yauhenidrobau · July 9, 2018 19:29
diff --git a/appropriate thumbnail size for pages of any aspect ratio in any containing view size b/appropriate thumbnail size for pages of any aspect ratio in any containing view size
 /// Returns an appropriate size for page thumbnails.
 ///
 /// - Parameters:
 ///   - pageSize: The page size. Only the aspect ratio is considered, so the units are irrelevant.
 ///   - containerSize: The size of the container that will display the thumbnails in points.
 ///   - interitemSpacing: The padding between thumbnails in points.
 /// - Returns: An appropriate size for thumbnails in points.
 func automaticThumbnailSize(for pageSize: CGSize, containerSize: CGSize, interitemSpacing: CGFloat) -> CGSize {
    // What is the total available area?
    let containerArea = containerSize.width * containerSize.height

    // We decided showing around 10 thumbnails is enough to be useful without being overwhelming.
    let approximateNumberOfThumbnailsToShow: CGFloat = 10

    // Divide the available area by the target number of thumbnails
    // to get the approximate area for each thumbnail.
    let approximateThumbnailArea = containerArea / approximateNumberOfThumbnailsToShow

    // We want to handle pages of any aspect ratio (portrait or landscape).
    let pageAspectRatio = pageSize.width / pageSize.height

    //                   area = width × height
    //           aspect ratio = width / height
    // => area × aspect ratio = width × width
    let approximateThumbnailWidthSquared = approximateThumbnailArea * pageAspectRatio

    // Take the square root of the value calculated above to find the approximate thumbnail width.
    let approximateThumbnailWidth = sqrt(approximateThumbnailWidthSquared)

    // We need a whole number of columns.
    let numberOfColumns = round(containerSize.width / approximateThumbnailWidth)

    // Account for padding between the thumbnails.
    let availableWidth = containerSize.width - interitemSpacing * (numberOfColumns - 1)

    // Divide the available width between the columns.
    let thumbnailWidth = availableWidth / numberOfColumns

    // Finally we have the thumbnail size. Round to a number of points or pixels.
    // We must round down. Otherwise, the thumbnails might not fit.
    return CGSize(width: floor(thumbnailWidth), height: floor(thumbnailWidth / pageAspectRatio))
 }
	/// Returns an appropriate size for page thumbnails.
	///
	/// - Parameters:
	/// - pageSize: The page size. Only the aspect ratio is considered, so the units are irrelevant.
	/// - containerSize: The size of the container that will display the thumbnails in points.
	/// - interitemSpacing: The padding between thumbnails in points.
	/// - Returns: An appropriate size for thumbnails in points.
	func automaticThumbnailSize(for pageSize: CGSize, containerSize: CGSize, interitemSpacing: CGFloat) -> CGSize {
	// What is the total available area?
	let containerArea = containerSize.width * containerSize.height

	// We decided showing around 10 thumbnails is enough to be useful without being overwhelming.
	let approximateNumberOfThumbnailsToShow: CGFloat = 10

	// Divide the available area by the target number of thumbnails
	// to get the approximate area for each thumbnail.
	let approximateThumbnailArea = containerArea / approximateNumberOfThumbnailsToShow

	// We want to handle pages of any aspect ratio (portrait or landscape).
	let pageAspectRatio = pageSize.width / pageSize.height

	// area = width × height
	// aspect ratio = width / height
	// => area × aspect ratio = width × width
	let approximateThumbnailWidthSquared = approximateThumbnailArea * pageAspectRatio

	// Take the square root of the value calculated above to find the approximate thumbnail width.
	let approximateThumbnailWidth = sqrt(approximateThumbnailWidthSquared)

	// We need a whole number of columns.
	let numberOfColumns = round(containerSize.width / approximateThumbnailWidth)

	// Account for padding between the thumbnails.
	let availableWidth = containerSize.width - interitemSpacing * (numberOfColumns - 1)

	// Divide the available width between the columns.
	let thumbnailWidth = availableWidth / numberOfColumns

	// Finally we have the thumbnail size. Round to a number of points or pixels.
	// We must round down. Otherwise, the thumbnails might not fit.
	return CGSize(width: floor(thumbnailWidth), height: floor(thumbnailWidth / pageAspectRatio))
	}
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