fix scroll

AmazonQ.md

@@ -0,0 +1,41 @@
+# Text Scrolling Implementation in Simplicitty
+
+This document outlines the implementation of text scrolling in the Simplicitty terminal emulator project.
+
+## Overview
+
+The implementation adds the ability to scroll through text content when it doesn't fit completely in the window. The scrolling is implemented on a line-by-line basis, allowing users to navigate through the content using keyboard shortcuts.
+
+## Key Components
+
+1. **Scroll State Management**:
+   - Added `scroll_offset` to track the current scroll position (in visual lines)
+   - Added `max_scroll_offset` to limit scrolling to available content
+
+2. **Viewport Calculation**:
+   - Modified `get_visible_line_range()` to consider the scroll offset when determining visible lines
+   - Added `update_max_scroll_offset()` to recalculate the maximum scroll position based on content and viewport size
+
+3. **Scrolling Methods**:
+   - `scroll_up(lines)`: Move viewport up by specified number of lines
+   - `scroll_down(lines)`: Move viewport down by specified number of lines
+   - `page_up()`: Scroll up by one page (viewport height)
+   - `page_down()`: Scroll down by one page (viewport height)
+
+4. **Keyboard Controls**:
+   - Ctrl+Up/Down: Scroll one line up/down
+   - Page Up/Down: Scroll one page up/down
+   - Ctrl+Home/End: Scroll to top/bottom of content
+
+## Implementation Details
+
+The scrolling implementation works by adjusting the `scroll_offset` value, which determines which visual lines are rendered in the viewport. The `get_visible_line_range()` function uses this offset to calculate which logical lines should be rendered.
+
+When the window is resized or content changes, the `max_scroll_offset` is recalculated to ensure scrolling remains within valid bounds.
+
+## Future Improvements
+
+1. Add mouse wheel support for scrolling
+2. Implement smooth scrolling animations
+3. Add a visual scrollbar indicator
+4. Preserve horizontal scroll position when navigating vertically

README.md

@@ -1,350 +1,11 @@
-# simplicitty
+# Simplicitty
 
-A simple terminal emulator
+## Roadmap
 
-## 1. Implement Incremental Rendering
-
-Currently, your renderer appears to redraw the entire terminal content on each
-frame. For a terminal emulator, this is inefficient since only small portions
-typically change at once.
-
-rust // Add to TerminalText struct dirty_regions: Vec<Rectangle>, // Store
-regions that need updating last_frame_content: String, // Store previous frame's
-content
-
-Only redraw areas that have changed since the last frame by tracking dirty
-regions.
-
-## 2. Implement Text Caching
-
-The current implementation reshapes all text on every frame. Instead:
-
-rust // Add to TerminalText cached_lines: HashMap<String, CachedTextLine>,
-
-Cache shaped text lines and only reshape when content changes or window resizes.
-
-## 3. Use Double Buffering for Text
-
-Maintain two buffers - one for the current frame and one for the next:
-
-rust // In TerminalText front_buffer: Buffer, back_buffer: Buffer,
-
-Prepare the back buffer while rendering the front buffer, then swap them.
-
-## 4. Optimize Atlas Trimming
-
-The trim() call after every frame can be expensive. Consider:
-
-rust // In TerminalText frames_since_trim: u32,
-
-pub fn trim(&mut self) { self.frames_since_trim += 1; if
-self.frames_since_trim > 30 { // Only trim every 30 frames self.atlas.trim();
-self.frames_since_trim = 0; } }
-
-## 5. Implement View Culling
-
-Only render text that's actually visible:
-
-rust // In prepare() method let visible_area = TextBounds { left: 0, top:
-scroll_position, right: config.width as i32, bottom: scroll_position +
-config.height as i32, };
-
-## 6. Use Asynchronous Text Preparation
-
-Move text shaping to a background thread:
-
-rust // In Application struct text_preparation_pool: ThreadPool,
-
-// Then queue text preparation tasks self.text_preparation_pool.spawn(move || {
-// Shape text here // Signal completion via channel });
-
-## 7. Optimize GPU Memory Usage
-
-The current implementation might be creating new GPU resources frequently.
-Implement resource pooling:
-
-rust // In TerminalText texture_pool: Vec<wgpu::Texture>, // Reuse textures
-instead of creating new ones
-
-## 8. Implement Partial Updates for the Text Atlas
-
-Instead of rebuilding the entire text atlas, update only changed glyphs:
-
-rust // Add method to TextAtlas pub fn update_region(&mut self, device: &Device,
-queue: &Queue, region: Rectangle) { // Update only the specified region }
-
-## 9. Use Compute Shaders for Text Processing
-
-For complex text operations, consider using compute shaders:
-
-rust // Create a compute pipeline for text processing let compute_pipeline =
-device.create_compute_pipeline(&wgpu::ComputePipelineDescriptor { // Configure
-for text processing });
-
-## 10. Implement Frame Skipping
-
-Skip rendering frames when nothing has changed:
-
-rust pub fn render(&mut self) -> Result<(), SurfaceError> { if !self.has_changes
-{ return Ok(()); } // Render as normal }
-
-## 11. Profile and Optimize Hot Paths
-
-Use a profiler to identify bottlenecks in your rendering pipeline. Common issues
-might be: • Excessive GPU state changes • Inefficient text shaping • Unnecessary
-buffer updates
-
-## 12. Implement Proper Vsync Control
-
-Your current implementation uses PresentMode::Fifo (VSync), which is good for
-power efficiency but might not be optimal for all cases:
-
-rust // Allow configurable present mode based on user preference present_mode:
-if vsync_enabled { wgpu::PresentMode::Fifo } else { wgpu::PresentMode::Immediate
-},
-
-Based on your project structure and the README.md optimization suggestions,
-here's how you can implement incremental text buffer updates:
-
-## 1. Track Changes with Dirty Regions
-
-First, modify your TerminalText struct to track which parts of the text have
-changed:
-
-rust pub struct TerminalText { font_system: FontSystem, cache: SwashCache,
-viewport: Viewport, atlas: TextAtlas, buffer: Buffer, renderer: TextRenderer,
-
-    // Add these fields to track changes
-    last_content: String,
-    dirty_regions: Vec<TextBounds>,
-    cursor_position: usize,
-
-}
-
-## 2. Implement Incremental Text Updates
-
-Instead of replacing the entire text on each update, implement methods to
-insert, delete, or modify text at specific positions:
-
-```rust
-impl TerminalText { // Add a character at the cursor position pub fn
-insert_char(&mut self, c: char) { let current_text =
-self.buffer.text().to_string(); let pos =
-self.cursor_position.min(current_text.len());
-
-        // Create new text with the character inserted
-        let mut new_text = current_text.clone();
-        new_text.insert(pos, c);
-
-        // Calculate the affected region
-        let affected_line = self.calculate_line_for_position(pos);
-        let line_bounds = self.get_line_bounds(affected_line);
-        self.dirty_regions.push(line_bounds);
-
-        // Update the buffer with the new text
-        self.buffer.set_text(
-            &mut self.font_system,
-            &new_text,
-            &Attrs::new().family(Family::Monospace),
-            Shaping::Advanced,
-        );
-
-        // Update cursor position
-        self.cursor_position = pos + 1;
-        self.last_content = new_text;
-    }
-
-    // Delete a character before the cursor
-    pub fn delete_char(&mut self) {
-        let current_text = self.buffer.text().to_string();
-        if self.cursor_position > 0 && !current_text.is_empty() {
-            let pos = self.cursor_position.min(current_text.len());
-
-            // Create new text with the character deleted
-            let mut new_text = current_text.clone();
-            new_text.remove(pos - 1);
-
-            // Calculate the affected region
-            let affected_line = self.calculate_line_for_position(pos - 1);
-            let line_bounds = self.get_line_bounds(affected_line);
-            self.dirty_regions.push(line_bounds);
-
-                // Update the buffer with the new text
-            self.buffer.set_text(
-                &mut self.font_system,
-                &new_text,
-                &Attrs::new().family(Family::Monospace),
-                Shaping::Advanced,
-            );
-
-            // Update cursor position
-            self.cursor_position = pos - 1;
-            self.last_content = new_text;
-        }
-    }
-
-    // Helper methods to calculate affected regions
-    fn calculate_line_for_position(&self, pos: usize) -> usize {
-        // Count newlines up to the position
-        self.buffer.text()[..pos].matches('\n').count()
-    }
-
-    fn get_line_bounds(&self, line: usize) -> TextBounds {
-        // Calculate the bounds for a specific line
-        // This is a simplified version - you'll need to implement this based on your text layout
-        TextBounds {
-            left: 0,
-            top: (line * self.get_line_height()) as i32,
-            right: self.viewport.width() as i32,
-            bottom: ((line + 1) * self.get_line_height()) as i32,
-        }
-    }
-
-    fn get_line_height(&self) -> usize {
-        // Get the line height based on your font metrics
-        self.buffer.metrics().line_height.ceil() as usize
-    }
-
-}
-```
-
-## 3. Optimize the Rendering Process
-
-Modify your prepare and render methods to only update the dirty regions:
-
-```rust
-pub fn prepare(&mut self, device: &Device, queue: &Queue, config:
-&SurfaceConfiguration) { // Update viewport with new dimensions
-self.viewport.update( queue, Resolution { width: config.width, height:
-config.height, }, );
-
-    // Make sure text is properly wrapped for the current width
-    self.resize(config.width, config.height);
-
-    // Only reshape if there are dirty regions
-    if !self.dirty_regions.is_empty() {
-        // Prepare only the dirty regions
-        for region in &self.dirty_regions {
-            self.renderer
-                .prepare(
-                    device,
-                    queue,
-                    &mut self.font_system,
-                    &mut self.atlas,
-                    &self.viewport,
-                    [TextArea {
-                        buffer: &self.buffer,
-                        left: 0.0,
-                        top: 0.0,
-                        scale: 1.0,
-                        bounds: *region,
-                        default_color: Color::rgb(255, 255, 255),
-                        custom_glyphs: &[],
-                    }],
-                    &mut self.cache,
-                )
-                .unwrap();
-        }
-
-        // Clear dirty regions after preparing
-        self.dirty_regions.clear();
-    }
-
-}
-```
-
-## 4. Implement a Double Buffer Approach
-
-To further optimize, implement a double buffer approach:
-
-```rust
-pub struct TerminalText { // ... existing fields front_buffer: Buffer,
-back_buffer: Buffer, buffer_swap_needed: bool, }
-
-impl TerminalText { // ... existing methods
-
-    pub fn swap_buffers(&mut self) {
-        if self.buffer_swap_needed {
-            std::mem::swap(&mut self.front_buffer, &mut self.back_buffer);
-            self.buffer_swap_needed = false;
-        }
-    }
-
-    pub fn prepare_back_buffer(&mut self, device: &Device, queue: &Queue) {
-        // Prepare the back buffer while the front buffer is being rendered
-        if !self.dirty_regions.is_empty() {
-            // Apply changes to the back buffer
-            // ...
-
-            self.buffer_swap_needed = true;
-        }
-    }
-
-}
-```
-
-## 5. Implement Cursor Rendering
-
-Add cursor rendering to provide visual feedback:
-
-rust pub fn render_cursor(&mut self, render_pass: &mut RenderPass) { //
-Calculate cursor position in screen coordinates let (x, y) =
-self.get_cursor_screen_position();
-
-    // Render cursor using a simple rectangle
-    // You'll need to implement this based on your rendering system
-
-}
-
-fn get_cursor_screen_position(&self) -> (f32, f32) { // Calculate screen
-position based on cursor_position // This will depend on your text layout system
-// ... }
-
-## 6. Handle Special Keys
-
-In your keyboard event handler, handle special keys like backspace, enter, and
-arrow keys:
-
-rust fn handle*key_event(&mut self, key_event: KeyEvent) { match key_event.key {
-Key::Character(c) => { if key_event.state == ElementState::Pressed {
-self.text.insert_char(c.chars().next().unwrap_or(' '));
-self.window.request_redraw(); } }, Key::Named(NamedKey::Backspace) => { if
-key_event.state == ElementState::Pressed { self.text.delete_char();
-self.window.request_redraw(); } }, Key::Named(NamedKey::Enter) => { if
-key_event.state == ElementState::Pressed { self.text.insert_char('\n');
-self.window.request_redraw(); } }, // Handle arrow keys for cursor movement
-Key::Named(NamedKey::ArrowLeft) => { if key_event.state == ElementState::Pressed
-{ self.text.move_cursor_left(); self.window.request_redraw(); } },
-Key::Named(NamedKey::ArrowRight) => { if key_event.state ==
-ElementState::Pressed { self.text.move_cursor_right();
-self.window.request_redraw(); } }, * => {} } }
-
-## 7. Implement Frame Skipping
-
-Skip rendering frames when nothing has changed:
-
-rust pub fn render(&mut self) -> Result<(), SurfaceError> { // Skip rendering if
-nothing has changed if self.dirty_regions.is_empty() && !self.buffer_swap_needed
-{ return Ok(()); }
-
-    // Swap buffers if needed
-    self.text.swap_buffers();
-
-    // Render as normal
-    // ...
-
-    Ok(())
-
-}
-
-These changes will significantly improve the efficiency of your text rendering
-by:
-
-1. Only updating parts of the text that have changed
-2. Using double buffering to prepare updates while rendering
-3. Skipping frames when nothing has changed
-4. Optimizing the text atlas updates
-
-This approach aligns with the optimization suggestions in your README.md and
-should provide a much more efficient text rendering system for your terminal
-emulator.
+1. [ ] Complete keyboard input handling (arrow keys, backspace, etc.)
+2. [ ] Implement a PTY interface to spawn and communicate with processes
+3. [ ] Add support for terminal protocols (ANSI escape sequences)
+4. [ ] Implement scrollback buffer and viewport scrolling
+5. [ ] Add color and text styling support
+6. [ ] Implement clipboard integration
+7. [ ] Add configuration options

src/app/mod.rs

@@ -2,7 +2,6 @@ use std::sync::Arc;
 use tokio::runtime::Runtime;
 use winit::dpi::LogicalSize;
 use winit::event::WindowEvent;
-use winit::keyboard::{Key, NamedKey};
 use winit::window::Window;
 
 mod rendering;
@@ -59,25 +58,10 @@ impl winit::application::ApplicationHandler for Application {
                 event,
                 is_synthetic: _,
             } => {
-                if event.state.is_pressed() {
-                    match event.logical_key {
-                        Key::Named(k) => match k {
-                            NamedKey::Enter => {
-                                state.handle_enter();
-                            }
-                            _ => todo!(),
-                        },
-                        Key::Character(c) => {
-                            state.add_text(&event.text.unwrap());
-                        }
-                        Key::Dead(_) => {
-                            todo!()
-                        }
-                        Key::Unidentified(_) => {
-                            todo!()
-                        }
-                    }
-                }
+                state.handle_keyboard_input(&event);
+            }
+            WindowEvent::ModifiersChanged(modifiers) => {
+                state.update_modifiers(modifiers.state());
             }
             WindowEvent::CloseRequested => event_loop.exit(),
             _ => {}

src/app/rendering/mod.rs

@@ -1,3 +1,4 @@
+use log::{debug, trace};
 use std::sync::Arc;
 use wgpu::{
     CommandEncoderDescriptor, CompositeAlphaMode, Device, DeviceDescriptor, Instance,
@@ -6,6 +7,8 @@ use wgpu::{
     TextureViewDescriptor,
 };
 use winit::dpi::PhysicalSize;
+use winit::event::{ElementState, KeyEvent};
+use winit::keyboard::{Key, KeyLocation, ModifiersState, NamedKey};
 use winit::window::Window;
 
 mod terminal_text;
@@ -21,20 +24,28 @@ pub struct State {
     text: terminal_text::TerminalText,
 
     window: Arc<Window>,
+
+    // Keyboard state tracking
+    modifiers: ModifiersState,
+    dead_key_state: Option<char>,
+    caps_lock_enabled: bool,
 }
 
 impl State {
     pub fn resize(&mut self, new_size: PhysicalSize<u32>) {
+        trace!("Resizing window");
         if new_size.width > 0 && new_size.height > 0 {
             self.size = new_size;
             self.config.width = new_size.width;
             self.config.height = new_size.height;
             self.surface.configure(&self.device, &self.config);
+            self.text.resize(new_size.width, new_size.height);
             self.window.request_redraw();
         }
     }
 
     pub fn render(&mut self) -> Result<(), SurfaceError> {
+        trace!("Rendering requested");
         // Prepare with current configuration (which includes the current window size)
         self.text.prepare(&self.device, &self.queue, &self.config);
 
@@ -64,14 +75,13 @@ impl State {
                 occlusion_query_set: None,
             });
 
+            trace!("Rendering...");
             self.text.render(&mut _render_pass);
         }
 
         self.queue.submit(Some(encoder.finish()));
         output.present();
 
-        self.text.trim();
-
         Ok(())
     }
 
@@ -184,18 +194,200 @@ impl State {
             text,
 
             window,
+
+            // Initialize keyboard state
+            modifiers: ModifiersState::empty(),
+            dead_key_state: None,
+            caps_lock_enabled: false,
         }
     }
 
-    pub fn add_text(&mut self, text: &str) {
-        for c in text.chars() {
-            self.text.insert_char(c);
+    pub fn update_modifiers(&mut self, state: ModifiersState) {
+        self.modifiers = state;
+        debug!("Modifiers updated: {:?}", self.modifiers);
+    }
+
+    pub fn handle_keyboard_input(&mut self, event: &KeyEvent) {
+        // Only process key presses, not releases (except for tracking caps lock)
+        if event.state == ElementState::Released {
+            // Special case for caps lock which toggles on release
+            if let Key::Named(NamedKey::CapsLock) = event.logical_key {
+                self.caps_lock_enabled = !self.caps_lock_enabled;
+                debug!("Caps lock toggled: {}", self.caps_lock_enabled);
+            }
+            return;
         }
+
+        match &event.logical_key {
+            Key::Named(k) => {
+                match k {
+                    NamedKey::Enter => {
+                        debug!("Receiver enter");
+                        self.text.handle_enter();
+                    }
+                    NamedKey::Backspace => {
+                        // Clear dead key state if backspace is pressed
+                        if self.dead_key_state.is_some() {
+                            self.dead_key_state = None;
+                            debug!("Dead key state cleared");
+                        } else if self.text.backspace() {
+                            debug!("Backspace processed");
+                        }
+                    }
+                    NamedKey::Tab => {
+                        // Insert tab character
+                        self.text.insert_char('\t');
+                    }
+                    NamedKey::Escape => {
+                        // Clear any pending dead key state
+                        if self.dead_key_state.is_some() {
+                            self.dead_key_state = None;
+                            debug!("Dead key state cleared by Escape");
+                        }
+                    }
+                    NamedKey::ArrowLeft => {
+                        if self.text.move_cursor(terminal_text::Motion::Left) {
+                            debug!("Cursor moved left");
+                        }
+                    }
+                    NamedKey::ArrowRight => {
+                        if self.text.move_cursor(terminal_text::Motion::Right) {
+                            debug!("Cursor moved right");
+                        }
+                    }
+                    NamedKey::ArrowUp => {
+                        if self.text.move_cursor(terminal_text::Motion::Up) {
+                            debug!("Cursor moved left");
+                        }
+                    }
+                    NamedKey::ArrowDown => {
+                        if self.text.move_cursor(terminal_text::Motion::Down) {
+                            debug!("Cursor moved right");
+                        }
+                    }
+                    _ => {
+                        debug!("Unhandled named key: {:?}", k);
+                    }
+                }
+            }
+            Key::Character(s) => {
+                // Handle character input, considering dead keys
+                if let Some(dead_char) = self.dead_key_state.take() {
+                    // Combine dead key with the current character if possible
+                    if let Some(combined) = self.combine_with_dead_key(dead_char, s) {
+                        for c in combined.chars() {
+                            debug!("Inserting character {c}");
+                            self.text.insert_char(c);
+                        }
+                    } else {
+                        // If combination not possible, insert both separately
+                        self.text.insert_char(dead_char);
+                        for c in s.chars() {
+                            debug!("Inserting character {c}");
+                            self.text.insert_char(c);
+                        }
+                    }
+                } else {
+                    // Normal character input
+                    for c in s.chars() {
+                        debug!("Inserting character {c}");
+                        self.text.insert_char(c);
+                    }
+                }
+            }
+            Key::Dead(dead_key) => {
+                // Store dead key for later combination
+                if let Some(c) = dead_key {
+                    self.dead_key_state = Some(*c);
+                    debug!("Dead key registered: {:?}", c);
+                }
+            }
+            Key::Unidentified(unidentified) => {
+                debug!(
+                    "Unidentified key: {:?}, location: {:?}",
+                    unidentified, event.physical_key
+                );
+            }
+        }
+
         self.window.request_redraw();
     }
 
-    pub fn handle_enter(&mut self) {
-        self.text.handle_enter();
-        self.window.request_redraw();
+    /// Attempts to combine a dead key with a character
+    fn combine_with_dead_key(&self, dead_key: char, input: &str) -> Option<String> {
+        // This is a simplified implementation - for a complete solution,
+        // you would need a more comprehensive mapping of dead key combinations
+
+        if input.chars().count() != 1 {
+            return None; // Can only combine with single characters
+        }
+
+        let base_char = input.chars().next().unwrap();
+
+        // Common dead key combinations
+        match (dead_key, base_char) {
+            // Acute accent (´)
+            ('´', 'a') => Some("á".to_string()),
+            ('´', 'e') => Some("é".to_string()),
+            ('´', 'i') => Some("í".to_string()),
+            ('´', 'o') => Some("ó".to_string()),
+            ('´', 'u') => Some("ú".to_string()),
+            ('´', 'A') => Some("Á".to_string()),
+            ('´', 'E') => Some("É".to_string()),
+            ('´', 'I') => Some("Í".to_string()),
+            ('´', 'O') => Some("Ó".to_string()),
+            ('´', 'U') => Some("Ú".to_string()),
+
+            // Grave accent (`)
+            ('`', 'a') => Some("à".to_string()),
+            ('`', 'e') => Some("è".to_string()),
+            ('`', 'i') => Some("ì".to_string()),
+            ('`', 'o') => Some("ò".to_string()),
+            ('`', 'u') => Some("ù".to_string()),
+            ('`', 'A') => Some("À".to_string()),
+            ('`', 'E') => Some("È".to_string()),
+            ('`', 'I') => Some("Ì".to_string()),
+            ('`', 'O') => Some("Ò".to_string()),
+            ('`', 'U') => Some("Ù".to_string()),
+
+            // Circumflex (^)
+            ('^', 'a') => Some("â".to_string()),
+            ('^', 'e') => Some("ê".to_string()),
+            ('^', 'i') => Some("î".to_string()),
+            ('^', 'o') => Some("ô".to_string()),
+            ('^', 'u') => Some("û".to_string()),
+            ('^', 'A') => Some("Â".to_string()),
+            ('^', 'E') => Some("Ê".to_string()),
+            ('^', 'I') => Some("Î".to_string()),
+            ('^', 'O') => Some("Ô".to_string()),
+            ('^', 'U') => Some("Û".to_string()),
+
+            // Diaeresis/umlaut (¨)
+            ('¨', 'a') => Some("ä".to_string()),
+            ('¨', 'e') => Some("ë".to_string()),
+            ('¨', 'i') => Some("ï".to_string()),
+            ('¨', 'o') => Some("ö".to_string()),
+            ('¨', 'u') => Some("ü".to_string()),
+            ('¨', 'A') => Some("Ä".to_string()),
+            ('¨', 'E') => Some("Ë".to_string()),
+            ('¨', 'I') => Some("Ï".to_string()),
+            ('¨', 'O') => Some("Ö".to_string()),
+            ('¨', 'U') => Some("Ü".to_string()),
+
+            // Tilde (~)
+            ('~', 'a') => Some("ã".to_string()),
+            ('~', 'n') => Some("ñ".to_string()),
+            ('~', 'o') => Some("õ".to_string()),
+            ('~', 'A') => Some("Ã".to_string()),
+            ('~', 'N') => Some("Ñ".to_string()),
+            ('~', 'O') => Some("Õ".to_string()),
+
+            // Cedilla (¸)
+            ('¸', 'c') => Some("ç".to_string()),
+            ('¸', 'C') => Some("Ç".to_string()),
+
+            // If no combination is defined, return None
+            _ => None,
+        }
     }
 }

src/app/rendering/terminal_text/mod.rs

@@ -1,8 +1,10 @@
 use glyphon::{
-    Attrs, Buffer, BufferLine, Cache, Color, Cursor, Family, FontSystem, Metrics, Resolution,
-    Shaping, SwashCache, TextArea, TextAtlas, TextBounds, TextRenderer, Viewport, Wrap,
+    Buffer, Cache, Color, Cursor, FontSystem, Metrics, Resolution, SwashCache, TextArea, TextAtlas,
+    TextBounds, TextRenderer, Viewport, Wrap,
 };
 
+pub use glyphon::cosmic_text::Motion;
+
 use wgpu::{Device, MultisampleState, Queue, RenderPass, SurfaceConfiguration, TextureFormat};
 
 pub struct TerminalText {
@@ -14,12 +16,28 @@ pub struct TerminalText {
     renderer: TextRenderer,
     dirty_regions: Vec<TextBounds>,
     cursor: Cursor,
+    max_scroll_lines: usize,
 }
 
-use log::info;
+// TODO
+// - need to update scroll when
+//  - inserting into a line and it causes line wrap, creating a new visual line (currently the
+//    scroll is only updated when creating a logical line or removing the last logical line)
+//
+// - need to keep track of the scroll vertical offset in two ways:
+//   - first logical line displayed
+//   - extra offset that covers possible wrapped lines before the first logical line
+//
+// - need to remove lines from the top of the buffer when the first logical line displayed is
+//   bigger than max_scroll_offset
+
+mod safe_casts;
+
+use log::{debug, error, trace};
 
 impl TerminalText {
     pub fn new(device: &Device, queue: &Queue, surface_format: TextureFormat) -> TerminalText {
+        debug!("Creating a new TerminalText object");
         let mut font_system = FontSystem::new();
         let swash_cache = SwashCache::new();
 
@@ -32,6 +50,7 @@ impl TerminalText {
         let mut buffer = Buffer::new(&mut font_system, Metrics::relative(13.0, 1.25));
         buffer.set_wrap(&mut font_system, Wrap::Glyph);
 
+        trace!("Loading system fonts");
         // Add a default font
         font_system.db_mut().load_system_fonts();
 
@@ -48,30 +67,122 @@ impl TerminalText {
                 index: 0,
                 affinity: glyphon::Affinity::After,
             },
+            max_scroll_lines: 100,
         }
     }
 
-    pub fn set_text(&mut self, text: &str) {
-        // Clear the buffer and set new text
-        self.buffer.set_text(
-            &mut self.font_system,
-            text,
-            &Attrs::new().family(Family::Monospace),
-            Shaping::Advanced,
-        );
-        self.buffer.set_wrap(&mut self.font_system, Wrap::Glyph);
+    // Calculate the bounds delimited by the `start` and `end` lines
+    fn get_text_bounds(&self, start: usize, end: usize) -> TextBounds {
+        if start >= self.buffer.lines.len() || end > self.buffer.lines.len() {
+            // Return default bounds for invalid line
+            return TextBounds {
+                left: 0,
+                top: 0,
+                right: 0,
+                bottom: 0,
+            };
+        }
+
+        let line_height = self.buffer.metrics().line_height;
+        let viewport_width = self.viewport.resolution().width;
+
+        let layout_iter = self.buffer.layout_runs();
+        let mut top_line = 0;
+        let mut bottom_line = 0;
+
+        let mut found_start_line = false;
+        let mut found_end_line = false;
+
+        for (visual_line_count, run) in layout_iter.enumerate() {
+            if run.line_i == start && !found_start_line {
+                top_line = visual_line_count;
+                found_start_line = true;
+            }
+            if run.line_i == end {
+                if !found_end_line {
+                    found_end_line = true;
+                }
+                bottom_line = visual_line_count + 1;
+            } else if found_end_line {
+                break;
+            }
+        }
+
+        // Calculate bounds based on visual line positions
+        let top_f32 = (safe_casts::usize_to_f32_or_max(top_line) * line_height).floor();
+        let bottom_f32 = (safe_casts::usize_to_f32_or_max(bottom_line) * line_height).ceil();
+
+        // Safe conversions with overflow checks
+        let top = safe_casts::f32_to_i32_or_bound(top_f32);
+        let bottom = safe_casts::f32_to_i32_or_bound(bottom_f32);
+
+        // Ensure viewport width doesn't exceed i32::MAX
+        let right = safe_casts::u32_to_i32_or_max(viewport_width.min(i32::MAX as u32));
+
+        TextBounds {
+            left: 0,
+            top,
+            right,
+            bottom,
+        }
     }
 
-    pub fn resize(&mut self, width: u32, height: u32) {
-        // Update the buffer's wrapping based on the new width
-        self.buffer.set_wrap(&mut self.font_system, Wrap::Glyph);
-        self.buffer.set_size(
-            &mut self.font_system,
-            Some(width as f32),
-            Some(height as f32),
-        );
-        // Reshape the text with the new dimensions
-        self.buffer.shape_until_scroll(&mut self.font_system, false);
+    fn get_visible_line_range(&self) -> (usize, usize) {
+        let viewport_height = safe_casts::u32_to_f32_or_max(self.viewport.resolution().height);
+        let line_height = self.buffer.metrics().line_height;
+
+        let start_line = self.buffer.scroll().line;
+
+        trace!("Current start line: {start_line}");
+
+        // Calculate visible lines based on wrapped text
+        let layout_iter = self.buffer.layout_runs();
+        let mut last_logical_line = 0;
+
+        // Count how many visual lines we have and map to logical lines
+        for (visual_line_count, run) in layout_iter.enumerate() {
+            last_logical_line = run.line_i;
+
+            // If we've exceeded the viewport height, we can stop counting
+            if (safe_casts::usize_to_f32_or_max(visual_line_count) * line_height) > viewport_height
+            {
+                break;
+            }
+        }
+
+        // Add 1 to include partially visible lines at the bottom
+        let end_line = last_logical_line;
+
+        trace!("visible line range goes from {start_line} to {end_line}");
+
+        (start_line, end_line)
+    }
+
+    fn ensure_visible_text_rendered(&mut self) {
+        let (start_line, end_line) = self.get_visible_line_range();
+        self.dirty_regions
+            .push(self.get_text_bounds(start_line, end_line));
+    }
+
+    fn merge_dirty_regions(&self) -> TextBounds {
+        if self.dirty_regions.is_empty() {
+            return TextBounds::default();
+        }
+
+        self.dirty_regions.iter().fold(
+            TextBounds {
+                left: 0,
+                top: 0,
+                right: 0,
+                bottom: 0,
+            },
+            |a, b| TextBounds {
+                left: a.left.min(b.left),
+                top: a.top.min(b.top),
+                right: a.right.max(b.right),
+                bottom: a.bottom.max(b.bottom),
+            },
+        )
     }
 
     pub fn prepare(&mut self, device: &Device, queue: &Queue, config: &SurfaceConfiguration) {
@@ -84,192 +195,189 @@ impl TerminalText {
             },
         );
 
-        // Make sure text is properly wrapped for the current width
-        self.resize(config.width, config.height);
-
-        if !self.dirty_regions.is_empty() {
-            for region in &self.dirty_regions {
-                self.renderer
-                    .prepare(
-                        device,
-                        queue,
-                        &mut self.font_system,
-                        &mut self.atlas,
-                        &self.viewport,
-                        [TextArea {
-                            buffer: &self.buffer,
-                            left: 0.0,
-                            top: 0.0,
-                            scale: 1.0,
-                            bounds: *region,
-                            default_color: Color::rgb(255, 255, 255),
-                            custom_glyphs: &[],
-                        }],
-                        &mut self.cache,
-                    )
-                    .unwrap();
-            }
-        } else {
-            // If no dirty regions, prepare the entire buffer (first render or after resize)
-            self.renderer
-                .prepare(
-                    device,
-                    queue,
-                    &mut self.font_system,
-                    &mut self.atlas,
-                    &self.viewport,
-                    [TextArea {
-                        buffer: &self.buffer,
-                        left: 0.0,
-                        top: 0.0,
-                        scale: 1.0,
-                        bounds: TextBounds {
-                            left: 0,
-                            top: 0,
-                            right: config.width as i32,
-                            bottom: config.height as i32,
-                        },
-                        default_color: Color::rgb(255, 255, 255),
-                        custom_glyphs: &[],
-                    }],
-                    &mut self.cache,
-                )
-                .unwrap();
-        }
+        let region = self.merge_dirty_regions();
+        trace!("Preparing region {:?}", region);
+        self.renderer
+            .prepare(
+                device,
+                queue,
+                &mut self.font_system,
+                &mut self.atlas,
+                &self.viewport,
+                [TextArea {
+                    buffer: &self.buffer,
+                    left: 0.0,
+                    top: 0.0,
+                    scale: 1.0,
+                    bounds: region,
+                    default_color: Color::rgb(255, 255, 255),
+                    custom_glyphs: &[],
+                }],
+                &mut self.cache,
+            )
+            .unwrap();
 
         self.dirty_regions.clear();
     }
 
-    pub fn render(&self, render_pass: &mut RenderPass) {
+    pub fn render(&mut self, render_pass: &mut RenderPass) {
         self.renderer
             .render(&self.atlas, &self.viewport, render_pass)
             .unwrap();
-    }
-
-    pub fn trim(&mut self) {
         self.atlas.trim()
     }
 
-    pub fn insert_char(&mut self, c: char) {
-        let line = self.cursor.line;
+    fn with_update<F, R>(&mut self, operation: F) -> R
+    where
+        F: FnOnce(&mut Self) -> R,
+    {
+        let result = operation(self);
 
-        if line >= self.buffer.lines.len() {
-            // TODO
-            return;
+        let mut scroll = self.buffer.scroll();
+        if self.buffer.lines.len() > self.max_scroll_lines {
+            self.buffer.lines.remove(0);
+            self.cursor.line -= 1;
         }
-        info!("line nr: {line}");
-
-        let current_line = self.buffer.lines[line].text().to_string();
-        let pos = self.cursor.index.min(current_line.len());
-
-        info!("cursor position: {pos}");
-
-        info!("Line text: {current_line}");
-
-        let mut new_text = current_line.clone();
-        new_text.insert(pos, c);
-
-        let line_bounds = self.get_line_bounds(line);
-        self.dirty_regions.push(line_bounds);
-
-        let ending = self.buffer.lines[line].ending();
-        let attrs = self.buffer.lines[line].attrs_list().clone();
-
-        // Update the buffer with the new text
-        self.buffer.lines[line].set_text(&new_text, ending, attrs);
-
-        // Update cursor position
-        self.cursor.index = pos + 1;
-
+        scroll.line = self.buffer.lines.len();
+        self.buffer.set_scroll(scroll);
         self.buffer.shape_until_scroll(&mut self.font_system, false);
+        self.ensure_visible_text_rendered();
+        result
     }
 
-    fn get_line_bounds(&self, line: usize) -> TextBounds {
-        // Calculate the bounds for a specific line
-        // This is a simplified version - you'll need to implement this based on your text layout
-        TextBounds {
-            left: 0,
-            top: (line * self.get_line_height()) as i32,
-            right: self.viewport.resolution().width as i32,
-            bottom: ((line + 1) * self.get_line_height()) as i32,
-        }
+    pub fn resize(&mut self, width: u32, height: u32) {
+        trace!("Resizing window - Width: {width} Height: {height}");
+
+        self.with_update(|this| {
+            this.buffer.set_size(
+                &mut this.font_system,
+                Some(safe_casts::u32_to_f32_or_max(width)),
+                Some(safe_casts::u32_to_f32_or_max(height)),
+            );
+            // Update the buffer's wrapping based on the new width
+            this.buffer.set_wrap(&mut this.font_system, Wrap::Glyph)
+        });
     }
 
-    fn get_line_height(&self) -> usize {
-        // Get the line height based on your font metrics
-        self.buffer.metrics().line_height.ceil() as usize
+    pub fn insert_char(&mut self, c: char) {
+        self.with_update(|this| {
+            let line = this.cursor.line;
+
+            if line >= this.buffer.lines.len() {
+                error!(
+                    "insert_char called when cursor is out of bounds! lines: {}, cursor: {}",
+                    this.buffer.lines.len(),
+                    line
+                );
+                return;
+            }
+
+            let mut text = this.buffer.lines[line].text().to_string().clone();
+            let pos = this.cursor.index.min(text.len());
+            trace!("Inserting char {c} in line {line}, position {pos}");
+            text.insert(pos, c);
+
+            let ending = this.buffer.lines[line].ending();
+            let attrs = this.buffer.lines[line].attrs_list().clone();
+
+            // Update the buffer with the new text
+            this.buffer.lines[line].set_text(&text, ending, attrs);
+            // Update cursor position
+            this.cursor.index = pos + 1;
+        })
     }
 
     pub fn handle_enter(&mut self) {
-        let line = self.cursor.line;
+        self.with_update(|this| {
+            let line = this.cursor.line;
 
-        // Ensure line is within bounds
-        if line >= self.buffer.lines.len() {
-            return;
-        }
-
-        // Get the current line text
-        let current_line = self.buffer.lines[line].text().to_string();
-        let pos = self.cursor.index.min(current_line.len());
-
-        // Split the line at cursor position
-        let text_before = &current_line[..pos];
-        let text_after = &current_line[pos..];
-
-        // Update the current line with text before cursor
-        let ending = self.buffer.lines[line].ending();
-        let attrs = self.buffer.lines[line].attrs_list().clone();
-        self.buffer.lines[line].set_text(text_before, ending, attrs.clone());
-
-        // Create a new line with text after cursor
-        let new_line = BufferLine::new(text_after, ending, attrs, Shaping::Advanced);
-
-        // Insert the new line after the current one
-        self.buffer.lines.insert(line + 1, new_line);
-
-        self.mark_all_dirty();
-
-        // Update cursor position to beginning of next line
-        self.cursor.line = line + 1;
-        self.cursor.index = 0;
-
-        // Reshape the buffer
-        self.buffer.shape_until_scroll(&mut self.font_system, false);
-    }
-
-    pub fn mark_all_dirty(&mut self) {
-        // Create a single region covering the entire viewport
-        let full_bounds = TextBounds {
-            left: 0,
-            top: 0,
-            right: self.viewport.resolution().width as i32,
-            bottom: self.viewport.resolution().height as i32,
-        };
-        self.dirty_regions = vec![full_bounds];
-    }
-
-    pub fn move_cursor_left(&mut self) {
-        if self.cursor.index > 0 {
-            self.cursor.index -= 1;
-        } else if self.cursor.line > 0 {
-            // Move to end of previous line
-            self.cursor.line -= 1;
-            let prev_line_len = self.buffer.lines[self.cursor.line].text().len();
-            self.cursor.index = prev_line_len;
-        }
-    }
-
-    pub fn move_cursor_right(&mut self) {
-        if self.cursor.line < self.buffer.lines.len() {
-            let current_line_len = self.buffer.lines[self.cursor.line].text().len();
-
-            if self.cursor.index < current_line_len {
-                self.cursor.index += 1;
-            } else if self.cursor.line < self.buffer.lines.len() - 1 {
-                // Move to beginning of next line
-                self.cursor.line += 1;
-                self.cursor.index = 0;
+            // Ensure line is within bounds
+            if line >= this.buffer.lines.len() {
+                error!(
+                    "handle_enter called when cursor is out of bounds! lines: {}, cursor: {}",
+                    this.buffer.lines.len(),
+                    line
+                );
+                return;
             }
-        }
+
+            let pos = this.cursor.index.min(this.buffer.lines[line].text().len());
+            trace!("Inserting newline in line {line}, position {pos}");
+            let new_line = this.buffer.lines[line].split_off(pos);
+
+            // Update cursor position to beginning of next line
+            this.cursor.line = line + 1;
+            this.cursor.index = 0;
+            // Create a new line with text after cursor
+            this.buffer.lines.insert(this.cursor.line, new_line);
+        })
+    }
+
+    pub fn backspace(&mut self) -> bool {
+        self.with_update(|this| {
+            let line = this.cursor.line;
+
+            // Ensure line is within bounds
+            if line >= this.buffer.lines.len() {
+                error!(
+                    "handle_enter called when cursor is out of bounds! lines: {}, cursor: {}",
+                    this.buffer.lines.len(),
+                    line
+                );
+                return false;
+            }
+
+            let current_line = this.buffer.lines[line].text().to_string();
+            let pos = this.cursor.index;
+
+            let mut ret = false;
+
+            if pos > 0 {
+                // Delete character before cursor in current line
+                let mut new_text = current_line.clone();
+                new_text.remove(pos - 1);
+
+                // Update the line
+                let ending = this.buffer.lines[line].ending();
+                let attrs = this.buffer.lines[line].attrs_list().clone();
+                this.buffer.lines[line].set_text(&new_text, ending, attrs);
+
+                // Move cursor back
+                this.cursor.index = pos - 1;
+
+                ret = true;
+            } else if line > 0 {
+                // Move cursor to join point
+                this.cursor.line = line - 1;
+                this.cursor.index = this.buffer.lines[this.cursor.line].text().len();
+                let current_line = this.buffer.lines[line].clone();
+                // At beginning of line, join with previous line
+                this.buffer.lines[this.cursor.line].append(current_line);
+                // Remove current line
+                this.buffer.lines.remove(line);
+
+                ret = true;
+            }
+
+            ret
+        })
+    }
+
+    // Cursor movement methods
+    pub fn move_cursor(&mut self, motion: Motion) -> bool {
+        self.with_update(|this| {
+            match this.buffer.cursor_motion(
+                &mut this.font_system,
+                this.cursor,
+                Some(safe_casts::usize_to_i32_or_max(this.cursor.index)),
+                motion,
+            ) {
+                None => false,
+                Some((cursor, _cursor_x_opt)) => {
+                    this.cursor = cursor;
+                    true
+                }
+            }
+        })
     }
 }

src/app/rendering/terminal_text/safe_casts.rs

@@ -0,0 +1,69 @@
+use log::trace;
+
+// Safe conversions with overflow checks
+
+pub fn u32_to_i32_or_max(n: u32) -> i32 {
+    if n > i32::MAX as u32 {
+        trace!(
+            "Overflow casting {n}::u32 as i32, defaulting to {}",
+            i32::MAX
+        );
+        i32::MAX
+    } else {
+        n as i32
+    }
+}
+
+pub fn u32_to_f32_or_max(n: u32) -> f32 {
+    if n > f32::MAX as u32 {
+        trace!(
+            "Overflow casting {n}::u32 as f32, defaulting to {}",
+            f32::MAX
+        );
+        f32::MAX
+    } else {
+        n as f32
+    }
+}
+
+pub fn usize_to_f32_or_max(n: usize) -> f32 {
+    if n > f32::MAX as usize {
+        trace!(
+            "Overflow casting {n}::usize as f32, defaulting to {}",
+            f32::MAX
+        );
+        f32::MAX
+    } else {
+        n as f32
+    }
+}
+
+pub fn usize_to_i32_or_max(n: usize) -> i32 {
+    if n > i32::MAX as usize {
+        trace!(
+            "Overflow casting {n}::usize as i32, defaulting to {}",
+            i32::MAX
+        );
+        i32::MAX
+    } else {
+        n as i32
+    }
+}
+
+pub fn f32_to_i32_or_bound(n: f32) -> i32 {
+    if n > i32::MAX as f32 {
+        trace!(
+            "Overflow casting {n}::f32 as i32, defaulting to {}",
+            i32::MAX
+        );
+        i32::MAX
+    } else if n < i32::MIN as f32 {
+        trace!(
+            "Underflow casting {n}::f32 as i32, defaulting to {}",
+            i32::MIN
+        );
+        i32::MIN
+    } else {
+        n as i32
+    }
+}