From 13ecd16685dccb701a3b76a4b59013f4c32467d5 Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Tue, 21 Dec 2021 12:36:46 -0800
Subject: [PATCH] Index max buffer row on MultiBuffer

---
 crates/editor/src/display_map.rs  |  4 ++--
 crates/editor/src/element.rs      |  2 +-
 crates/editor/src/multi_buffer.rs | 18 ++++++++++++++++++
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/crates/editor/src/display_map.rs b/crates/editor/src/display_map.rs
index 469dac5802cf59f616b6873d5fa926ad0e3d6de4..a3c95ad4bfa9ef89b9025495cd382cb72aca8aed 100644
--- a/crates/editor/src/display_map.rs
+++ b/crates/editor/src/display_map.rs
@@ -198,8 +198,8 @@ impl DisplaySnapshot {
         self.blocks_snapshot.buffer_rows(start_row)
     }
 
-    pub fn buffer_row_count(&self) -> u32 {
-        self.buffer_snapshot.max_point().row + 1
+    pub fn max_buffer_row(&self) -> u32 {
+        self.buffer_snapshot.max_buffer_row()
     }
 
     pub fn prev_row_boundary(&self, input_display_point: DisplayPoint) -> (DisplayPoint, Point) {
diff --git a/crates/editor/src/element.rs b/crates/editor/src/element.rs
index e790973c8c9e15cefcd8b191fc58b1bf6c9f65be..9c45207bb01ac5cf02c6f2d0deeaf37ed954ec43 100644
--- a/crates/editor/src/element.rs
+++ b/crates/editor/src/element.rs
@@ -436,7 +436,7 @@ impl EditorElement {
     }
 
     fn max_line_number_width(&self, snapshot: &EditorSnapshot, cx: &LayoutContext) -> f32 {
-        let digit_count = (snapshot.buffer_row_count() as f32).log10().floor() as usize + 1;
+        let digit_count = (snapshot.max_buffer_row() as f32).log10().floor() as usize + 1;
         let style = &self.settings.style;
 
         cx.text_layout_cache
diff --git a/crates/editor/src/multi_buffer.rs b/crates/editor/src/multi_buffer.rs
index f66ed061ad47fb7537a0962372295fab201c076b..f4c55f2b8601e5748eb5f3251047b09ede80a7e3 100644
--- a/crates/editor/src/multi_buffer.rs
+++ b/crates/editor/src/multi_buffer.rs
@@ -97,6 +97,7 @@ struct Excerpt {
     buffer_id: usize,
     buffer: BufferSnapshot,
     range: Range<text::Anchor>,
+    max_buffer_row: u32,
     text_summary: TextSummary,
     has_trailing_newline: bool,
 }
@@ -104,6 +105,7 @@ struct Excerpt {
 #[derive(Clone, Debug, Default)]
 struct ExcerptSummary {
     excerpt_id: ExcerptId,
+    max_buffer_row: u32,
     text: TextSummary,
 }
 
@@ -884,6 +886,10 @@ impl MultiBufferSnapshot {
         self.excerpts.summary().text.bytes
     }
 
+    pub fn max_buffer_row(&self) -> u32 {
+        self.excerpts.summary().max_buffer_row
+    }
+
     pub fn clip_offset(&self, offset: usize, bias: Bias) -> usize {
         let mut cursor = self.excerpts.cursor::<usize>();
         cursor.seek(&offset, Bias::Right, &());
@@ -1565,6 +1571,7 @@ impl Excerpt {
     ) -> Self {
         Excerpt {
             id,
+            max_buffer_row: range.end.to_point(&buffer).row,
             text_summary: buffer.text_summary_for_range::<TextSummary, _>(range.to_offset(&buffer)),
             buffer_id,
             buffer,
@@ -1660,6 +1667,7 @@ impl sum_tree::Item for Excerpt {
         }
         ExcerptSummary {
             excerpt_id: self.id.clone(),
+            max_buffer_row: self.max_buffer_row,
             text,
         }
     }
@@ -1672,6 +1680,7 @@ impl sum_tree::Summary for ExcerptSummary {
         debug_assert!(summary.excerpt_id > self.excerpt_id);
         self.excerpt_id = summary.excerpt_id.clone();
         self.text.add_summary(&summary.text, &());
+        self.max_buffer_row = cmp::max(self.max_buffer_row, summary.max_buffer_row);
     }
 }
 
@@ -2266,6 +2275,15 @@ mod tests {
                 );
             }
 
+            assert_eq!(
+                snapshot.max_buffer_row(),
+                expected_buffer_rows
+                    .into_iter()
+                    .filter_map(|r| r)
+                    .max()
+                    .unwrap()
+            );
+
             let mut excerpt_starts = excerpt_starts.into_iter();
             for (buffer, range) in &expected_excerpts {
                 let buffer_id = buffer.id();