Lua Programming Help Thread

[Mr_Shizzy]

Just a heads up:

JaX3RiR has recompiled Lua Player V0.16 to 3.XX kernel now
(The other one you guys linked to above, was V0.20)

[RELEASE]3.XX Kernel homebrew pack

[FaT3oYCG]

doesn't work

[Anti-QuickJay]

Just a heads up:

JaX3RiR has recompiled Lua Player V0.16 to 3.XX kernel now
(The other one you guys linked to above, was V0.20)

[RELEASE]3.XX Kernel homebrew pack

Sweet!

[Foxhull]

blue = Color.new(0,0,255)
white = Color.new(255,255,255)
red = Color.new(255,0,0)
green = Color.new(0,255,0)

test = {x = -8, y = 243, speed = 3, img = Image.createEmpty(8, 8)}
test.img:clear(green)

box1 = Image.createEmpty(480, 80)
box1:clear(blue)

line = Image.createEmpty(5, 80)
line:clear(white)

line1 = Image.createEmpty(90, 5)
line1:clear(white)

line2 = Image.createEmpty(3, 52)
line2:clear(white)

back = Image.createEmpty(480, 140)
back:clear(red)

function drawimages()
   screen:blit(0, 141, box1)
   screen:blit(101, 141, line)
   screen:blit(196, 141, line)
   screen:blit(0, 0, back)
   screen:blit(106, 141, line1)
   screen:blit(106, 216, line1)
   screen:blit(239, 221, line2)
   screen:blit(test.x, test.y, test.img)
end

function drawtext()
   screen:print(116, 151, "Fight", white)
   screen:print(116, 166, "Harmony", white)
   screen:print(116, 181, "Dissonance", white)
   screen:print(116, 196, "Items", white)
end

function test()
   if test.x < 500 then
      test.x = test.x + test.speed
   end
end

while true do
   screen:clear()

   drawimages()
   drawtext()
   test()
   
   screen.waitVblankStart()
   screen.flip()
end

Alright, I've been learning Lua for couple months now, and I'm stumped by this error message:

34:attempt to index global 'test' (a function value)

What am I doing wrong?
Note: The code should cause an 8x8 green block scroll from offscreen on the left side of the screen to offscreen on the right side.

[michaelp]

I'm pretty sure it's because you have a function called test and an array/table called test. Rename one of them. Then I THINK it will work.

[EminentJonFrost]

blue = Color.new(0,0,255)
white = Color.new(255,255,255)
red = Color.new(255,0,0)
green = Color.new(0,255,0)

test = {x = -8, y = 243, speed = 3, img = Image.createEmpty(8, 8)}
test.img:clear(green)

box1 = Image.createEmpty(480, 80)
box1:clear(blue)

line = Image.createEmpty(5, 80)
line:clear(white)

line1 = Image.createEmpty(90, 5)
line1:clear(white)

line2 = Image.createEmpty(3, 52)
line2:clear(white)

back = Image.createEmpty(480, 140)
back:clear(red)

function drawimages()
   screen:blit(0, 141, box1)
   screen:blit(101, 141, line)
   screen:blit(196, 141, line)
   screen:blit(0, 0, back)
   screen:blit(106, 141, line1)
   screen:blit(106, 216, line1)
   screen:blit(239, 221, line2)
   screen:blit(test.x, test.y, test.img)
end

function drawtext()
   screen:print(116, 151, "Fight", white)
   screen:print(116, 166, "Harmony", white)
   screen:print(116, 181, "Dissonance", white)
   screen:print(116, 196, "Items", white)
end

function test()
   if test.x < 500 then
      test.x = test.x + test.speed
   end
end

while true do
   screen:clear()

   drawimages()
   drawtext()
   test()
   
   screen.waitVblankStart()
   screen.flip()
end

Alright, I've been learning Lua for couple months now, and I'm stumped by this error message:


What am I doing wrong?
Note: The code should cause an 8x8 green block scroll from offscreen on the left side of the screen to offscreen on the right side.

You named "test" a table AND a function.
Rename one of them.

Dang it, michaelp beat me to it. lol

[Foxhull]

thanks, i'll try that

EDIT: Thanks, works now.

[EminentJonFrost]

Come back for any help you need. :)

[Highsight]

This is bugging the hell out of me. What EXACTLY is the screen object? I used to think it was an image, but when I tried to use it like one, it told me it was a table (With no elements in it). Can someone please explain it to me? I need to find a way to use it like an image object.

[FaT3oYCG]

it is like a container

- if you blit an image to it it contains that data like a table if you want to use it like an image you cant i like to blit a blank image to it 480 x 272 and use that instead then it will act like a screen and an image

just remember

image_screen = image.createEmpty(480, 272)

then

image_screen.flip() and so on

thanks

[Highsight]

I see.... I was trying to copy the screen into another variable:

zoomOut = screen

But obviously this didn't work. Do you know any way I could make it work?

[FaT3oYCG]

why may i ask do you want to do that

from what you have said i can hazzard a guess that you want to take the screen content and soom out from it you could do this one of two ways that i can think of

screen:save() the screen and resize that
or
use the gu functions i dont know the specific commands off my head as i try to avoid using them where i dont need to and also because i havent learnt to use them properly

thanks

[Anti-QuickJay]

Learn the GU functions.
Its faster.

[Highsight]

why may i ask do you want to do that

from what you have said i can hazzard a guess that you want to take the screen content and soom out from it you could do this one of two ways that i can think of

screen:save() the screen and resize that
or
use the gu functions i dont know the specific commands off my head as i try to avoid using them where i dont need to and also because i havent learnt to use them properly

thanks

Your dead on. It's not REALLY a zoom effect though, more of a cropping effect. I was considering doing the screen:save(), but it wouldn't really be that efferent since I would have to save a file and delete it every time. I guess I'll have to learn the GU functions. Thanks. :)

[eldiablov]

Your dead on. It's not REALLY a zoom effect though, more of a cropping effect. I was considering doing the screen:save(), but it wouldn't really be that efferent since I would have to save a file and delete it every time. I guess I'll have to learn the GU functions. Thanks. :)

What did you use for mazegen then ?

[Highsight]

That was 3DGU, I believe they are referring to non 3D GU functions... right? XD

Incidentally, where can I learn about the GU functions Anti? I can't seem to find anything other than 3D GU, and I don't see how those would help. :/

[FaT3oYCG]

its gu and gum commands if i am correct the 3d cube shows most of the commands but if you want to crop an image im sure that there is a much simpler way

for example create a blank image the size that you would like to crop to this will act like a view finder then blit the original image to that with minus co ordinate for that image and only the part that you want to see should be shown - that isnt a very good way though

im sure that screen:blit() accepts about 7 commands max which will do what you want with ease one mo ill try and find out the specific order they are in

EDIT:

screen:blit(x position, y position, full image to use, tile x start position on that image, tile y start position on that image, tile width, tile height)

an example of this would be

lua_image = Image.load("lua_image.png") -- for example 200 x 200 image

screen:blit(10, 10, lua_image, 30, 40, 100, 100) -- blits the image to 10, 10 x and y co-ordinates, tells it to use the lua_image and start 30 across from the start position in the image and 40 down, then takes 100 x 100 pixels of the image and blits that

[Highsight]

its gu and gum commands if i am correct the 3d cube shows most of the commands but if you want to crop an image im sure that there is a much simpler way

for example create a blank image the size that you would like to crop to this will act like a view finder then blit the original image to that with minus co ordinate for that image and only the part that you want to see should be shown - that isnt a very good way though

im sure that screen:blit() accepts about 7 commands max which will do what you want with ease one mo ill try and find out the specific order they are in

EDIT:

screen:blit(x position, y position, full image to use, tile x start position on that image, tile y start position on that image, tile width, tile height)

an example of this would be

lua_image = Image.load("lua_image.png") -- for example 200 x 200 image

screen:blit(10, 10, lua_image, 30, 40, 100, 100) -- blits the image to 10, 10 x and y co-ordinates, tells it to use the lua_image and start 30 across from the start position in the image and 40 down, then takes 100 x 100 pixels of the image and blits that

Er, my code is already set up just like that, but that's not the problem. XD The problem is that the image I want to crop is an image that I get from the screen. What I am trying to do is create a transition between the player playing the game, and the brief pause between each game. So to do that, I need to get a picture of the screen and use that for the cropping process. The only thing is, I would like to be able to do this WITHOUT saving it as a PNG first, I would much rather use it as an Image object, if that is possible.

[yaustar]

Try creating a smaller blank image that is size of the crop and blitting the screen onto the blank image. No idea if it works though.

[FaT3oYCG]

in that case wouldn't cropping_image = screen:save() do the trick and use that ??? not sure but anyway if you dont want to keep the image there is a function in lua to save a file as a temporary file and it is deleted after it has finished being used - you would have to search for that though

EDIT:

oh and yaustar i mentioned that before

for example create a blank image the size that you would like to crop to this will act like a view finder then blit the original image to that with minus co ordinate for that image and only the part that you want to see should be shown - that isn't a very good way though

[yaustar]

screen:save returns nil and ALWAYS saves to the memory stick.
-= Double Post =-

EDIT:

oh and yaustar i mentioned that before

Why wouldn't it be a good way?

[FaT3oYCG]

fair enough oh and i wasn't trying to undermine you sorry if it seemed that way

because it is using minus values what i meant was there may be better ways but i dont like using minus values in my code, most of the time you could use an addition instead just by revising your code but i guess this is an exception

[yaustar]

because it is using minus values what i meant was there may be better ways but i dont like using minus values in my code, most of the time you could use an addition instead just by revising your code but i guess this is an exception

Why don't you like using minus numbers? It really seems a little odd especially in programming.

[FaT3oYCG]

because most of the time using a negative number will make your code more hard to understand and sometimes more complicated than it needs to be

not that this would happen but say for example you wanted to print some text at 10, 10 then you could use this

screen:print(480 - 470, 272 - 262, "text", white)

but that is much harder than just putting

screen:print(10, 10, "text", white)

i just used that as an example but you should get what i mean as when it does occur it is usually with complex code

but as i said that is why i try to avoid using minus numbers where i can

[Grimfate126]

thats just bad programing. you're unnecessarily doing two subtractions every frame. but i dont usually have a problem with minus values, unless they're used the way you mentioned. other than that, they're ok.

[FaT3oYCG]

thats just bad programing. you're unnecessarily doing two subtractions every frame. but i dont usually have a problem with minus values, unless they're used the way you mentioned. other than that, they're ok.

thats my point basically what im trying to say is that i dont like using minuses as they make the code sometimes do unnecesary calculations that is why i try to avoid using them i was only using that as an example to show that i dont use them because it sometimes makes the code unefficient i will use them where needed but as you say if you use a minus where none is needed its bad programming - if you are doing complex coding whith lots of variables and values then you may unnececarily use a subtraction where the value can be obtained by not doing one which is uneficcient coding

if you still dont understand what i mean then dont try to instead read my sig and you will understand why

but anyway i think we have had enough discussion on using minuses on the help thread so lets leave it there

[Andysan]

Hi all,

Am new to Lua and relatively new to programming too i guess, anyway can anoyne help me with this problem please. I am getting the "loop in gettable" error when i try to mute my music. Code below:

-- Activate USB Mode
System.usbDiskModeActivate()

-- Define Color White
white=Color.new(255,255,255)

-- Load Loading Image
loadingImage = Image.load("images/loading.jpg")


-- Print Loading Image as Background
screen:blit(0, 0, loadingImage, false)

screen.waitVblankStart()
screen:print(200,130,"Loading - 0%",white)
screen.flip()


-- Begin Loading All Other Images
backgroundImage = Image.load("images/background.jpg")
screen:clear()
screen:print(200,130,"Loading - 20%",white)
screen.flip()
gameimageImage = Image.load("images/game.jpg")
screen:clear()
screen:print(200,130,"Loading - 40%",white)
screen.flip()
dartImage = Image.load("images/dart.jpg")
screen:clear()
screen:print(200,130,"Loading - 60%",white)
screen.flip()
gameoverImage = Image.load("images/gameover.jpg")
screen:clear()
screen:print(200,130,"Loading - 80%",white)
screen.flip()
themeSound = Sound.load("sounds/theme.wav", true)
splashImage = Image.load("images/splash.jpg")
screen:clear()
screen:print(200,130,"Loading - 100%",white)
screen.flip()

--Pause At 100%
screen.waitVblankStart(60)


--Clear The Screen Of Loading Text
screen:clear()

--Load The Splash Screen
screen:blit(0, 0, splashImage, false)
screen.flip()

--Pause For One Second
screen.waitVblankStart(180)

--Load The Background Image
screen:blit(0, 0, backgroundImage, false)
screen.flip()

--Play The Theme Music
Music.volume(128)
themeSound:play()

--Update The Screen
screen.waitVblankStart()


while true do
pad = Controls.read()
	if pad:start() then
	   break
	end
	if pad:select() then 
      screen:save("screenshot.png") 
  end
		if pad:l() then
		  if themeSound:playing() then
	      themeSound:stop()
	    else
	       themeSound:play()
	    end
		end
end

The screenshot and quit functions mapped to Select and Start respectively work fine, however when i try to stop the music or set Music.volume(0) i get "error - loop in gettable".:Argh:

If anyone can offer some pointers please i would be most grateful.

Many thanks.

[SuperBatXS]

Ok, i haven't seen lua in a while (concept is same though), but here are some tips:

1) Try to indent properly. It helps when you have your code organized.
2) It seems that you are loading a lot of images, but not blitting them.
3) Instead of having a lot of "Loading..." printing, you could make a only one "Loading" printing when "if" blah is true, then change the "%" of loading. For example, if some image finishes loading, update the loading "%".

[Judas]

Also, when blitting an image, you don't need the fourth argument. You only need it if it's true.

[FaT3oYCG]

Hi all,

Am new to Lua and relatively new to programming too i guess, anyway can anoyne help me with this problem please. I am getting the "loop in gettable" error when i try to mute my music. Code below:

-- Activate USB Mode
System.usbDiskModeActivate()

-- Define Color White
white=Color.new(255,255,255)

-- Load Loading Image
loadingImage = Image.load("images/loading.jpg")


-- Print Loading Image as Background
screen:blit(0, 0, loadingImage, false)

screen.waitVblankStart()
screen:print(200,130,"Loading - 0%",white)
screen.flip()


-- Begin Loading All Other Images
backgroundImage = Image.load("images/background.jpg")
screen:clear()
screen:print(200,130,"Loading - 20%",white)
screen.flip()
gameimageImage = Image.load("images/game.jpg")
screen:clear()
screen:print(200,130,"Loading - 40%",white)
screen.flip()
dartImage = Image.load("images/dart.jpg")
screen:clear()
screen:print(200,130,"Loading - 60%",white)
screen.flip()
gameoverImage = Image.load("images/gameover.jpg")
screen:clear()
screen:print(200,130,"Loading - 80%",white)
screen.flip()
themeSound = Sound.load("sounds/theme.wav", true)
splashImage = Image.load("images/splash.jpg")
screen:clear()
screen:print(200,130,"Loading - 100%",white)
screen.flip()

--Pause At 100%
screen.waitVblankStart(60)


--Clear The Screen Of Loading Text
screen:clear()

--Load The Splash Screen
screen:blit(0, 0, splashImage, false)
screen.flip()

--Pause For One Second
screen.waitVblankStart(180)

--Load The Background Image
screen:blit(0, 0, backgroundImage, false)
screen.flip()

--Play The Theme Music
Music.volume(128)
themeSound:play()

--Update The Screen
screen.waitVblankStart()


while true do
pad = Controls.read()
    if pad:start() then
       break
    end
    if pad:select() then 
      screen:save("screenshot.png") 
  end
        if pad:l() then
          if themeSound:playing() then
          themeSound:stop()
        else
           themeSound:play()
        end
        end
end

The screenshot and quit functions mapped to Select and Start respectively work fine, however when i try to stop the music or set Music.volume(0) i get "error - loop in gettable".:Argh:

If anyone can offer some pointers please i would be most grateful.

Many thanks.

other than the fact your code is set out wrong well its in the wrong order - logical order

for a start the Music.volume(128) is before while true do

so threfore if you change it its not true so it will crash

looks like you have some logic and indenting errors

- try fix your logic and indenting and see if it works

EDIT:

here i fixed most of it for you and laid it out better with proper indentations

-- Activate USB Mode - should only be done while testing or creating a game with a game refresh function to start ti again if you save a file currently in use
System.usbDiskModeActivate()

-- Define Color White
white = Color.new(255,255,255)

-- Load Loading Image
loadingImage = Image.load("images/loading.jpg")

-- Load All Other Images
backgroundImage = Image.load("images/background.jpg")
gameimageImage = Image.load("images/game.jpg")
dartImage = Image.load("images/dart.jpg")
gameoverImage = Image.load("images/gameover.jpg")
splashImage = Image.load("images/splash.jpg")
themeSound = Sound.load("sounds/theme.wav", true)


-- Print Loading Image as Background
screen:blit(0, 0, loadingImage, false)
screen.waitVblankStart()

-- display loading text
screen:clear()
screen:print(200,130,"Loading - 0%",white)
screen.flip()
screen:clear()
screen:print(200,130,"Loading - 20%",white)
screen.flip()
screen:clear()
screen:print(200,130,"Loading - 40%",white)
screen.flip()
screen:clear()
screen:print(200,130,"Loading - 60%",white)
screen.flip()
screen:clear()
screen:print(200,130,"Loading - 80%",white)
screen.flip()
screen:clear()
screen:print(200,130,"Loading - 100%",white)
screen.flip()

--Pause At 100% - for 1 second
screen.waitVblankStart(60)

--Clear The Screen Of all previous data
screen:clear()

--"display" The Splash Screen
screen:blit(0, 0, splashImage, false)
screen.flip()

--Pause For One Second - that is three seconds 60 miliseconds in one second
screen.waitVblankStart(180)

-- "display" The Background Image
screen:blit(0, 0, backgroundImage, false)
screen.flip()

--Update The Screen - keep whatever is on the screen untill told not to
screen.waitVblankStart()

while true do

pad = Controls.read()

--Play The Theme Music
Music.volume(128)
themeSound:play()

if pad:start() then
	break
end

if pad:select() then 
	screen:save("screenshot.png") 
end

if pad:l() then
	if themeSound:playing() then
		themeSound:stop()
	else
		themeSound:play()
	end
end

end

here is a simple lua file template aswell

white = color.new(255, 255, 255) -- create white as a colour

oldpad = Controls.read() -- set oldpad as a secondary controller setup

while true do -- while the above is true

pad = Controls.read() -- set pad as a primary controller setup

screen:clear() -- clear anything previously on the screen

-- insert your main code here

-- e.g.
if pad:cross() then
	-- if cross is being held
	screen:print(10, 10, "i pressed cross", white)
end

if pad:cross() and oldpad:cross() ~= pad:cross() then
	-- do something if cross is pressed and not held
end

-- insert your main code here

if Controls.read():start() then -- if you press start exit
	break -- break the current state
end -- end the if

oldpad = pad -- oldpad is the same as pad

screen.flip() -- flip the screen at the end of every while loop - if set right the while loop should be continuous
screen.waitVblankStart() -- keep any of that data on the screen untill specified otherwise

end

thanks