Events: Difference between revisions

Lingo/Director uses (stateless) events for system/application state change notifications, user action notifications and inter-sprite communication.

To catch an event, a corresponding event handler - a function with a predefined name - has to be definined in the code. Examples for such event handlers are:

<lang lingo>-- the current window was closed

on closeWindow

...

end

-- the left mouse button was pressed by the user

on mouseDown

...

end</lang>

Also "Sprites" (visual elements) receive events by setting up such event handlers in scripts attached to them. Both predefined and custom events can be sent programmatically to sprites, e.g. using:

<lang lingo>-- send event #mouseDown programmatically to sprite 1

sendSprite(1, #mouseDown)

-- send custom event #foo to named sprite "bar"

sendSprite("bar", #foo)

-- send a custom event #fooBar to all existing sprites

sendAllSprites(#fooBar)</lang>

Using a binary plugin ("Xtra"), in Windows also lower level window messages can be both sent and received:

{{libheader|Msg Xtra}}

<lang lingo>mx = xtra("Msg").new()

-- send message WM_LBUTTONDOWN to a specific window identified by HWND hwnd

WM_LBUTTONDOWN = 513

MK_LBUTTON = 1

lParam = 65536*y + x

mx.send_msg (hwnd, WM_LBUTTONDOWN, MK_LBUTTON, lParam)

-- listen for WM_COPYDATA and WM_MOUSEWHEEL messages sent to current application

-- window, notify Lingo callback function 'msgReceived' when such messages occur

WM_COPYDATA = 74

WM_MOUSEWHEEL = 522

mx.msg_listen([WM_COPYDATA, WM_MOUSEWHEEL], VOID, #msgReceived)</lang>