Add offsetFirstPage preference for fixed-layout EPUBs (#697)

Author: mickael-menu

CHANGELOG.md

@@ -10,6 +10,7 @@ All notable changes to this project will be documented in this file. Take a look
 
 * Support for displaying Divina (image-based publications like CBZ) in the fixed-layout EPUB navigator.
 * Bitmap images in the EPUB reading order are now supported as a fixed layout resource.
+* Added `offsetFirstPage` preference for fixed-layout EPUBs to control whether the first page is displayed alone or alongside the second page when spreads are enabled.
 
 #### Streamer
 

Sources/Navigator/EPUB/EPUBFixedSpreadView.swift

@@ -47,7 +47,7 @@ final class EPUBFixedSpreadView: EPUBSpreadView {
         scrollView.backgroundColor = UIColor.clear
 
         // Loads the wrapper page into the web view.
-        let spreadFile = "fxl-spread-\(spread.spread ? "two" : "one")"
+        let spreadFile = "fxl-spread-\(viewModel.spreadEnabled ? "two" : "one")"
         if
             let wrapperPageURL = Bundle.module.url(forResource: spreadFile, withExtension: "html", subdirectory: "Assets"),
             var wrapperPage = try? String(contentsOf: wrapperPageURL, encoding: .utf8)
@@ -107,7 +107,7 @@ final class EPUBFixedSpreadView: EPUBSpreadView {
         // to be executed before the spread is loaded.
         let spreadJSON = spread.jsonString(
             forBaseURL: viewModel.publicationBaseURL,
-            readingOrder: viewModel.readingOrder
+            readingProgression: viewModel.readingProgression
         )
         webView.evaluateJavaScript("spread.load(\(spreadJSON));")
     }

Sources/Navigator/EPUB/EPUBNavigatorViewController.swift

@@ -399,7 +399,7 @@ open class EPUBNavigatorViewController: InputObservableViewController,
 
         if needsReloadSpreadsOnActive {
             needsReloadSpreadsOnActive = false
-            reloadSpreads(force: true)
+            reloadSpreads()
         }
     }
 
@@ -420,7 +420,7 @@ open class EPUBNavigatorViewController: InputObservableViewController,
 
         applySettings()
 
-        _reloadSpreads(force: true)
+        _reloadSpreads()
 
         onInitializedCallbacks.complete()
     }
@@ -556,7 +556,7 @@ open class EPUBNavigatorViewController: InputObservableViewController,
         }
 
         paginationView.isScrollEnabled = isPaginationViewScrollingEnabled
-        reloadSpreads(force: true)
+        reloadSpreads()
     }
 
     private var spreads: [EPUBSpread] = []
@@ -568,7 +568,7 @@ open class EPUBNavigatorViewController: InputObservableViewController,
 
     private var needsReloadSpreadsOnActive = false
 
-    private func reloadSpreads(force: Bool) {
+    private func reloadSpreads() {
         guard
             state != .initializing,
             isViewLoaded
@@ -585,16 +585,14 @@ open class EPUBNavigatorViewController: InputObservableViewController,
             return
         }
 
-        _reloadSpreads(force: force)
+        _reloadSpreads()
     }
 
-    private func _reloadSpreads(force: Bool) {
+    private func _reloadSpreads() {
         let locator = currentLocation
 
         guard
             let paginationView = paginationView,
-            // Already loaded with the expected amount of spreads?
-            force || spreads.first?.spread != viewModel.spreadEnabled,
             on(.load(locator))
         else {
             return
@@ -604,7 +602,8 @@ open class EPUBNavigatorViewController: InputObservableViewController,
             for: publication,
             readingOrder: readingOrder,
             readingProgression: viewModel.readingProgression,
-            spread: viewModel.spreadEnabled
+            spread: viewModel.spreadEnabled,
+            offsetFirstPage: viewModel.offsetFirstPage
         )
 
         let initialIndex: ReadingOrder.Index = {
@@ -1256,7 +1255,7 @@ extension EPUBNavigatorViewController: EPUBSpreadViewDelegate {
     }
 
     func spreadViewDidTerminate() {
-        reloadSpreads(force: true)
+        reloadSpreads()
     }
 }
 

Sources/Navigator/EPUB/EPUBNavigatorViewModel.swift

@@ -225,6 +225,7 @@ final class EPUBNavigatorViewModel: Loggable {
                 || oldSettings.scroll != newSettings.scroll
                 || oldSettings.spread != newSettings.spread
                 || oldSettings.fit != newSettings.fit
+                || oldSettings.offsetFirstPage != newSettings.offsetFirstPage
 
         // We don't commit the CSS changes if we invalidate the pagination, as
         // the resources will be reloaded anyway.
@@ -248,6 +249,7 @@ final class EPUBNavigatorViewModel: Loggable {
     var scroll: Bool { settings.scroll }
     var verticalText: Bool { settings.verticalText }
     var spread: Spread { settings.spread }
+    var offsetFirstPage: Bool? { settings.offsetFirstPage }
 
     // MARK: Spread
 

Sources/Navigator/EPUB/EPUBReflowableSpreadView.swift

@@ -81,8 +81,7 @@ final class EPUBReflowableSpreadView: EPUBSpreadView {
             log(.error, "Only one document at a time can be displayed in a reflowable spread")
             return
         }
-        let link = viewModel.readingOrder[spread.leading]
-        let url = viewModel.url(to: link)
+        let url = viewModel.url(to: spread.first.link)
         webView.load(URLRequest(url: url.url))
     }
 
@@ -135,7 +134,7 @@ final class EPUBReflowableSpreadView: EPUBSpreadView {
 
     override func progression(in index: ReadingOrder.Index) -> ClosedRange<Double> {
         guard
-            spread.leading == index,
+            spread.first.index == index,
             let progression = progression
         else {
             return 0 ... 0
@@ -144,10 +143,8 @@ final class EPUBReflowableSpreadView: EPUBSpreadView {
     }
 
     override func spreadDidLoad() async {
-        if
-            let link = viewModel.readingOrder.getOrNil(spread.leading),
-            let linkJSON = serializeJSONString(link.json)
-        {
+        let link = spread.first.link
+        if let linkJSON = serializeJSONString(link.json) {
             await evaluateScript("readium.link = \(linkJSON);")
         }