PSPDFStackViewLayout

Objective-C


@interface PSPDFStackViewLayout : PSPDFDocumentViewLayout

Swift

class StackViewLayout : PDFDocumentViewLayout

The stack view layout produces a similar look than a UIStackView. It lays out its content either in a vertical or horizontal line.

By default all items in a stack view layout have the same size and this size is deduced from the viewport of the layout.

Note

A stack view layout can only be used in a document view. It will not work properly when assigned to an arbitrary collection view.

Subclassing

If you want to create your own document view layout, subclassing PSPDFStackViewLayout is a good starting point. As long as you stick with the general idea that content only expands in one direction, all you need to override to customize the layout is the layoutAttributesForItemAtIndexPath: method. It is used by the other methods that deal with layout attributes.

If you just want to change the size of items, overriding sizeForSpreadAtIndex: should be enough.

Make sure when overriding layoutAttributesForItemAtIndexPath: to get the size for each attribute from sizeForSpreadAtIndex: as other parts of the layout are using this as well.

  • The insets to apply to the layout.

    While interitemSpacing defines the space between two consecutive items, the contentInset defines the top, left, bottom, and right inset define — depending on the concrete implementation — either the spacing around all items or around each individual item.

    For ScrollPerSpreadLayout, the contentInset defines the space between each item and the edge of the scrollable area.

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└─────────────────────────────────┘

    For ContinuousScrollingLayout, the contentInset defines the space between all items and the edge of the scrollable area. E.g., for a horizontally scrolling layout, the left inset will define the space before the first item, the right inset will define the space after the last item, while the top and bottom insets will define space to the edge of the scrollable area for each item.

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└─────────────────────────────────┘

    Subclasses can override this to change the content inset that is needed to layout spreads properly. If you override this, make sure to apply the additionalContentInsets or otherwise setting additional content insets will have no effect.

    See

    interitemSpacing

    See

    additionalContentInsets

    Declaration

    Objective-C

    @property (nonatomic, readonly) UIEdgeInsets contentInsets;

    Swift

    var contentInsets: UIEdgeInsets { get }

  • Additional insets to apply to the layout’s content.

    These insets will be added to the overall content insets. Users of the layout can set insets here to customize the appearance of the layout.

    Defaults to .zero.

    See

    contentInsets

    Declaration

    Objective-C

    @property (nonatomic) UIEdgeInsets additionalContentInsets;

    Swift

    var additionalContentInsets: UIEdgeInsets { get set }

  • The spacing between two items alongside the scroll direction.

    Defaults to 20 for ScrollPerSpreadLayout and 10 for ContinuousScrollingLayout.

    See

    contentInsets

    Declaration

    Objective-C

    @property (nonatomic) CGFloat interitemSpacing;

    Swift

    var interitemSpacing: CGFloat { get set }

  • The layout direction in which the stack view layout should position its content.

    Declaration

    Objective-C

    @property (nonatomic) PSPDFStackViewLayoutDirection direction;

    Swift

    var direction: StackViewLayout.Direction { get set }

Subclassing

  • The spread size for the passed in spreadIndex.

    This method can be subclassed to alter the size of a spread. If the size of a spread changes at runtime, be sure to invalidate the spread index in question.

    Defaults to the spread size scaled so that it fits the viewport’s size, inset by the scrollViewFrameInsets and contentInsets. This means the returned size will always fit on screen and does not require any scrolling.

    Declaration

    Objective-C

    - (CGSize)sizeForSpreadAtIndex:(NSInteger)spreadIndex;

    Swift

    func sizeForSpread(at spreadIndex: Int) -> CGSize