Add backgroundColor preference for fixed-layout EPUB

CHANGELOG.md

@@ -10,6 +10,7 @@ All notable changes to this project will be documented in this file. Take a look
 
 #### Navigator
 
+* The EPUB `backgroundColor` preference is now available with fixed-layout publications.
 * New `EPUBNavigatorFragment.Configuration.useReadiumCssFontSize` option to revert to the 2.2.0 strategy for setting the font size of reflowable EPUB publications.
     * The native font size strategy introduced in 2.3.0 uses the Android web view's [`WebSettings.textZoom`](https://developer.android.com/reference/android/webkit/WebSettings#setTextZoom(int)) property to adjust the font size. 2.2.0 was using Readium CSS's [`--USER__fontSize` variable](https://readium.org/readium-css/docs/CSS12-user_prefs.html#font-size).
     * `WebSettings.textZoom` will work with more publications than `--USER__fontSize`, even the ones poorly authored. However the page width is not adjusted when changing the font size to keep the optimal line length.

readium/navigator/src/main/java/org/readium/r2/navigator/epub/EpubNavigatorFragment.kt

@@ -508,14 +508,15 @@ class EpubNavigatorFragment internal constructor(
     }
 
     private fun onSettingsChange(previous: EpubSettings, new: EpubSettings) {
-        if (viewModel.layout == EpubLayout.FIXED) return
-
-        if (previous.fontSize != new.fontSize) {
-            r2PagerAdapter?.setFontSize(new.fontSize)
-        }
         if (previous.effectiveBackgroundColor != new.effectiveBackgroundColor) {
             resourcePager.setBackgroundColor(new.effectiveBackgroundColor)
         }
+
+        if (viewModel.layout == EpubLayout.REFLOWABLE) {
+            if (previous.fontSize != new.fontSize) {
+                r2PagerAdapter?.setFontSize(new.fontSize)
+            }
+        }
     }
 
     private fun R2PagerAdapter.setFontSize(fontSize: Double) {

readium/navigator/src/main/java/org/readium/r2/navigator/epub/EpubPreferencesEditor.kt

@@ -52,16 +52,18 @@ class EpubPreferencesEditor internal constructor(
     }
 
     /**
-     * Default page background color.
+     * Default background color.
+     *
+     * For fixed-layout publications, it applies to the navigator background but not the publication
+     * pages.
      *
      * When unset, the current [theme] background color is effective.
-     * Only effective with fixed-layout publications.
      */
     val backgroundColor: Preference<Color> =
         PreferenceDelegate(
             getValue = { preferences.backgroundColor },
             getEffectiveValue = { state.settings.backgroundColor ?: Color((theme.value ?: theme.effectiveValue).backgroundColor) },
-            getIsEffective = { layout == EpubLayout.REFLOWABLE && preferences.backgroundColor != null },
+            getIsEffective = { preferences.backgroundColor != null },
             updateValue = { value -> updateValues { it.copy(backgroundColor = value) } },
         )
 

test-app/src/main/java/org/readium/r2/testapp/reader/preferences/UserPreferences.kt

@@ -125,6 +125,7 @@ private fun <P : Configurable.Preferences<P>, E : PreferencesEditor<P>> UserPref
                     EpubLayout.FIXED ->
                         FixedLayoutUserPreferences(
                             commit = commit,
+                            backgroundColor = editor.backgroundColor,
                             language = editor.language,
                             readingProgression = editor.readingProgression,
                             spread = editor.spread,
@@ -142,6 +143,7 @@ private fun ColumnScope.FixedLayoutUserPreferences(
     commit: () -> Unit,
     language: Preference<Language?>? = null,
     readingProgression: EnumPreference<ReadingProgression>? = null,
+    backgroundColor: Preference<ReadiumColor>? = null,
     scroll: Preference<Boolean>? = null,
     scrollAxis: EnumPreference<Axis>? = null,
     fit: EnumPreference<Fit>? = null,
@@ -175,6 +177,16 @@ private fun ColumnScope.FixedLayoutUserPreferences(
         Divider()
     }
 
+    if (backgroundColor != null) {
+        ColorItem(
+            title = "Background color",
+            preference = backgroundColor,
+            commit = commit
+        )
+
+        Divider()
+    }
+
     if (scroll != null) {
         SwitchItem(
             title = "Scroll",