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