Hints and Tips

Dave

Posted this in response to a question elsewhere and @pianofire rightly suggested it be put in hints and tips.

Here is a really handy breakPoint function used by JonBoy in many of his programs. Really useful if you want to stop your program at any point check a value/values:

function breakPoint( info )
    press = false
    while !press loop
        j = controls(0)
        if j.x then 
            press = true
        endif
        clear()
        print( "Breakpoint: ", info )
        print( "Press X to continue" )
        update()
    repeat
    sleep( 0.2 )
return void

Simply call the function, pass it what you want to see and Bob is your proverbial uncle.

Dave

Hi folks, just to let you know as I don't think this is as apparent as it should be...

You can copy and paste code between projects. When you copy code to the clipboard, the clipboard is kept when you open a new project.

This allows you to "transfer" important sections of code, for example, a whole load of music data, between projects.

If it's images or maps you want to transfer, you can do this from the image and map editor file managers. Press the X button when viewing the thumbnail for an image or map, then select "copy image" or "copy map", then choose the project file to copy to!

pianofire

I am not sure how useful this is really. I was experimenting with saving variable length data to a file and came up with this:

text = [ "The", "Quick", "Brown", "Fox" ]

// Write to file
handle=open()
entries = len(text)
write(handle, padstr(str(entries), 4, " "))
for i = 0 to entries loop
  write(handle, padstr(str(len(text[i])), 4, " "))
  write(handle, text[i])
repeat
close(handle)

//Read back from file
handle = open()
entries = int(read(handle, 4))
for i = 0 to entries loop
  strlen = int(read(handle, 4))
  print(read(handle, strlen),"*")
repeat
 
update()
sleep(3)
 
function padstr(string, padlen, padchar)
  result = string
  while len(result) < padlen loop
    result = result + padchar
  repeat
return result

pianofire

You can create sprites in code by using setDrawTarget to draw onto an image rather than the screen buffer and then create a sprite from the image

palette = [ black, red, white, grey, blue, yellow, green, deeppink ]

shipData = [ 0, 0, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
             0, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
             1, 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0,
             0, 1, 7, 7, 3, 3, 3, 3, 3, 4, 4, 5, 0, 0, 0,
             1, 3, 7, 7, 7, 7, 3, 3, 3, 3, 3, 3, 3, 2, 6,
             0, 0, 7, 7, 7, 3, 2, 6, 0, 0, 0, 0, 0, 0, 0 ]

shipImage = createImage(15, 6, false, image_rgb)
setDrawTarget(shipImage)
for x = 0 to 15 loop
  for y = 0 to 6 loop
    pixel = shipData[ y * 15 + x ]
    if pixel > 0 then
      plot(x + 1, y + 1, palette[pixel])
    endif
  repeat
repeat
update()

ship = createSprite()
setSpriteImage(ship, shipImage)
setSpriteScale(ship, { 10, 10 } )
setSpriteLocation(ship, gwidth() / 2, gheight() / 2)

loop
  drawSprites()
  update()
repeat

Jaywalker

@pianofire So you are storing metadata file information in the 4 first chars and that way you know how long the contents are. Good approach!

Nisse5

@pianofire Thanks for the code sample regarding creating the sprite in code. However, we need to know if the pixel-based coordinate system is 1-based or 0-based, as discussed elsewhere. Your code will obviously break it it's changed to 0-based.

pianofire

Yes it appears to be 1-based at the moment. I only noticed that this morning

Discostew

@pianofire That's a similar approach to using uploadImage(), but rather than referencing the colors directly in the Data, you index to them and plot the pixels yourself. Honestly though, I wish we had the ability to load indexed-images and not just direct-color images, and then be able to edit the palette to alter all referenced pixels on the next draw call, like how the NES, SNES, Genesis, etc did it.

(Just to note, your code might error out due to out-of-boundaries, as shipData only contains 15x6 entries, but plotting can reference 16x16 entries)

pianofire

@Discostew agreed but this way you can use any of the drawing commands not just plot. Why don't you add the palette colour image request to the wishlist?

Discostew

@pianofire Have to see whether I requested the indexed-image support in the Wishlist. I think I did.

pianofire

@Discostew Yes you did https://fuzearena.com/forum/topic/11/wishlist/11

Nisse5

If you want to be able to return from a function at any point, here's an approach I also use for various other programming languages.
By using a "one-pass loop", you can make the function behave as if it has a return statement from any place. (The technique can be used for other situations than function returns as well.)

Here's a simple example:

function myFunction(arg)
    retval = false
    while true loop
       if (arg <= 0) then break endif   // First "function return"
       print("Argument is positive\n")
       if (arg > 100) then break endif // Second "function return"
       print("Argument is less than 100\n")
       if (arg % 10) then break endif // Third "function return"
       print("Argument is not divisible by 10\n")
       // And so on...
       retval = true
       break // This line is crucial, otherwise it becomes an endless loop!
    repeat
return retval
// End of function

pico8-jihem

Hello, I made a console to facilitate debugging. Let me know if you're interrested in. It's a shared program.

Nisse5

@pico8-jihem I tested your debug console right now. Very handy!

Feature request: how about d-pad up/down to browse up/down? D-pad down would basically be the same as the A button.

Discostew

@Nisse5 It's good, but once you get into utilizing actual loops in a function, including nested ones, and you want to have the function return from within those, you'll have to make a break case after each one.

Spacemario

I've wrapped up a first version of my template program, which could be used as the start of a game! It displays graphics, gets user input, and plays music plus sound effects. It even "filters" the input with a simple polling implementation, which is nice when you don't want menu cursors going ninety miles per hour. You can see it via my friend code, feel free for anyone to add me:

SW-1537-8645-5886

One caveat about the polling: If I call "setTimer" only when a button is pressed, like should happen, I get a very weird error. So in the template, I'm setting the timer every frame: not quite right, but it doesn't crash.

In my other shared project, the polling code works perfectly, and I copy and pasted it from there. Weird! I'll do a separate post about this in the future if I dig more, and it doesn't look like a bug in my own code.

Zero Division

@Discostew The string slice tricks you posted came in handy!

Zero Division

On the Programs screen, you can toggle between the example programs and your own programs from the keyboard using CTRL-R and CTRL-L. Handy to avoid having to reach for a controller.

Wanderer1412

I don't think you actually need the CTRL key. Just "r" or "l" on the keyboard works for me.

Discostew

One thing to take into account when working with any language that runs under an interpreter is that every character in code counts towards CPU usage. For instance, a variable name that is 16 characters long is going to take longer to parse in the interpreter prior to processing its contents than a variable name that's only 4 characters long. I do believe that comments are ignored, so they shouldn't interfere with the parsing scheme, thus won't affect CPU usage.

~~Just be sure to comment on what things do if you do decide to shorten variable names. Don't want to forget what something does because the name becomes less readable.~~

I was quick in my assumption that this was the case, but it is not. Variable name length doesn't have an impact on speed.