image)
    s:moveTo(x, y)
    s:add()
    
    function s:update()
        if s.timer == 0 then
            s:remove()
        else
            s.timer -= 1
        end
    end
end
1 Like
4

Nice! @Nino's bitwise stuff was a little too galaxy brain for me, so here's what I landed on. It works quite well for now but is not optimized at all. I laughed when I saw that you used 10 frames as the timing for yours, because that's the same that I ended up using after testing :rofl: feels right, man

function playdate.update()
	playdate.frameTimer.updateTimers()
	customButtonHoldCheck()
end

local customButtonHoldTimer = nil
function customButtonHoldCheck()
	local current, justPressed, justReleased = playdate.getButtonState()
	
	-- Check if both buttons are held and timer isn't already running
	if current == kButtonA|kButtonB and customButtonHoldTimer == nil then		
		customButtonHoldTimer = playdate.frameTimer.new(10)
		ABButtonHeld()
	end
	
	-- Reset the timer if the input is abandoned before it's complete
	-- PreventMenuOpen() is used to check global things like if keyboard is visible
	if current == 0 or preventMenuOpen() then
		customButtonHoldTimer = nil
	end
end

function ABButtonHeld()	
	customButtonHoldTimer.timerEndedCallback = function(timer)
		-- Check that both buttons are still pressed when the timer is complete
		if playdate.buttonIsPressed(kButtonA) and playdate.buttonIsPressed(kButtonB) then
			-- Open the menu 
		end
	end
end
2 Likes