editor: Do not lay out task indicators outside of the viewport (#17250)

Piotr Osiewicz created 1 year ago

A friend of mine shared a Rust file with me that crashed Zed
consistently due to Arena space exhaustion. It is a dump of a proc macro
output that generates tests (among other things).
TL;DR: we were always laying out all run indicators, irrespective of
current scroll position. In his case, we were redundantly rendering
about 3k elements.
Obviously, this doesn't just fix the problems with Arena space
exhaustion - it should also improve perf in files with many runnables.

Release Notes:

- Improved editor performance in presence of many runnable indicators in
the gutter.

Change summary

crates/editor/src/element.rs | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

Detailed changes

crates/editor/src/element.rs

@@ -1590,6 +1590,7 @@ impl EditorElement {
     fn layout_run_indicators(
         &self,
         line_height: Pixels,
+        range: Range<DisplayRow>,
         scroll_pixel_position: gpui::Point<Pixels>,
         gutter_dimensions: &GutterDimensions,
         gutter_hitbox: &Hitbox,
@@ -1613,16 +1614,20 @@ impl EditorElement {
                 } else {
                     None
                 };
+
             editor
                 .tasks
                 .iter()
                 .filter_map(|(_, tasks)| {
                     let multibuffer_point = tasks.offset.0.to_point(&snapshot.buffer_snapshot);
                     let multibuffer_row = MultiBufferRow(multibuffer_point.row);
+                    let display_row = multibuffer_point.to_display_point(snapshot).row();
+                    if range.start > display_row || range.end < display_row {
+                        return None;
+                    }
                     if snapshot.is_line_folded(multibuffer_row) {
                         return None;
                     }
-                    let display_row = multibuffer_point.to_display_point(snapshot).row();
                     let button = editor.render_run_indicator(
                         &self.style,
                         Some(display_row) == active_task_indicator_row,
@@ -5489,6 +5494,7 @@ impl Element for EditorElement {
                     let test_indicators = if gutter_settings.runnables {
                         self.layout_run_indicators(
                             line_height,
+                            start_row..end_row,
                             scroll_pixel_position,
                             &gutter_dimensions,
                             &gutter_hitbox,
@@ -5499,7 +5505,6 @@ impl Element for EditorElement {
                     } else {
                         Vec::new()
                     };
-
                     let close_indicators = self.layout_hunk_diff_close_indicators(
                         line_height,
                         scroll_pixel_position,