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/documents/document/edit.rs

@@ -97,7 +97,10 @@ impl MarkdownDocument {
                     InputEvent::Blur => {
                         document.commit(cx);
                     }
-                    InputEvent::Changed => cx.emit(DocumentEvent::Changed),
+                    InputEvent::Changed => {
+                        document.typed += 1;
+                        cx.emit(DocumentEvent::Changed)
+                    }
                     _ => {}
                 }),
             ];

src/documents/document/look.rs

@@ -0,0 +1,80 @@
+//! A writing view: how text shows, not what it says.
+
+use gpui::{Context, Rems, SharedString};
+
+use super::MarkdownDocument;
+use crate::documents::MarkdownMode;
+
+/// How the document shows its text (MARK-09).
+#[derive(Clone, Debug, PartialEq)]
+pub struct DocumentLook {
+    /// All but the current block or line fade.
+    pub focus: bool,
+    /// The current block or line stays mid-view.
+    pub typewriter: bool,
+    /// The widest the text column grows.
+    pub measure: Option<Rems>,
+    /// The prose font; none keeps the theme's.
+    pub font: Option<SharedString>,
+    /// Text size against the theme's.
+    pub scale: f32,
+}
+
+impl Default for DocumentLook {
+    fn default() -> Self {
+        Self {
+            focus: false,
+            typewriter: false,
+            measure: None,
+            font: None,
+            scale: 1.0,
+        }
+    }
+}
+
+impl MarkdownDocument {
+    pub fn look(&self) -> &DocumentLook {
+        &self.look
+    }
+
+    pub fn set_look(&mut self, look: DocumentLook, cx: &mut Context<Self>) {
+        log::info!("markdown document: look {look:?}");
+        self.editor.update(cx, |editor, cx| {
+            editor.set_scale(look.scale, cx);
+            editor.set_focus_line(look.focus, cx);
+            editor.set_typewriter(look.typewriter, cx);
+        });
+        self.look = look;
+        self.centered = None;
+        cx.notify();
+    }
+
+    /// The reader's block: the open one, or the caret's.
+    pub(super) fn current_block(&self, cx: &gpui::App) -> usize {
+        match &self.open {
+            Some(open) if open.append => self.parsed.blocks.len(),
+            Some(open) => self.block_at(open.range.start),
+            None => self.block_at(self.editor.read(cx).primary().head),
+        }
+    }
+
+    /// The current block mid-view once it or its text moves.
+    pub(super) fn center_current(&mut self, cx: &gpui::App) {
+        if !self.look.typewriter || self.mode != MarkdownMode::Visual {
+            return;
+        }
+        let ix = self.current_block(cx);
+        let Some(block) = self.list.bounds_for_item(ix) else {
+            return;
+        };
+        // A new layout moves it too: its height counts.
+        let height = f32::from(block.size.height).round() as u64;
+        let moved = (ix, self.edits, self.typed, height);
+        if self.centered == Some(moved) {
+            return;
+        }
+        let view = self.list.viewport_bounds();
+        self.list.scroll_by(block.center().y - view.center().y);
+        self.centered = Some(moved);
+    }
+}

src/documents/document/mod.rs

@@ -2,6 +2,7 @@ mod attach;
 mod edit;
 mod finding;
 mod lists;
+mod look;
 mod parse;
 mod place;
 mod tables;
@@ -19,6 +20,7 @@ use gpui::{
 };
 
 pub use attach::Attachment;
+pub use look::DocumentLook;
 pub use parse::DocumentHeading;
 use parse::{Parsed, alike, parsed};
 pub use tables::{TableEdit, TableRefusal};
@@ -83,6 +85,11 @@ pub struct MarkdownDocument {
     writes: usize,
     /// A match asked before its text was read; its version.
     showing: Option<(Range<usize>, u64)>,
+    look: DocumentLook,
+    /// Typing in the open block, counted.
+    typed: u64,
+    /// The block, text, typing and height last centered.
+    centered: Option<(usize, u64, u64, u64)>,
     focus: FocusHandle,
     on_link: Option<OnLink>,
     _subscriptions: Vec<Subscription>,
@@ -136,6 +143,9 @@ impl MarkdownDocument {
             asks: 0,
             writes: 0,
             showing: None,
+            look: DocumentLook::default(),
+            typed: 0,
+            centered: None,
             focus,
             on_link: None,
             _subscriptions: subscriptions,

src/documents/document/tests/look.rs

@@ -0,0 +1,108 @@
+use gpui::{TestAppContext, px, rems};
+
+use super::{MarkdownMode, frames, open};
+use crate::documents::DocumentLook;
+
+/// Sixty short paragraphs, each its own block.
+fn long() -> String {
+    (0..60).map(|n| format!("Paragraph {n}.\n\n")).collect()
+}
+
+#[gpui::test]
+fn the_measure_narrows_the_column(cx: &mut TestAppContext) {
+    let (document, cx) = open("A paragraph.\n", MarkdownMode::Visual, cx);
+    let look = DocumentLook {
+        measure: Some(rems(20.)),
+        ..DocumentLook::default()
+    };
+    document.update(cx, |document, cx| document.set_look(look, cx));
+    frames(cx);
+    let block = cx.debug_bounds("markdown-block-0").expect("drawn");
+    assert!(block.size.width <= px(320.0), "{:?}", block.size);
+}
+
+#[gpui::test]
+fn typewriter_keeps_the_open_block_mid_view(cx: &mut TestAppContext) {
+    let (document, cx) = open(&long(), MarkdownMode::Visual, cx);
+    let look = DocumentLook {
+        typewriter: true,
+        ..DocumentLook::default()
+    };
+    document.update_in(cx, |document, window, cx| {
+        document.set_look(look, cx);
+        document.open(Some(40), false, window, cx);
+        document.list.scroll_to_reveal_item(40);
+    });
+    frames(cx);
+    let (block, view) = document.read_with(cx, |document, _| {
+        (
+            document.list.bounds_for_item(40),
+            document.list.viewport_bounds(),
+        )
+    });
+    let block = block.expect("block 40 is laid out");
+    let off = (block.center().y - view.center().y).abs();
+    assert!(off < px(4.0), "{off:?} from the middle");
+}
+
+#[gpui::test]
+fn typewriter_keeps_the_source_caret_mid_view(cx: &mut TestAppContext) {
+    let (document, cx) = open(&long(), MarkdownMode::Source, cx);
+    let look = DocumentLook {
+        typewriter: true,
+        ..DocumentLook::default()
+    };
+    document.update(cx, |document, cx| {
+        document.set_look(look, cx);
+        document.set_caret(90, 0, cx);
+    });
+    frames(cx);
+    let before = document.read_with(cx, |document, cx| document.top_line(cx));
+    let editor = document.read_with(cx, |document, _| document.editor().clone());
+    let focus = editor.read_with(cx, gpui::Focusable::focus_handle);
+    cx.update(|window, cx| window.focus(&focus, cx));
+    cx.simulate_input(
+        "
+
+
+
+
+
+
+
+
+
+",
+    );
+    frames(cx);
+    let after = document.read_with(cx, |document, cx| document.top_line(cx));
+    assert_eq!(after, before + 10, "the view follows the caret");
+}
+
+#[gpui::test]
+fn the_scale_sizes_source_lines(cx: &mut TestAppContext) {
+    let (document, cx) = open("a\n", MarkdownMode::Source, cx);
+    let editor = document.read_with(cx, |document, _| document.editor().clone());
+    frames(cx);
+    let plain = editor.read_with(cx, |editor, _| editor.metrics.line);
+    let look = DocumentLook {
+        scale: 2.0,
+        ..DocumentLook::default()
+    };
+    document.update(cx, |document, cx| document.set_look(look, cx));
+    frames(cx);
+    let large = editor.read_with(cx, |editor, _| editor.metrics.line);
+    assert!(large > plain * 1.8, "{plain:?} to {large:?}");
+}
+
+#[gpui::test]
+fn focus_counts_the_open_block_as_the_readers(cx: &mut TestAppContext) {
+    let (document, cx) = open(&long(), MarkdownMode::Visual, cx);
+    document.update_in(cx, |document, window, cx| {
+        document.open(Some(3), false, window, cx)
+    });
+    assert_eq!(
+        document.read_with(cx, |document, cx| document.current_block(cx)),
+        3
+    );
+}

src/documents/document/tests/mod.rs

@@ -368,6 +368,7 @@ fn a_press_after_a_write_back_waits_for_the_long_read(cx: &mut TestAppContext) {
 mod attach;
 mod history;
 mod links;
+mod look;
 mod place;
 mod tools;
 

src/documents/document/visual.rs

@@ -1,7 +1,7 @@
 use gpui::{
     AnyElement, App, ClickEvent, Context, ExternalPaths, FontWeight, InteractiveElement,
     IntoElement, KeyBinding, MouseButton, MouseDownEvent, ParentElement, Render,
-    StatefulInteractiveElement, Styled, Window, actions, div, list,
+    StatefulInteractiveElement, Styled, Window, actions, div, list, prelude::FluentBuilder as _,
 };
 
 use super::MarkdownDocument;
@@ -16,6 +16,14 @@ actions!(markdown_document, [Undo, Redo, Indent, Outdent, Paste]);
 
 const CONTEXT: &str = "MarkdownDocument";
 
+/// How far a faded block recedes.
+const FADED: f32 = 0.35;
+
+/// Modes with a reader's block to keep.
+fn editing_mode(mode: MarkdownMode) -> bool {
+    mode == MarkdownMode::Visual
+}
+
 /// Undo and redo; Tab shifts an open block's lines.
 pub(crate) fn bind_keys(cx: &mut App) {
     let context = Some(CONTEXT);
@@ -40,9 +48,11 @@ impl MarkdownDocument {
         let colors = theme.colors.clone();
         let (radius, body, mono) = (
             theme.radius(Radius::Md),
-            theme.text_size(TextSize::Base),
+            theme.text_size(TextSize::Base) * self.look.scale,
             theme.mono_family.clone(),
         );
+        // Focus fades all but the reader's block.
+        let faded = self.look.focus && editing_mode(self.mode) && ix != self.current_block(cx);
         let editing = self.mode == MarkdownMode::Visual;
         let open = self.open.as_ref();
         let field = |open: &super::Open| {
@@ -79,9 +89,11 @@ impl MarkdownDocument {
                     nodes,
                     &self.base,
                     &self.on_link,
+                    self.look.scale,
                     cx,
                 )),
             None => div()
+                .text_size(body)
                 .font_family(mono)
                 .text_color(colors.fg_muted)
                 .child(self.parsed.text[block.range.clone()].to_string()),
@@ -92,6 +104,7 @@ impl MarkdownDocument {
             .px_3()
             .py_1()
             .rounded(radius)
+            .when(faded, |block| block.opacity(FADED))
             .child(shown);
         match editing {
             true => self.pressable(block, Some(ix), cx).into_any_element(),
@@ -150,7 +163,21 @@ impl Render for MarkdownDocument {
                 log::info!("markdown document: {} files dropped", dropped.paths().len());
                 cx.emit(super::Attachment::Files(dropped.paths().to_vec()));
             }));
+        self.center_current(cx);
         let blocks = list(self.list.clone(), cx.processor(Self::item)).size_full();
+        // The text column: its measure, font, centered.
+        let column = |content: gpui::AnyElement, look: &super::DocumentLook| {
+            div().size_full().flex().justify_center().child(
+                div()
+                    .h_full()
+                    .w_full()
+                    .when_some(look.measure, |column, measure| column.max_w(measure))
+                    .when_some(look.font.clone(), |column, font| column.font_family(font))
+                    .child(content),
+            )
+        };
+        let blocks = column(blocks.into_any_element(), &self.look);
+        let source = column(self.editor.clone().into_any_element(), &self.look);
         match self.mode {
             MarkdownMode::Source => root
                 .capture_action(cx.listener(|document, _: &crate::editor::Paste, _, cx| {
@@ -163,7 +190,7 @@ impl Render for MarkdownDocument {
                         cx.stop_propagation();
                     }
                 }))
-                .child(self.editor.clone())
+                .child(source)
                 .into_any_element(),
             MarkdownMode::Split => root
                 .flex()

src/documents/mod.rs

@@ -35,8 +35,8 @@ pub use contents::outline;
 pub use counts::{ReadingTime, WordCount};
 pub use diagram::Diagram;
 pub use document::{
-    Attachment, DocumentEvent, DocumentHeading, LARGEST_READ, MarkdownDocument, TableEdit,
+    Attachment, DocumentEvent, DocumentHeading, DocumentLook, LARGEST_READ, MarkdownDocument,
-    TableRefusal,
+    TableEdit, TableRefusal,
 };
 pub use epub::{Chapter, EpubReader};
 pub use format::{Format, format};

src/documents/render.rs

@@ -92,6 +92,8 @@ struct Draw<'a> {
     headings: std::cell::Cell<usize>,
     code: &'a Option<DrawCode>,
     base: &'a Option<Arc<Path>>,
+    /// Text size against the theme's.
+    scale: f32,
 }
 
 impl Draw<'_> {
@@ -186,7 +188,7 @@ impl Draw<'_> {
                 };
                 let heading = div()
                     .pt_2()
-                    .text_size(theme.text_size(size))
+                    .text_size(theme.text_size(size) * self.scale)
                     .font_weight(if *level <= 2 {
                         FontWeight::SEMIBOLD
                     } else {
@@ -238,11 +240,11 @@ impl Draw<'_> {
                     .rounded(theme.radius(Radius::Md))
                     .bg(colors.sunken)
                     .font_family(theme.mono_family.clone())
-                    .text_size(theme.text_size(TextSize::Sm))
+                    .text_size(theme.text_size(TextSize::Sm) * self.scale)
                     .text_color(colors.syntax.variable)
                     .children(language.clone().map(|name| {
                         div()
-                            .text_size(theme.text_size(TextSize::Xs))
+                            .text_size(theme.text_size(TextSize::Xs) * self.scale)
                             .text_color(colors.fg_subtle)
                             .child(name)
                     }))
@@ -422,6 +424,7 @@ pub(crate) fn draw_nodes(
     nodes: &[Node],
     base: &Option<Arc<Path>>,
     on_link: &Option<OnLink>,
+    scale: f32,
     cx: &App,
 ) -> Vec<AnyElement> {
     let draw = Draw {
@@ -432,6 +435,7 @@ pub(crate) fn draw_nodes(
         headings: std::cell::Cell::new(0),
         code: &None,
         base,
+        scale,
     };
     draw.nodes(nodes, cx)
 }
@@ -448,6 +452,7 @@ impl RenderOnce for MarkdownRenderer {
             headings: std::cell::Cell::new(0),
             code: &self.code,
             base: &self.base,
+            scale: 1.0,
         };
         div()
             .flex()

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,
+    MouseDownEvent, MouseMoveEvent, ParentElement, Pixels, Render, ScrollStrategy, Styled,
-    canvas, div, fill, font, point, size, uniform_list,
+    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();
+    }
+}