From 32108959cc1fc41b19d07d089cb079c446aaa066 Mon Sep 17 00:00:00 2001
From: Nico Burns <nico@nicoburns.com>
Date: Fri, 11 Oct 2024 00:27:06 +0100
Subject: [PATCH] Add BoxSizing to Style

---
 crates/bevy_ui/src/layout/convert.rs | 15 ++++++++--
 crates/bevy_ui/src/ui_node.rs        | 42 ++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/crates/bevy_ui/src/layout/convert.rs b/crates/bevy_ui/src/layout/convert.rs
index 433f87785ce969..347547081c803f 100644
--- a/crates/bevy_ui/src/layout/convert.rs
+++ b/crates/bevy_ui/src/layout/convert.rs
@@ -1,7 +1,7 @@
 use taffy::style_helpers;
 
 use crate::{
-    AlignContent, AlignItems, AlignSelf, Display, FlexDirection, FlexWrap, GridAutoFlow,
+    AlignContent, AlignItems, AlignSelf, BoxSizing, Display, FlexDirection, FlexWrap, GridAutoFlow,
     GridPlacement, GridTrack, GridTrackRepetition, JustifyContent, JustifyItems, JustifySelf,
     MaxTrackSizingFunction, MinTrackSizingFunction, OverflowAxis, PositionType, RepeatedGridTrack,
     Style, UiRect, Val,
@@ -70,7 +70,7 @@ pub fn from_style(
 ) -> taffy::style::Style {
     taffy::style::Style {
         display: style.display.into(),
-        box_sizing: taffy::BoxSizing::BorderBox,
+        box_sizing: style.box_sizing.into(),
         item_is_table: false,
         text_align: taffy::TextAlign::Auto,
         overflow: taffy::Point {
@@ -255,6 +255,15 @@ impl From<Display> for taffy::style::Display {
     }
 }
 
+impl From<BoxSizing> for taffy::style::BoxSizing {
+    fn from(value: BoxSizing) -> Self {
+        match value {
+            BoxSizing::BorderBox => taffy::style::BoxSizing::BorderBox,
+            BoxSizing::ContentBox => taffy::style::BoxSizing::ContentBox,
+        }
+    }
+}
+
 impl From<OverflowAxis> for taffy::style::Overflow {
     fn from(value: OverflowAxis) -> Self {
         match value {
@@ -453,6 +462,7 @@ mod tests {
 
         let bevy_style = Style {
             display: Display::Flex,
+            box_sizing: BoxSizing::ContentBox,
             position_type: PositionType::Absolute,
             left: Val::ZERO,
             right: Val::Percent(50.),
@@ -520,6 +530,7 @@ mod tests {
         let viewport_values = LayoutContext::new(1.0, bevy_math::Vec2::new(800., 600.));
         let taffy_style = from_style(&viewport_values, &bevy_style, false);
         assert_eq!(taffy_style.display, taffy::style::Display::Flex);
+        assert_eq!(taffy_style.box_sizing, taffy::style::BoxSizing::ContentBox);
         assert_eq!(taffy_style.position, taffy::style::Position::Absolute);
         assert_eq!(
             taffy_style.inset.left,
diff --git a/crates/bevy_ui/src/ui_node.rs b/crates/bevy_ui/src/ui_node.rs
index 2d6e763bc0868a..6f74562cef602d 100644
--- a/crates/bevy_ui/src/ui_node.rs
+++ b/crates/bevy_ui/src/ui_node.rs
@@ -271,6 +271,20 @@ pub struct Style {
     /// <https://developer.mozilla.org/en-US/docs/Web/CSS/display>
     pub display: Display,
 
+    /// Which layout algorithm to use when laying out this node's contents:
+    ///   - [`Display::Flex`]: Use the Flexbox layout algorithm
+    ///   - [`Display::Grid`]: Use the CSS Grid layout algorithm
+    ///   - [`Display::None`]: Hide this node and perform layout as if it does not exist.
+    ///
+    /// Which part of a Node's box length styles like width and height control
+    ///   - [`BoxSizing::BorderBox`]: They refer to the "border box" size (size including padding and border)
+    ///   - [`BoxSizing::ContentBox`]: They refer to the "content box" size (size excluding padding and border)
+    ///
+    /// `BoxSizing::BorderBox` is generally considered more intuitive and is the default in Bevy even though it is not on the web.
+    ///
+    /// See: <https://developer.mozilla.org/en-US/docs/Web/CSS/box-sizing>
+    pub box_sizing: BoxSizing,
+
     /// Whether a node should be laid out in-flow with, or independently of its siblings:
     ///  - [`PositionType::Relative`]: Layout this node in-flow with other nodes using the usual (flexbox/grid) layout algorithm.
     ///  - [`PositionType::Absolute`]: Layout this node on top and independently of other nodes.
@@ -533,6 +547,7 @@ pub struct Style {
 impl Style {
     pub const DEFAULT: Self = Self {
         display: Display::DEFAULT,
+        box_sizing: BoxSizing::DEFAULT,
         position_type: PositionType::DEFAULT,
         left: Val::Auto,
         right: Val::Auto,
@@ -866,6 +881,33 @@ impl Default for Display {
     }
 }
 
+/// Whether to show or hide overflowing items
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Reflect)]
+#[reflect(Default, PartialEq)]
+#[cfg_attr(
+    feature = "serialize",
+    derive(serde::Serialize, serde::Deserialize),
+    reflect(Serialize, Deserialize)
+)]
+
+/// Which part of a Node's box length styles like width and height control
+///
+/// See: <https://developer.mozilla.org/en-US/docs/Web/CSS/box-sizing>
+pub enum BoxSizing {
+    /// Length styles like width and height refer to the "border box" size (size including padding and border)
+    BorderBox,
+    /// Length styles like width and height refer to the "content box" size (size excluding padding and border)
+    ContentBox,
+}
+impl BoxSizing {
+    pub const DEFAULT: Self = Self::BorderBox;
+}
+impl Default for BoxSizing {
+    fn default() -> Self {
+        Self::DEFAULT
+    }
+}
+
 /// Defines how flexbox items are ordered within a flexbox
 #[derive(Copy, Clone, PartialEq, Eq, Debug, Reflect)]
 #[reflect(Default, PartialEq)]