feat(layout): detect reflowable vs fixed-layout EPUB, fix pagination overflow

src/book.rs

@@ -187,22 +187,57 @@ pub struct Section {
     pub pages: Vec<usize>,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum BookLayout {
+    Reflowable,
+    FixedLayout,
+}
+
+impl BookLayout {
+    pub fn label(&self) -> &str {
+        match self {
+            BookLayout::Reflowable => "重排",
+            BookLayout::FixedLayout => "固定",
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct Book {
     pub title: String,
     pub author: String,
     pub cover: Option<Vec<u8>>,
+    pub layout: BookLayout,
     pub sections: Vec<Section>,
     pub toc: Vec<TocEntry>,
 }
 
 use std::path::Path;
 
+fn detect_layout(doc: &mut epub::doc::EpubDoc<std::io::BufReader<std::fs::File>>) -> BookLayout {
+    if let Some(vals) = doc.metadata.get("rendition:layout") {
+        if vals.iter().any(|v| v == "pre-paginated") {
+            return BookLayout::FixedLayout;
+        }
+    }
+    if let Ok(opf) = doc.get_resource_str_by_path(&doc.root_file.clone()) {
+        if opf.contains("rendition:layout") && opf.contains("pre-paginated") {
+            return BookLayout::FixedLayout;
+        }
+        if opf.contains("rendition:layout-pre-paginated") {
+            return BookLayout::FixedLayout;
+        }
+    }
+    BookLayout::Reflowable
+}
+
 pub fn load_epub(path: impl AsRef<Path>) -> Result<Book, String> {
     let path = path.as_ref();
     let mut doc = epub::doc::EpubDoc::new(path)
         .map_err(|e| format!("无法打开文件: {}", e))?;
 
+    let layout = detect_layout(&mut doc);
+
     let title = doc.mdata("title").unwrap_or_else(|| "未知标题".to_string());
     let author = doc.mdata("creator").unwrap_or_else(|| "未知作者".to_string());
     let cover = doc.get_cover().ok();
@@ -225,7 +260,7 @@ pub fn load_epub(path: impl AsRef<Path>) -> Result<Book, String> {
     let raw_toc = std::mem::take(&mut doc.toc);
     let toc = build_toc(&raw_toc, &spine);
 
-    Ok(Book { title, author, cover, sections, toc })
+    Ok(Book { title, author, cover, layout, sections, toc })
 }
 
 fn extract_title(html: &str) -> Option<String> {

src/reader.rs

@@ -5,14 +5,15 @@ use crate::theme::{self, BgType, Theme};
 
 pub fn recalculate_pages(book: &mut Book, font_size: f32, line_height: f32, panel_width: f32, panel_height: f32, style: &StyleProfile) {
     let char_width = font_size * 1.0;
-    let safety = 0.95;
+    let safety_w = 0.95;
+    let safety_h = 0.96;
     let chars_per_line = if char_width > 0.0 {
-        ((panel_width / char_width) * safety).max(1.0) as usize
+        ((panel_width / char_width) * safety_w).max(1.0) as usize
     } else {
         1
     };
     let lines_per_page = if line_height > 0.0 {
-        ((panel_height / line_height) * safety).max(1.0) as usize
+        ((panel_height / line_height) * safety_h).max(1.0) as usize
     } else {
         1
     };
@@ -101,7 +102,8 @@ pub fn reading_view(
                     action.go_back = true;
                 }
                 ui.separator();
-                ui.label(&book.title);
+                ui.label(format!("《{}》", &book.title));
+                ui.label(format!("[{}]", book.layout.label()));
                 ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
                     let (theme_icon, theme_hint) = match theme {
                         Theme::Dark => ("🌞", "切换到浅色主题"),
@@ -412,9 +414,9 @@ pub fn calculate_pages(text: &str, chars_per_page: usize) -> Vec<usize> {
             break;
         }
 
-        // Search backward from next for paragraph (\n\n) or line (\n) breaks
+        // 在页面后半段查找段落边界(\n\n)或行边界(\n)，不回超理想页长
         let search_start = pos + chars_per_page / 2;
-        let search_end = (next + chars_per_page / 2).min(total_chars);
+        let search_end = next.min(total_chars);
         let mut split = next;
 
         // Prefer double newline (paragraph), then single newline