Configuring Scroll Directions and Page Transitions in Our Viewer

You can configure the page transition, scroll direction, and scroll mode of a PDFViewController in PDFConfiguration (see the PDF configuration guide for more information).

In SettingsExample from the Catalog app, you’ll see a complete example of how these properties interact together in the context of a PDFSettingsViewController. A PDFSettingsViewController is used to change key UX settings that are configurable via the PDFConfiguration.settingsOptions property.

For the best user experience, we recommend using one of the following two combinations of settings.

Book/Magazine-Style Scrolling

let configuration = PDFConfiguration { builder in
    builder.scrollDirection = .horizontal
    builder.pageTransition = .scrollPerSpread
    builder.pageMode = .automatic
    builder.spreadFitting = .fit
}

This will show two pages at a time when there is sufficient space (typically on iPad in landscape), and one page at a time in all other situations.

Continuous Vertical Scrolling

let configuration = PDFConfiguration { builder in
    builder.scrollDirection = .vertical
    builder.pageTransition = .scrollContinuous
    builder.pageMode = .single
    builder.spreadFitting = .adaptive
}

This will show pages fit to the window size in most cases or filling the width on iPhone in landscape.

Valid Combinations

You need to be aware of the following constraints when using the PDFConfiguration properties (pageTransition, scrollDirection, and pageMode) simultaneously.

Per-Spread Scrolling

If the page transition is PageTransition.scrollPerSpread, there are no constraints:

let configuration = PDFConfiguration { builder in
	// When the page transition is `scrollPerPage`.
	builder.pageTransition = .scrollPerSpread
	builder.scrollDirection = .vertical // Can also be `.horizontal`.
	builder.pageMode = .single // Can also be `.double` or `.automatic`.
}
PSPDFConfiguration *configuration = [PSPDFConfiguration configurationWithBuilder:^(PSPDFConfigurationBuilder *builder) {
	// When the page transition is `PSPDFPageTransitionScrollPerSpread`.
	builder.pageTransition = PSPDFPageTransitionScrollPerSpread;
	builder.scrollDirection = PSPDFScrollDirectionVertical; // Can also be `PSPDFScrollDirectionHorizontal`.
	builder.pageMode = PSPDFPageModeSingle; // Can also be `PSPDFPageModeDouble` or `PSPDFPageModeAutomatic`.
}];

Continuous Scrolling

If the page transition is PageTransition.scrollContinuous:

let configuration = PDFConfiguration { builder in
	// When the page transition is `scrollContinuous`.
	builder.pageTransition = .scrollContinuous
	builder.scrollDirection = .vertical // Can also be `.horizontal`.
	builder.pageMode = .single // Setting a value to `pageMode` will only be honored if `scrollDirection` is `.vertical`. It will be forced to single otherwise.
}
PSPDFConfiguration *configuration = [PSPDFConfiguration configurationWithBuilder:^(PSPDFConfigurationBuilder *builder) {
	// When the page transition is `PSPDFPageTransitionScrollContinuous`.
	builder.pageTransition = PSPDFPageTransitionScrollContinuous;
	builder.scrollDirection = PSPDFScrollDirectionVertical; // Can also be `PSPDFScrollDirectionHorizontal`.
	builder.pageMode = PSPDFPageModeSingle; // Setting a value to `pageMode` will only be honored if `scrollDirection` is `PSPDFScrollDirectionVertical`. It will be forced to `PSPDFPageModeSingle` otherwise.
}];

Page Curl

If the page transition is PageTransition.curl:

let configuration = PDFConfiguration { builder in
	// When the page transition is `curl`.
	builder.pageTransition = .curl
	builder.scrollDirection = .horizontal // Setting a value to the `scrollDirection` property will be ignored. It will be forced to `.horizontal`.
	builder.pageMode = .single // Can also be `.double` or `.automatic`.
}
PSPDFConfiguration *configuration = [PSPDFConfiguration configurationWithBuilder:^(PSPDFConfigurationBuilder *builder) {
	// When the page transition is `PSPDFPageTransitionCurl`.
	builder.pageTransition = PSPDFPageTransitionCurl;
	builder.scrollDirection = PSPDFScrollDirectionHorizontal; // Setting a value to the `scrollDirection` property will be ignored. It will be forced to `PSPDFScrollDirectionHorizontal`.
        builder.pageMode = PSPDFPageModeSingle; // Can also be `PSPDFPageModeDouble` or `PSPDFPageModeAutomatic`.
}];

Persisting the Settings Options with User Defaults

You can persist the settings options for your PDFSettingsViewController in your app’s UserDefaults.

Saving the Settings Options

You can save the settings in your app’s user defaults in PDFViewControllerDelegate.pdfViewControllerDidDismiss(_:), like so:

func pdfViewControllerDidDismiss(_ pdfController: PDFViewController) {
	// Persist the settings options in the user defaults.
	let defaults = UserDefaults.standard
	defaults.set(pdfController.configuration.pageTransition.rawValue, forKey: "pageTransition")
	defaults.set(pdfController.configuration.pageMode.rawValue, forKey: "pageMode")
	defaults.set(pdfController.configuration.scrollDirection.rawValue, forKey: "scrollDirection")
	defaults.set(pdfController.configuration.spreadFitting.rawValue, forKey: "spreadFitting")
}
- (void)pdfViewControllerDidDismiss:(PSPDFViewController *)pdfController {
	// Persist the settings options in the user defaults.
	NSUserDefaults *defaults = NSUserDefaults.standardUserDefaults;
	[defaults setInteger:pdfController.configuration.pageTransition forKey: @"pageTransition"];
	[defaults setInteger:pdfController.configuration.pageMode forKey: @"pageMode"];
	[defaults setInteger:pdfController.configuration.scrollDirection forKey: @"scrollDirection"];
	[defaults setInteger:pdfController.configuration.spreadFitting forKey: @"spreadFitting"];
}

Restoring the Settings Options

You can restore the saved settings options from your app’s user defaults in your PDFConfiguration, as seen below:

let configuration = PDFConfiguration { builder in
	// Restore the settings from the user defaults.
	let defaults = UserDefaults.standard
	builder.pageTransition = PageTransition(rawValue: UInt(defaults.integer(forKey: "pageTransition")))!
	builder.pageMode = PageMode(rawValue: UInt(defaults.integer(forKey: "pageMode")))!
	builder.scrollDirection = ScrollDirection(rawValue: UInt(defaults.integer(forKey: "scrollDirection")))!
	builder.spreadFitting = PDFConfiguration.SpreadFitting(rawValue: defaults.integer(forKey: "spreadFitting"))!
}
PSPDFConfiguration *configuration = [PSPDFConfiguration configurationWithBuilder:^(PSPDFConfigurationBuilder *builder) {
	// Restore the settings from the user defaults.
	NSUserDefaults *defaults = NSUserDefaults.standardUserDefaults;
	builder.pageTransition = [defaults integerForKey:@"pageTransition"];
	builder.pageMode = [defaults integerForKey:@"pageMode"];
	builder.scrollDirection = [defaults integerForKey:@"scrollDirection"];
	builder.spreadFitting = [defaults integerForKey:@"spreadFitting"];
}];

For more details and sample code, take a look at PersistViewSettingsExample.swift from the Catalog app.