documents and editor: a writing view - measure, font, scale, focus fading, typewriter centering

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/editor/mod.rs

@@ -33,6 +33,7 @@ mod tasks;
 mod tests;
 mod view;
 mod welcome;
+mod writing;
 
 pub use buffer::Buffer;
 pub use chat::InlineChat;

src/editor/row.rs

@@ -11,6 +11,9 @@ use super::{
 };
 use crate::theme::{ActiveTheme, TextSize};
 
+/// How far a faded line recedes.
+const FADED: f32 = 0.35;
+
 impl CodeEditor {
     /// Row `ix` as the list draws it.
     pub(crate) fn row(&self, ix: usize, window: &mut Window, cx: &mut Context<Self>) -> AnyElement {
@@ -19,7 +22,11 @@ impl CodeEditor {
             .w_full()
             .h(self.frame.line)
             .flex();
+        let caret = self.buffer.line_of(self.primary().head);
         match self.frame.rows[ix] {
+            Row::Line(line) if self.options.focus_line && line != caret => {
+                self.line_row(base.opacity(FADED), ix, line, window, cx)
+            }
             Row::Line(line) => self.line_row(base, ix, line, window, cx),
             Row::Lens(at) => self.lens_row(base, ix, at, cx),
             Row::Removed(hunk, at) => self.removed_row(base, ix, hunk, at, cx),

src/editor/state.rs

@@ -64,6 +64,12 @@ pub(crate) struct Options {
     pub read_only: bool,
     pub tab: usize,
     pub highlighter: Option<super::prose::LineHighlighter>,
+    /// Text size against the theme's.
+    pub scale: f32,
+    /// Lines but the caret's fade.
+    pub focus_line: bool,
+    /// The caret's line stays mid-view.
+    pub typewriter: bool,
 }
 
 /// What the owner lays over the code.
@@ -114,6 +120,8 @@ pub struct CodeEditor {
     /// The text before an input method's composition began, while it runs.
     pub(crate) composing: Option<Snapshot>,
     pub(crate) metrics: Metrics,
+    /// The caret row typewriter scrolling last centered.
+    pub(crate) centered: Option<usize>,
     pub(crate) dragging: bool,
     pub(crate) caret_on: bool,
     /// Blink runs only while focused, or unseen cursors redraw forever.
@@ -191,11 +199,15 @@ impl CodeEditor {
                 read_only: false,
                 tab: 4,
                 highlighter: None,
+                scale: 1.0,
+                focus_line: false,
+                typewriter: false,
             },
             marks: Marks::default(),
             marked: None,
             composing: None,
             metrics: Metrics::default(),
+            centered: None,
             dragging: false,
             caret_on: true,
             focused: false,

src/editor/view.rs

@@ -2,8 +2,8 @@ use std::ops::Range;
 
 use gpui::{
     AnyElement, Bounds, Context, ElementInputHandler, InteractiveElement, IntoElement, MouseButton,
-    MouseDownEvent, MouseMoveEvent, ParentElement, Pixels, Render, Styled, StyledText, Window,
-    canvas, div, fill, font, point, size, uniform_list,
+    MouseDownEvent, MouseMoveEvent, ParentElement, Pixels, Render, ScrollStrategy, Styled,
+    StyledText, Window, canvas, div, fill, font, point, size, uniform_list,
 };
 
 use super::{
@@ -225,7 +225,7 @@ impl Render for CodeEditor {
         let theme = cx.theme();
         let colors = theme.colors.clone();
         let mono_family = theme.mono_family.clone();
-        let size = theme.text_size(TextSize::Sm);
+        let size = theme.text_size(TextSize::Sm) * self.options.scale;
         let pixels = size.to_pixels(window.rem_size());
         let mono = window
             .text_system()
@@ -263,6 +263,13 @@ impl Render for CodeEditor {
         };
         self.metrics.advance = advance;
         self.metrics.line = line;
+        // Typewriter: the caret's row centers as it moves.
+        let row = self.primary_row();
+        if self.options.typewriter && self.centered != Some(row) {
+            self.scroll
+                .scroll_to_item_strict(row, ScrollStrategy::Center);
+            self.centered = Some(row);
+        }
         let sticky = if self.options.sticky {
             self.sticky(cx)
         } else {

src/editor/writing.rs

@@ -0,0 +1,26 @@
+//! Settings for a writing view over the code.
+
+use gpui::Context;
+
+use super::CodeEditor;
+
+impl CodeEditor {
+    /// Text size against the theme's, for a writing view.
+    pub fn set_scale(&mut self, scale: f32, cx: &mut Context<Self>) {
+        self.options.scale = scale;
+        cx.notify();
+    }
+
+    /// Fades every line but the caret's.
+    pub fn set_focus_line(&mut self, on: bool, cx: &mut Context<Self>) {
+        self.options.focus_line = on;
+        cx.notify();
+    }
+
+    /// Keeps the caret's line mid-view.
+    pub fn set_typewriter(&mut self, on: bool, cx: &mut Context<Self>) {
+        self.options.typewriter = on;
+        self.centered = None;
+        cx.notify();
+    }
+}