[#51] Ability to print message with any rgb color

[dariodsa]

Files changed

• colourista.cabal
• src/Colourista/IO.hs
• src/Colourista/Pure.hs

New behaviour

Added ability to print message using any colour which can be expressed using classic RGB representation (HEX values). If user provides a hex value with a length lower than 6, that value will be truncated with leading zeroes. So ff will produce a blue colour.

Test

*Colourista> rgbMessage "123456" "Strange colour"
Strange colour
*Colourista> rgbMessage "čć123456" "Strange color"
  🛑 Invalid hex value - čć123456
*Colourista> rgbMessage "ff" "Blue colour"
Blue colour

If the PR is going to be accepted, afterwards I can update README.md to point the users to the new feature.

[vrom911]

Hey @dariodsa ,

Thanks a lot for your contribution!

I have a few comments/ideas I would like to discuss about this solution.

First of all, I see that the rgbMessage takes a String. I would propose to take 3 Word8 arguments instead and leave all the colour handling to the sRGB24 function of the package.

Also, Haskell supports Hex numbers on a lexical level, so no need to implement a parser here, it should be possible to write 0x.... 🙂

Also, I don't think that the incorrect colour should lead to error. We need to think better, what to do in this case. Maybe just warning and uncoloured text? 🤔

[dariodsa]

Thank you @vrom911 for your comments. Indeed, code now looks much more concise. 😄
Currently, I don't know to handle or even catch "overflow" errors using Word8. Currently, Haskell is kind enough to return a warning when some tries to send literal which is not in the given range.

<interactive>:34:12: warning: [-Woverflowed-literals]
    Literal 2293760 is out of the GHC.Word.Word8 range 0..255

So, now when someone tries to run a function with too high or too low literals, Haskell simply cuts its value and continue using it like it is Word8. To sum up, I think that this new error handling is much more acceptable to the end-user because the message is going to be written including the warning errors.

*Colourista> rgbMessage 0x00 0x00 0xff "I am blue."
I am blue.
*Colourista> rgbMessage 0x00 0xff 0x00 "Forest, grass, grasshopper."
Forest, grass, grasshopper.
*Colourista> rgbMessage 0xfda 0xff 0xdaa "Too much, I can't handle it."

<interactive>:39:12: warning: [-Woverflowed-literals]
    Literal 4058 is out of the GHC.Word.Word8 range 0..255

<interactive>:39:23: warning: [-Woverflowed-literals]
    Literal 3498 is out of the GHC.Word.Word8 range 0..255
Too much, I can't handle it.

[chshersh]

Hey @dariodsa, the implementation looks good 👍🏻 I left a few comments with some remaining improvements. And I think that relying on GHC warnings (overflow literals specifically) is a good way to go.

Ideally, for the best UI, we would like to have a compile-time compilation and allow literals only of the form 0xABCDEF but there's no easy way to achieve this in Haskell without requiring some heavyweight machinery. So API like rgbMessage 0x00 0x00 0xff looks good for me 👍🏻

[chshersh]

Hey, @dariodsa. I see there are still some conflicts in this branch with the main branch. I believe, you need to resolve them, before this branch can be merged. You can do this by either rebasing on top of main and resolving all conflicts or merging the main branch to this one. I prefer rebasing, but feel free to choose whatever method you find more convenient 🙂

[chshersh]

Hey @dariodsa! The changes in this PR look great 👍🏻 Thanks for resolving conflicts! I see, that the code mentions the Colourista.Mode import and the HasColourMode constraint in some functions. Since those functions and modules are no longer exist, they can be removed.