From b2c88e5471dbde3a5925cff92c882a026b651847 Mon Sep 17 00:00:00 2001
From: Halit Can <hc1281622@outlook.com>
Date: Fri, 17 Jul 2026 23:15:27 +0300
Subject: [PATCH] feat(canvas): enhance composite shader with selection overlay
 and marching ants

- Updated the canvas composite shader to include a selection mask fill and animated marching ants border.
- Added new uniforms for animation time, selection mask presence, and quick mask mode.
- Modified the fragment shader to handle selection rendering, including color tinting for selected areas and a dash pattern for the marching ants effect.
- Refactored the OverlayProgram to remove the old marching ants rendering logic, now handled by the GPU shader.
- Introduced new data structures in the shader pipeline for managing selection mask textures and samplers.
- Implemented functionality to upload selection mask data to the GPU.
- Updated selection state handling to ensure correct bounds calculations.
- Enhanced sidebar tool button rendering with fallback for missing icons.
---
 hcie-engine-api/src/lib.rs                    |  55 +++++
 hcie-iced-app/crates/hcie-iced-gui/src/app.rs | 229 +++++++++++++++---
 .../src/canvas/.mimocode/.cron-lock           |   1 +
 .../hcie-iced-gui/src/canvas/canvas.wgsl      | 122 ++++++++--
 .../crates/hcie-iced-gui/src/canvas/mod.rs    | 214 ++++++----------
 .../hcie-iced-gui/src/canvas/shader_canvas.rs | 181 +++++++++++++-
 .../hcie-iced-gui/src/selection/state.rs      |   7 +-
 .../crates/hcie-iced-gui/src/sidebar/mod.rs   |  34 ++-
 8 files changed, 634 insertions(+), 209 deletions(-)
 create mode 100644 hcie-iced-app/crates/hcie-iced-gui/src/canvas/.mimocode/.cron-lock

diff --git a/hcie-engine-api/src/lib.rs b/hcie-engine-api/src/lib.rs
index 96bd490..15a9fb2 100644
--- a/hcie-engine-api/src/lib.rs
+++ b/hcie-engine-api/src/lib.rs
@@ -751,6 +751,9 @@ impl Engine {
     // ── Filter Ops ───────────────────────────────────────────────────────
 
     pub fn apply_filter(&mut self, filter_id: &str, params: serde_json::Value) {
+        // Clone the selection mask before borrowing the layer mutably, to avoid
+        // borrow-checker conflict between `active_layer_mut()` and `selection_mask`.
+        let mask = self.document.selection_mask.clone();
         if let Some(layer) = self.document.active_layer_mut() {
             let before_pixels = layer.pixels.clone();
             let _ = apply_filter(
@@ -760,6 +763,30 @@ impl Engine {
                 layer.width,
                 layer.height,
             );
+            // When a selection is active, restore original pixels for unselected
+            // areas so the filter is confined to the selected region.
+            if let Some(ref mask) = mask {
+                let w = layer.width as usize;
+                let h = layer.height as usize;
+                if mask.len() == w * h {
+                    for y in 0..h {
+                        for x in 0..w {
+                            let idx = y * w + x;
+                            if mask[idx] == 0 {
+                                let pidx = idx * 4;
+                                if pidx + 3 < layer.pixels.len()
+                                    && pidx + 3 < before_pixels.len()
+                                {
+                                    layer.pixels[pidx] = before_pixels[pidx];
+                                    layer.pixels[pidx + 1] = before_pixels[pidx + 1];
+                                    layer.pixels[pidx + 2] = before_pixels[pidx + 2];
+                                    layer.pixels[pidx + 3] = before_pixels[pidx + 3];
+                                }
+                            }
+                        }
+                    }
+                }
+            }
             layer.dirty = true;
             self.document.push_draw_snapshot(
                 self.document.active_layer,
@@ -773,7 +800,11 @@ impl Engine {
     }
 
     pub fn apply_filter_preview(&mut self, filter_id: &str, params: serde_json::Value) {
+        let mask = self.document.selection_mask.clone();
         if let Some(layer) = self.document.active_layer_mut() {
+            // Save the current pixels before applying the filter, so we can
+            // restore unselected areas afterwards.
+            let saved_before = layer.pixels.clone();
             let _ = apply_filter(
                 filter_id,
                 &params,
@@ -781,6 +812,30 @@ impl Engine {
                 layer.width,
                 layer.height,
             );
+            // When a selection is active, restore original pixels for unselected
+            // areas so the filter preview is confined to the selected region.
+            if let Some(ref mask) = mask {
+                let w = layer.width as usize;
+                let h = layer.height as usize;
+                if mask.len() == w * h {
+                    for y in 0..h {
+                        for x in 0..w {
+                            let idx = y * w + x;
+                            if mask[idx] == 0 {
+                                let pidx = idx * 4;
+                                if pidx + 3 < layer.pixels.len()
+                                    && pidx + 3 < saved_before.len()
+                                {
+                                    layer.pixels[pidx] = saved_before[pidx];
+                                    layer.pixels[pidx + 1] = saved_before[pidx + 1];
+                                    layer.pixels[pidx + 2] = saved_before[pidx + 2];
+                                    layer.pixels[pidx + 3] = saved_before[pidx + 3];
+                                }
+                            }
+                        }
+                    }
+                }
+            }
             layer.dirty = true;
             self.document.composite_dirty = true;
         }
diff --git a/hcie-iced-app/crates/hcie-iced-gui/src/app.rs b/hcie-iced-app/crates/hcie-iced-gui/src/app.rs
index 0ce8509..187254a 100644
--- a/hcie-iced-app/crates/hcie-iced-gui/src/app.rs
+++ b/hcie-iced-app/crates/hcie-iced-gui/src/app.rs
@@ -386,8 +386,14 @@ pub struct IcedDocument {
     pub internal_clipboard: Option<SelectionTransform>,
     /// Selection mask (alpha channel) for the current selection
     pub selection_mask: Option<Vec<u8>>,
+    /// Whether the selection mask has changed since last GPU upload
+    pub selection_mask_dirty: std::cell::Cell<bool>,
     /// Selection bounds (x, y, width, height)
     pub selection_bounds: Option<(u32, u32, u32, u32)>,
+    /// History of selection masks for undo support.
+    pub selection_history: Vec<Option<Vec<u8>>>,
+    /// Engine history index when the selection was last modified.
+    pub selection_history_marker: i32,
     /// Crop tool state
     pub crop_state: CropState,
     /// Accumulated lasso points (freehand selection) in canvas coordinates.
@@ -1142,6 +1148,14 @@ impl HcieIcedApp {
     /// through `hcie-engine-api` when add/subtract/intersect mode is active.
     fn combine_current_selection(&mut self, previous: Option<Vec<u8>>) {
         let doc = &mut self.documents[self.active_doc];
+        
+        let current_marker = doc.engine.history_current();
+        if current_marker != doc.selection_history_marker {
+            doc.selection_history.clear();
+            doc.selection_history_marker = current_marker;
+        }
+        doc.selection_history.push(previous.clone());
+
         let Some(new_mask) = doc.engine.get_selection_mask().map(ToOwned::to_owned) else {
             return;
         };
@@ -1194,7 +1208,10 @@ impl HcieIcedApp {
             transform_source: None,
             internal_clipboard: None,
             selection_mask: None,
+            selection_mask_dirty: std::cell::Cell::new(false),
             selection_bounds: None,
+            selection_history: Vec::new(),
+            selection_history_marker: 0,
             crop_state: CropState::default(),
             lasso_points: Vec::new(),
             polygon_points: Vec::new(),
@@ -1673,22 +1690,89 @@ impl HcieIcedApp {
         let doc = &mut self.documents[self.active_doc];
 
         if doc.engine.is_composite_dirty() {
-            // Use get_composite_pixels() instead of render_composite_region()
-            // to avoid segfaults when canvas dimensions change (e.g. after PSD import).
-            // get_composite_pixels() returns a safe Vec<u8> via composite_layers().
-            let composite = doc.engine.get_composite_pixels();
-            let size = composite.len();
-            if size > 0 {
-                doc.composite_raw = composite;
-                // Update the shared Arc — if no other reference exists, mutate in-place
-                if let Some(pixels) = Arc::get_mut(&mut doc.composite_pixels) {
-                    pixels.resize(doc.composite_raw.len(), 0);
-                    pixels.copy_from_slice(&doc.composite_raw);
-                } else {
-                    doc.composite_pixels = Arc::new(doc.composite_raw.clone());
+            let (dirty_rect, ptr, len) = doc.engine.render_composite_region();
+            if len > 0 && !ptr.is_null() {
+                let mut is_full_copy = false;
+                // Resize composite_raw if canvas dimensions changed (e.g. after PSD import)
+                if doc.composite_raw.len() != len {
+                    doc.composite_raw.resize(len, 0);
+                    doc.full_upload.replace(true);
+                    is_full_copy = true;
                 }
-                doc.full_upload.replace(true);
-                doc.dirty_region.replace(None);
+
+                // If the canvas changed size, we MUST force a full upload because the old memory
+                // structure is no longer valid, and a partial copy would leave zeros in the new buffer.
+                if let Some(rect) = dirty_rect.filter(|_| !is_full_copy) {
+                    let w = doc.engine.canvas_width() as usize;
+                    let h = doc.engine.canvas_height() as usize;
+                    let [x0, y0, x1, y1] = rect;
+                    let x0 = x0 as usize;
+                    let y0 = y0 as usize;
+                    let x1 = x1 as usize;
+                    let y1 = y1 as usize;
+                    
+                    let row_bytes = (x1 - x0) * 4;
+                    if row_bytes > 0 {
+                        unsafe {
+                            let src_ptr = ptr;
+                            let dst_raw_ptr = doc.composite_raw.as_mut_ptr();
+                            
+                            let mut pixels_ptr = std::ptr::null_mut();
+                            let mut need_new_arc = false;
+                            
+                            if let Some(pixels) = Arc::get_mut(&mut doc.composite_pixels) {
+                                // Important: resize arc if needed before taking mutable pointer
+                                if pixels.len() != len {
+                                    pixels.resize(len, 0);
+                                }
+                                pixels_ptr = pixels.as_mut_ptr();
+                            } else {
+                                need_new_arc = true;
+                            }
+
+                            for y in y0..y1 {
+                                let offset = (y * w + x0) * 4;
+                                std::ptr::copy_nonoverlapping(
+                                    src_ptr.add(offset),
+                                    dst_raw_ptr.add(offset),
+                                    row_bytes
+                                );
+                                if !pixels_ptr.is_null() {
+                                    std::ptr::copy_nonoverlapping(
+                                        src_ptr.add(offset),
+                                        pixels_ptr.add(offset),
+                                        row_bytes
+                                    );
+                                }
+                            }
+                            
+                            if need_new_arc {
+                                doc.composite_pixels = Arc::new(doc.composite_raw.clone());
+                            }
+                        }
+                    }
+
+                    let current = doc.dirty_region.replace(None);
+                    doc.dirty_region.replace(Some(union_regions(current, rect)));
+                } else {
+                    // Full update
+                    unsafe {
+                        std::ptr::copy_nonoverlapping(ptr, doc.composite_raw.as_mut_ptr(), len);
+                    }
+                    if let Some(pixels) = Arc::get_mut(&mut doc.composite_pixels) {
+                        if pixels.len() != len {
+                            pixels.resize(len, 0);
+                        }
+                        unsafe {
+                            std::ptr::copy_nonoverlapping(ptr, pixels.as_mut_ptr(), len);
+                        }
+                    } else {
+                        doc.composite_pixels = Arc::new(doc.composite_raw.clone());
+                    }
+                    doc.full_upload.replace(true);
+                    doc.dirty_region.replace(None);
+                }
+
                 doc.render_generation = doc.render_generation.wrapping_add(1);
             }
 
@@ -1698,6 +1782,7 @@ impl HcieIcedApp {
         // Update selection edge cache if mask changed
         if let Some(mask) = doc.engine.get_selection_mask() {
             doc.selection_mask = Some(mask.to_vec());
+            doc.selection_mask_dirty.set(true);
             doc.selection_bounds = selection::state::mask_bounds(
                 mask,
                 doc.engine.canvas_width(),
@@ -1718,6 +1803,7 @@ impl HcieIcedApp {
             doc.marching_ants_edges = Some(edges);
         } else {
             doc.selection_mask = None;
+            doc.selection_mask_dirty.set(true);
             doc.selection_bounds = None;
             doc.selection_fill_spans = None;
             doc.marching_ants_edges = None;
@@ -2202,6 +2288,7 @@ impl HcieIcedApp {
                                     }
                                     doc.engine.selection_clear();
                                     doc.selection_mask = Some(mask_data);
+                                    doc.selection_mask_dirty.set(true);
                                     doc.transform_source = Some(tr.clone());
                                     doc.selection_transform = Some(tr);
                                 }
@@ -2288,6 +2375,20 @@ impl HcieIcedApp {
                 }
 
                 if self.tool_state.is_drawing {
+                    // Selection tools (Lasso, Polygon, Vision, Rect) use is_drawing
+                    // to track drag state but must not enter the brush code path.
+                    let is_selection_tool = matches!(
+                        self.tool_state.active_tool,
+                        Tool::Lasso
+                            | Tool::PolygonSelect
+                            | Tool::Select
+                            | Tool::VisionSelect
+                            | Tool::MagicWand
+                            | Tool::SmartSelect
+                    );
+                    if is_selection_tool {
+                        // Fall through to the dedicated selection drag handlers below.
+                    } else {
                     let is_ctrl = self.modifiers.control() || self.modifiers.logo();
                     if is_ctrl {
                         // Pick color
@@ -2388,6 +2489,7 @@ impl HcieIcedApp {
                             self.tool_state.last_stroke_pos = Some((x, y));
                         }
                     }
+                    } // end else (non-selection tool)
                 }
 
                 // Handle selection drag
@@ -2503,6 +2605,19 @@ impl HcieIcedApp {
                 }
 
                 if self.tool_state.is_drawing {
+                    // Selection tools use is_drawing to track drag state but never
+                    // start a brush stroke — skip end_stroke / commit_pending_history
+                    // so they don't push a bogus undo entry that empties the canvas.
+                    let is_selection_tool = matches!(
+                        self.tool_state.active_tool,
+                        Tool::Lasso
+                            | Tool::PolygonSelect
+                            | Tool::Select
+                            | Tool::VisionSelect
+                            | Tool::MagicWand
+                            | Tool::SmartSelect
+                    );
+                    if !is_selection_tool {
                     let layer_id = self.documents[self.active_doc].engine.active_layer_id();
                     self.documents[self.active_doc].engine.end_stroke(layer_id);
                     self.documents[self.active_doc]
@@ -2514,6 +2629,7 @@ impl HcieIcedApp {
                     self.documents[self.active_doc].modified = true;
 
                     self.refresh_composite_if_needed();
+                    } // end if !is_selection_tool
                 }
 
                 // End selection drag
@@ -2599,10 +2715,26 @@ impl HcieIcedApp {
             Message::CompositeRefresh | Message::Undo | Message::Redo => {
                 match message {
                     Message::Undo => {
-                        self.documents[self.active_doc].engine.undo();
+                        let doc = &mut self.documents[self.active_doc];
+                        let current_marker = doc.engine.history_current();
+                        if current_marker == doc.selection_history_marker && !doc.selection_history.is_empty() {
+                            // Undo selection
+                            if let Some(prev_mask) = doc.selection_history.pop() {
+                                if let Some(mask) = prev_mask {
+                                    doc.engine.set_selection_mask(mask);
+                                } else {
+                                    doc.engine.selection_clear();
+                                }
+                                doc.selection_mask_dirty.set(true);
+                            }
+                        } else {
+                            doc.engine.undo();
+                            doc.selection_history.clear();
+                        }
                     }
                     Message::Redo => {
                         self.documents[self.active_doc].engine.redo();
+                        self.documents[self.active_doc].selection_history.clear();
                     }
                     _ => {}
                 }
@@ -4254,7 +4386,10 @@ impl HcieIcedApp {
                     transform_source: None,
                     internal_clipboard: None,
                     selection_mask: None,
+                    selection_mask_dirty: std::cell::Cell::new(false),
                     selection_bounds: None,
+            selection_history: Vec::new(),
+            selection_history_marker: 0,
                     crop_state: CropState::default(),
                     lasso_points: Vec::new(),
                     polygon_points: Vec::new(),
@@ -4465,6 +4600,9 @@ impl HcieIcedApp {
                         // Store selection bounds for marching ants display
                         self.documents[self.active_doc].selection_bounds =
                             Some((sx, sy, ex - sx, ey - sy));
+                        // Clear the drag-preview rect so the blue rectangle
+                        // disappears and the marching ants overlay takes over.
+                        self.documents[self.active_doc].selection_rect = None;
                         self.refresh_composite_if_needed();
                         return Task::perform(async {}, |_| Message::CompositeRefresh);
                     }
@@ -4473,19 +4611,39 @@ impl HcieIcedApp {
                 self.documents[self.active_doc].selection_rect = None;
             }
             Message::SelectAll => {
+                let previous = self.documents[self.active_doc].engine.get_selection_mask().map(ToOwned::to_owned);
+                let current_marker = self.documents[self.active_doc].engine.history_current();
+                if current_marker != self.documents[self.active_doc].selection_history_marker {
+                    self.documents[self.active_doc].selection_history.clear();
+                    self.documents[self.active_doc].selection_history_marker = current_marker;
+                }
+                self.documents[self.active_doc].selection_history.push(previous);
+
                 let w = self.documents[self.active_doc].engine.canvas_width();
                 let h = self.documents[self.active_doc].engine.canvas_height();
                 self.documents[self.active_doc].engine.selection_all();
                 self.documents[self.active_doc].selection_bounds = Some((0, 0, w, h));
             }
             Message::Deselect => {
-                self.documents[self.active_doc].selection_rect = None;
-                self.documents[self.active_doc].selection_bounds = None;
-                self.documents[self.active_doc].selection_transform = None;
-                self.documents[self.active_doc].transform_drag_handle = TransformHandle::None;
-                self.documents[self.active_doc].engine.selection_clear();
-                self.documents[self.active_doc].selection_fill_spans = None;
-                self.documents[self.active_doc].marching_ants_edges = None;
+                let doc = &mut self.documents[self.active_doc];
+                let previous = doc.engine.get_selection_mask().map(ToOwned::to_owned);
+                let current_marker = doc.engine.history_current();
+                if current_marker != doc.selection_history_marker {
+                    doc.selection_history.clear();
+                    doc.selection_history_marker = current_marker;
+                }
+                doc.selection_history.push(previous);
+
+                doc.selection_rect = None;
+                doc.selection_bounds = None;
+                doc.selection_transform = None;
+                doc.transform_drag_handle = TransformHandle::None;
+                doc.engine.selection_clear();
+                doc.selection_mask = None;
+                doc.selection_mask_dirty.set(true);
+                doc.selection_fill_spans = None;
+                doc.marching_ants_edges = None;
+                return Task::perform(async {}, |_| Message::CompositeRefresh);
             }
             Message::SelectInverse => {
                 self.documents[self.active_doc].engine.selection_invert();
@@ -4632,6 +4790,7 @@ impl HcieIcedApp {
                     self.documents[self.active_doc].engine.selection_clear();
                     self.documents[self.active_doc].selection_bounds = None;
                     self.documents[self.active_doc].selection_mask = None;
+                    self.documents[self.active_doc].selection_mask_dirty.set(true);
                     self.documents[self.active_doc].transform_drag_handle = TransformHandle::None;
                     self.documents[self.active_doc].transform_drag_start = None;
                     self.documents[self.active_doc].transform_original = None;
@@ -6604,7 +6763,10 @@ impl HcieIcedApp {
                     transform_source: None,
                     internal_clipboard: None,
                     selection_mask: None,
+                    selection_mask_dirty: std::cell::Cell::new(false),
                     selection_bounds: None,
+            selection_history: Vec::new(),
+            selection_history_marker: 0,
                     crop_state: CropState::default(),
                     lasso_points: Vec::new(),
                     polygon_points: Vec::new(),
@@ -7544,7 +7706,9 @@ impl HcieIcedApp {
                     Some(Message::SelectAll)
                 }
                 // Ctrl+D = Deselect
-                iced::keyboard::Key::Character(ref c) if c.as_str() == "d" && ctrl && !shift => {
+                iced::keyboard::Key::Character(ref c)
+                    if c.as_str().eq_ignore_ascii_case("d") && ctrl && !shift =>
+                {
                     Some(Message::Deselect)
                 }
                 // Ctrl+Shift+I = Inverse Selection
@@ -7749,21 +7913,18 @@ impl HcieIcedApp {
             }
         });
 
-        // Timer for marching ants animation - fires every 50ms when selection is active
+        // The marching ants are rendered in the persistent GPU canvas shader.
+        // Use a real timer rather than an immediately-ready async loop: the old
+        // loop generated an unbounded stream of CompositeRefresh messages and
+        // starved pointer events while drawing.
         let marching_ants = if self
             .documents
             .iter()
             .any(|doc| doc.selection_bounds.is_some())
+            && !self.tool_state.is_drawing
         {
-            iced::Subscription::run_with_id(
-                std::time::Instant::now(),
-                iced::futures::stream::unfold((), |_| async {
-                    // Wait 50ms between animation frames (~20fps for smooth marching ants)
-                    iced::futures::future::ready(()).await;
-                    // Use a simple yield to create animation frames
-                    Some((Message::CompositeRefresh, ()))
-                }),
-            )
+            iced::time::every(std::time::Duration::from_millis(50))
+                .map(|_| Message::CompositeRefresh)
         } else {
             iced::Subscription::none()
         };
diff --git a/hcie-iced-app/crates/hcie-iced-gui/src/canvas/.mimocode/.cron-lock b/hcie-iced-app/crates/hcie-iced-gui/src/canvas/.mimocode/.cron-lock
new file mode 100644
index 0000000..64ded12
--- /dev/null
+++ b/hcie-iced-app/crates/hcie-iced-gui/src/canvas/.mimocode/.cron-lock
@@ -0,0 +1 @@
+{"pid":293615,"startedAt":1784244897004}
\ No newline at end of file
diff --git a/hcie-iced-app/crates/hcie-iced-gui/src/canvas/canvas.wgsl b/hcie-iced-app/crates/hcie-iced-gui/src/canvas/canvas.wgsl
index b954e39..8c563e0 100644
--- a/hcie-iced-app/crates/hcie-iced-gui/src/canvas/canvas.wgsl
+++ b/hcie-iced-app/crates/hcie-iced-gui/src/canvas/canvas.wgsl
@@ -1,22 +1,32 @@
-// Canvas composite shader — draws the composite texture with zoom/pan/checkerboard.
+// Canvas composite shader — draws composite texture with zoom/pan/checkerboard
+// and GPU-accelerated marching ants selection overlay.
 //
 // ## Purpose
 // Single-pass fragment shader that renders:
 // 1. Procedural checkerboard background (no CPU geometry)
 // 2. Composite texture from the engine (partial-updated via queue.write_texture)
+// 3. Selection mask fill (purple/red tint over selected pixels)
+// 4. Marching ants border (animated black+white dashes along selection edge)
 //
 // ## Uniforms
-// - transform: 2D affine transform (zoom + pan → NDC)
+// - transform: 2D affine transform (zoom + pan -> NDC)
 // - canvas_size: engine canvas dimensions in pixels
 // - viewport_size: widget viewport dimensions in pixels
 // - checker_size: checkerboard square size in pixels
+// - anim_time: marching ants animation time in seconds
+// - has_selection: 1.0 if selection mask is bound, 0.0 otherwise
+// - quick_mask: 1.0 for red quick-mask, 0.0 for normal blue tint
+// - _pad: padding for 16-byte alignment
 //
-// ## Vertex Layout
-// Two triangles forming a fullscreen quad. Positions are in NDC [-1,1].
-// UV coordinates map to the composite texture.
+// ## Bindings
+// - @binding(0): Uniforms
+// - @binding(1): Composite texture (RGBA)
+// - @binding(2): Sampler
+// - @binding(3): Selection mask (R8: >0.5 = selected)
+// - @binding(4): Selection mask sampler
 
 struct Uniforms {
-    // Column-major 2×2 scale/rotation (we only use scale)
+    // Column-major 2x2 scale/rotation (we only use scale)
     scale_x:       f32,
     scale_y:       f32,
     // Translation in NDC
@@ -30,10 +40,12 @@ struct Uniforms {
     viewport_h:    f32,
     // Checkerboard square size (pixels)
     checker_size:  f32,
-    // Padding for 16-byte alignment
-    _pad1:         f32,
-    _pad2:         f32,
-    _pad3:         f32,
+    // Animation time (seconds) for marching ants
+    anim_time:     f32,
+    // 1.0 if selection mask is bound, 0.0 otherwise
+    has_selection: f32,
+    // 1.0 for red quick-mask tint, 0.0 for normal blue tint
+    quick_mask:    f32,
 }
 
 @group(0) @binding(0)
@@ -45,6 +57,12 @@ var composite_texture: texture_2d<f32>;
 @group(0) @binding(2)
 var composite_sampler: sampler;
 
+@group(0) @binding(3)
+var selection_texture: texture_2d<f32>;
+
+@group(0) @binding(4)
+var selection_sampler: sampler;
+
 struct VertexInput {
     @location(0) position: vec2<f32>,
     @location(1) uv: vec2<f32>,
@@ -75,21 +93,87 @@ fn vs_main(in: VertexInput) -> VertexOutput {
 
 @fragment
 fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
-    // Checkerboard pattern (screen-space, fixed pixel size)
+    // ── 1. Checkerboard pattern (screen-space, fixed pixel size) ──────────
     let checker_col = floor(in.screen_pos.x / uniforms.checker_size);
     let checker_row = floor(in.screen_pos.y / uniforms.checker_size);
     let is_light = ((i32(checker_col) + i32(checker_row)) % 2) == 0;
     let light_color = vec4<f32>(0.70, 0.70, 0.70, 1.0);
     let dark_color  = vec4<f32>(0.50, 0.50, 0.50, 1.0);
-    let checker = select(dark_color, light_color, is_light);
+    var color = select(dark_color, light_color, is_light);
 
-    // Sample composite texture
+    // ── 2. Composite texture ─────────────────────────────────────────────
     let tex_color = textureSample(composite_texture, composite_sampler, in.uv);
+    color = vec4<f32>(mix(color.rgb, tex_color.rgb, tex_color.a), 1.0);
 
-    // Alpha-blend composite over checkerboard
-    let blended = vec4<f32>(
-        mix(checker.rgb, tex_color.rgb, tex_color.a),
-        1.0,
-    );
-    return blended;
+    // ── 3. Selection overlay (if selection mask is bound) ─────────────────
+    if uniforms.has_selection > 0.5 {
+        let sel_val = textureSample(selection_texture, selection_sampler, in.uv).r;
+
+        if sel_val > 0.5 {
+            // This pixel is selected — compute distance to nearest border
+            // by sampling 8 neighbors at 1-pixel offset in canvas space
+            let texel_w = 1.0 / uniforms.canvas_w;
+            let texel_h = 1.0 / uniforms.canvas_h;
+
+            // Sample 8 neighbors to detect border (unrolled — WGSL forbids variable-indexed textureSample)
+            var is_border = false;
+            let n0 = textureSample(selection_texture, selection_sampler, in.uv + vec2<f32>(-texel_w, 0.0)).r;
+            let n1 = textureSample(selection_texture, selection_sampler, in.uv + vec2<f32>( texel_w, 0.0)).r;
+            let n2 = textureSample(selection_texture, selection_sampler, in.uv + vec2<f32>(0.0, -texel_h)).r;
+            let n3 = textureSample(selection_texture, selection_sampler, in.uv + vec2<f32>(0.0,  texel_h)).r;
+            let n4 = textureSample(selection_texture, selection_sampler, in.uv + vec2<f32>(-texel_w, -texel_h)).r;
+            let n5 = textureSample(selection_texture, selection_sampler, in.uv + vec2<f32>( texel_w, -texel_h)).r;
+            let n6 = textureSample(selection_texture, selection_sampler, in.uv + vec2<f32>(-texel_w,  texel_h)).r;
+            let n7 = textureSample(selection_texture, selection_sampler, in.uv + vec2<f32>( texel_w,  texel_h)).r;
+
+            if n0 <= 0.5 || n1 <= 0.5 || n2 <= 0.5 || n3 <= 0.5 || n4 <= 0.5 || n5 <= 0.5 || n6 <= 0.5 || n7 <= 0.5 {
+                is_border = true;
+            }
+
+            if is_border {
+                // ── Marching ants border ──────────────────────────────────
+                // Use canvas-space position for the dash pattern
+                let canvas_x = in.uv.x * uniforms.canvas_w;
+                let canvas_y = in.uv.y * uniforms.canvas_h;
+
+                // Diagonal dash pattern (combines X and Y for diagonal movement)
+                let dash_length = 8.0;
+                let gap_length = 4.0;
+                let cycle = dash_length + gap_length;
+                let speed = 22.0; // pixels per second
+
+                // Diagonal offset: moves dashes diagonally for the marching effect
+                let pattern_pos = (canvas_x + canvas_y + uniforms.anim_time * speed) % cycle;
+
+                if pattern_pos < dash_length {
+                    // White dash
+                    color = vec4<f32>(1.0, 1.0, 1.0, 0.9);
+                } else {
+                    // Black gap
+                    color = vec4<f32>(0.0, 0.0, 0.0, 0.8);
+                }
+            } else {
+                // ── Selected area fill ────────────────────────────────────
+                if uniforms.quick_mask > 0.5 {
+                    // Quick mask: red tint
+                    color = vec4<f32>(
+                        mix(color.r, 1.0, 0.35),
+                        mix(color.g, 0.1, 0.35),
+                        mix(color.b, 0.1, 0.35),
+                        1.0
+                    );
+                } else {
+                    // Normal selection: blue/purple tint
+                    color = vec4<f32>(
+                        mix(color.r, 0.4, 0.12),
+                        mix(color.g, 0.5, 0.12),
+                        mix(color.b, 1.0, 0.12),
+                        1.0
+                    );
+                }
+            }
+        }
+    }
+
+    return color;
 }
diff --git a/hcie-iced-app/crates/hcie-iced-gui/src/canvas/mod.rs b/hcie-iced-app/crates/hcie-iced-gui/src/canvas/mod.rs
index 5637a55..0c1e9fa 100644
--- a/hcie-iced-app/crates/hcie-iced-gui/src/canvas/mod.rs
+++ b/hcie-iced-app/crates/hcie-iced-gui/src/canvas/mod.rs
@@ -77,6 +77,10 @@ struct OverlayProgram {
     rect_radius: f32,
     /// Gradient drag preview endpoints in canvas-space.
     gradient_drag: Option<((f32, f32), (f32, f32))>,
+    /// Lasso freehand path points accumulated during drag (canvas-space).
+    lasso_points: Vec<(u32, u32)>,
+    /// Polygon selection points accumulated during click-by-click (canvas-space).
+    polygon_points: Vec<(u32, u32)>,
     /// Extracted edges for marching ants rendering.
     marching_ants_edges: Option<std::sync::Arc<Vec<(u32, u32, u32, u32)>>>,
     /// Exact horizontal selected-pixel spans for irregular selection fill.
@@ -578,7 +582,9 @@ impl canvas::Program<Message> for OverlayProgram {
             || self.vector_draw.is_some()
             || self.selected_vector_bounds.is_some()
             || self.selection_transform.is_some()
-            || self.crop_state.as_ref().map_or(false, |c| c.active);
+            || self.crop_state.as_ref().map_or(false, |c| c.active)
+            || !self.lasso_points.is_empty()
+            || !self.polygon_points.is_empty();
 
         if has_overlays {
             let mut frame = Frame::new(renderer, bounds.size());
@@ -605,142 +611,75 @@ impl canvas::Program<Message> for OverlayProgram {
                 }
             }
 
-            // Draw marching ants for active selection (after selection is created)
-            if let Some((sx, sy, sw, sh)) = self.selection_bounds {
-                if self.selection_transform.is_none() && self.selection_rect.is_none() {
-                    let sel_x = origin_x + sx as f32 * self.zoom;
-                    let sel_y = origin_y + sy as f32 * self.zoom;
-                    let sel_w = sw as f32 * self.zoom;
-                    let sel_h = sh as f32 * self.zoom;
+            // Selection overlay (fill + marching ants) is now rendered by the GPU shader.
+            // Fill exact mask runs are handled in the fragment shader via selection mask texture.
+            // The shader computes:
+            // - Purple/red fill for selected pixels
+            // - Animated black+white dashes along the selection border
 
-                    // Fill exact mask runs rather than the irregular selection's bounding box.
-                    let fill_color = if self.quick_mask {
-                        iced::Color::from_rgba(1.0, 0.1, 0.1, 0.35)
-                    } else {
-                        iced::Color::from_rgba(0.4, 0.5, 1.0, 0.12)
-                    };
-                    if let Some(spans) = &self.selection_fill_spans {
-                        for &(start_x, y, end_x) in spans.iter() {
-                            frame.fill(
-                                &Path::rectangle(
-                                    Point::new(
-                                        origin_x + start_x as f32 * self.zoom,
-                                        origin_y + y as f32 * self.zoom,
-                                    ),
-                                    Size::new(
-                                        (end_x - start_x) as f32 * self.zoom,
-                                        self.zoom.max(1.0),
-                                    ),
-                                ),
-                                fill_color,
-                            );
-                        }
-                    }
-
-                    // Calculate dash offset for marching ants animation
-                    // The offset moves the dash pattern to create the marching effect
-                    let dash_length = 8.0;
-                    let gap_length = 4.0;
-                    let total_cycle = dash_length + gap_length;
-                    let animated_offset = (self.marching_ants_offset * total_cycle) as usize;
-
-                    // Draw white dashes (foreground) - offset by half cycle for marching effect
-                    let white_offset =
-                        (animated_offset + (total_cycle / 2.0) as usize) % (total_cycle as usize);
-
-                    if let Some(edges) = &self.marching_ants_edges {
-                        // Irregular selection bounds (marching ants along extracted edges)
-                        for &(x1, y1, x2, y2) in edges.iter() {
-                            let s1 = Point::new(
-                                origin_x + x1 as f32 * self.zoom,
-                                origin_y + y1 as f32 * self.zoom,
-                            );
-                            let s2 = Point::new(
-                                origin_x + x2 as f32 * self.zoom,
-                                origin_y + y2 as f32 * self.zoom,
-                            );
-
-                            // Optimization: we could clip, but `Path::line` handles it generally.
-                            let dist = ((s1.x - s2.x).powi(2) + (s1.y - s2.y).powi(2)).sqrt();
-                            if dist < 1e-6 {
-                                continue;
-                            }
-
-                            let line_path = Path::line(s1, s2);
-                            frame.stroke(
-                                &line_path,
-                                Stroke {
-                                    style: canvas::stroke::Style::Solid(iced::Color::from_rgb(
-                                        0.0, 0.0, 0.0,
-                                    )),
-                                    width: 1.5,
-                                    ..Default::default()
-                                },
-                            );
-
-                            let dir_x = (s2.x - s1.x) / dist;
-                            let dir_y = (s2.y - s1.y) / dist;
-
-                            let mut curr = -(self.marching_ants_offset * total_cycle);
-                            let mut iter = 0u32;
-                            while curr < dist && iter < 1000 {
-                                iter += 1;
-                                let start_d = curr.max(0.0);
-                                let end_d = (curr + dash_length).min(dist);
-                                if end_d > start_d {
-                                    let p_start =
-                                        Point::new(s1.x + dir_x * start_d, s1.y + dir_y * start_d);
-                                    let p_end =
-                                        Point::new(s1.x + dir_x * end_d, s1.y + dir_y * end_d);
-                                    let dash_path = Path::line(p_start, p_end);
-                                    frame.stroke(
-                                        &dash_path,
-                                        Stroke {
-                                            style: canvas::stroke::Style::Solid(
-                                                iced::Color::from_rgb(1.0, 1.0, 1.0),
-                                            ),
-                                            width: 1.5,
-                                            ..Default::default()
-                                        },
-                                    );
-                                }
-                                curr += total_cycle;
-                            }
-                        }
-                    } else {
-                        // Fallback to bounding box marching ants
-                        let sel_path =
-                            Path::rectangle(Point::new(sel_x, sel_y), Size::new(sel_w, sel_h));
-                        frame.stroke(
-                            &sel_path,
-                            Stroke {
-                                style: canvas::stroke::Style::Solid(iced::Color::from_rgb(
-                                    0.0, 0.0, 0.0,
-                                )),
-                                width: 2.0 / self.zoom.max(1.0),
-                                line_dash: canvas::LineDash {
-                                    segments: &[dash_length, gap_length],
-                                    offset: animated_offset,
-                                },
-                                ..Default::default()
-                            },
-                        );
-
-                        frame.stroke(
-                            &sel_path,
-                            Stroke {
-                                style: canvas::stroke::Style::Solid(iced::Color::from_rgb(
-                                    1.0, 1.0, 1.0,
-                                )),
-                                width: 2.0 / self.zoom.max(1.0),
-                                line_dash: canvas::LineDash {
-                                    segments: &[dash_length, gap_length],
-                                    offset: white_offset,
-                                },
-                                ..Default::default()
-                            },
+            // Draw lasso freehand path while dragging
+            if self.lasso_points.len() > 1 {
+                let lasso_path = Path::new(|b| {
+                    let first = &self.lasso_points[0];
+                    let start = Point::new(
+                        origin_x + first.0 as f32 * self.zoom,
+                        origin_y + first.1 as f32 * self.zoom,
+                    );
+                    b.move_to(start);
+                    for pt in &self.lasso_points[1..] {
+                        let p = Point::new(
+                            origin_x + pt.0 as f32 * self.zoom,
+                            origin_y + pt.1 as f32 * self.zoom,
                         );
+                        b.line_to(p);
                     }
+                    b.close();
+                });
+                frame.stroke(
+                    &lasso_path,
+                    Stroke {
+                        style: canvas::stroke::Style::Solid(iced::Color::from_rgb(0.0, 0.6, 1.0)),
+                        width: 1.5 / self.zoom.max(1.0),
+                        ..Default::default()
+                    },
+                );
+            }
+
+            // Draw polygon selection points while placing vertices
+            if self.polygon_points.len() > 1 {
+                let poly_path = Path::new(|b| {
+                    let first = &self.polygon_points[0];
+                    let start = Point::new(
+                        origin_x + first.0 as f32 * self.zoom,
+                        origin_y + first.1 as f32 * self.zoom,
+                    );
+                    b.move_to(start);
+                    for pt in &self.polygon_points[1..] {
+                        let p = Point::new(
+                            origin_x + pt.0 as f32 * self.zoom,
+                            origin_y + pt.1 as f32 * self.zoom,
+                        );
+                        b.line_to(p);
+                    }
+                });
+                frame.stroke(
+                    &poly_path,
+                    Stroke {
+                        style: canvas::stroke::Style::Solid(iced::Color::from_rgb(0.0, 0.6, 1.0)),
+                        width: 1.5 / self.zoom.max(1.0),
+                        ..Default::default()
+                    },
+                );
+                // Draw vertex dots
+                for pt in &self.polygon_points {
+                    let p = Point::new(
+                        origin_x + pt.0 as f32 * self.zoom,
+                        origin_y + pt.1 as f32 * self.zoom,
+                    );
+                    frame.fill(
+                        &Path::circle(p, 3.0 / self.zoom.max(1.0)),
+                        iced::Color::from_rgb(0.0, 0.6, 1.0),
+                    );
                 }
             }
 
@@ -1465,7 +1404,12 @@ pub fn view<'a>(
         dirty_region: doc.dirty_region.take(),
         full_upload: doc.full_upload.replace(false),
         space_pan: tool_state.space_pan,
+        selection_mask: doc.selection_mask.clone(),
+        selection_dirty: doc.selection_mask_dirty.get(),
+        anim_time: marching_ants_offset * 2.0, // Convert 0..1 to seconds (2s cycle)
+        quick_mask: doc.quick_mask,
     };
+    doc.selection_mask_dirty.set(false);
 
     let shader_canvas = Shader::new(shader_program)
         .width(Length::Fill)
@@ -1508,6 +1452,8 @@ pub fn view<'a>(
         polygon_sides,
         rect_radius,
         gradient_drag: doc.gradient_drag,
+        lasso_points: doc.lasso_points.clone(),
+        polygon_points: doc.polygon_points.clone(),
         marching_ants_edges: doc.marching_ants_edges.clone(),
         selection_fill_spans: doc.selection_fill_spans.clone(),
         quick_mask: doc.quick_mask,
diff --git a/hcie-iced-app/crates/hcie-iced-gui/src/canvas/shader_canvas.rs b/hcie-iced-app/crates/hcie-iced-gui/src/canvas/shader_canvas.rs
index 4a3bb63..b0afe83 100644
--- a/hcie-iced-app/crates/hcie-iced-gui/src/canvas/shader_canvas.rs
+++ b/hcie-iced-app/crates/hcie-iced-gui/src/canvas/shader_canvas.rs
@@ -56,10 +56,12 @@ struct CanvasUniforms {
     viewport_h: f32,
     /// Checkerboard square size in pixels
     checker_size: f32,
-    /// Padding for 16-byte alignment
-    _pad1: f32,
-    _pad2: f32,
-    _pad3: f32,
+    /// Marching ants animation time in seconds
+    anim_time: f32,
+    /// 1.0 if selection mask is bound, 0.0 otherwise
+    has_selection: f32,
+    /// 1.0 for red quick-mask tint, 0.0 for normal blue tint
+    quick_mask: f32,
 }
 
 // ─── Vertex struct ───────────────────────────────────────────────────────────
@@ -149,6 +151,12 @@ struct CanvasShaderPipeline {
     /// Current texture dimensions (to detect resize)
     texture_w: u32,
     texture_h: u32,
+    /// Selection mask texture (R8, canvas_w × canvas_h)
+    sel_texture: wgpu::Texture,
+    /// Selection mask texture view
+    sel_texture_view: wgpu::TextureView,
+    /// Selection mask sampler
+    sel_sampler: wgpu::Sampler,
 }
 
 impl CanvasShaderPipeline {
@@ -236,6 +244,33 @@ impl CanvasShaderPipeline {
             ..Default::default()
         });
 
+        // ── Selection mask texture (R8, same size as canvas) ─────────────
+        let sel_texture = device.create_texture(&wgpu::TextureDescriptor {
+            label: Some("hcie-selection-texture"),
+            size: wgpu::Extent3d {
+                width: canvas_w.max(1),
+                height: canvas_h.max(1),
+                depth_or_array_layers: 1,
+            },
+            mip_level_count: 1,
+            sample_count: 1,
+            dimension: wgpu::TextureDimension::D2,
+            format: wgpu::TextureFormat::R8Unorm,
+            usage: wgpu::TextureUsages::TEXTURE_BINDING | wgpu::TextureUsages::COPY_DST,
+            view_formats: &[],
+        });
+        let sel_texture_view = sel_texture.create_view(&wgpu::TextureViewDescriptor::default());
+        let sel_sampler = device.create_sampler(&wgpu::SamplerDescriptor {
+            label: Some("hcie-selection-sampler"),
+            address_mode_u: wgpu::AddressMode::ClampToEdge,
+            address_mode_v: wgpu::AddressMode::ClampToEdge,
+            address_mode_w: wgpu::AddressMode::ClampToEdge,
+            mag_filter: wgpu::FilterMode::Nearest,
+            min_filter: wgpu::FilterMode::Nearest,
+            mipmap_filter: wgpu::FilterMode::Nearest,
+            ..Default::default()
+        });
+
         // ── Uniform buffer ───────────────────────────────────────────────
         let uniform_data = CanvasUniforms {
             scale_x: 1.0,
@@ -247,9 +282,9 @@ impl CanvasShaderPipeline {
             viewport_w: 800.0,
             viewport_h: 600.0,
             checker_size: CHECKER_SQUARE,
-            _pad1: 0.0,
-            _pad2: 0.0,
-            _pad3: 0.0,
+            anim_time: 0.0,
+            has_selection: 0.0,
+            quick_mask: 0.0,
         };
 
         let uniform_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
@@ -284,13 +319,31 @@ impl CanvasShaderPipeline {
                     },
                     count: None,
                 },
-                // @binding(2): Sampler
+                // @binding(2): Composite sampler
                 wgpu::BindGroupLayoutEntry {
                     binding: 2,
                     visibility: wgpu::ShaderStages::FRAGMENT,
                     ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
                     count: None,
                 },
+                // @binding(3): Selection mask texture (R8)
+                wgpu::BindGroupLayoutEntry {
+                    binding: 3,
+                    visibility: wgpu::ShaderStages::FRAGMENT,
+                    ty: wgpu::BindingType::Texture {
+                        sample_type: wgpu::TextureSampleType::Float { filterable: true },
+                        view_dimension: wgpu::TextureViewDimension::D2,
+                        multisampled: false,
+                    },
+                    count: None,
+                },
+                // @binding(4): Selection mask sampler
+                wgpu::BindGroupLayoutEntry {
+                    binding: 4,
+                    visibility: wgpu::ShaderStages::FRAGMENT,
+                    ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
+                    count: None,
+                },
             ],
         });
 
@@ -311,6 +364,14 @@ impl CanvasShaderPipeline {
                     binding: 2,
                     resource: wgpu::BindingResource::Sampler(&sampler),
                 },
+                wgpu::BindGroupEntry {
+                    binding: 3,
+                    resource: wgpu::BindingResource::TextureView(&sel_texture_view),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 4,
+                    resource: wgpu::BindingResource::Sampler(&sel_sampler),
+                },
             ],
         });
 
@@ -385,6 +446,9 @@ impl CanvasShaderPipeline {
             sampler,
             texture_w: canvas_w,
             texture_h: canvas_h,
+            sel_texture,
+            sel_texture_view,
+            sel_sampler,
         }
     }
 
@@ -454,7 +518,26 @@ impl CanvasShaderPipeline {
             );
         }
 
-        // Recreate bind group with new texture view
+        // Recreate selection mask texture with new dimensions
+        self.sel_texture = device.create_texture(&wgpu::TextureDescriptor {
+            label: Some("hcie-selection-texture"),
+            size: wgpu::Extent3d {
+                width: canvas_w.max(1),
+                height: canvas_h.max(1),
+                depth_or_array_layers: 1,
+            },
+            mip_level_count: 1,
+            sample_count: 1,
+            dimension: wgpu::TextureDimension::D2,
+            format: wgpu::TextureFormat::R8Unorm,
+            usage: wgpu::TextureUsages::TEXTURE_BINDING | wgpu::TextureUsages::COPY_DST,
+            view_formats: &[],
+        });
+        self.sel_texture_view = self
+            .sel_texture
+            .create_view(&wgpu::TextureViewDescriptor::default());
+
+        // Recreate bind group with new texture views
         self.bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
             label: Some("hcie-canvas-bind-group"),
             layout: &self.bind_group_layout,
@@ -471,6 +554,14 @@ impl CanvasShaderPipeline {
                     binding: 2,
                     resource: wgpu::BindingResource::Sampler(&self.sampler),
                 },
+                wgpu::BindGroupEntry {
+                    binding: 3,
+                    resource: wgpu::BindingResource::TextureView(&self.sel_texture_view),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 4,
+                    resource: wgpu::BindingResource::Sampler(&self.sel_sampler),
+                },
             ],
         });
 
@@ -540,6 +631,45 @@ impl CanvasShaderPipeline {
         );
     }
 
+    /// Upload the full selection mask to the GPU texture.
+    ///
+    /// Called when the selection mask changes (new selection, selection modified).
+    /// The mask is a single-channel (R8) texture matching the canvas dimensions.
+    ///
+    /// ## Arguments
+    /// * `queue` — wgpu queue for the upload
+    /// * `mask` — selection mask bytes (1 byte per pixel, >128 = selected)
+    /// * `canvas_w` — mask width in pixels
+    /// * `canvas_h` — mask height in pixels
+    fn upload_selection_mask(&self, queue: &wgpu::Queue, mask: &[u8], canvas_w: u32, canvas_h: u32) {
+        if mask.len() != (canvas_w * canvas_h) as usize {
+            log::warn!(
+                "[CanvasShaderPipeline::upload_selection_mask] Size mismatch: mask={} but canvas={}×{}={}",
+                mask.len(), canvas_w, canvas_h, canvas_w * canvas_h
+            );
+            return;
+        }
+        queue.write_texture(
+            wgpu::ImageCopyTexture {
+                texture: &self.sel_texture,
+                mip_level: 0,
+                origin: wgpu::Origin3d::ZERO,
+                aspect: wgpu::TextureAspect::All,
+            },
+            mask,
+            wgpu::ImageDataLayout {
+                offset: 0,
+                bytes_per_row: Some(canvas_w),
+                rows_per_image: Some(canvas_h),
+            },
+            wgpu::Extent3d {
+                width: canvas_w,
+                height: canvas_h,
+                depth_or_array_layers: 1,
+            },
+        );
+    }
+
     /// Update the uniform buffer with current zoom/pan/viewport values.
     ///
     /// ## Arguments
@@ -574,6 +704,14 @@ pub struct CanvasShaderPrimitive {
     pub full_upload: bool,
     /// Absolute widget bounds in the window
     pub bounds: Rectangle,
+    /// Selection mask data (1 byte per pixel, >128 = selected), if any
+    pub selection_mask: Option<Vec<u8>>,
+    /// Whether the selection mask has changed since last upload
+    pub selection_dirty: bool,
+    /// Animation time in seconds for marching ants
+    pub anim_time: f32,
+    /// Whether quick-mask mode is active (red tint vs blue)
+    pub quick_mask: bool,
 }
 
 impl shader::Primitive for CanvasShaderPrimitive {
@@ -634,6 +772,13 @@ impl shader::Primitive for CanvasShaderPrimitive {
             pipeline.upload_dirty_region(queue, region, &self.composite_pixels, self.canvas_w);
         }
 
+        // ── Upload selection mask if changed ──────────────────────────────
+        if self.selection_dirty {
+            if let Some(ref mask) = self.selection_mask {
+                pipeline.upload_selection_mask(queue, mask, self.canvas_w, self.canvas_h);
+            }
+        }
+
         // ── Compute uniforms ─────────────────────────────────────────────
         let viewport_w = bounds.width;
         let viewport_h = bounds.height;
@@ -675,9 +820,9 @@ impl shader::Primitive for CanvasShaderPrimitive {
             viewport_w,
             viewport_h,
             checker_size: CHECKER_SQUARE,
-            _pad1: 0.0,
-            _pad2: 0.0,
-            _pad3: 0.0,
+            anim_time: self.anim_time,
+            has_selection: if self.selection_mask.is_some() { 1.0 } else { 0.0 },
+            quick_mask: if self.quick_mask { 1.0 } else { 0.0 },
         };
 
         pipeline.update_uniforms(queue, &uniforms);
@@ -792,6 +937,14 @@ pub struct CanvasShaderProgram {
     pub full_upload: bool,
     /// Whether Space temporarily changes left-drag into panning.
     pub space_pan: bool,
+    /// Selection mask data (1 byte per pixel, >128 = selected), if any.
+    pub selection_mask: Option<Vec<u8>>,
+    /// Whether the selection mask has changed since last upload.
+    pub selection_dirty: bool,
+    /// Animation time in seconds for marching ants.
+    pub anim_time: f32,
+    /// Whether quick-mask mode is active (red tint vs blue).
+    pub quick_mask: bool,
 }
 
 /// Convert a viewport-local point to canvas-space coordinates.
@@ -1120,6 +1273,10 @@ impl shader::Program<Message> for CanvasShaderProgram {
             composite_pixels: self.composite_pixels.clone(),
             full_upload: self.full_upload,
             bounds,
+            selection_mask: self.selection_mask.clone(),
+            selection_dirty: self.selection_dirty,
+            anim_time: self.anim_time,
+            quick_mask: self.quick_mask,
         }
     }
 
diff --git a/hcie-iced-app/crates/hcie-iced-gui/src/selection/state.rs b/hcie-iced-app/crates/hcie-iced-gui/src/selection/state.rs
index ddb5e1c..9be9230 100644
--- a/hcie-iced-app/crates/hcie-iced-gui/src/selection/state.rs
+++ b/hcie-iced-app/crates/hcie-iced-gui/src/selection/state.rs
@@ -65,7 +65,12 @@ pub fn mask_bounds(mask: &[u8], width: u32, height: u32) -> Option<(u32, u32, u3
             }
         }
     }
-    found.then_some((min_x, min_y, max_x - min_x + 1, max_y - min_y + 1))
+    found.then_some((
+        min_x,
+        min_y,
+        max_x.saturating_sub(min_x).saturating_add(1),
+        max_y.saturating_sub(min_y).saturating_add(1),
+    ))
 }
 
 /// Compresses selected pixels into horizontal spans for efficient irregular overlay filling.
diff --git a/hcie-iced-app/crates/hcie-iced-gui/src/sidebar/mod.rs b/hcie-iced-app/crates/hcie-iced-gui/src/sidebar/mod.rs
index 9957f3a..59721c6 100644
--- a/hcie-iced-app/crates/hcie-iced-gui/src/sidebar/mod.rs
+++ b/hcie-iced-app/crates/hcie-iced-gui/src/sidebar/mod.rs
@@ -582,18 +582,34 @@ fn tool_button<'a>(
             let is_tool_active = tool == tool_state.active_tool;
             let c = colors;
 
+            let tool_icon_path = tool_icon(tool);
+            let resolved_path = resolve_icon_path(tool_icon_path);
+
             let popup_icon: Element<'_, Message> =
-                svg(svg::Handle::from_path(resolve_icon_path(tool_icon(tool))))
-                    .width(18)
-                    .height(18)
-                    .style(move |_theme, _status| svg::Style {
-                        color: Some(if is_tool_active {
+                if resolved_path.exists() {
+                    let handle = svg::Handle::from_path(&resolved_path);
+                    svg(handle)
+                        .width(18)
+                        .height(18)
+                        .style(move |_theme, _status| svg::Style {
+                            color: Some(if is_tool_active {
+                                iced::Color::WHITE
+                            } else {
+                                c.text_primary
+                            }),
+                        })
+                        .into()
+                } else {
+                    // Fallback: show first letter of tool name when icon is missing
+                    text(tool_name.chars().next().unwrap_or('?').to_string())
+                        .size(14)
+                        .color(if is_tool_active {
                             iced::Color::WHITE
                         } else {
                             c.text_primary
-                        }),
-                    })
-                    .into();
+                        })
+                        .into()
+                };
 
             let item = button(container(popup_icon).width(32).height(28).center(18))
                 .on_press(Message::ToolSelected(tool))
@@ -658,7 +674,7 @@ fn tool_button<'a>(
             .padding(1)
             .width(68)
             .style(move |_theme| iced::widget::container::Style {
-                background: Some(iced::Background::Color(colors.bg_active)),
+                background: Some(iced::Background::Color(colors.bg_panel)),
                 border: iced::Border::default().color(colors.border_high).width(1),
                 shadow: iced::Shadow {
                     color: iced::Color::from_rgba(0.0, 0.0, 0.0, 0.4),