Rework diff rendering to allow putting the cursor into deleted text, soft-wrapping and scrolling deleted text correctly (#22994)

Closes #12553

* [x] Fix `diff_hunk_before`
* [x] Fix failure to show deleted text when expanding hunk w/ cursor on
second line of the hunk
* [x] Failure to expand diff hunk below the cursor.
* [x] Delete the whole file, and expand the diff. Backspace over the
deleted hunk, panic!
* [x] Go-to-line now counts the diff hunks, but it should not
* [x] backspace at the beginning of a deleted hunk deletes too much text
* [x] Indent guides are rendered incorrectly 
* [ ] Fix randomized multi buffer tests

Maybe:
* [ ] Buffer search should include deleted text (in vim mode it turns
out I use `/x` all the time to jump to the next x I can see).
* [ ] vim: should refuse to switch into insert mode if selection is
fully within a diff.
* [ ] vim `o` command when cursor is on last line of deleted hunk.
* [ ] vim `shift-o` on first line of deleted hunk moves cursor but
doesn't insert line
* [x] `enter` at end of diff hunk inserts a new line but doesn't move
cursor
* [x] (`shift-enter` at start of diff hunk does nothing)
* [ ] Inserting a line just before an expanded hunk collapses it

Release Notes:


- Improved diff rendering, allowing you to navigate with your cursor
inside of deleted text in diff hunks.

---------

Co-authored-by: Conrad <conrad@zed.dev>
Co-authored-by: Cole <cole@zed.dev>
Co-authored-by: Mikayla <mikayla@zed.dev>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
Co-authored-by: Michael <michael@zed.dev>
Co-authored-by: Agus <agus@zed.dev>
Co-authored-by: João <joao@zed.dev>

crates/editor/src/indent_guides.rs

@@ -2,17 +2,16 @@ use std::{ops::Range, time::Duration};
 
 use collections::HashSet;
 use gpui::{AppContext, Task};
-use language::{language_settings::language_settings, BufferRow};
-use multi_buffer::{MultiBufferIndentGuide, MultiBufferRow};
-use text::{BufferId, LineIndent, Point};
+use language::language_settings::language_settings;
+use multi_buffer::{IndentGuide, MultiBufferRow};
+use text::{LineIndent, Point};
 use ui::ViewContext;
 use util::ResultExt;
 
 use crate::{DisplaySnapshot, Editor};
 
 struct ActiveIndentedRange {
-    buffer_id: BufferId,
-    row_range: Range<BufferRow>,
+    row_range: Range<MultiBufferRow>,
     indent: LineIndent,
 }
 
@@ -36,7 +35,7 @@ impl Editor {
         visible_buffer_range: Range<MultiBufferRow>,
         snapshot: &DisplaySnapshot,
         cx: &mut ViewContext<Editor>,
-    ) -> Option<Vec<MultiBufferIndentGuide>> {
+    ) -> Option<Vec<IndentGuide>> {
         let show_indent_guides = self.should_show_indent_guides().unwrap_or_else(|| {
             if let Some(buffer) = self.buffer().read(cx).as_singleton() {
                 language_settings(
@@ -66,7 +65,7 @@ impl Editor {
 
     pub fn find_active_indent_guide_indices(
         &mut self,
-        indent_guides: &[MultiBufferIndentGuide],
+        indent_guides: &[IndentGuide],
         snapshot: &DisplaySnapshot,
         cx: &mut ViewContext<Editor>,
     ) -> Option<HashSet<usize>> {
@@ -134,9 +133,7 @@ impl Editor {
             .iter()
             .enumerate()
             .filter(|(_, indent_guide)| {
-                indent_guide.buffer_id == active_indent_range.buffer_id
-                    && indent_guide.indent_level()
-                        == active_indent_range.indent.len(indent_guide.tab_size)
+                indent_guide.indent_level() == active_indent_range.indent.len(indent_guide.tab_size)
             });
 
         let mut matches = HashSet::default();
@@ -158,7 +155,7 @@ pub fn indent_guides_in_range(
     ignore_disabled_for_language: bool,
     snapshot: &DisplaySnapshot,
     cx: &AppContext,
-) -> Vec<MultiBufferIndentGuide> {
+) -> Vec<IndentGuide> {
     let start_anchor = snapshot
         .buffer_snapshot
         .anchor_before(Point::new(visible_buffer_range.start.0, 0));
@@ -169,14 +166,12 @@ pub fn indent_guides_in_range(
     snapshot
         .buffer_snapshot
         .indent_guides_in_range(start_anchor..end_anchor, ignore_disabled_for_language, cx)
-        .into_iter()
         .filter(|indent_guide| {
-            if editor.buffer_folded(indent_guide.buffer_id, cx) {
+            if editor.is_buffer_folded(indent_guide.buffer_id, cx) {
                 return false;
             }
 
-            let start =
-                MultiBufferRow(indent_guide.multibuffer_row_range.start.0.saturating_sub(1));
+            let start = MultiBufferRow(indent_guide.start_row.0.saturating_sub(1));
             // Filter out indent guides that are inside a fold
             // All indent guides that are starting "offscreen" have a start value of the first visible row minus one
             // Therefore checking if a line is folded at first visible row minus one causes the other indent guides that are not related to the fold to disappear as well
@@ -193,24 +188,11 @@ async fn resolve_indented_range(
     snapshot: DisplaySnapshot,
     buffer_row: MultiBufferRow,
 ) -> Option<ActiveIndentedRange> {
-    let (buffer_row, buffer_snapshot, buffer_id) =
-        if let Some((_, buffer_id, snapshot)) = snapshot.buffer_snapshot.as_singleton() {
-            (buffer_row.0, snapshot, buffer_id)
-        } else {
-            let (snapshot, point) = snapshot.buffer_snapshot.buffer_line_for_row(buffer_row)?;
-
-            let buffer_id = snapshot.remote_id();
-            (point.start.row, snapshot, buffer_id)
-        };
-
-    buffer_snapshot
+    snapshot
+        .buffer_snapshot
         .enclosing_indent(buffer_row)
         .await
-        .map(|(row_range, indent)| ActiveIndentedRange {
-            row_range,
-            indent,
-            buffer_id,
-        })
+        .map(|(row_range, indent)| ActiveIndentedRange { row_range, indent })
 }
 
 fn should_recalculate_indented_range(
@@ -222,23 +204,23 @@ fn should_recalculate_indented_range(
     if prev_row.0 == new_row.0 {
         return false;
     }
-    if let Some((_, _, snapshot)) = snapshot.buffer_snapshot.as_singleton() {
-        if !current_indent_range.row_range.contains(&new_row.0) {
+    if snapshot.buffer_snapshot.is_singleton() {
+        if !current_indent_range.row_range.contains(&new_row) {
             return true;
         }
 
-        let old_line_indent = snapshot.line_indent_for_row(prev_row.0);
-        let new_line_indent = snapshot.line_indent_for_row(new_row.0);
+        let old_line_indent = snapshot.buffer_snapshot.line_indent_for_row(prev_row);
+        let new_line_indent = snapshot.buffer_snapshot.line_indent_for_row(new_row);
 
         if old_line_indent.is_line_empty()
             || new_line_indent.is_line_empty()
             || old_line_indent != new_line_indent
-            || snapshot.max_point().row == new_row.0
+            || snapshot.buffer_snapshot.max_point().row == new_row.0
         {
             return true;
         }
 
-        let next_line_indent = snapshot.line_indent_for_row(new_row.0 + 1);
+        let next_line_indent = snapshot.buffer_snapshot.line_indent_for_row(new_row + 1);
         next_line_indent.is_line_empty() || next_line_indent != old_line_indent
     } else {
         true