~animations~

src/config.rs

@@ -367,6 +367,11 @@ pub struct Config {
     pub inactive_pane_fade_ms: u64,
     /// Dim factor for inactive panes (0.0 = fully dimmed/black, 1.0 = no dimming).
     pub inactive_pane_dim: f32,
+    /// Process names that should receive pane navigation keys instead of zterm handling them.
+    /// When the foreground process matches one of these names, Alt+Arrow keys are passed
+    /// to the application (e.g., for Neovim buffer navigation) instead of switching panes.
+    /// Example: ["nvim", "vim", "helix"]
+    pub pass_keys_to_programs: Vec<String>,
     /// Keybindings.
     pub keybindings: Keybindings,
 }
@@ -380,6 +385,7 @@ impl Default for Config {
             scrollback_lines: 50_000,
             inactive_pane_fade_ms: 150,
             inactive_pane_dim: 0.6,
+            pass_keys_to_programs: vec!["nvim".to_string(), "vim".to_string()],
             keybindings: Keybindings::default(),
         }
     }

src/main.rs

@@ -6,8 +6,8 @@
 use zterm::config::{Action, Config};
 use zterm::keyboard::{FunctionalKey, KeyEncoder, KeyEventType, KeyboardState, Modifiers};
 use zterm::pty::Pty;
-use zterm::renderer::{PaneRenderInfo, Renderer};
-use zterm::terminal::{Terminal, MouseTrackingMode};
+use zterm::renderer::{EdgeGlow, PaneRenderInfo, Renderer};
+use zterm::terminal::{Direction, Terminal, TerminalCommand, MouseTrackingMode};
 
 use std::collections::HashMap;
 use std::io::Write;
@@ -199,6 +199,19 @@ impl Pane {
         self.pty.child_exited()
     }
     
+    /// Check if the foreground process matches any of the given program names.
+    /// Used for pass-through keybindings (e.g., passing Alt+Arrow to Neovim).
+    fn foreground_matches(&self, programs: &[String]) -> bool {
+        if programs.is_empty() {
+            return false;
+        }
+        if let Some(fg_name) = self.pty.foreground_process_name() {
+            programs.iter().any(|p| p == &fg_name)
+        } else {
+            false
+        }
+    }
+    
     /// Calculate the current dim factor based on animation progress.
     /// Returns a value between `inactive_dim` (for unfocused) and 1.0 (for focused).
     fn calculate_dim_factor(&mut self, is_focused: bool, fade_duration_ms: u64, inactive_dim: f32) -> f32 {
@@ -508,15 +521,6 @@ impl SplitNode {
     }
 }
 
-/// Direction for pane navigation.
-#[derive(Debug, Clone, Copy)]
-enum Direction {
-    Up,
-    Down,
-    Left,
-    Right,
-}
-
 /// Unique identifier for a tab.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 struct TabId(u64);
@@ -812,6 +816,8 @@ struct App {
     last_frame_log: std::time::Instant,
     /// Whether window should be created on next opportunity.
     should_create_window: bool,
+    /// Edge glow animation state (for when navigation fails).
+    edge_glow: Option<EdgeGlow>,
 }
 
 const PTY_KEY: usize = 1;
@@ -842,6 +848,7 @@ impl App {
             frame_count: 0,
             last_frame_log: std::time::Instant::now(),
             should_create_window: false,
+            edge_glow: None,
         }
     }
     
@@ -1045,7 +1052,10 @@ impl App {
     /// Process PTY data for a specific pane.
     /// Returns true if any data was processed.
     fn poll_pane(&mut self, pane_id: PaneId) -> bool {
-        // Find the pane across all tabs
+        // Find the pane across all tabs and process data
+        let mut processed = false;
+        let mut commands = Vec::new();
+        
         for tab in &mut self.tabs {
             if let Some(pane) = tab.get_pane_mut(pane_id) {
                 // Take all pending data atomically
@@ -1066,10 +1076,29 @@ impl App {
                         len);
                 }
                 
-                return true;
+                // Collect any commands from the terminal
+                commands = pane.terminal.take_commands();
+                processed = true;
+                break;
+            }
+        }
+        
+        // Handle commands outside the borrow
+        for cmd in commands {
+            self.handle_terminal_command(cmd);
+        }
+        
+        processed
+    }
+    
+    /// Handle a command from the terminal (triggered by OSC sequences).
+    fn handle_terminal_command(&mut self, cmd: TerminalCommand) {
+        match cmd {
+            TerminalCommand::NavigatePane(direction) => {
+                log::debug!("Terminal requested pane navigation: {:?}", direction);
+                self.focus_pane(direction);
             }
         }
-        false
     }
     
     /// Send bytes to the active tab's PTY.
@@ -1259,16 +1288,16 @@ impl App {
                 self.split_pane(false);
             }
             Action::FocusPaneUp => {
-                self.focus_pane(Direction::Up);
+                self.focus_pane_or_pass_key(Direction::Up, b'A');
             }
             Action::FocusPaneDown => {
-                self.focus_pane(Direction::Down);
+                self.focus_pane_or_pass_key(Direction::Down, b'B');
             }
             Action::FocusPaneLeft => {
-                self.focus_pane(Direction::Left);
+                self.focus_pane_or_pass_key(Direction::Left, b'D');
             }
             Action::FocusPaneRight => {
-                self.focus_pane(Direction::Right);
+                self.focus_pane_or_pass_key(Direction::Right, b'C');
             }
         }
     }
@@ -1314,14 +1343,48 @@ impl App {
         }
     }
     
+    /// Focus neighbor pane or pass keys through to applications like Neovim.
+    /// If the foreground process matches `pass_keys_to_programs`, send the Alt+Arrow
+    /// escape sequence to the PTY. Otherwise, focus the neighboring pane.
+    fn focus_pane_or_pass_key(&mut self, direction: Direction, arrow_letter: u8) {
+        // Check if we should pass keys to the foreground process
+        let should_pass = if let Some(tab) = self.tabs.get(self.active_tab) {
+            if let Some(pane) = tab.active_pane() {
+                pane.foreground_matches(&self.config.pass_keys_to_programs)
+            } else {
+                false
+            }
+        } else {
+            false
+        };
+        
+        if should_pass {
+            // Send Alt+Arrow escape sequence: \x1b[1;3X where X is A/B/C/D
+            let escape_seq = [0x1b, b'[', b'1', b';', b'3', arrow_letter];
+            self.write_to_pty(&escape_seq);
+        } else {
+            self.focus_pane(direction);
+        }
+    }
+    
     fn focus_pane(&mut self, direction: Direction) {
-        if let Some(tab) = self.tabs.get_mut(self.active_tab) {
+        let navigated = if let Some(tab) = self.tabs.get_mut(self.active_tab) {
+            let old_pane = tab.active_pane;
             tab.focus_neighbor(direction);
+            tab.active_pane != old_pane
+        } else {
+            false
+        };
+        
+        if !navigated {
+            // No neighbor in that direction - trigger edge glow animation
+            self.edge_glow = Some(EdgeGlow::new(direction));
+        }
+        
         if let Some(window) = &self.window {
             window.request_redraw();
         }
     }
-    }
     
     fn close_active_pane(&mut self) {
         let should_close_tab = if let Some(tab) = self.tabs.get_mut(self.active_tab) {
@@ -1851,7 +1914,11 @@ impl ApplicationHandler<UserEvent> for App {
                             }
                         }
                         
-                        match renderer.render_panes(&pane_render_data, num_tabs, active_tab_idx) {
+                        // Handle edge glow animation
+                        let edge_glow_ref = self.edge_glow.as_ref();
+                        let glow_in_progress = edge_glow_ref.map(|g| !g.is_finished()).unwrap_or(false);
+                        
+                        match renderer.render_panes(&pane_render_data, num_tabs, active_tab_idx, edge_glow_ref) {
                             Ok(_) => {}
                             Err(wgpu::SurfaceError::Lost) => {
                                 renderer.resize(renderer.width, renderer.height);
@@ -1864,8 +1931,21 @@ impl ApplicationHandler<UserEvent> for App {
                                 log::error!("Render error: {:?}", e);
                             }
                         }
+                        
+                        // Request redraw if edge glow is animating
+                        if glow_in_progress {
+                            if let Some(window) = &self.window {
+                                window.request_redraw();
                             }
                         }
+                    }
+                }
+                
+                // Clean up finished edge glow animation
+                if self.edge_glow.as_ref().map(|g| g.is_finished()).unwrap_or(false) {
+                    self.edge_glow = None;
+                }
+                
                 let render_time = render_start.elapsed();
                 let frame_time = frame_start.elapsed();
                 

src/pty.rs

@@ -188,6 +188,31 @@ impl Pty {
         // If it returns -1, there was an error (child might have already been reaped)
         result != 0
     }
+    
+    /// Get the foreground process group ID of this PTY.
+    /// Returns None if the query fails.
+    pub fn foreground_pgid(&self) -> Option<i32> {
+        let fd = self.master.as_raw_fd();
+        let pgid = unsafe { libc::tcgetpgrp(fd) };
+        if pgid > 0 {
+            Some(pgid)
+        } else {
+            None
+        }
+    }
+    
+    /// Get the name of the foreground process running in this PTY.
+    /// Returns the process name (e.g., "nvim", "zsh") or None if unavailable.
+    pub fn foreground_process_name(&self) -> Option<String> {
+        let pgid = self.foreground_pgid()?;
+        
+        // Read the command line from /proc/<pid>/comm
+        // (comm gives just the process name, cmdline gives full command)
+        let comm_path = format!("/proc/{}/comm", pgid);
+        std::fs::read_to_string(&comm_path)
+            .ok()
+            .map(|s| s.trim().to_string())
+    }
 }
 
 impl AsRawFd for Pty {

src/renderer.rs

@@ -2,7 +2,7 @@
 //! Uses rustybuzz (HarfBuzz port) for text shaping to support font features.
 
 use crate::config::TabBarPosition;
-use crate::terminal::{Color, ColorPalette, CursorShape, Terminal};
+use crate::terminal::{Color, ColorPalette, CursorShape, Direction, Terminal};
 use fontdue::Font as FontdueFont;
 use rustybuzz::UnicodeBuffer;
 use ttf_parser::Tag;
@@ -37,6 +37,43 @@ pub struct PaneRenderInfo {
     pub dim_factor: f32,
 }
 
+/// Edge glow animation state for visual feedback when navigation fails.
+/// Creates an organic glow effect: a single light node appears at center,
+/// then splits into two that travel outward to the corners while fading.
+/// Animation logic is handled in the shader (shader.wgsl).
+#[derive(Debug, Clone, Copy)]
+pub struct EdgeGlow {
+    /// Which edge to glow (based on the direction the user tried to navigate).
+    pub direction: Direction,
+    /// When the animation started.
+    pub start_time: std::time::Instant,
+}
+
+impl EdgeGlow {
+    /// Duration of the glow animation in milliseconds.
+    pub const DURATION_MS: u64 = 500;
+    
+    /// Create a new edge glow animation.
+    pub fn new(direction: Direction) -> Self {
+        Self {
+            direction,
+            start_time: std::time::Instant::now(),
+        }
+    }
+    
+    /// Get the current animation progress (0.0 to 1.0).
+    pub fn progress(&self) -> f32 {
+        let elapsed = self.start_time.elapsed().as_millis() as f32;
+        let duration = Self::DURATION_MS as f32;
+        (elapsed / duration).min(1.0)
+    }
+    
+    /// Check if the animation has completed.
+    pub fn is_finished(&self) -> bool {
+        self.progress() >= 1.0
+    }
+}
+
 /// Size of the glyph atlas texture.
 const ATLAS_SIZE: u32 = 1024;
 
@@ -96,6 +133,25 @@ impl GlyphVertex {
     }
 }
 
+/// GPU-compatible edge glow uniform data.
+/// Must match the layout in shader.wgsl exactly.
+#[repr(C)]
+#[derive(Copy, Clone, Debug, bytemuck::Pod, bytemuck::Zeroable)]
+struct EdgeGlowUniforms {
+    screen_width: f32,
+    screen_height: f32,
+    terminal_y_offset: f32,
+    direction: u32,
+    progress: f32,
+    color_r: f32,
+    color_g: f32,
+    color_b: f32,
+    enabled: u32,
+    _padding1: u32,
+    _padding2: u32,
+    _padding3: u32,
+}
+
 /// The terminal renderer.
 pub struct Renderer {
     surface: wgpu::Surface<'static>,
@@ -107,6 +163,11 @@ pub struct Renderer {
     glyph_pipeline: wgpu::RenderPipeline,
     glyph_bind_group: wgpu::BindGroup,
     
+    // Edge glow rendering pipeline
+    edge_glow_pipeline: wgpu::RenderPipeline,
+    edge_glow_bind_group: wgpu::BindGroup,
+    edge_glow_uniform_buffer: wgpu::Buffer,
+
     // Atlas texture
     atlas_texture: wgpu::Texture,
     atlas_data: Vec<u8>,
@@ -873,6 +934,96 @@ impl Renderer {
             cache: None,
         });
 
+        // ═══════════════════════════════════════════════════════════════════════════════
+        // EDGE GLOW PIPELINE SETUP
+        // ═══════════════════════════════════════════════════════════════════════════════
+        
+        // Create edge glow shader
+        let edge_glow_shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
+            label: Some("Edge Glow Shader"),
+            source: wgpu::ShaderSource::Wgsl(include_str!("shader.wgsl").into()),
+        });
+        
+        // Create uniform buffer for edge glow parameters
+        let edge_glow_uniform_buffer = device.create_buffer(&wgpu::BufferDescriptor {
+            label: Some("Edge Glow Uniform Buffer"),
+            size: std::mem::size_of::<EdgeGlowUniforms>() as u64,
+            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
+            mapped_at_creation: false,
+        });
+        
+        // Create bind group layout for edge glow
+        let edge_glow_bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+            label: Some("Edge Glow Bind Group Layout"),
+            entries: &[
+                wgpu::BindGroupLayoutEntry {
+                    binding: 0,
+                    visibility: wgpu::ShaderStages::FRAGMENT,
+                    ty: wgpu::BindingType::Buffer {
+                        ty: wgpu::BufferBindingType::Uniform,
+                        has_dynamic_offset: false,
+                        min_binding_size: None,
+                    },
+                    count: None,
+                },
+            ],
+        });
+        
+        // Create bind group for edge glow
+        let edge_glow_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
+            label: Some("Edge Glow Bind Group"),
+            layout: &edge_glow_bind_group_layout,
+            entries: &[
+                wgpu::BindGroupEntry {
+                    binding: 0,
+                    resource: edge_glow_uniform_buffer.as_entire_binding(),
+                },
+            ],
+        });
+        
+        // Create pipeline layout for edge glow
+        let edge_glow_pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
+            label: Some("Edge Glow Pipeline Layout"),
+            bind_group_layouts: &[&edge_glow_bind_group_layout],
+            push_constant_ranges: &[],
+        });
+        
+        // Create edge glow render pipeline
+        let edge_glow_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+            label: Some("Edge Glow Pipeline"),
+            layout: Some(&edge_glow_pipeline_layout),
+            vertex: wgpu::VertexState {
+                module: &edge_glow_shader,
+                entry_point: Some("vs_main"),
+                buffers: &[], // Fullscreen triangle, no vertex buffer needed
+                compilation_options: wgpu::PipelineCompilationOptions::default(),
+            },
+            fragment: Some(wgpu::FragmentState {
+                module: &edge_glow_shader,
+                entry_point: Some("fs_main"),
+                targets: &[Some(wgpu::ColorTargetState {
+                    format: surface_config.format,
+                    // Premultiplied alpha blending for proper glow compositing
+                    blend: Some(wgpu::BlendState::PREMULTIPLIED_ALPHA_BLENDING),
+                    write_mask: wgpu::ColorWrites::ALL,
+                })],
+                compilation_options: wgpu::PipelineCompilationOptions::default(),
+            }),
+            primitive: wgpu::PrimitiveState {
+                topology: wgpu::PrimitiveTopology::TriangleList,
+                strip_index_format: None,
+                front_face: wgpu::FrontFace::Ccw,
+                cull_mode: None,
+                polygon_mode: wgpu::PolygonMode::Fill,
+                unclipped_depth: false,
+                conservative: false,
+            },
+            depth_stencil: None,
+            multisample: wgpu::MultisampleState::default(),
+            multiview: None,
+            cache: None,
+        });
+
         // Create initial buffers with some capacity
         let initial_vertex_capacity = 4096;
         let initial_index_capacity = 6144;
@@ -898,6 +1049,9 @@ impl Renderer {
             surface_config,
             glyph_pipeline,
             glyph_bind_group,
+            edge_glow_pipeline,
+            edge_glow_bind_group,
+            edge_glow_uniform_buffer,
             atlas_texture,
             atlas_data: vec![0u8; (ATLAS_SIZE * ATLAS_SIZE) as usize],
             atlas_dirty: false,
@@ -3271,17 +3425,51 @@ impl Renderer {
         ]);
     }
     
+    /// Prepare edge glow uniform data for shader-based rendering.
+    /// Returns the uniform data to be uploaded to the GPU.
+    fn prepare_edge_glow_uniforms(&self, glow: &EdgeGlow, terminal_y_offset: f32) -> EdgeGlowUniforms {
+        // Use the same color as the active pane border (palette color 4 - typically blue)
+        let [r, g, b] = self.palette.colors[4];
+        let color_r = Self::srgb_to_linear(r as f32 / 255.0);
+        let color_g = Self::srgb_to_linear(g as f32 / 255.0);
+        let color_b = Self::srgb_to_linear(b as f32 / 255.0);
+        
+        let direction = match glow.direction {
+            Direction::Up => 0,
+            Direction::Down => 1,
+            Direction::Left => 2,
+            Direction::Right => 3,
+        };
+        
+        EdgeGlowUniforms {
+            screen_width: self.width as f32,
+            screen_height: self.height as f32,
+            terminal_y_offset,
+            direction,
+            progress: glow.progress(),
+            color_r,
+            color_g,
+            color_b,
+            enabled: 1,
+            _padding1: 0,
+            _padding2: 0,
+            _padding3: 0,
+        }
+    }
+    
     /// Render multiple panes with borders.
     /// 
     /// Arguments:
     /// - `panes`: List of (terminal, pane_info, selection) tuples
     /// - `num_tabs`: Number of tabs for the tab bar
     /// - `active_tab`: Index of the active tab
+    /// - `edge_glow`: Optional edge glow animation for visual feedback
     pub fn render_panes(
         &mut self,
         panes: &[(&Terminal, PaneRenderInfo, Option<(usize, usize, usize, usize)>)],
         num_tabs: usize,
         active_tab: usize,
+        edge_glow: Option<&EdgeGlow>,
     ) -> Result<(), wgpu::SurfaceError> {
         // Sync palette from first terminal
         if let Some((terminal, _, _)) = panes.first() {
@@ -3560,6 +3748,15 @@ impl Renderer {
             }
         }
         
+        // ═══════════════════════════════════════════════════════════════════
+        // PREPARE EDGE GLOW UNIFORMS (if navigation failed)
+        // ═══════════════════════════════════════════════════════════════════
+        let edge_glow_uniforms = if let Some(glow) = edge_glow {
+            Some(self.prepare_edge_glow_uniforms(glow, terminal_y_offset))
+        } else {
+            None
+        };
+        
         // ═══════════════════════════════════════════════════════════════════
         // SUBMIT TO GPU
         // ═══════════════════════════════════════════════════════════════════
@@ -3698,6 +3895,38 @@ impl Renderer {
             render_pass.draw_indexed(0..total_index_count as u32, 0, 0..1);
         }
         
+        // ═══════════════════════════════════════════════════════════════════
+        // EDGE GLOW PASS (shader-based, after main rendering)
+        // ═══════════════════════════════════════════════════════════════════
+        if let Some(uniforms) = edge_glow_uniforms {
+            // Upload uniforms
+            self.queue.write_buffer(
+                &self.edge_glow_uniform_buffer,
+                0,
+                bytemuck::cast_slice(&[uniforms]),
+            );
+            
+            // Second render pass for edge glow (load existing content)
+            let mut glow_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
+                label: Some("Edge Glow Pass"),
+                color_attachments: &[Some(wgpu::RenderPassColorAttachment {
+                    view: &view,
+                    resolve_target: None,
+                    ops: wgpu::Operations {
+                        load: wgpu::LoadOp::Load, // Preserve existing content
+                        store: wgpu::StoreOp::Store,
+                    },
+                })],
+                depth_stencil_attachment: None,
+                occlusion_query_set: None,
+                timestamp_writes: None,
+            });
+            
+            glow_pass.set_pipeline(&self.edge_glow_pipeline);
+            glow_pass.set_bind_group(0, &self.edge_glow_bind_group, &[]);
+            glow_pass.draw(0..3, 0..1); // Fullscreen triangle
+        }
+        
         self.queue.submit(std::iter::once(encoder.finish()));
         output.present();
         

src/shader.wgsl

@@ -1,26 +1,202 @@
-// Vertex shader
+// Edge Glow Shader
+// Renders a soft glow effect at terminal edges for failed pane navigation feedback.
+// The glow appears as a light node at center that splits into two and travels to corners.
 
-struct VertexInput {
-    @location(0) position: vec2<f32>,
-    @location(1) color: vec4<f32>,
+// Uniform buffer with glow parameters
+struct EdgeGlowParams {
+    // Screen dimensions in pixels
+    screen_width: f32,
+    screen_height: f32,
+    // Terminal area offset (for tab bar)
+    terminal_y_offset: f32,
+    // Direction: 0=Up, 1=Down, 2=Left, 3=Right
+    direction: u32,
+    // Animation progress (0.0 to 1.0)
+    progress: f32,
+    // Glow color (linear RGB) - stored as separate floats to avoid vec3 alignment issues
+    color_r: f32,
+    color_g: f32,
+    color_b: f32,
+    // Whether glow is enabled (1 = yes, 0 = no)
+    enabled: u32,
+    // Padding to align to 16 bytes
+    _padding1: u32,
+    _padding2: u32,
+    _padding3: u32,
 }
 
+@group(0) @binding(0)
+var<uniform> params: EdgeGlowParams;
+
 struct VertexOutput {
     @builtin(position) clip_position: vec4<f32>,
-    @location(0) color: vec4<f32>,
+    @location(0) uv: vec2<f32>,  // 0-1 normalized screen coordinates
 }
 
+// Fullscreen triangle vertex shader
+// Uses vertex_index 0,1,2 to create a triangle that covers the screen
 @vertex
-fn vs_main(in: VertexInput) -> VertexOutput {
+fn vs_main(@builtin(vertex_index) vertex_index: u32) -> VertexOutput {
     var out: VertexOutput;
-    out.clip_position = vec4<f32>(in.position, 0.0, 1.0);
-    out.color = in.color;
+    
+    // Generate fullscreen triangle vertices
+    // This creates a triangle that covers [-1,1] in clip space
+    let x = f32(i32(vertex_index) - 1);
+    let y = f32(i32(vertex_index & 1u) * 2 - 1);
+    
+    // Positions for a fullscreen triangle
+    var pos: vec2<f32>;
+    switch vertex_index {
+        case 0u: { pos = vec2<f32>(-1.0, -1.0); }
+        case 1u: { pos = vec2<f32>(3.0, -1.0); }
+        case 2u: { pos = vec2<f32>(-1.0, 3.0); }
+        default: { pos = vec2<f32>(0.0, 0.0); }
+    }
+    
+    out.clip_position = vec4<f32>(pos, 0.0, 1.0);
+    // Convert to 0-1 UV (flip Y since clip space Y is up, pixel Y is down)
+    out.uv = vec2<f32>((pos.x + 1.0) * 0.5, (1.0 - pos.y) * 0.5);
+    
     return out;
 }
 
-// Fragment shader
+// Constants
+const PI: f32 = 3.14159265359;
+const PHASE1_END: f32 = 0.15;      // Phase 1 ends at 15% progress
+const GLOW_RADIUS: f32 = 90.0;     // Base radius of glow
+const GLOW_ASPECT: f32 = 2.0;      // Stretch factor along edge (ellipse)
+
+// Smooth gaussian-like falloff
+fn glow_falloff(dist: f32, radius: f32) -> f32 {
+    let normalized = dist / radius;
+    if normalized > 1.0 {
+        return 0.0;
+    }
+    // Smooth falloff: (1 - x^2)^3 gives nice soft edges
+    let t = 1.0 - normalized * normalized;
+    return t * t * t;
+}
+
+// Ease-out cubic
+fn ease_out_cubic(t: f32) -> f32 {
+    let t1 = 1.0 - t;
+    return 1.0 - t1 * t1 * t1;
+}
+
+// Calculate distance from point to glow center, accounting for ellipse shape
+fn ellipse_distance(point: vec2<f32>, center: vec2<f32>, radius_along: f32, radius_perp: f32, is_horizontal: bool) -> f32 {
+    let delta = point - center;
+    var normalized: vec2<f32>;
+    if is_horizontal {
+        normalized = vec2<f32>(delta.x / radius_along, delta.y / radius_perp);
+    } else {
+        normalized = vec2<f32>(delta.x / radius_perp, delta.y / radius_along);
+    }
+    return length(normalized) * min(radius_along, radius_perp);
+}
 
 @fragment
 fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
-    return in.color;
+    // Early out if not enabled
+    if params.enabled == 0u {
+        return vec4<f32>(0.0, 0.0, 0.0, 0.0);
+    }
+    
+    let progress = params.progress;
+    
+    // Convert UV to pixel coordinates
+    let pixel = vec2<f32>(
+        in.uv.x * params.screen_width,
+        in.uv.y * params.screen_height
+    );
+    
+    let terminal_height = params.screen_height - params.terminal_y_offset;
+    let is_horizontal = params.direction == 0u || params.direction == 1u;
+    
+    // Calculate glow parameters based on animation phase
+    var alpha: f32;
+    var size_factor: f32;
+    var split: f32;
+    
+    if progress < PHASE1_END {
+        // Phase 1: Fade in, grow
+        let t = progress / PHASE1_END;
+        let ease = ease_out_cubic(t);
+        alpha = ease * 0.8;
+        size_factor = 0.3 + 0.7 * ease;
+        split = 0.0;
+    } else {
+        // Phase 2: Split and fade out
+        let t = (progress - PHASE1_END) / (1.0 - PHASE1_END);
+        let fade = 1.0 - t;
+        alpha = fade * fade * 0.8;
+        size_factor = 1.0 - 0.3 * t;
+        split = ease_out_cubic(t);
+    }
+    
+    let base_radius = GLOW_RADIUS * size_factor;
+    let radius_along = base_radius * GLOW_ASPECT;
+    let radius_perp = base_radius;
+    
+    // Calculate edge center and travel distance based on direction
+    var edge_center: vec2<f32>;
+    var travel: vec2<f32>;
+    
+    switch params.direction {
+        // Up - top edge
+        case 0u: {
+            edge_center = vec2<f32>(params.screen_width / 2.0, params.terminal_y_offset);
+            travel = vec2<f32>(params.screen_width / 2.0, 0.0);
+        }
+        // Down - bottom edge
+        case 1u: {
+            edge_center = vec2<f32>(params.screen_width / 2.0, params.screen_height);
+            travel = vec2<f32>(params.screen_width / 2.0, 0.0);
+        }
+        // Left - left edge
+        case 2u: {
+            edge_center = vec2<f32>(0.0, params.terminal_y_offset + terminal_height / 2.0);
+            travel = vec2<f32>(0.0, terminal_height / 2.0);
+        }
+        // Right - right edge
+        case 3u: {
+            edge_center = vec2<f32>(params.screen_width, params.terminal_y_offset + terminal_height / 2.0);
+            travel = vec2<f32>(0.0, terminal_height / 2.0);
+        }
+        default: {
+            edge_center = vec2<f32>(0.0, 0.0);
+            travel = vec2<f32>(0.0, 0.0);
+        }
+    }
+    
+    var glow_intensity: f32 = 0.0;
+    
+    if split < 0.01 {
+        // Single glow at center
+        let dist = ellipse_distance(pixel, edge_center, radius_along, radius_perp, is_horizontal);
+        glow_intensity = glow_falloff(dist, base_radius);
+    } else {
+        // Two glows splitting apart
+        let split_radius = base_radius * (1.0 - 0.2 * split);
+        let split_radius_along = radius_along * (1.0 - 0.2 * split);
+        let split_radius_perp = radius_perp * (1.0 - 0.2 * split);
+        
+        let center1 = edge_center - travel * split;
+        let center2 = edge_center + travel * split;
+        
+        let dist1 = ellipse_distance(pixel, center1, split_radius_along, split_radius_perp, is_horizontal);
+        let dist2 = ellipse_distance(pixel, center2, split_radius_along, split_radius_perp, is_horizontal);
+        
+        // Combine both glows (additive but capped)
+        let glow1 = glow_falloff(dist1, split_radius);
+        let glow2 = glow_falloff(dist2, split_radius);
+        glow_intensity = min(glow1 + glow2, 1.0);
+    }
+    
+    // Apply alpha
+    let final_alpha = glow_intensity * alpha;
+    
+    // Output with premultiplied alpha for proper blending
+    let color = vec3<f32>(params.color_r, params.color_g, params.color_b);
+    return vec4<f32>(color * final_alpha, final_alpha);
 }

src/terminal.rs

@@ -3,6 +3,24 @@
 use crate::keyboard::{query_response, KeyboardState};
 use crate::vt_parser::{CsiParams, Handler, Parser};
 
+/// Commands that the terminal can send to the application.
+/// These are triggered by special escape sequences from programs like Neovim.
+#[derive(Clone, Debug, PartialEq)]
+pub enum TerminalCommand {
+    /// Navigate to a neighboring pane in the given direction.
+    /// Triggered by OSC 51;navigate;<direction> ST
+    NavigatePane(Direction),
+}
+
+/// Direction for pane navigation.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum Direction {
+    Up,
+    Down,
+    Left,
+    Right,
+}
+
 /// A single cell in the terminal grid.
 #[derive(Clone, Copy, Debug)]
 pub struct Cell {
@@ -467,6 +485,9 @@ pub struct Terminal {
     parser: Option<Parser>,
     /// Performance timing stats (for debugging).
     pub stats: ProcessingStats,
+    /// Command queue for terminal-to-application communication.
+    /// Commands are added by OSC handlers and consumed by the application.
+    command_queue: Vec<TerminalCommand>,
 }
 
 impl Terminal {
@@ -523,6 +544,7 @@ impl Terminal {
             line_pool,
             parser: Some(Parser::new()),
             stats: ProcessingStats::default(),
+            command_queue: Vec::new(),
         }
     }
     
@@ -570,6 +592,13 @@ impl Terminal {
         self.dirty_lines = [0u64; 4];
     }
     
+    /// Take all pending commands from the queue.
+    /// Returns an empty Vec if no commands are pending.
+    #[inline]
+    pub fn take_commands(&mut self) -> Vec<TerminalCommand> {
+        std::mem::take(&mut self.command_queue)
+    }
+    
     /// Get the dirty lines bitmap (for passing to shm).
     #[inline]
     pub fn get_dirty_lines(&self) -> u64 {
@@ -1336,6 +1365,38 @@ impl Handler for Terminal {
                     }
                 }
             }
+            // OSC 51 - ZTerm custom commands
+            // Format: OSC 51;command;args ST
+            // Currently supported:
+            //   OSC 51;navigate;up/down/left/right ST - Navigate to neighboring pane
+            51 => {
+                if parts.len() >= 2 {
+                    if let Ok(command) = std::str::from_utf8(parts[1]) {
+                        match command {
+                            "navigate" => {
+                                if parts.len() >= 3 {
+                                    if let Ok(direction_str) = std::str::from_utf8(parts[2]) {
+                                        let direction = match direction_str {
+                                            "up" => Some(Direction::Up),
+                                            "down" => Some(Direction::Down),
+                                            "left" => Some(Direction::Left),
+                                            "right" => Some(Direction::Right),
+                                            _ => None,
+                                        };
+                                        if let Some(dir) = direction {
+                                            log::debug!("OSC 51: Navigate {:?}", dir);
+                                            self.command_queue.push(TerminalCommand::NavigatePane(dir));
+                                        }
+                                    }
+                                }
+                            }
+                            _ => {
+                                log::debug!("OSC 51: Unknown command '{}'", command);
+                            }
+                        }
+                    }
+                }
+            }
             _ => {
                 log::debug!("Unhandled OSC {}", osc_num);
             }