editor: typewriter room as rows, so drawing and text queries share one origin; a placement resets centering

src/documents/document/place.rs

@@ -106,7 +106,7 @@ impl MarkdownDocument {
         if matches!(self.mode, MarkdownMode::Source | MarkdownMode::Split) {
             editor
                 .scroll
-                .scroll_to_item_strict(line, ScrollStrategy::Top);
+                .scroll_to_item_strict(line + editor.pad, ScrollStrategy::Top);
             self.placing(ask);
             // The editor's offset holds it from the next frame.
             return cx.on_next_frame(window, move |document, _, cx| {
@@ -158,6 +158,8 @@ impl MarkdownDocument {
             });
         }
         self.top = None;
+        // The view moved: center again.
+        self.centered = None;
         cx.notify();
     }
 

src/documents/document/tests/look.rs

@@ -216,3 +216,67 @@ fn the_last_source_line_centers_and_a_resize_follows(cx: &mut TestAppContext) {
         "top {top} to {resized}; mid-view is {middle}"
     );
 }
+
+/// Typewriter source, caret on line 60 of 120.
+fn centered_source(
+    cx: &mut TestAppContext,
+) -> (
+    gpui::Entity<super::MarkdownDocument>,
+    &mut gpui::VisualTestContext,
+) {
+    let text: String = (0..120).map(|n| format!("Line {n}.\n")).collect();
+    let (document, cx) = open(&text, MarkdownMode::Source, cx);
+    document.update(cx, |document, cx| {
+        document.set_look(typewriter(), cx);
+        document.set_caret(60, 0, cx);
+    });
+    frames(cx);
+    (document, cx)
+}
+
+#[gpui::test]
+fn source_lines_below_the_center_draw(cx: &mut TestAppContext) {
+    let (_, cx) = centered_source(cx);
+    let caret = cx.debug_bounds("editor-line-60").expect("caret line");
+    let next = cx.debug_bounds("editor-line-61").expect("the line below");
+    assert!(next.top() >= caret.bottom() - px(1.0));
+}
+
+#[gpui::test]
+fn platform_text_queries_meet_the_drawn_line(cx: &mut TestAppContext) {
+    use gpui::EntityInputHandler as _;
+    let (document, cx) = centered_source(cx);
+    let drawn = cx.debug_bounds("editor-line-60").expect("caret line");
+    let editor = document.read_with(cx, |document, _| document.editor().clone());
+    let (anchor, line) = editor.update_in(cx, |editor, window, cx| {
+        let at = editor.text()[..editor.primary().head]
+            .encode_utf16()
+            .count();
+        let anchor = editor.bounds_for_range(at..at, gpui::Bounds::default(), window, cx);
+        let point = gpui::point(editor.metrics.left, drawn.center().y);
+        let index = editor.character_index_for_point(point, window, cx);
+        let line = index.map(|at| editor.buffer.line_of(editor.byte_range(&(at..at)).start));
+        (anchor.expect("anchor"), line)
+    });
+    assert!(
+        (anchor.top() - drawn.top()).abs() < px(2.0),
+        "{anchor:?} vs {drawn:?}"
+    );
+    assert_eq!(line, Some(60));
+}
+
+#[gpui::test]
+fn switching_to_visual_centers_the_caret_block(cx: &mut TestAppContext) {
+    let (document, cx) = open(&long(), MarkdownMode::Source, cx);
+    document.update(cx, |document, cx| {
+        document.set_look(typewriter(), cx);
+        document.set_caret(100, 0, cx);
+    });
+    frames(cx);
+    document.update_in(cx, |document, window, cx| {
+        document.set_mode(MarkdownMode::Visual, window, cx)
+    });
+    frames(cx);
+    let off = off_middle(&document, 50, cx);
+    assert!(off < px(4.0), "{off:?} from the middle");
+}

src/editor/ime.rs

@@ -104,7 +104,7 @@ impl CodeEditor {
         to_utf16(text, range.start)..to_utf16(text, range.end)
     }
 
-    fn byte_range(&self, range: &Range<usize>) -> Range<usize> {
+    pub(crate) fn byte_range(&self, range: &Range<usize>) -> Range<usize> {
         let text = self.buffer.text();
         from_utf16(text, range.start)..from_utf16(text, range.end)
     }

src/editor/layout.rs

@@ -19,6 +19,8 @@ pub(crate) enum Row {
     Ghost(usize),
     /// The inline chat's rows; the first draws it.
     Chat(usize),
+    /// Typewriter room past an end.
+    Room,
 }
 
 /// Which lines folds hide.

src/editor/moves.rs

@@ -158,6 +158,7 @@ impl CodeEditor {
             .iter()
             .rposition(|row| matches!(row, Row::Line(shown) if *shown <= line))
             .unwrap_or(0)
+            + self.pad
     }
 
     /// Scrolls the primary cursor into view: from below when moving down, from above when moving up.

src/editor/row.rs

@@ -23,6 +23,10 @@ impl CodeEditor {
             .h(self.frame.line)
             .flex();
         let caret = self.buffer.line_of(self.primary().head);
+        let base = match self.frame.rows[ix] {
+            Row::Line(line) => base.debug_selector(move || format!("editor-line-{line}")),
+            _ => base,
+        };
         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)
@@ -32,6 +36,7 @@ impl CodeEditor {
             Row::Removed(hunk, at) => self.removed_row(base, ix, hunk, at, cx),
             Row::Ghost(at) => self.ghost_row(base, ix, at, cx),
             Row::Chat(at) => self.chat_row(base, ix, at, cx),
+            Row::Room => base.into_any_element(),
         }
     }
 

src/editor/state.rs

@@ -100,7 +100,7 @@ pub(crate) struct Metrics {
     pub top: Pixels,
     pub advance: Pixels,
     pub line: Pixels,
-    /// The view's height, under any typewriter room.
+    /// The view's height.
     pub height: Pixels,
 }
 
@@ -124,8 +124,8 @@ pub struct CodeEditor {
     pub(crate) metrics: Metrics,
     /// The caret row typewriter scrolling last centered.
     pub(crate) centered: Option<usize>,
-    /// Typewriter room past each end, as last drawn.
+    /// Typewriter room rows at each end.
-    pub(crate) room: Pixels,
+    pub(crate) pad: usize,
     pub(crate) dragging: bool,
     pub(crate) caret_on: bool,
     /// Blink runs only while focused, or unseen cursors redraw forever.
@@ -212,7 +212,7 @@ impl CodeEditor {
             composing: None,
             metrics: Metrics::default(),
             centered: None,
-            room: Pixels::ZERO,
+            pad: 0,
             dragging: false,
             caret_on: true,
             focused: false,

src/editor/view.rs

@@ -54,8 +54,7 @@ impl CodeEditor {
 
     /// The first line the list shows, after scrolling.
     pub(crate) fn top_line(&self) -> Option<usize> {
-        // Typewriter room above the first line is no line.
+        let scrolled = -self.scroll.0.borrow().base_handle.offset().y;
-        let scrolled = -self.scroll.0.borrow().base_handle.offset().y - self.room;
         let first = (scrolled / self.frame.line).floor().max(0.0) as usize;
         self.frame.rows[first.min(self.frame.rows.len().saturating_sub(1))..]
             .iter()
@@ -252,8 +251,16 @@ impl Render for CodeEditor {
             _ => Vec::new(),
         };
         let minimap = self.frame.minimap;
+        // Half a view of room rows: the ends center too.
+        self.pad = match self.options.typewriter && line > Pixels::ZERO {
+            true => (self.metrics.height / 2.0 / line).ceil() as usize,
+            false => 0,
+        };
+        let mut shown = vec![Row::Room; self.pad];
+        shown.extend(rows(&self.buffer, &hide, &self.marks));
+        shown.extend(std::iter::repeat_n(Row::Room, self.pad));
         self.frame = Frame {
-            rows: rows(&self.buffer, &hide, &self.marks),
+            rows: shown,
             folds: found,
             brackets: found_brackets,
             advance,
@@ -271,13 +278,6 @@ impl Render for CodeEditor {
                 .scroll_to_item_strict(row, ScrollStrategy::Center);
             self.centered = Some(row);
         }
-        // Half a view of room: a resize keeps the center.
-        let height = self.metrics.height;
-        self.room = match self.options.typewriter {
-            true => height / 2.0,
-            false => gpui::px(0.0),
-        };
-        let room = self.room;
         let sticky = if self.options.sticky {
             self.sticky(cx)
         } else {
@@ -292,9 +292,7 @@ impl Render for CodeEditor {
             }),
         )
         .track_scroll(&self.scroll)
-        .size_full()
+        .size_full();
-        .pt(room)
-        .pb(room);
         let (top, focus, input) = (cx.entity(), self.focus.clone(), cx.entity());
         let unlock = cx.entity();
         let banner = self.options.read_only.then(|| {