feat: add kraft paper tiled background texture for comfortable reading

src/app.rs

@@ -8,6 +8,7 @@ pub struct App {
     pub state: AppState,
     settings: Settings,
     settings_dir: std::path::PathBuf,
+    kraft_texture: Option<egui::TextureHandle>,
 }
 
 pub struct AppState {
@@ -51,6 +52,7 @@ impl App {
         let settings_dir = persistence::settings_dir();
         let settings = persistence::load_settings(&settings_dir).unwrap_or_default();
         cc.egui_ctx.set_style(theme::create_style(&settings.theme));
+        let kraft_texture = Some(crate::texture::generate_kraft_paper(&cc.egui_ctx));
         Self {
             state: AppState {
                 book: None,
@@ -62,6 +64,7 @@ impl App {
             },
             settings,
             settings_dir,
+            kraft_texture,
         }
     }
 
@@ -189,6 +192,8 @@ impl eframe::App for App {
                 &mut self.settings.font_size,
                 &self.settings.theme,
                 &file_path,
+                self.kraft_texture.as_ref(),
+                self.settings.use_kraft_bg,
             );
 
             if action.go_back {
@@ -198,6 +203,10 @@ impl eframe::App for App {
                 self.state.current_page = 0;
             }
 
+            if action.toggle_kraft_bg {
+                self.settings.use_kraft_bg = !self.settings.use_kraft_bg;
+            }
+
             if action.toggle_theme {
                 self.settings.theme = match self.settings.theme {
                     theme::Theme::Light => theme::Theme::Dark,

src/main.rs

@@ -5,6 +5,7 @@ mod book;
 mod font;
 mod persistence;
 mod reader;
+mod texture;
 mod theme;
 
 fn main() -> eframe::Result {

src/reader.rs

@@ -25,6 +25,7 @@ pub struct ReaderAction {
     pub go_back: bool,
     pub toggle_theme: bool,
     pub toggle_bookmark: bool,
+    pub toggle_kraft_bg: bool,
     pub page_next: bool,
     pub page_prev: bool,
 }
@@ -38,11 +39,14 @@ pub fn reading_view(
     font_size: &mut f32,
     theme: &Theme,
     _file_path: &str,
+    kraft_texture: Option<&egui::TextureHandle>,
+    use_kraft_bg: bool,
 ) -> ReaderAction {
     let mut action = ReaderAction {
         go_back: false,
         toggle_theme: false,
         toggle_bookmark: false,
+        toggle_kraft_bg: false,
         page_next: false,
         page_prev: false,
     };
@@ -91,6 +95,10 @@ pub fn reading_view(
                     if ui.button("A⁺").on_hover_text("放大字体").clicked() {
                         *font_size = (*font_size + 2.0).min(48.0);
                     }
+                    let kraft_icon = if use_kraft_bg { "📄" } else { "📋" };
+                    if ui.button(kraft_icon).on_hover_text("牛皮纸背景").clicked() {
+                        action.toggle_kraft_bg = true;
+                    }
                     if ui.button("☰").on_hover_text("打开/关闭目录").clicked() {
                         *sidebar_open = !*sidebar_open;
                     }
@@ -163,6 +171,13 @@ pub fn reading_view(
         let available = ui.available_size();
         let (rect, response) = ui.allocate_at_least(available, egui::Sense::click());
 
+        // Draw kraft paper background if enabled
+        if use_kraft_bg {
+            if let Some(tex) = kraft_texture {
+                crate::texture::draw_tiled_bg(ui.painter(), rect, tex);
+            }
+        }
+
         // Add reading margins (inset)
         let inset = 24.0;
         let text_rect = egui::Rect::from_min_size(

src/texture.rs

@@ -0,0 +1,66 @@
+use eframe::egui;
+
+fn hash(x: u32, y: u32) -> u32 {
+    let mut h = x.wrapping_mul(374761393) ^ y.wrapping_mul(668265263);
+    h = h.wrapping_mul(h ^ (h >> 13));
+    h ^ (h >> 15)
+}
+
+fn paper_noise(x: u32, y: u32) -> u8 {
+    // Combine multiple hash values for more natural-looking noise
+    let n1 = hash(x, y);
+    let n2 = hash(x.wrapping_add(137), y.wrapping_add(251));
+    let n3 = hash(x.wrapping_mul(7), y.wrapping_mul(13));
+    ((n1 ^ n2.wrapping_add(n3)) % 18) as u8
+}
+
+pub fn generate_kraft_paper(ctx: &egui::Context) -> egui::TextureHandle {
+    let size = 128usize;
+    let mut pixels = Vec::with_capacity(size * size);
+
+    for y in 0..size {
+        for x in 0..size {
+            let n = paper_noise(x as u32, y as u32);
+            // Warm brown-beige base with slight variation
+            let r = 212u8.wrapping_add(n);
+            let g = 194u8.wrapping_add(n);
+            let b = 168u8.wrapping_add(n);
+            pixels.push(egui::Color32::from_rgb(r, g, b));
+        }
+    }
+
+    let image = egui::ColorImage {
+        size: [size, size],
+        pixels,
+    };
+    ctx.load_texture("kraft_paper", image, Default::default())
+}
+
+pub fn draw_tiled_bg(
+    painter: &egui::Painter,
+    rect: egui::Rect,
+    texture: &egui::TextureHandle,
+) {
+    let tile_size = 128.0f32;
+    let mut ty = rect.min.y;
+    while ty < rect.max.y {
+        let mut tx = rect.min.x;
+        while tx < rect.max.x {
+            let tile_rect = egui::Rect::from_min_max(
+                egui::pos2(tx, ty),
+                egui::pos2(
+                    (tx + tile_size).min(rect.max.x),
+                    (ty + tile_size).min(rect.max.y),
+                ),
+            );
+            painter.image(
+                texture.id(),
+                tile_rect,
+                egui::Rect::from_min_max(egui::pos2(0.0, 0.0), egui::pos2(1.0, 1.0)),
+                egui::Color32::WHITE,
+            );
+            tx += tile_size;
+        }
+        ty += tile_size;
+    }
+}

src/theme.rs

@@ -170,6 +170,7 @@ pub fn create_style(theme: &Theme) -> Style {
 pub struct Settings {
     pub font_size: f32,
     pub theme: Theme,
+    pub use_kraft_bg: bool,
     pub recent_files: Vec<String>,
     pub reading_positions: std::collections::HashMap<String, ReadingPosition>,
     pub bookmarks: std::collections::HashMap<String, Vec<Bookmark>>,
@@ -181,6 +182,7 @@ impl Default for Settings {
         Self {
             font_size: 20.0,
             theme: Theme::Light,
+            use_kraft_bg: false,
             recent_files: Vec::new(),
             reading_positions: std::collections::HashMap::new(),
             bookmarks: std::collections::HashMap::new(),