Fix 12 medium-severity bugs across all crates

- Escape backslashes in Nautilus preset names preventing Python injection
- Fix tiled watermarks starting at (spacing,spacing) instead of (0,0)
- Fix text watermark width overestimation (1.0x to 0.6x multiplier)
- Fix output_dpi forcing re-encoding for metadata-only presets
- Fix AVIF/WebP compression detection comparing against wrong preset values
- Add shared batch_updating guard for Ctrl+A/Ctrl+Shift+A select actions
- Fix overwrite conflict check ignoring preserve_directory_structure
- Add changes_filename()/changes_extension() for smarter overwrite checks
- Fix watch folder hardcoding "Blog Photos" preset
- Fix undo dropping history for partially-trashed batches
- Fix skipped files inflating size statistics
- Make CLI watch config writes atomic

pixstrip-cli/src/main.rs

@@ -573,25 +573,27 @@ fn cmd_undo(count: usize) {
                     entry.total, entry.input_dir
                 );
 
-                let mut batch_trashed = 0;
+                let mut remaining_files = Vec::new();
                 for file_path in &entry.output_files {
                     let path = PathBuf::from(file_path);
                     if path.exists() {
                         match trash::delete(&path) {
                             Ok(()) => {
-                                batch_trashed += 1;
                                 total_trashed += 1;
                             }
                             Err(e) => {
                                 eprintln!("  Failed to trash {}: {}", path.display(), e);
+                                remaining_files.push(file_path.clone());
                             }
                         }
                     }
                 }
 
-                // Keep entry in history if no files were trashed
+                // Keep entry with remaining files if some could not be trashed
-                if batch_trashed == 0 {
+                if !remaining_files.is_empty() {
-                    failed_entries.push(entry);
+                    let mut kept = entry;
+                    kept.output_files = remaining_files;
+                    failed_entries.push(kept);
                 }
             }
 
@@ -665,7 +667,7 @@ fn cmd_watch_add(path: &str, preset_name: &str, recursive: bool) {
     }
     match serde_json::to_string_pretty(&watches) {
         Ok(json) => {
-            if let Err(e) = std::fs::write(&watches_path, json) {
+            if let Err(e) = pixstrip_core::storage::atomic_write(&watches_path, &json) {
                 eprintln!("Failed to write watch config: {}", e);
                 std::process::exit(1);
             }
@@ -743,7 +745,7 @@ fn cmd_watch_remove(path: &str) {
 
     match serde_json::to_string_pretty(&watches) {
         Ok(json) => {
-            if let Err(e) = std::fs::write(&watches_path, json) {
+            if let Err(e) = pixstrip_core::storage::atomic_write(&watches_path, &json) {
                 eprintln!("Failed to write watch config: {}", e);
                 std::process::exit(1);
             }

pixstrip-core/src/executor.rs

@@ -398,7 +398,7 @@ impl PipelineExecutor {
 
             let output_path = match job.overwrite_behavior {
                 crate::operations::OverwriteAction::Skip if output_path.exists() => {
-                    return Ok((input_size, 0, std::path::PathBuf::new()));
+                    return Ok((0, 0, std::path::PathBuf::new()));
                 }
                 crate::operations::OverwriteAction::AutoRename if output_path.exists() => {
                     find_unique_path(&output_path)
@@ -563,7 +563,7 @@ impl PipelineExecutor {
             crate::operations::OverwriteAction::Skip => {
                 if output_path.exists() {
                     // Return 0 bytes written - file was skipped
-                    return Ok((input_size, 0, std::path::PathBuf::new()));
+                    return Ok((0, 0, std::path::PathBuf::new()));
                 }
                 output_path
             }

pixstrip-core/src/fm_integration.rs

@@ -151,8 +151,8 @@ fn install_nautilus() -> Result<()> {
              \x20       item.connect('activate', self._on_preset, '{}', files)\n\
              \x20       submenu.append_item(item)\n\n",
             name.replace(' ', "_"),
-            name.replace('\'', "\\'"),
+            name.replace('\\', "\\\\").replace('\'', "\\'"),
-            name.replace('\'', "\\'"),
+            name.replace('\\', "\\\\").replace('\'', "\\'"),
         ));
     }
 

pixstrip-core/src/operations/mod.rs

@@ -120,6 +120,11 @@ impl ConvertConfig {
             }
         }
     }
+
+    /// Returns true if this conversion will change at least some file extensions.
+    pub fn changes_extension(&self) -> bool {
+        !matches!(self, Self::KeepOriginal)
+    }
 }
 
 // --- Compress ---
@@ -318,6 +323,18 @@ pub struct RenameConfig {
 fn default_counter_position() -> u32 { 3 }
 
 impl RenameConfig {
+    /// Returns true if this rename config would actually change any filename.
+    pub fn changes_filename(&self) -> bool {
+        !self.prefix.is_empty()
+            || !self.suffix.is_empty()
+            || self.counter_enabled
+            || !self.regex_find.is_empty()
+            || self.case_mode > 0
+            || self.replace_spaces > 0
+            || self.special_chars > 0
+            || self.template.is_some()
+    }
+
     /// Pre-compile the regex for batch use. Call once before a loop of apply_simple_compiled.
     pub fn compile_regex(&self) -> Option<regex::Regex> {
         rename::compile_rename_regex(&self.regex_find)

pixstrip-core/src/operations/watermark.rs

@@ -198,7 +198,7 @@ fn render_text_to_image(
     opacity: f32,
 ) -> image::RgbaImage {
     let scale = ab_glyph::PxScale::from(font_size);
-    let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 1.0) as u32).saturating_add(4).min(16384);
+    let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 0.6) as u32).saturating_add(4).min(16384);
     let text_height = ((font_size.min(1000.0) * 1.4) as u32).saturating_add(4).min(4096);
 
     let alpha = (opacity * 255.0).clamp(0.0, 255.0) as u8;
@@ -296,7 +296,7 @@ fn apply_text_watermark(
     } else {
         // No rotation - draw text directly (faster)
         let scale = ab_glyph::PxScale::from(font_size);
-        let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 1.0) as u32).saturating_add(4).min(16384);
+        let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 0.6) as u32).saturating_add(4).min(16384);
         let text_height = ((font_size.min(1000.0) * 1.4) as u32).saturating_add(4).min(4096);
         let text_dims = Dimensions {
             width: text_width,
@@ -351,9 +351,9 @@ fn apply_tiled_text_watermark(
         let tw = tile.width();
         let th = tile.height();
 
-        let mut y: i64 = spacing as i64;
+        let mut y: i64 = 0;
         while y < ih as i64 {
-            let mut x: i64 = spacing as i64;
+            let mut x: i64 = 0;
             while x < iw as i64 {
                 image::imageops::overlay(&mut rgba, &tile, x, y);
                 x += tw as i64 + spacing as i64;
@@ -366,12 +366,12 @@ fn apply_tiled_text_watermark(
         let alpha = (opacity * 255.0).clamp(0.0, 255.0) as u8;
         let draw_color = Rgba([color[0], color[1], color[2], alpha]);
 
-        let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 1.0) as i64 + 4).min(16384);
+        let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 0.6) as i64 + 4).min(16384);
         let text_height = ((font_size.min(1000.0) * 1.4) as i64 + 4).min(4096);
 
-        let mut y = spacing as i64;
+        let mut y: i64 = 0;
         while y < ih as i64 {
-            let mut x = spacing as i64;
+            let mut x: i64 = 0;
             while x < iw as i64 {
                 draw_text_mut(&mut rgba, draw_color, x as i32, y as i32, scale, &font, text);
                 x += text_width + spacing as i64;
@@ -413,9 +413,9 @@ fn apply_tiled_image_watermark(
     let mut base = img.into_rgba8();
     let (iw, ih) = (base.width(), base.height());
 
-    let mut ty = spacing;
+    let mut ty = 0u32;
     while ty < ih {
-        let mut tx = spacing;
+        let mut tx = 0u32;
         while tx < iw {
             for oy in 0..oh {
                 for ox in 0..ow {

pixstrip-core/src/preset.rs

@@ -67,7 +67,7 @@ impl Preset {
                 crate::operations::CompressConfig::Preset(p) => p.avif_speed(),
                 _ => 6,
             }).unwrap_or(6),
-            output_dpi: 72,
+            output_dpi: 0,
         }
     }
 

pixstrip-gtk/src/app.rs

@@ -115,6 +115,8 @@ pub struct AppState {
     pub detailed_mode: bool,
     pub batch_queue: Rc<RefCell<BatchQueue>>,
     pub expanded_sections: Rc<RefCell<std::collections::HashMap<String, bool>>>,
+    /// Guard flag to suppress per-checkbox callbacks during bulk select/deselect
+    pub batch_updating: Rc<std::cell::Cell<bool>>,
 }
 
 impl AppState {
@@ -327,6 +329,7 @@ fn build_ui(app: &adw::Application) {
         detailed_mode: app_cfg.skill_level.is_advanced(),
         batch_queue: Rc::new(RefCell::new(BatchQueue::default())),
         expanded_sections: Rc::new(RefCell::new(sess_state.expanded_sections.clone())),
+        batch_updating: Rc::new(std::cell::Cell::new(false)),
         job_config: Rc::new(RefCell::new(JobConfig {
             preset_mode: false,
             resize_enabled: if remember { sess_state.resize_enabled.unwrap_or(true) } else { true },
@@ -942,7 +945,9 @@ fn setup_window_actions(window: &adw::ApplicationWindow, ui: &WizardUi) {
                 && let Some(stack) = page.child().and_downcast::<gtk::Stack>()
                 && let Some(loaded) = stack.child_by_name("loaded")
             {
+                ui.state.batch_updating.set(true);
                 crate::steps::step_images::set_all_checkboxes_in(&loaded, true);
+                ui.state.batch_updating.set(false);
                 let files = ui.state.loaded_files.borrow();
                 let count = files.len();
                 drop(files);
@@ -969,7 +974,9 @@ fn setup_window_actions(window: &adw::ApplicationWindow, ui: &WizardUi) {
                 && let Some(stack) = page.child().and_downcast::<gtk::Stack>()
                 && let Some(loaded) = stack.child_by_name("loaded")
             {
+                ui.state.batch_updating.set(true);
                 crate::steps::step_images::set_all_checkboxes_in(&loaded, false);
+                ui.state.batch_updating.set(false);
                 let files = ui.state.loaded_files.borrow();
                 let count = files.len();
                 drop(files);
@@ -1799,11 +1806,14 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
         // Check if user has customized per-format quality values beyond the preset defaults
         let preset_jpeg = cfg.quality_preset.jpeg_quality();
         let preset_webp = cfg.quality_preset.webp_quality();
+        let preset_avif = cfg.quality_preset.avif_quality();
+        let preset_avif_speed = cfg.quality_preset.avif_speed();
+        let preset_webp_effort = cfg.quality_preset.webp_effort();
         let has_custom = cfg.jpeg_quality != preset_jpeg
             || cfg.webp_quality != preset_webp as u8
-            || cfg.avif_quality != preset_webp as u8
+            || cfg.avif_quality != preset_avif
-            || cfg.avif_speed != 6
+            || cfg.avif_speed != preset_avif_speed
-            || cfg.webp_effort != 4;
+            || cfg.webp_effort != preset_webp_effort;
 
         if has_custom {
             job.compress = Some(pixstrip_core::operations::CompressConfig::Custom {
@@ -1967,8 +1977,9 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
     }
 
     // Check for existing output files when "Ask" overwrite behavior is set.
-    // Skip check if rename or format conversion is active (output names will differ).
+    // Skip check if rename or format conversion will actually change output names.
-    let has_rename_or_convert = job.rename.is_some() || job.convert.is_some();
+    let has_rename_or_convert = job.rename.as_ref().is_some_and(|r| r.changes_filename())
+        || job.convert.as_ref().is_some_and(|c| c.changes_extension());
     if ask_overwrite && !has_rename_or_convert {
         let output_dir = ui.state.output_dir.borrow().clone()
             .unwrap_or_else(|| {
@@ -1980,7 +1991,19 @@ fn run_processing(_window: &adw::ApplicationWindow, ui: &WizardUi) {
             let conflicts: Vec<String> = files.iter()
                 .filter_map(|f| {
                     let name = f.file_name()?;
-                    let out_path = output_dir.join(name);
+                    let out_path = if job.preserve_directory_structure {
+                        if let Ok(rel) = f.strip_prefix(&job.input_dir) {
+                            if let Some(parent) = rel.parent() {
+                                output_dir.join(parent).join(name)
+                            } else {
+                                output_dir.join(name)
+                            }
+                        } else {
+                            output_dir.join(name)
+                        }
+                    } else {
+                        output_dir.join(name)
+                    };
                     if out_path.exists() { Some(name.to_string_lossy().into()) } else { None }
                 })
                 .take(10)
@@ -3464,9 +3487,14 @@ fn build_watch_folder_panel() -> gtk::Box {
                     if let Ok(file) = result
                         && let Some(path) = file.path()
                     {
+                        // Use first available preset name
+                        let default_preset = pixstrip_core::preset::Preset::all_builtins()
+                            .first()
+                            .map(|p| p.name.clone())
+                            .unwrap_or_else(|| "Blog Photos".to_string());
                         let new_folder = pixstrip_core::watcher::WatchFolder {
                             path: path.clone(),
-                            preset_name: "Blog Photos".to_string(),
+                            preset_name: default_preset,
                             recursive: false,
                             active: true,
                         };

pixstrip-gtk/src/steps/step_images.rs

@@ -550,8 +550,8 @@ fn build_loaded_state(state: &AppState) -> gtk::Box {
         .spacing(0)
         .build();
 
-    // Guard flag to prevent O(n^2) update cascade during batch checkbox operations
+    // Use the shared batch_updating flag from AppState
-    let batch_updating: Rc<std::cell::Cell<bool>> = Rc::new(std::cell::Cell::new(false));
+    let batch_updating = state.batch_updating.clone();
 
     // Toolbar
     let toolbar = gtk::Box::builder()