From 169a298af1f5e55f33963743027e6c543ce2e89b Mon Sep 17 00:00:00 2001
From: Antonio Scandurra <me@as-cii.com>
Date: Wed, 28 Jul 2021 13:29:56 +0200
Subject: [PATCH] Expand edits correctly when there are folds or multi-byte
 chars

Previously, we were mistakenly adding `tab_size` to the extent
produced by the fold edits but that could cause the edit to land on
a multi-byte character (like a fold or an emoji).

In practice, we only need to expand the edit's extent by 1 because
we are operating in the fold coordinate space and all we need to
convey is that we want to encapsulate the first tab next to whatever
edit has just occurred in the `FoldMap`.
---
 zed/src/editor/display_map/tab_map.rs  | 10 +++-------
 zed/src/editor/display_map/wrap_map.rs |  8 ++++++++
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/zed/src/editor/display_map/tab_map.rs b/zed/src/editor/display_map/tab_map.rs
index 75049e40ca..fb11e08024 100644
--- a/zed/src/editor/display_map/tab_map.rs
+++ b/zed/src/editor/display_map/tab_map.rs
@@ -2,7 +2,7 @@ use parking_lot::Mutex;
 
 use super::fold_map::{self, FoldEdit, FoldPoint, Snapshot as FoldSnapshot};
 use crate::{editor::rope, settings::StyleId, util::Bias};
-use std::{cmp, mem, ops::Range};
+use std::{mem, ops::Range};
 
 pub struct TabMap(Mutex<Snapshot>);
 
@@ -36,8 +36,8 @@ impl TabMap {
                 let patterns: &[_] = &['\t', '\n'];
                 if let Some(ix) = chunk.find(patterns) {
                     if &chunk[ix..ix + 1] == "\t" {
-                        fold_edit.old_bytes.end.0 += delta + ix + old_snapshot.tab_size;
-                        fold_edit.new_bytes.end.0 += delta + ix + new_snapshot.tab_size;
+                        fold_edit.old_bytes.end.0 += delta + ix + 1;
+                        fold_edit.new_bytes.end.0 += delta + ix + 1;
                     }
 
                     break;
@@ -45,10 +45,6 @@ impl TabMap {
 
                 delta += chunk.len();
             }
-            fold_edit.old_bytes.end =
-                cmp::min(fold_edit.old_bytes.end, old_snapshot.fold_snapshot.len());
-            fold_edit.new_bytes.end =
-                cmp::min(fold_edit.new_bytes.end, new_snapshot.fold_snapshot.len());
         }
 
         let mut ix = 1;
diff --git a/zed/src/editor/display_map/wrap_map.rs b/zed/src/editor/display_map/wrap_map.rs
index 68a649ff0d..d2f38971a8 100644
--- a/zed/src/editor/display_map/wrap_map.rs
+++ b/zed/src/editor/display_map/wrap_map.rs
@@ -902,6 +902,10 @@ mod tests {
             });
             let (mut fold_map, folds_snapshot) = cx.read(|cx| FoldMap::new(buffer.clone(), cx));
             let (tab_map, tabs_snapshot) = TabMap::new(folds_snapshot.clone(), settings.tab_size);
+            log::info!(
+                "Unwrapped text (no folds): {:?}",
+                buffer.read_with(&cx, |buf, _| buf.text())
+            );
             log::info!(
                 "Unwrapped text (unexpanded tabs): {:?}",
                 folds_snapshot.text()
@@ -957,6 +961,10 @@ mod tests {
                     }
                 }
 
+                log::info!(
+                    "Unwrapped text (no folds): {:?}",
+                    buffer.read_with(&cx, |buf, _| buf.text())
+                );
                 let (folds_snapshot, edits) = cx.read(|cx| fold_map.read(cx));
                 log::info!(
                     "Unwrapped text (unexpanded tabs): {:?}",