From 5ab32a23cc610ff8167ffbaec8d01a7fa05ba412 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bart=C5=82omiej=20Mary=C5=84czak?=
 <marynczak.bartlomiej@gmail.com>
Date: Sat, 11 Jan 2025 23:34:22 +0100
Subject: [PATCH] Use taffy for scroll container layouting (#731)

---
 src/style.rs        | 19 +++++++++++++++++--
 src/views/scroll.rs | 18 +++++++++++++++---
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/src/style.rs b/src/style.rs
index bec1f8dd..5eef9fc0 100644
--- a/src/style.rs
+++ b/src/style.rs
@@ -26,8 +26,8 @@ use taffy::{
     geometry::{MinMax, Size},
     prelude::{GridPlacement, Line, Rect},
     style::{
-        LengthPercentage, MaxTrackSizingFunction, MinTrackSizingFunction, Style as TaffyStyle,
-        TrackSizingFunction,
+        LengthPercentage, MaxTrackSizingFunction, MinTrackSizingFunction, Overflow,
+        Style as TaffyStyle, TrackSizingFunction,
     },
 };
 
@@ -74,6 +74,7 @@ impl StylePropValue for f64 {
         Some(*self * (1.0 - value) + *other * value)
     }
 }
+impl StylePropValue for Overflow {}
 impl StylePropValue for Display {}
 impl StylePropValue for Position {}
 impl StylePropValue for FlexDirection {}
@@ -1674,6 +1675,16 @@ define_builtin_props!(
     Rotation rotate: Px {} = Px(0.),
 );
 
+prop!(
+    /// How children overflowing their container in Y axis should affect layout
+    pub(crate) OverflowX: Overflow {} = Overflow::default()
+);
+
+prop!(
+    /// How children overflowing their container in X axis should affect layout
+    pub(crate) OverflowY: Overflow {} = Overflow::default()
+);
+
 prop_extractor! {
     pub FontProps {
         pub size: FontSize,
@@ -2357,6 +2368,10 @@ impl Style {
         let style = self.builtin();
         TaffyStyle {
             display: style.display(),
+            overflow: taffy::Point {
+                x: self.get(OverflowX),
+                y: self.get(OverflowY),
+            },
             position: style.position(),
             size: taffy::prelude::Size {
                 width: style.width().into(),
diff --git a/src/views/scroll.rs b/src/views/scroll.rs
index a5ce1a7e..fc79fa99 100644
--- a/src/views/scroll.rs
+++ b/src/views/scroll.rs
@@ -5,7 +5,7 @@ use floem_reactive::create_effect;
 use peniko::kurbo::{Point, Rect, Size, Stroke, Vec2};
 use peniko::{Brush, Color};
 
-use crate::style::CustomStylable;
+use crate::style::{CustomStylable, OverflowX, OverflowY};
 use crate::unit::PxPct;
 use crate::{
     app_state::AppState,
@@ -425,7 +425,14 @@ impl Scroll {
     fn child_size(&self) -> Size {
         self.child
             .get_layout()
-            .map(|layout| Size::new(layout.size.width as f64, layout.size.height as f64))
+            .map(|layout| {
+                // Whenever content overflows the container use content_size,
+                // otherwise just use size
+                Size::new(
+                    layout.size.width.max(layout.content_size.width) as f64,
+                    layout.size.height.max(layout.content_size.width) as f64,
+                )
+            })
             .unwrap()
     }
 
@@ -733,7 +740,12 @@ impl View for Scroll {
     }
 
     fn view_style(&self) -> Option<Style> {
-        Some(Style::new().items_start())
+        Some(
+            Style::new()
+                .items_start()
+                .set(OverflowX, taffy::Overflow::Scroll)
+                .set(OverflowY, taffy::Overflow::Scroll),
+        )
     }
 
     fn update(&mut self, cx: &mut crate::context::UpdateCx, state: Box<dyn std::any::Any>) {