ArChessBoardScreen.kt

package ch.epfl.sdp.mobile.ui.game.ar

import androidx.compose.runtime.*
import androidx.compose.ui.Modifier
import androidx.compose.ui.platform.LocalView
import androidx.compose.ui.semantics.contentDescription
import androidx.compose.ui.semantics.semantics
import androidx.compose.ui.viewinterop.AndroidView
import ch.epfl.sdp.mobile.state.LocalLocalizedStrings
import ch.epfl.sdp.mobile.ui.game.ChessBoardState
import com.google.ar.core.Anchor
import com.gorisse.thomas.lifecycle.lifecycleScope
import io.github.sceneview.ar.ArSceneView

private const val BoardScale = 0.2f

/**
 * Composable used to display a AR chess board
 *
 * @param state The state of the game, it's used to track the modification on the game
 * @param modifier modifier the [Modifier] for this composable.
 */
@Composable
fun <Piece : ChessBoardState.Piece> ArChessBoardScreen(
    state: ChessBoardState<Piece>,
    modifier: Modifier = Modifier
) {
  val view = LocalView.current
  val strings = LocalLocalizedStrings.current

  var chessScene by remember { mutableStateOf<ChessScene<Piece>?>(null) }

  // Keep the screen on only for this composable
  DisposableEffect(view) {
    view.keepScreenOn = true
    onDispose { view.keepScreenOn = false }
  }

  AndroidView(
      factory = { context ->

        // Create the view
        val arSceneView = ArSceneView(context)

        chessScene =
            ChessScene(context, view.lifecycleScope, state.pieces).apply {

              // Scale the board
              this.scale(BoardScale)

              // Place the chess board on the tapped position.
              arSceneView.onTouchAr =
                  { hitResult, _ ->
                    anchorOrMoveBoard(arSceneView, chessScene, hitResult.createAnchor())
                  }
            }

        arSceneView
      },
      modifier = modifier.semantics { this.contentDescription = strings.arContentDescription },
      update = { chessScene?.update(state.pieces) })
}

/**
 * If not already in the scene, the board will be added. Update the board anchor with the given one
 * and change the displayed position
 *
 * @param arSceneView The view where the scene will be displayed
 * @param chessScene The scene that contains the boards node
 * @param anchor The (new) board's anchor position
 */
private fun <Piece : ChessBoardState.Piece> anchorOrMoveBoard(
    arSceneView: ArSceneView,
    chessScene: ChessScene<Piece>?,
    anchor: Anchor
) {

  val currentChessScene = chessScene ?: return

  currentChessScene.let {
    // Add only one instance of the node
    if (!arSceneView.children.contains(it.boardNode)) {
      arSceneView.addChild(it.boardNode)
    }
    it.boardNode.anchor = anchor
  }
}