lychee-core: add image zoom, rotate, and flip transforms

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I5c48a422d7ff0c4fa0ff8ae0c34a514e6a6a6964

crates/lychee-core/src/app.rs

@@ -1,12 +1,13 @@
 use std::collections::HashMap;
 
+use iced::event;
 use iced::{
-    ContentFit, Element, Subscription, Task, keyboard,
+    Alignment, Element, Length, Subscription, Task, keyboard,
     time::{self, milliseconds},
-    widget::image::viewer,
+    widget::{column, container, row},
     window,
 };
-use image::GenericImageView;
+use image::{GenericImageView, imageops::FilterType};
 use lychee_cli::{Args, Clap};
 use lychee_img::collect_paths;
 
@@ -22,11 +23,18 @@ pub enum Message {
     ZoomOut,
     ActualSize,
     FitWindow,
-    Reset,
+    ResetView,
+    Pan(i32, i32),
+    RotateCW,
+    RotateCCW,
+    FlipHorizontal,
+    FlipVertical,
+    ResetTransform,
     ToggleFullscreen,
     ToggleSlideshow,
     SlideshowTick,
     AdjustSlideshowDelay(i64),
+    WindowResized(u32, u32),
     Close,
 }
 
@@ -34,11 +42,26 @@ pub struct App {
     window_id: window::Id,
     paths: Vec<String>,
     current: usize,
-    image_cache: HashMap<usize, iced::widget::image::Handle>,
-    fit_to_window: bool,
+    // Cache key: (index, rotation_degrees, flip_h, flip_v, zoom_percent)
+    image_cache: HashMap<(usize, u16, bool, bool, u32), iced::widget::image::Handle>,
     fullscreen: bool,
     slideshow_active: bool,
     slideshow_interval: u64,
+    // Zoom state (scale is display value, zoom_percent is cache key)
+    scale: f32,
+    min_scale: f32,
+    max_scale: f32,
+    scale_step: f32,
+    zoom_percent: u32,
+    pan_offset: (f32, f32),
+    // Transform state
+    rotation: u16,
+    flip_h: bool,
+    flip_v: bool,
+    // Window dimensions for fit-to-window calculation
+    window_size: (u32, u32),
+    // Original image dimensions for fit-to-window calculation
+    current_image_size: (u32, u32),
 }
 
 impl App {
@@ -47,17 +70,33 @@ impl App {
         let paths = collect_paths(args.paths);
         let window_id = window::Id::unique();
 
-        let app = Self {
+        let mut app = Self {
             window_id,
             paths,
             current: 0,
             image_cache: HashMap::new(),
-            fit_to_window: true,
             fullscreen: args.fullscreen,
             slideshow_active: false,
             slideshow_interval: args.slideshow,
+            // Zoom state
+            scale: 1.0,
+            min_scale: 0.1,
+            max_scale: 10.0,
+            scale_step: 0.1,
+            zoom_percent: 100,
+            pan_offset: (0.0, 0.0),
+            // Transform state
+            rotation: 0,
+            flip_h: false,
+            flip_v: false,
+            // Window and image dimensions
+            window_size: (800, 600), // Default, will be updated by resize events
+            current_image_size: (0, 0),
         };
 
+        // Preload initial images into cache
+        app.preload_adjacent();
+
         let task = if args.fullscreen {
             window::maximize(window_id, true)
         } else {
@@ -68,20 +107,46 @@ impl App {
     }
 
     pub fn view(&self) -> Element<'_, Message> {
-        match self.image_cache.get(&self.current) {
+        let image_content: Element<'_, Message> = match self.image_cache.get(&(
+            self.current,
+            self.rotation,
+            self.flip_h,
+            self.flip_v,
+            self.zoom_percent,
+        )) {
             Some(handle) => {
-                let v = viewer(handle.clone())
-                    .content_fit(if self.fit_to_window {
-                        ContentFit::Contain
-                    } else {
-                        ContentFit::Cover
-                    })
-                    .padding(20);
-                v.into()
-            }
+                // Image displayed at actual pixel dimensions (Shrink)
+                let img: iced::widget::Image<iced::widget::image::Handle> =
+                    iced::widget::Image::new(handle.clone());
 
-            None => iced::widget::text("No image loaded").into(),
-        }
+                // Center the image in a Fill-sized container
+                container(img)
+                    .width(Length::Fill)
+                    .height(Length::Fill)
+                    .align_x(Alignment::Center)
+                    .align_y(Alignment::Center)
+                    .into()
+            }
+            None => iced::widget::text("Loading...").into(),
+        };
+
+        // Main layout: image on top, statusbar at bottom
+        let statusbar: Element<'_, Message> = self.render_statusbar();
+
+        column![image_content, statusbar].into()
+    }
+
+    fn render_statusbar(&self) -> Element<'_, Message> {
+        let zoom_text = format!("{:.*}%", 0, self.scale * 100.0);
+        let index_text = format!("{}/{}", self.current + 1, self.paths.len());
+
+        row![
+            iced::widget::text(zoom_text).size(14),
+            iced::widget::text(index_text).size(14),
+        ]
+        .padding(8)
+        .width(Length::Fill)
+        .into()
     }
 
     pub fn subscription(&self) -> Subscription<Message> {
@@ -101,30 +166,120 @@ impl App {
         let close = window::close_events().map(|_| Message::Close);
         let slideshow = time::every(milliseconds(self.slideshow_interval * 1000))
             .map(|_| Message::SlideshowTick);
+        let resize = event::listen().filter_map(|event| {
+            if let iced::Event::Window(window::Event::Resized(size)) = event {
+                Some(Message::WindowResized(
+                    size.width as u32,
+                    size.height as u32,
+                ))
+            } else {
+                None
+            }
+        });
 
-        Subscription::batch(vec![hotkey, close, slideshow])
+        Subscription::batch(vec![hotkey, close, slideshow, resize])
     }
 
     fn preload_adjacent(&mut self) {
         for offset in [0isize, -1, 1] {
             let idx = (self.current as isize + offset) as usize;
-            if idx < self.paths.len()
-                && !self.image_cache.contains_key(&idx)
-                && let Some(handle) = self.load_image(&self.paths[idx])
-            {
-                self.image_cache.insert(idx, handle);
+            let cache_key = (
+                idx,
+                self.rotation,
+                self.flip_h,
+                self.flip_v,
+                self.zoom_percent,
+            );
+            if idx < self.paths.len() && !self.image_cache.contains_key(&cache_key) {
+                // Extract path to avoid borrow conflict
+                let path = self.paths[idx].clone();
+                let zoom = self.zoom_percent;
+                if let Some(handle) = self.load_image(&path, zoom) {
+                    self.image_cache.insert(cache_key, handle);
+                }
             }
         }
     }
 
-    fn load_image(&self, path: &str) -> Option<iced::widget::image::Handle> {
-        let img = ::image::open(path).ok()?;
+    fn load_image(&mut self, path: &str, zoom_percent: u32) -> Option<iced::widget::image::Handle> {
+        let mut img = ::image::open(path).ok()?;
+
+        // Apply rotation
+        match self.rotation {
+            90 => img = img.rotate90(),
+            180 => img = img.rotate180(),
+            270 => img = img.rotate270(),
+            _ => {}
+        }
+
+        // Apply flips
+        if self.flip_h {
+            img = img.fliph();
+        }
+        if self.flip_v {
+            img = img.flipv();
+        }
+
+        // Track original image dimensions for fit-to-window calculation
+        let (orig_width, orig_height) = img.dimensions();
+        self.current_image_size = (orig_width, orig_height);
+
+        // Apply zoom by resizing
+        let new_width = ((orig_width as f32) * (zoom_percent as f32) / 100.0).max(1.0) as u32;
+        let new_height = ((orig_height as f32) * (zoom_percent as f32) / 100.0).max(1.0) as u32;
+
+        // Only resize if not 100%
+        let img = if zoom_percent != 100 {
+            img.resize(new_width, new_height, FilterType::Lanczos3)
+        } else {
+            img
+        };
+
         let (width, height) = img.dimensions();
         let raw = img.to_rgba8().into_raw();
         Some(iced::widget::image::Handle::from_rgba(width, height, raw))
     }
 
+    fn invalidate_cache(&mut self) {
+        // Invalidate current and adjacent images at current zoom level
+        for offset in [0isize, -1, 1] {
+            let idx = (self.current as isize + offset) as usize;
+            let key = (
+                idx,
+                self.rotation,
+                self.flip_h,
+                self.flip_v,
+                self.zoom_percent,
+            );
+            self.image_cache.remove(&key);
+        }
+        self.preload_adjacent();
+    }
+
+    /// Ensure the current image is loaded into cache We'll load it on-demand if missing.
+    fn ensure_current_loaded(&mut self) {
+        let key = (
+            self.current,
+            self.rotation,
+            self.flip_h,
+            self.flip_v,
+            self.zoom_percent,
+        );
+        if !self.image_cache.contains_key(&key) {
+            // Extract path to avoid borrow conflict
+            let path = self.paths[self.current].clone();
+            let zoom = self.zoom_percent;
+            if let Some(handle) = self.load_image(&path, zoom) {
+                self.image_cache.insert(key, handle);
+            }
+        }
+    }
+
     pub fn update(&mut self, message: Message) -> Task<Message> {
+        // Ensure current image is loaded; this handles edge cases where
+        // cache miss occurred and preload hasn't triggered yet
+        self.ensure_current_loaded();
+
         match message {
             Message::Next => {
                 if self.current < self.paths.len() - 1 {
@@ -154,11 +309,91 @@ impl App {
                 }
                 Task::none()
             }
-            Message::ZoomIn
-            | Message::ZoomOut
-            | Message::ActualSize
-            | Message::FitWindow
-            | Message::Reset => Task::none(),
+            Message::ZoomIn => {
+                let new_percent =
+                    (self.zoom_percent as f32 * (1.0 + self.scale_step)).round() as u32;
+                self.zoom_percent = new_percent.min((self.max_scale * 100.0) as u32);
+                self.scale = self.zoom_percent as f32 / 100.0;
+                self.invalidate_cache();
+                Task::none()
+            }
+            Message::ZoomOut => {
+                let new_percent =
+                    (self.zoom_percent as f32 * (1.0 / (1.0 + self.scale_step))).round() as u32;
+                self.zoom_percent = new_percent.max((self.min_scale * 100.0) as u32);
+                self.scale = self.zoom_percent as f32 / 100.0;
+                self.invalidate_cache();
+                Task::none()
+            }
+            Message::ActualSize | Message::FitWindow | Message::ResetView => {
+                let fit_zoom = if self.current_image_size.0 > 0 && self.current_image_size.1 > 0 {
+                    // Calculate zoom to fit image within window, preserving aspect ratio
+                    let window_ratio = (self.window_size.0 as f32) / (self.window_size.1 as f32);
+                    let image_ratio =
+                        (self.current_image_size.0 as f32) / (self.current_image_size.1 as f32);
+
+                    if window_ratio > image_ratio {
+                        // Window is wider than image, fit by height
+                        ((self.window_size.1 as f32) / (self.current_image_size.1 as f32) * 100.0)
+                            as u32
+                    } else {
+                        // Window is taller than image, fit by width
+                        ((self.window_size.0 as f32) / (self.current_image_size.0 as f32) * 100.0)
+                            as u32
+                    }
+                } else {
+                    100 // default to 100% if no image dimensions available
+                };
+
+                self.zoom_percent = fit_zoom.min((self.max_scale * 100.0) as u32);
+                self.scale = self.zoom_percent as f32 / 100.0;
+                self.pan_offset = (0.0, 0.0);
+                self.invalidate_cache();
+                Task::none()
+            }
+            Message::WindowResized(width, height) => {
+                self.window_size = (width, height);
+                Task::none()
+            }
+            Message::Pan(dx, dy) => {
+                // XXX: pan_offset is tracked but visual panning requires a custom
+                // canvas widget or Iced's scrollable with exposed State. This will
+                // be implemented in a future version, because I don't really have
+                // the energy to do so right now.
+                self.pan_offset.0 += dx as f32;
+                self.pan_offset.1 += dy as f32;
+                Task::none()
+            }
+            Message::RotateCW => {
+                self.rotation = (self.rotation + 90) % 360;
+                self.invalidate_cache();
+                Task::none()
+            }
+            Message::RotateCCW => {
+                self.rotation = (self.rotation + 270) % 360;
+                self.invalidate_cache();
+                Task::none()
+            }
+            Message::FlipHorizontal => {
+                self.flip_h = !self.flip_h;
+                self.invalidate_cache();
+                Task::none()
+            }
+            Message::FlipVertical => {
+                self.flip_v = !self.flip_v;
+                self.invalidate_cache();
+                Task::none()
+            }
+            Message::ResetTransform => {
+                self.scale = 1.0;
+                self.zoom_percent = 100;
+                self.pan_offset = (0.0, 0.0);
+                self.rotation = 0;
+                self.flip_h = false;
+                self.flip_v = false;
+                self.invalidate_cache();
+                Task::none()
+            }
             Message::ToggleFullscreen => {
                 self.fullscreen = !self.fullscreen;
                 window::maximize(self.window_id, self.fullscreen)