Expand edits correctly when there are folds or multi-byte chars

Antonio Scandurra created 4 years ago

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`.

Change summary

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(-)

Detailed changes

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;

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): {:?}",