fix: exclude scroll area padding from pane sizing

crates/layout/tests/resize_handle.rs

@@ -1,6 +1,7 @@
 use std::cell::RefCell;
 use std::rc::Rc;
 
+use gpui::prelude::FluentBuilder as _;
 use gpui::{
     Axis, Modifiers, MouseButton, MouseDownEvent, MouseMoveEvent, MouseUpEvent, ParentElement as _,
     Pixels, Render, Styled as _, TestAppContext, VisualTestContext, Window, div, point, px,
@@ -26,11 +27,17 @@ impl Render for Harness {
     ) -> impl gpui::IntoElement {
         let deltas = self.deltas.clone();
         let resets = self.resets.clone();
+        let horizontal = self.axis == Axis::Horizontal;
         div()
             .size_full()
             .flex()
-            .flex_row()
-            .child(div().w(px(120.)).h_full())
+            .when(horizontal, |layout| layout.flex_row())
+            .when(!horizontal, |layout| layout.flex_col())
+            .child(if horizontal {
+                div().w(px(120.)).h_full()
+            } else {
+                div().h(px(120.)).w_full()
+            })
             .child(
                 ResizeHandle::new("test-handle")
                     .axis(self.axis)
@@ -38,7 +45,11 @@ impl Render for Harness {
                     .on_resize(move |delta, _, _| deltas.borrow_mut().push(delta))
                     .on_reset(move |_, _| *resets.borrow_mut() += 1),
             )
-            .child(div().flex_1().h_full())
+            .child(if horizontal {
+                div().flex_1().h_full()
+            } else {
+                div().flex_1().w_full()
+            })
     }
 }