Lua: Wait command?

[Galuhad]

Hey,

I'm working on a plugin at the moment but need some advice. I've created a message box that asks a question with yes/no buttons to select. The function that creates the message box needs to return a string saying which button was pressed. What I need is some way to pause the script, like a wait command or something, so the plugin stops until one of the buttons is pressed. Otherwise it returns the default value.

Any ideas please would be most appreciated. Thanks.

[Galuhad]

I found a possible solution in coroutines, but keep getting the message, "attempt to yield across metamethod/C-call boundary". Are coroutines disabled in Lotro?

[Garan]

There doesn't seem to be any way in LoTRO's version of Lua to yield processing. However, you can use the Update event handler to asynchronously handle responses. This usually means restructuring the code so that the part of the code before the dialog and the part after the dialog can be separated into two separate functions.

Assuming you have a function that needs multiple sequential responses (this example uses 3) and you want to reuse the message box dialog, you would do something like:

SomeWindow.waitFlag=0;

SomeWindow.SomeFunctionPart1=function()
    -- first part of code up to the first dialog
    SomeWindow.waitFlag=1;

    -- display dialog with first question text buttons
    SomeDialog.TextMsg:SetText("this is the first question");
    SomeDialog:SetVisible(true);
end
SomeWindow.SomeFunctionPart2=function()
    if SomeDialog:GetButtonString()=="string1" then
        -- button 1 code
    elseif SomeDialog:GetButtonString()=="string2" then
        -- button 2 code
    end
    -- other code
    SomeWindow.waitFlag=2;
    -- display dialog with second question text buttons
    SomeDialog.TextMsg:SetText("this is the second question");
    SomeDialog:SetVisible(true);
end
SomeWindow.SomeFunctionPart3=function()
    if SomeDialog:GetButtonString()=="string1" then
        -- button 1 code
    elseif SomeDialog:GetButtonString()=="string2" then
        -- button 2 code
    end
    -- other code
    SomeWindow.waitFlag=3;
    -- display dialog with third question text buttons
    SomeDialog.TextMsg:SetText("this is the third question");
    SomeDialog:SetVisible(true);
end

SomeWindow.SomeFunctionPart4=function()
    if SomeDialog:GetButtonString()=="string1" then
        -- button 1 code
    elseif SomeDialog:GetButtonString()=="string2" then
        -- button 2 code
    end
    -- other code
end

SomeWindow.Update=function()
    if SomeWindow.waitFlag==1 then
        SomeWindow:SetWantsUpdates(false);
        SomeWindow.SomeFunctionPart2();
    elseif SomeWindow.waitFlag==2 then
        SomeWindow:SetWantsUpdates(false);
        SomeWindow.SomeFunctionPart3();
    elseif SomeWindow.waitFlag==3 then
        SomeWindow:SetWantsUpdates(false);
        SomeWindow.SomeFunctionPart4();
    end
end

SomeDialog.buttonString="";
SomeDialog.GetButtonString=function()
    return SomeDialog.buttonString;
end
SomeDialog.Button1.MouseClick=function()
    SomeDialog.buttonString="string1";
    SomeWindow:SetWantsUpdates(true);
    SomeDialog:SetVisible(false);
end
SomeDialog.Button2.MouseClick=function()
    SomeDialog.buttonString="string2";
    SomeWindow:SetWantsUpdates(true);
    SomeDialog:SetVisible(false);
end

Note that the Update event handler is only enabled when a response button is clicked so as to prevent wasting machine cycles. You would want to be sure the window can't be closed without responding, otherwise you would have to set an appropriate default response code and only enable the Update handler when the dialog visibility changes to false but that is a fairly trivial change.

Of course, in the simplistic case of just needing one of two response, restructuring the code would allow you to simply call the second part of the function from the button mouseclick event handlers.

[Equendil]

I found a possible solution in coroutines, but keep getting the message, "attempt to yield across metamethod/C-call boundary". Are coroutines disabled in Lotro?

I haven't tried using co-coroutines in lotro, but that message you might get from trying to "yield" in a section of your code that wasn't being run in a co-routine, and that would indicate to me that co-routines are enabled.

Still, co-routines won't help you, if you do not return from your script, then the runtime cannot dispatch events, even a "busy wait loop" wouldn't work, Button.Click() would never be called. No parallel execution.

You are going to have to handle things in an asynchronous way, as Garan suggested.

Using Update() along with some sort of state automaton might be unnecessary complicated for what you are trying to do, a simplistic asynchronous way of doing something akin to :

...
if MessageBox() == Affirmative then
	-- do something
else
	-- do something else
end

Might be

function affirmativeCase()
	-- do something
end

function negativeCase()
	-- do something else
end

OpenMessageBox( { <whatever list of windows you want to 'block'> }, affirmativeCase, negativeCase )

with a rough version of a message box being:

local function SetWindowsEnabled( windows, enabled )
	for _,window in pairs( windows ) do
		window:SetEnabled( enabled );
	end
end

local MessageBox = class(Turbine.UI.Window);
function MessageBox:Constructor( windows, affirmativeCase, negativeCase )
	Turbine.UI.Lotro.Window.Constructor(self);
	
	self.affirmativeButton = Turbine.UI.Lotro.Button();
	self.affirmativeButton:SetParent( self );
	...
	self.affirmativeButton.Click = function( sender, args )
		EnableWindows( windows );
		self:Close();
		affirmativeCase();
	end

	self.negativeButton = Turbine.UI.Lotro.Button();
	self.negativeButton:SetParent( self );
	...
	self.negativeButton.Click = function( sender, args )
		EnableWindows( windows );
		self:Close();
		negativeCase();
	end

	self:SetVisible( true );
	DisableWindows( windows );
end	

function OpenMessageBox( windows, affirmativeCase, negativeCase )
	messageBoxSingleton = MessageBox( windows, affirmativeCase, negativeCase );
end

Two tricks here being to disable your other windows so they do not receive user input, and to keep the message box in a global variable so that it does not get garbage collected right away. Come to think about it though, I've never tried disabling an entire window, I assume that works.

[Galuhad]

Thank you both for your replies.

I ended up making a MessageBox class instead which is working exactly as I hoped.
If it were just one message box I wanted then it would have been easy because I would have just put the relative code into the Button.Click events.. However I wanted to use the message box for other things as well so I needed each message box to handle their own responses. I tried coroutines (with the .yield() being called within the coroutine) but kept getting errors.. I had hoped that the .yield command would pause the script while it waited for a response but no such luck. Never mind, the class is working as I want so I'm happy

[Almagnus1]

When I was trying to break the backpack in the RoI Beta, I found out that plugins are, in fact, part of the same thread as the LotRO client. Or it's coded in such a way that that's effectively true.