Refactor of scroll and shaping

- Scroll is identified by line index and layout index, instead of just
  layout index
- Shaping has the option to prune, where caches outside of the scroll
  view are cleared
- Syntax editor no longer requires layout of all lines, only of lines
  inside scroll
- BufferLine has a metadata field that can be used by other abstractions
  to know when text was changed

examples/editor-libcosmic/src/text_box.rs

@@ -131,12 +131,10 @@ where
     fn layout(&self, _renderer: &Renderer, limits: &layout::Limits) -> layout::Node {
         let limits = limits.width(Length::Fill).height(Length::Fill);
 
-        //TODO: allow lazy shape
         let mut editor = self.editor.lock().unwrap();
         editor
             .borrow_with(&mut FONT_SYSTEM.lock().unwrap())
-            .buffer_mut()
-            .shape_until(i32::max_value());
+            .shape_as_needed(true);
 
         let mut layout_lines = 0;
         for line in editor.buffer().lines.iter() {
@@ -148,7 +146,6 @@ where
 
         let height = layout_lines as f32 * editor.buffer().metrics().line_height;
         let size = Size::new(limits.max().width, height);
-        log::info!("size {:?}", size);
 
         layout::Node::new(limits.resolve(size))
     }
@@ -228,7 +225,7 @@ where
         editor.buffer_mut().set_size(image_w as f32, image_h as f32);
 
         // Shape and layout
-        editor.shape_as_needed();
+        editor.shape_as_needed(true);
 
         // Draw to pixel buffer
         let mut pixels = vec![0; image_w as usize * image_h as usize * 4];

examples/editor-orbclient/src/main.rs

@@ -88,7 +88,7 @@ fn main() {
     let mut mouse_y = -1;
     let mut mouse_left = false;
     loop {
-        editor.shape_as_needed();
+        editor.shape_as_needed(true);
         if editor.buffer().redraw() {
             let instant = Instant::now();
 

examples/editor-test/src/main.rs

@@ -16,7 +16,7 @@ fn redraw(
     let bg_color = orbclient::Color::rgb(0x34, 0x34, 0x34);
     let font_color = Color::rgb(0xFF, 0xFF, 0xFF);
 
-    editor.shape_as_needed();
+    editor.shape_as_needed(true);
     if editor.buffer().redraw() {
         let instant = Instant::now();
 

examples/multiview/src/main.rs

@@ -1,6 +1,8 @@
 // SPDX-License-Identifier: MIT OR Apache-2.0
 
-use cosmic_text::{Action, Attrs, Buffer, Edit, Family, FontSystem, Metrics, Shaping, SwashCache};
+use cosmic_text::{
+    Action, Attrs, Buffer, Edit, Family, FontSystem, Metrics, Scroll, Shaping, SwashCache,
+};
 use std::{collections::HashMap, env, fs, num::NonZeroU32, rc::Rc, slice};
 use tiny_skia::{Color, Paint, PixmapMut, Rect, Transform};
 use winit::{
@@ -41,7 +43,7 @@ fn main() {
         window: Rc<WinitWindow>,
         context: softbuffer::Context<Rc<WinitWindow>>,
         surface: softbuffer::Surface<Rc<WinitWindow>, Rc<WinitWindow>>,
-        scroll: i32,
+        scroll: Scroll,
     }
     let mut windows = HashMap::new();
     for _ in 0..2 {
@@ -54,7 +56,7 @@ fn main() {
                 window,
                 context,
                 surface,
-                scroll: 0,
+                scroll: Scroll::default(),
             },
         );
     }
@@ -102,7 +104,8 @@ fn main() {
                         // Set size, will relayout and shape until scroll if changed
                         buffer.set_size(width as f32, height as f32);
                         // Shape until scroll, ensures scroll is clamped
-                        buffer.shape_until_scroll();
+                        //TODO: ability to prune with multiple views?
+                        buffer.shape_until_scroll(true);
                         // Update scroll after buffer clamps it
                         *scroll = buffer.scroll();
 
@@ -145,16 +148,16 @@ fn main() {
                         if state == ElementState::Pressed {
                             match logical_key {
                                 Key::Named(NamedKey::ArrowDown) => {
-                                    *scroll += 1;
+                                    scroll.layout += 1;
                                 }
                                 Key::Named(NamedKey::ArrowUp) => {
-                                    *scroll -= 1;
+                                    scroll.layout -= 1;
                                 }
                                 Key::Named(NamedKey::PageDown) => {
-                                    *scroll += buffer.visible_lines();
+                                    scroll.layout += buffer.visible_lines();
                                 }
                                 Key::Named(NamedKey::PageUp) => {
-                                    *scroll -= buffer.visible_lines();
+                                    scroll.layout -= buffer.visible_lines();
                                 }
                                 _ => {}
                             }

examples/rich-text/src/main.rs

@@ -131,7 +131,7 @@ fn main() {
         let bg_color = orbclient::Color::rgb(0x34, 0x34, 0x34);
         let font_color = Color::rgb(0xFF, 0xFF, 0xFF);
 
-        editor.shape_as_needed();
+        editor.shape_as_needed(true);
         if editor.buffer().redraw() {
             let instant = Instant::now();
 

examples/terminal/src/main.rs

@@ -39,7 +39,7 @@ fn main() {
     buffer.set_text(&text, attrs, Shaping::Advanced);
 
     // Perform shaping as desired
-    buffer.shape_until_scroll();
+    buffer.shape_until_scroll(true);
 
     // Default text color (0xFF, 0xFF, 0xFF is white)
     const TEXT_COLOR: Color = Color::rgb(0xFF, 0xFF, 0xFF);