How to draw a chess board in gloss haskell?

Question

I am just started haskell gloss. I learnt a little about it functions. I am trying to draw a chess board in haskell. The main problem is that everything is being drawn in the center. If I used the function translate the board is being draw at random position. That's probably because translate moves from moves the distance given from current position not to the exact point which is given.

Is there a way in gloss haskell so that we can move to a specific point like setTransform or translateTo. Or is there any function which tells coordinates of current point at which we are at.

module Main where

import Graphics.Gloss
import Lib (someFunc)

blockSize :: Float
blockSize = 50

board :: [[Int]]
board = replicate 8 (replicate 8 0)

drawTile :: Float -> Float -> Color -> Picture
drawTile a b col = translate a b $ color col $ rectangleSolid blockSize blockSize

-- drawRow :: Int -> Pictur
-- drawRow =

toInt :: Float -> Integer
toInt = round

getColor :: Float -> Float -> Color
getColor i j = if even $ toInt ((i * 8) + j) then red else blue

screenHeight = 700

screenWidth = 1000

drawing :: Picture
drawing = pictures [drawTile (row * blockSize) (e * blockSize) (getColor row e) | row <- [0 .. 8], e <- [0 .. 8]]

-- moveToStart = viewPortTranslate

main :: IO ()
main = display (InWindow (show board) (screenWidth, screenHeight) (10, 10)) white (translate 0 0 drawing)

Edit: I don't want to fix this specific problem by using some math tricks. What I want to know is that how can I translate to a specfic position. Like when I do someFunc 0 0 the position should go to 0 0 top right corner.

If its not possible please tell the way to get the current transform point.

I can not reproduce this: If I replace the `getColor` with `even $ toInt (i + j)`, I get https://imgur.com/a/vuqYe8d — Willem Van Onsem, Dec 29 '20 at 14:06
@WillemVanOnsem You can't understand my question I guess. The order of board is not a problem. The problem is its drawn in center. While I want it to start from top left corner. — Maheer Ali, Dec 29 '20 at 14:10
ah, but then you should simply translate it 4 blocks to the left and bottom, so `drawing = translate (-4*blockSize) (-4*blocksize) $ pictures ...`. — Willem Van Onsem, Dec 29 '20 at 14:11
@WillemVanOnsem That's kind of center of window. I want it at top right corner — Maheer Ali, Dec 29 '20 at 14:15
@WillemVanOnsem I have edited and rephrased my question. Please check it out. — Maheer Ali, Dec 29 '20 at 14:21
then you should look at the window size as well, so `translate (fromIntegral screenWidth/2-8.5*blockSize) (fromIntegral screenHeight/2-8.5*blockSize) $ pictures ...` (this is for a 9x9 board, since you used `[0 .. 8]`, or you can use `translate (fromIntegral screenWidth/2-7.5*blockSize) (fromIntegral screenHeight/2-7.5*blockSize) $ pictures` for a 8x8 board. — Willem Van Onsem, Dec 29 '20 at 14:21
@WillemVanOnsem Yes I am trying to do that. But isn't there any function for what I asked? — Maheer Ali, Dec 29 '20 at 14:23

score 1 · Accepted Answer · answered Dec 29 '20 at 21:04

There is no existing Gloss function that will take an arbitrary picture and move it so its top-left corner is in the top-left corner of the screen. All existing transformation functions in Gloss are relative, so there's no way to make an "absolute" move to a specific point.

The best you can probably do is arrange to draw your picture so its origin matches its top-left corner, and then translate it up and left by half the screen height and width.

import Graphics.Gloss

-- chess board with top-left corner at (0,0), one unit in width and height
chess = scale (1/8) (1/8) $ pictures [square x y | x <- [0..7], y <- [0..8]]
  where square x y =
          Color (if even (x+y) then red else black) $
          translate (fromIntegral x+0.5) (-fromIntegral y -0.5) $ rectangleSolid 1 1

main = display (InWindow "Layout" (1000,700) (10,10)) white $
  -- scale to a 700x700 square (with origin still at top-level corner)
  -- then translate origin from default position at center of window
  -- to top-left corner, by moving half the window width and height
  translate (-500) 350 $ scale 700 700 chess

Thanks for answer. Two side questions, 1) Is there any library better than gloss for 2d graphics(by better I mean more features) 2) Is haskell a good for making 2d apps? — Maheer Ali, Dec 30 '20 at 03:15
I think `diagrams` (see [gallery](https://archives.haskell.org/projects.haskell.org/diagrams/gallery.html)) is probably the most sophisticated 2D drawing package I've seen, but I haven't used it much. — K. A. Buhr, Jan 03 '21 at 19:53

How to draw a chess board in gloss haskell?

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