agent: Render diffs for the edit file tool (#29234)

This PR implements the `ToolCard` for the edit file tool, which allow us
to display an editor with a diff in the thread view with the changes
performed by the model.

- [x] Fix buffer sometimes displaying empty
- [x] Stop buffer from scrolling together with the thread
- [x] Fix multibuffer header sometimes appearing
- [x] Fix buffer height issue
- [x] Implement "full height" expand button
- [x] Add "Jump To File" functionality
- [x] Polish and refine styles

Release Notes:

- agent: Added diff preview cards in the thread view for edits performed
by the agent.

---------

Co-authored-by: João Marcos <marcospb19@hotmail.com>
Co-authored-by: Richard Feldman <oss@rtfeldman.com>
Co-authored-by: Agus Zubiaga <hi@aguz.me>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/editor/src/editor.rs

@@ -433,6 +433,8 @@ pub enum EditorMode {
         scale_ui_elements_with_buffer_font_size: bool,
         /// When set to `true`, the editor will render a background for the active line.
         show_active_line_background: bool,
+        /// When set to `true`, the editor's height will be determined by its content.
+        sized_by_content: bool,
     },
 }
 
@@ -441,6 +443,7 @@ impl EditorMode {
         Self::Full {
             scale_ui_elements_with_buffer_font_size: true,
             show_active_line_background: true,
+            sized_by_content: false,
         }
     }
 
@@ -798,6 +801,8 @@ pub struct Editor {
     show_breadcrumbs: bool,
     show_gutter: bool,
     show_scrollbars: bool,
+    disable_scrolling: bool,
+    disable_expand_excerpt_buttons: bool,
     show_line_numbers: Option<bool>,
     use_relative_line_numbers: Option<bool>,
     show_git_diff_gutter: Option<bool>,
@@ -1589,11 +1594,13 @@ impl Editor {
             blink_manager: blink_manager.clone(),
             show_local_selections: true,
             show_scrollbars: true,
+            disable_scrolling: true,
             mode,
             show_breadcrumbs: EditorSettings::get_global(cx).toolbar.breadcrumbs,
             show_gutter: mode.is_full(),
             show_line_numbers: None,
             use_relative_line_numbers: None,
+            disable_expand_excerpt_buttons: false,
             show_git_diff_gutter: None,
             show_code_actions: None,
             show_runnables: None,
@@ -16175,11 +16182,21 @@ impl Editor {
         cx.notify();
     }
 
+    pub fn disable_scrolling(&mut self, cx: &mut Context<Self>) {
+        self.disable_scrolling = true;
+        cx.notify();
+    }
+
     pub fn set_show_line_numbers(&mut self, show_line_numbers: bool, cx: &mut Context<Self>) {
         self.show_line_numbers = Some(show_line_numbers);
         cx.notify();
     }
 
+    pub fn disable_expand_excerpt_buttons(&mut self, cx: &mut Context<Self>) {
+        self.disable_expand_excerpt_buttons = true;
+        cx.notify();
+    }
+
     pub fn set_show_git_diff_gutter(&mut self, show_git_diff_gutter: bool, cx: &mut Context<Self>) {
         self.show_git_diff_gutter = Some(show_git_diff_gutter);
         cx.notify();

crates/editor/src/editor_tests.rs

@@ -10419,6 +10419,7 @@ async fn test_completion_in_multibuffer_with_replace_range(cx: &mut TestAppConte
                     EditorMode::Full {
                         scale_ui_elements_with_buffer_font_size: false,
                         show_active_line_background: false,
+                        sized_by_content: false,
                     },
                     multi_buffer.clone(),
                     Some(project.clone()),

crates/editor/src/element.rs

@@ -2184,6 +2184,10 @@ impl EditorElement {
         window: &mut Window,
         cx: &mut App,
     ) -> Vec<Option<(AnyElement, gpui::Point<Pixels>)>> {
+        if self.editor.read(cx).disable_expand_excerpt_buttons {
+            return vec![];
+        }
+
         let editor_font_size = self.style.text.font_size.to_pixels(window.rem_size()) * 1.2;
 
         let scroll_top = scroll_position.y * line_height;
@@ -5537,7 +5541,9 @@ impl EditorElement {
     }
 
     fn paint_mouse_listeners(&mut self, layout: &EditorLayout, window: &mut Window, cx: &mut App) {
-        self.paint_scroll_wheel_listener(layout, window, cx);
+        if !self.editor.read(cx).disable_scrolling {
+            self.paint_scroll_wheel_listener(layout, window, cx);
+        }
 
         window.on_mouse_event({
             let position_map = layout.position_map.clone();
@@ -6588,10 +6594,21 @@ impl Element for EditorElement {
                             },
                         )
                     }
-                    EditorMode::Full { .. } => {
+                    EditorMode::Full {
+                        sized_by_content, ..
+                    } => {
                         let mut style = Style::default();
                         style.size.width = relative(1.).into();
-                        style.size.height = relative(1.).into();
+                        if sized_by_content {
+                            let snapshot = editor.snapshot(window, cx);
+                            let line_height =
+                                self.style.text.line_height_in_pixels(window.rem_size());
+                            let scroll_height =
+                                (snapshot.max_point().row().next_row().0 as f32) * line_height;
+                            style.size.height = scroll_height.into();
+                        } else {
+                            style.size.height = relative(1.).into();
+                        }
                         window.request_layout(style, None, cx)
                     }
                 };