base: read the pointer only under hovered text, and ask no frame for a closed popup

crates/base/src/popup.rs

@@ -140,6 +140,9 @@ impl RenderOnce for Popup {
             offset,
         )));
 
+        // A closed popup places nothing: it notes its trigger's bounds, for when
+        // it opens, without asking for another frame.
+        let has_content = self.content.is_some();
         let root = self
             .base
             .child(self.trigger)
@@ -158,7 +161,7 @@ impl RenderOnce for Popup {
                                 state.captured = true;
                                 first
                             });
-                            if first {
+                            if first && has_content {
                                 window.request_animation_frame();
                             }
                         }
@@ -307,6 +310,53 @@ mod tests {
         assert!(background_hovered.get());
     }
 
+    /// A popup that may open later.
+    struct ClosedHarness {
+        open: bool,
+    }
+
+    impl Render for ClosedHarness {
+        fn render(&mut self, _: &mut Window, _: &mut Context<Self>) -> impl IntoElement {
+            let popup = Popup::new(
+                "popup",
+                div()
+                    .debug_selector(|| "popup-trigger".into())
+                    .size(px(100.)),
+            );
+            if self.open {
+                popup.content(
+                    div()
+                        .debug_selector(|| "popup-content".into())
+                        .size(px(20.)),
+                )
+            } else {
+                popup
+            }
+        }
+    }
+
+    /// A closed popup notes its trigger's bounds without asking for another
+    /// frame: a list of rows holding closed popups is not drawn again for
+    /// each row that shows. Opened, it places its content at once.
+    #[gpui::test]
+    fn a_closed_popup_asks_for_no_frame_and_opens_at_once(cx: &mut gpui::TestAppContext) {
+        let (view, window) = cx.add_window_view(|_, _| ClosedHarness { open: false });
+        window.update(|window, cx| {
+            window.draw(cx).clear(cx);
+            assert_eq!(window.simulate_next_frame(cx), 0, "no frame was asked for");
+        });
+
+        view.update(window, |harness, cx| {
+            harness.open = true;
+            cx.notify();
+        });
+        window.update(|window, cx| window.draw(cx).clear(cx));
+        assert_eq!(
+            window.debug_bounds("popup-content").unwrap().size,
+            gpui::Size::new(px(20.), px(20.))
+        );
+    }
+
     #[gpui::test]
     fn trigger_capture_enables_deferred_content_on_the_next_frame(cx: &mut gpui::TestAppContext) {
         let (_, window) = cx.add_window_view(|_, _| Harness);

crates/base/src/text/inline.rs

@@ -992,9 +992,16 @@ impl Element for Inline {
             window.set_cursor_style(CursorStyle::IBeam, &hitbox);
         }
 
-        // link cursor pointer
-        let hovered_link =
-            Self::link_range_for_position(&text_layout, &self.links, window.mouse_position());
+        // link cursor pointer. Only text under the pointer reads where the pointer
+        // is: under GPUI's retained views, reading it makes the text depend on
+        // every pointer move, so a transcript of markdown would be drawn again
+        // whenever the pointer moved anywhere.
+        let hovered_link = hitbox
+            .is_hovered(window)
+            .then(|| {
+                Self::link_range_for_position(&text_layout, &self.links, window.mouse_position())
+            })
+            .flatten();
         if hovered_link.is_some() {
             window.set_cursor_style(CursorStyle::PointingHand, &hitbox);
         }