Roku Developer Program

[tvjay]

I am trying to do a custom canvas. In doing so I want to present the user a back button. What I am having trouble with is returning a variable to tell the main function to clsoe. The variable in question is goBack. Basically. I define goBack as 0. I then track the users selection (0,1 or 2), pass it a function to make a decision to either play a video or close. If they chose the close button (selectedIndex 2) then change the variable goBack to be 1. However, it changes it in the subfunction (onOk) but inside showImageCanvas it is still 0.

function showImageCanvas(episodes, selectedEpisode, leftBread, rightBread)
	
	episode = episodes[selectedEpisode]
	goBack = 0
	
	canvas = CreateObject("roImageCanvas")
    port = CreateObject("roMessagePort")
    posArray = GetPositions()
    items = []
    selectedIndex = 0  
	
    canvas.SetMessagePort(port)
    canvasRect = canvas.GetCanvasRect()
    'onOK(2)
    'stop        
    items.Push({
		url:"http://apache.303north.com/Roku/1280x165_overhang.png"
        TargetRect: {x: 0, y: 0}
    })
    items.Push({
		url:episode.hdposterurl
		TargetRect: {x: 200, y: 200}
    })
    items.Push({
		url:"pkg:/images/ptl-button-play.png"
		TargetRect: posArray[0]
    })
	items.Push({
		url:"pkg:/images/ptl-button-playall.png"
		TargetRect: posArray[1]
    })
	items.Push({
		url:"pkg:/images/ptl-button-back.png"
		TargetRect: posArray[2]
    })
    items.Push({
		Text:episode.description
		TextAttrs:{Color:"#FFCCCCCC", Font:"Medium",
        HAlign:"HCenter", VAlign:"VCenter",
        Direction:"LeftToRight"}
        TargetRect: {x: -50, y: 200}
    })
    ring = {
        url: "pkg:/images/ptl-button-selection.png",
        TargetRect: {x: posArray[selectedIndex].x-2, y: posArray[selectedIndex].y-2}
    }            
    canvas.SetLayer(0, { Color: "#1d2535", CompositionMode: "Source" })
    canvas.SetLayer(1, items)
    canvas.SetLayer(2, ring)
    canvas.Show()
   
    while true
        event = wait(0, port)
        if (event<> invalid)
            if (event.isRemoteKeyPressed())
                index = event.GetIndex()
                print selectedIndex
                if (index = 4) OR (index = 2) 'Left or Up
                    selectedIndex = selectedIndex-1
                    if (selectedIndex < 0)
                        selectedIndex = 2
                    endif
                else if (index = 5) OR (index = 3) 'Right or Down
                    selectedIndex = selectedIndex+1
                    if (selectedIndex > 2)
                        selectedIndex = 0
                    endif
                else if (index = 6) 'OK
                    onOK(selectedIndex, episode, goBack)
					
					print goBack
					print "POST OK"
					
						if goBack = 1
							print "EXIT WHILE"
							exit while
						endif
					
					print "END"
					
				endif
				
                ring.TargetRect = {x: posArray[selectedIndex].x-2, y: posArray[selectedIndex].y-2}
                canvas.SetLayer(0, { Color: "#1d2535", CompositionMode: "Source" })
                canvas.SetLayer(1, items)
                canvas.SetLayer(2, ring)                
            endif
        endif
    end while
	
	return selectedEpisode
End Function

function onOK(selectedIndex, episode, goBack)

	
	screen = CreateObject("roVideoScreen")
	screen.SetMessagePort(CreateObject("roMessagePort"))
	screen.SetPositionNotificationPeriod(1)
	
	screen.SetContent(episode)
	
	print goBack

	if selectedIndex = 0
		print "Test 0"
		episode.playStart = 0 ' Play
		PlayVideo(episode)
		
	else if selectedIndex = 1 ' Play All
		print "Test 1"

		PlayVideo(episode)
	else if selectedIndex = 2 ' Back
		print "Test 2"
		goBack = 1
		print goBack
	end if

	return goBack
end function

Function GetPositions() as object
    posArray = []
    posArray.Push({x: 500, y: 250})
    posArray.Push({x: 500, y: 300})
	posArray.Push({x: 500, y: 350})
    return posArray
End Function

[TheEndless]

Primitives are passed by value. You'll need to box them in order to pass them by reference, then call the appropriate SetXXX() method to update the value.

Something along the lines of (stupidly verbose to illustrate the steps)...

Sub Main()
    x = 0
    x = Box(x)
    print "x=";x
    UpdateX(x)
    print "x=";x
End Sub

Sub UpdateX(x)
    ' You have to call SetInt() to update the value, otherwise
    ' you'll just be re-assigning the local variable
    x.SetInt(2)
End Sub

Should output:

------ Running ------
x= 0
x= 2

If you skip the Box() step, you'll get what you're running into now...

------ Running ------
x= 0
x= 0

Alternatively, you could pass it in as part of an AA, which always get passed by reference.

[Komag]

Wow, that's very clear TheEndless. I discovered using AAs to always get referencing, but it's nice to know the exact method you outlined if only to have a better understanding of how it really works. 🙂

[RokuMarkn]

The more usual technique to return a single value from a function is to pass it as the return value. You already have a "return goBack" as the last statement in your onOK function, so instead of

onOK(selectedIndex, episode, goBack)

you could just call it as

goBack = onOK(selectedIndex, episode)

--Mark

[Komag]

Slightly messier if you need a few variables returned is to bundle them in an array and return that.

FUNCTION Main()
   answerArray = getAnswers(input1, input2, input3)
   PRINT answers[0] ' prints whatever answer1 is
END FUNCTION

FUNCTION getAnswers(input1, input2, input3) AS OBJECT
   doThis()
   doThat()
   answer1 = input1.doSomething()
   answer2 = input2.doOtherThing()
   answer3 = answer1 + answer3.else()
   answers = [answer1, answer2, answer3]
   RETURN answers
END FUNCTION

[tvjay]

Thank you guys for the great information and the fast response.

I did have two questions though...

What do you guys mean using AA's?

What happens if I want to pass text instead of a number. Is there a different SetXXX() setup? I have been searching the Roku SDK documentation but can't find anything.

[Komag]

The documentation has all this info, but its spread out a little.
Read this whole thing about 5 times:
http://sdkdocs.roku.com/display/sdkdoc/ ... +Reference
And go through "all" of these, especially things like roArray, roAssociativeArray (AA), roBoolean, roFloat, etc, all the stuff mentioned in the language reference.
Passing text is no different, just using "string" instead of "integer/float/double float"

[EnTerr]

"tvjay" wrote:
What do you guys mean using AA's? What happens if I want to pass text instead of a number.

meaning doing something like this, it's idiomatic:

function someFun()
    ...
    it = {x: 10, y: 100, alpha: 0.5, visible: true, text: "something something"}
    return it
end function

...
obj = someFun()
print "and the text is:", obj.text

Is there a different SetXXX() setup? I have been searching the Roku SDK documentation but can't find anything.

"SetXXX()" in particular, if existing - i am sure is undocumented for NSFW NC-17 reasons