From 5012603e03f380defac510df970d6b2cc635131a Mon Sep 17 00:00:00 2001
From: rustbasic <127506429+rustbasic@users.noreply.github.com>
Date: Wed, 10 Jun 2026 16:57:44 +0900
Subject: [PATCH] Fix: ScrollArea layout jitter with floating bars and zoom
 levels (#7944)

Fix: ScrollArea layout jitter with floating bars and zoom levels

* Closes #7937
* Closes #7942

This PR improves the stability of `ScrollArea` by addressing two layout
issues:

1. **Discrete Layout for Floating Bars:** Fixed content "shaking" in
`floating` mode when a non-zero `allocated_width` is used. By using
discrete visibility (`show_bars`) instead of the animated factor for
space allocation, we ensure the layout remains stable during scrollbar
animations.
2. **Zoom-level Stability:** Introduced a small epsilon (0.1) when
checking if content exceeds the viewport. This prevents scrollbars from
flickering on and off due to floating-point rounding errors at specific
zoom factors (e.g., 1.01 or 0.95).
---
 crates/egui/src/containers/scroll_area.rs | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/crates/egui/src/containers/scroll_area.rs b/crates/egui/src/containers/scroll_area.rs
index 5e0c69936..0fa4bba0c 100644
--- a/crates/egui/src/containers/scroll_area.rs
+++ b/crates/egui/src/containers/scroll_area.rs
@@ -753,7 +753,12 @@ impl ScrollArea {
             ctx.animate_bool_responsive(id.with("v"), show_bars[1]),
         );
 
-        let current_bar_use = show_bars_factor.yx() * ui.spacing().scroll.allocated_width();
+        let scroll_style = ui.spacing().scroll;
+        let current_bar_use = if scroll_style.floating {
+            show_bars.to_vec2().yx() * scroll_style.allocated_width()
+        } else {
+            show_bars_factor.yx() * scroll_style.allocated_width()
+        };
 
         let available_outer = ui.available_rect_before_wrap();
 
@@ -1187,9 +1192,15 @@ impl Prepared {
 
         let outer_rect = Rect::from_min_size(inner_rect.min, inner_rect.size() + current_bar_use);
 
+        let limit_rect = if ui.spacing().scroll.floating {
+            outer_rect
+        } else {
+            inner_rect
+        };
+
         let content_is_too_large = Vec2b::new(
-            direction_enabled[0] && inner_rect.width() < content_size.x,
-            direction_enabled[1] && inner_rect.height() < content_size.y,
+            direction_enabled[0] && (limit_rect.width().ceil() < content_size.x),
+            direction_enabled[1] && (limit_rect.height().ceil() < content_size.y),
         );
 
         let max_offset = content_size - inner_rect.size();