Support HTML IDs and CSS selectors with EPUB decorations

CHANGELOG.md

@@ -57,6 +57,7 @@ All notable changes to this project will be documented in this file. Take a look
     * `hyphens` - Enable hyphenation.
     * `ligatures` - Enable ligatures in Arabic.
 * Fixed scroll inertia when scrolling an EPUB.
+* EPUB decorations can now be attached to `Locator` objects containing only an HTML ID (`locations.fragments`) or a CSS selector (`locations.cssSelector`).
 
 ### Changed
 

readium/navigator/src/main/assets/_scripts/src/utils.js

@@ -228,29 +228,53 @@ export function snapCurrentOffset() {
 }
 
 export function rangeFromLocator(locator) {
-  let text = locator.text;
-  if (!text || !text.highlight) {
-    return null;
-  }
   try {
-    var root;
     let locations = locator.locations;
-    if (locations && locations.cssSelector) {
-      root = document.querySelector(locations.cssSelector);
-    }
-    if (!root) {
-      root = document.body;
+    let text = locator.text;
+    if (text && text.highlight) {
+      var root;
+      if (locations && locations.cssSelector) {
+        root = document.querySelector(locations.cssSelector);
+      }
+      if (!root) {
+        root = document.body;
+      }
+
+      let anchor = new TextQuoteAnchor(root, text.highlight, {
+        prefix: text.before,
+        suffix: text.after,
+      });
+      return anchor.toRange();
     }
 
-    let anchor = new TextQuoteAnchor(root, text.highlight, {
-      prefix: text.before,
-      suffix: text.after,
-    });
-    return anchor.toRange();
+    if (locations) {
+      var element = null;
+
+      if (!element && locations.cssSelector) {
+        element = document.querySelector(locations.cssSelector);
+      }
+
+      if (!element && locations.fragments) {
+        for (const htmlId of locations.fragments) {
+          element = document.getElementById(htmlId);
+          if (element) {
+            break;
+          }
+        }
+      }
+
+      if (element) {
+        let range = document.createRange();
+        range.setStartBefore(element);
+        range.setEndAfter(element);
+        return range;
+      }
+    }
   } catch (e) {
     logError(e);
-    return null;
   }
+
+  return null;
 }
 
 /// User Settings.

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

@@ -17,6 +17,9 @@ import androidx.appcompat.widget.SearchView
 import androidx.fragment.app.FragmentResultListener
 import androidx.fragment.app.commit
 import androidx.fragment.app.commitNow
+import androidx.lifecycle.lifecycleScope
+import org.readium.r2.navigator.DecorableNavigator
+import org.readium.r2.navigator.Decoration
 import org.readium.r2.navigator.ExperimentalDecorator
 import org.readium.r2.navigator.epub.*
 import org.readium.r2.navigator.epub.css.FontStyle
@@ -25,6 +28,7 @@ import org.readium.r2.navigator.html.toCss
 import org.readium.r2.navigator.preferences.FontFamily
 import org.readium.r2.shared.ExperimentalReadiumApi
 import org.readium.r2.shared.publication.Locator
+import org.readium.r2.shared.publication.epub.pageList
 import org.readium.r2.testapp.LITERATA
 import org.readium.r2.testapp.R
 import org.readium.r2.testapp.reader.preferences.UserPreferencesViewModel
@@ -66,8 +70,9 @@ class EpubReaderFragment : VisualReaderFragment(), EpubNavigatorFragment.Listene
                         "annotation-icon.svg"
                     )
 
-                    // Register the HTML template for our custom [DecorationStyleAnnotationMark].
+                    // Register the HTML templates for our custom decoration styles.
                     decorationTemplates[DecorationStyleAnnotationMark::class] = annotationMarkTemplate()
+                    decorationTemplates[DecorationStylePageNumber::class] = pageNumberTemplate()
 
                     // Declare a custom font family for reflowable EPUBs.
                     addFontFamilyDeclaration(FontFamily.LITERATA) {
@@ -126,6 +131,33 @@ class EpubReaderFragment : VisualReaderFragment(), EpubNavigatorFragment.Listene
         @Suppress("Unchecked_cast")
         (model.settings as UserPreferencesViewModel<EpubSettings, EpubPreferences>)
             .bind(navigator, viewLifecycleOwner)
+
+        viewLifecycleOwner.lifecycleScope.launchWhenStarted {
+            // Display page number labels if the book contains a `page-list` navigation document.
+            (navigator as? DecorableNavigator)?.applyPageNumberDecorations()
+        }
+    }
+
+    /**
+     * Will display margin labels next to page numbers in an EPUB publication with a `page-list`
+     * navigation document.
+     *
+     * See http://kb.daisy.org/publishing/docs/navigation/pagelist.html
+     */
+    private suspend fun DecorableNavigator.applyPageNumberDecorations() {
+        val decorations = publication.pageList
+            .mapIndexedNotNull { index, link ->
+                val label = link.title ?: return@mapIndexedNotNull null
+                val locator = publication.locatorFromLink(link) ?: return@mapIndexedNotNull null
+
+                Decoration(
+                    id = "page-$index",
+                    locator = locator,
+                    style = DecorationStylePageNumber(label = label),
+                )
+            }
+
+        applyDecorations(decorations, "pageNumbers")
     }
 
     override fun onCreateOptionsMenu(menu: Menu, menuInflater: MenuInflater) {
@@ -218,11 +250,11 @@ class EpubReaderFragment : VisualReaderFragment(), EpubNavigatorFragment.Listene
     }
 }
 
+// Examples of HTML templates for custom Decoration Styles.
+
 /**
- * Example of an HTML template for a custom Decoration Style.
- *
- * This one will display a tinted "pen" icon in the page margin to show that a highlight has an
- * associated note.
+ * This Decorator Style will display a tinted "pen" icon in the page margin to show that a highlight
+ * has an associated note.
  *
  * Note that the icon is served from the app assets folder.
  */
@@ -256,3 +288,39 @@ private fun annotationMarkTemplate(@ColorInt defaultTint: Int = Color.YELLOW): H
             """
     )
 }
+
+/**
+ * This Decoration Style is used to display the page number labels in the margins, when a book
+ * provides a `page-list`. The label is stored in the [DecorationStylePageNumber] itself.
+ *
+ * See http://kb.daisy.org/publishing/docs/navigation/pagelist.html
+ */
+@OptIn(ExperimentalDecorator::class)
+private fun pageNumberTemplate(): HtmlDecorationTemplate {
+    val className = "testapp-page-number"
+    return HtmlDecorationTemplate(
+        layout = HtmlDecorationTemplate.Layout.BOUNDS,
+        width = HtmlDecorationTemplate.Width.PAGE,
+        element = { decoration ->
+            val style = decoration.style as? DecorationStylePageNumber
+
+            // Using `var(--RS__backgroundColor)` is a trick to use the same background color as
+            // the Readium theme. If we don't set it directly inline in the HTML, it might be
+            // forced transparent by Readium CSS.
+            """
+            <div><span class="$className" style="background-color: var(--RS__backgroundColor) !important">${style?.label}</span></div>"
+            """
+        },
+        stylesheet = """
+            .$className {
+                float: left;
+                margin-left: 8px;
+                padding: 0px 4px 0px 4px;
+                border: 1px solid;
+                border-radius: 20%;
+                box-shadow: rgba(50, 50, 93, 0.25) 0px 2px 5px -1px, rgba(0, 0, 0, 0.3) 0px 1px 3px -1px;
+                opacity: 0.8;
+            }
+            """
+    )
+}

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

@@ -536,3 +536,14 @@ abstract class VisualReaderFragment : BaseReaderFragment(), VisualNavigator.List
 @Parcelize
 @OptIn(ExperimentalDecorator::class)
 data class DecorationStyleAnnotationMark(@ColorInt val tint: Int) : Decoration.Style
+
+/**
+ * Decoration Style for a page number label.
+ *
+ * This is an example of a custom Decoration Style declaration.
+ *
+ * @param label Page number label as declared in the `page-list` link object.
+ */
+@Parcelize
+@OptIn(ExperimentalDecorator::class)
+data class DecorationStylePageNumber(val label: String) : Decoration.Style