Tidier multibuffer (zed-industries#26954)

Makes multibuffer headers less close to the top of the file.

Moves multibuffer line numbers one em to the right to make space for the
expand excerpt button on large line numbers.

Release Notes:

- N/A

---------

Co-authored-by: Danilo Leal <[email protected]>

Author: ConradIrwin

crates/editor/src/editor.rs

@@ -211,6 +211,7 @@ pub(crate) const SCROLL_CENTER_TOP_BOTTOM_DEBOUNCE_TIMEOUT: Duration = Duration:
 
 pub(crate) const EDIT_PREDICTION_KEY_CONTEXT: &str = "edit_prediction";
 pub(crate) const EDIT_PREDICTION_CONFLICT_KEY_CONTEXT: &str = "edit_prediction_conflict";
+pub(crate) const MIN_LINE_NUMBER_DIGITS: u32 = 4;
 
 const COLUMNAR_SELECTION_MODIFIERS: Modifiers = Modifiers {
     alt: true,
@@ -17618,7 +17619,7 @@ impl EditorSnapshot {
             .unwrap_or(gutter_settings.line_numbers);
         let line_gutter_width = if show_line_numbers {
             // Avoid flicker-like gutter resizes when the line number gains another digit and only resize the gutter on files with N*10^5 lines.
-            let min_width_for_number_on_gutter = em_advance * 4.0;
+            let min_width_for_number_on_gutter = em_advance * MIN_LINE_NUMBER_DIGITS as f32;
             max_line_number_width.max(min_width_for_number_on_gutter)
         } else {
             0.0.into()
@@ -17647,8 +17648,12 @@ impl EditorSnapshot {
                     em_advance * max_char_count
                 });
 
+        let is_singleton = self.buffer_snapshot.is_singleton();
+
         let mut left_padding = git_blame_entries_width.unwrap_or(Pixels::ZERO);
-        left_padding += if show_code_actions || show_runnables {
+        left_padding += if !is_singleton {
+            em_width * 4.0
+        } else if show_code_actions || show_runnables {
             em_width * 3.0
         } else if show_git_gutter && show_line_numbers {
             em_width * 2.0
@@ -17658,9 +17663,11 @@ impl EditorSnapshot {
             px(0.)
         };
 
-        let right_padding = if gutter_settings.folds && show_line_numbers {
+        let shows_folds = is_singleton && gutter_settings.folds;
+
+        let right_padding = if shows_folds && show_line_numbers {
             em_width * 4.0
-        } else if gutter_settings.folds {
+        } else if shows_folds || (!is_singleton && show_line_numbers) {
             em_width * 3.0
         } else if show_line_numbers {
             em_width

crates/editor/src/element.rs

@@ -23,7 +23,7 @@ use crate::{
     InlineCompletion, JumpData, LineDown, LineHighlight, LineUp, OpenExcerpts, PageDown, PageUp,
     Point, RowExt, RowRangeExt, SelectPhase, SelectedTextHighlight, Selection, SoftWrap,
     StickyHeaderExcerpt, ToPoint, ToggleFold, COLUMNAR_SELECTION_MODIFIERS, CURSORS_VISIBLE_FOR,
-    FILE_HEADER_HEIGHT, GIT_BLAME_MAX_AUTHOR_CHARS_DISPLAYED, MAX_LINE_LEN,
+    FILE_HEADER_HEIGHT, GIT_BLAME_MAX_AUTHOR_CHARS_DISPLAYED, MAX_LINE_LEN, MIN_LINE_NUMBER_DIGITS,
     MULTI_BUFFER_EXCERPT_HEADER_HEIGHT,
 };
 use buffer_diff::{DiffHunkStatus, DiffHunkStatusKind};
@@ -2119,9 +2119,11 @@ impl EditorElement {
         })
     }
 
-    fn layout_excerpt_gutter(
+    fn layout_expand_toggles(
         &self,
         gutter_hitbox: &Hitbox,
+        gutter_dimensions: GutterDimensions,
+        em_width: Pixels,
         line_height: Pixels,
         scroll_position: gpui::Point<f32>,
         buffer_rows: &[RowInfo],
@@ -2130,19 +2132,17 @@ impl EditorElement {
     ) -> Vec<Option<(AnyElement, gpui::Point<Pixels>)>> {
         let editor_font_size = self.style.text.font_size.to_pixels(window.rem_size()) * 1.2;
 
-        let icon_size = editor_font_size.round();
-        let button_h_padding = ((icon_size - px(1.0)) / 2.0).round() - px(2.0);
-
         let scroll_top = scroll_position.y * line_height;
 
-        let max_line_number_length = 1 + self
+        let max_line_number_length = self
             .editor
             .read(cx)
             .buffer()
             .read(cx)
             .snapshot(cx)
             .widest_line_number()
-            .ilog10();
+            .ilog10()
+            + 1;
 
         let elements = buffer_rows
             .into_iter()
@@ -2159,20 +2159,27 @@ impl EditorElement {
                     ExpandExcerptDirection::UpAndDown => IconName::ExpandVertical,
                 };
 
+                let git_gutter_width = Self::gutter_strip_width(line_height);
+                let available_width = gutter_dimensions.left_padding - git_gutter_width;
+
                 let editor = self.editor.clone();
-                let is_wide = max_line_number_length > 3
+                let is_wide = max_line_number_length >= MIN_LINE_NUMBER_DIGITS
                     && row_info
                         .buffer_row
-                        .is_some_and(|row| (row + 1).ilog10() + 1 == max_line_number_length);
+                        .is_some_and(|row| (row + 1).ilog10() + 1 == max_line_number_length)
+                    || gutter_dimensions.right_padding == px(0.);
+
+                let width = if is_wide {
+                    available_width - px(2.)
+                } else {
+                    available_width + em_width - px(2.)
+                };
 
                 let toggle = IconButton::new(("expand", ix), icon_name)
                     .icon_color(Color::Custom(cx.theme().colors().editor_line_number))
                     .selected_icon_color(Color::Custom(cx.theme().colors().editor_foreground))
                     .icon_size(IconSize::Custom(rems(editor_font_size / window.rem_size())))
-                    .width((icon_size + button_h_padding * 2).into())
-                    .when(is_wide, |el| {
-                        el.width((icon_size + button_h_padding).into())
-                    })
+                    .width(width.into())
                     .on_click(move |_, _, cx| {
                         editor.update(cx, |editor, cx| {
                             editor.expand_excerpt(excerpt_id, direction, cx);
@@ -2185,7 +2192,7 @@ impl EditorElement {
                     .into_any_element();
 
                 let position = point(
-                    px(1.),
+                    git_gutter_width + px(1.),
                     ix as f32 * line_height - (scroll_top % line_height) + px(1.),
                 );
                 let origin = gutter_hitbox.origin + position;
@@ -2709,7 +2716,7 @@ impl EditorElement {
         for_excerpt: &ExcerptInfo,
         is_folded: bool,
         is_selected: bool,
-        _is_sticky: bool,
+        is_sticky: bool,
         jump_data: JumpData,
         window: &mut Window,
         cx: &mut App,
@@ -2744,8 +2751,7 @@ impl EditorElement {
         let colors = cx.theme().colors();
 
         div()
-            .px_2()
-            .pt_2()
+            .p_1()
             .w_full()
             .h(FILE_HEADER_HEIGHT as f32 * window.line_height())
             .child(
@@ -2756,7 +2762,7 @@ impl EditorElement {
                     .pl_0p5()
                     .pr_5()
                     .rounded_sm()
-                    // .when(is_sticky, |el| el.shadow_md())
+                    .when(is_sticky, |el| el.shadow_md())
                     .border_1()
                     .map(|div| {
                         let border_color = if is_selected
@@ -2784,7 +2790,7 @@ impl EditorElement {
                                     ButtonLike::new("toggle-buffer-fold")
                                         .style(ui::ButtonStyle::Transparent)
                                         .size(ButtonSize::Large)
-                                        .width(px(30.).into())
+                                        .width(px(24.).into())
                                         .children(toggle_chevron_icon)
                                         .tooltip({
                                             let focus_handle = focus_handle.clone();
@@ -4413,6 +4419,10 @@ impl EditorElement {
         });
     }
 
+    fn gutter_strip_width(line_height: Pixels) -> Pixels {
+        (0.275 * line_height).floor()
+    }
+
     fn diff_hunk_bounds(
         snapshot: &EditorSnapshot,
         line_height: Pixels,
@@ -4421,7 +4431,7 @@ impl EditorElement {
     ) -> Bounds<Pixels> {
         let scroll_position = snapshot.scroll_position();
         let scroll_top = scroll_position.y * line_height;
-        let gutter_strip_width = (0.275 * line_height).floor();
+        let gutter_strip_width = Self::gutter_strip_width(line_height);
 
         match hunk {
             DisplayDiffHunk::Folded { display_row, .. } => {
@@ -6887,8 +6897,10 @@ impl Element for EditorElement {
 
                     let mut expand_toggles =
                         window.with_element_namespace("expand_toggles", |window| {
-                            self.layout_excerpt_gutter(
+                            self.layout_expand_toggles(
                                 &gutter_hitbox,
+                                gutter_dimensions,
+                                em_width,
                                 line_height,
                                 scroll_position,
                                 &row_infos,