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Events: Difference between revisions
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OTP comes with a <code>gen_even</code>t behavior that is more robust and resilient than this version. That is what should be used for any non-toy example or project.
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>
=={{header|JavaScript}}==
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