override suspend fun onWrite()

in printing/src/main/java/com/zachklipp/richtext/ui/printing/ComposePrintAdapter.kt [71:121]
33 lines of code
1 McCabe index (conditional complexity)

  override suspend fun onWrite(
    pages: Array<out PageRange>,
    destination: ParcelFileDescriptor
  ): Array<out PageRange> {
    var currentPageIndex by mutableStateOf(0)
    val pageCountDeferred = CompletableDeferred<Int>()

    // Initialize the composition, and reuse the same composition to render all the pages.
    composeToPdf(activity, pdfDocument, pageDpi, content = {
      // This is the actual composable that will be rendered to the PDF.
      // Paged tries to ensure that we don't cut off leaf composables in the middle.
      Paged(
        pageIndex = currentPageIndex,
        pageModifier = pageModifier,
        drawBreakpoints = printBreakpoints,
        onPageLayout = { pageCountDeferred.complete(it) },
        content = content
      )
    }) {
      // We need to know the total page count before we can start iterating. This waits for the
      // first composition and frame to commit.
      val pageCount = pageCountDeferred.await()

      (0 until pageCount).asSequence()
        .filter { page -> pages.any { page in it.start..it.end } }
        .forEach { pageNumber ->
          val page = pdfDocument.startPage(pageNumber)

          // Update the Paged to "flip" to the page.
          currentPageIndex = pageNumber

          // Render the page to the PDF. This function will automatically wait for the next frame to
          // finish drawing. It also does not do any IO, so we don't need to switch dispatchers.
          composePage(page)
          pdfDocument.finishPage(page)

          // We're on the main thread, so be a good citizen.
          // Also ensures we handle cancellation in a timely fashion.
          yield()
        }
    }

    // The PDF currently only exists in memory, so to dump it to the printing system we use a
    // background thread.
    withContext(ioDispatcher) {
      @Suppress("BlockingMethodInNonBlockingContext")
      pdfDocument.writeTo(FileOutputStream(destination.fileDescriptor))
    }
    pdfDocument.close()
    return pages
  }