feat(tui2): copy tui crate and normalize snapshots (#7833)

Introduce a full codex-tui source snapshot under the new codex-tui2
crate so viewport work can be replayed in isolation.

This change copies the entire codex-rs/tui/src tree into
codex-rs/tui2/src in one atomic step, rather than piecemeal, to keep
future diffs vs the original viewport bookmark easy to reason about.

The goal is for codex-tui2 to render identically to the existing TUI
behind the `features.tui2` flag while we gradually port the
viewport/history commits from the joshka/viewport bookmark onto this
forked tree.

While on this baseline change, we also ran the codex-tui2 snapshot test
suite and accepted all insta snapshots for the new crate, so the
snapshot files now use the codex-tui2 naming scheme and encode the
unmodified legacy TUI behavior. This keeps later viewport commits
focused on intentional behavior changes (and their snapshots) rather
than on mechanical snapshot renames.

codex-rs/tui2/src/render/highlight.rs

@@ -0,0 +1,236 @@
+use ratatui::style::Style;
+use ratatui::style::Stylize;
+use ratatui::text::Line;
+use ratatui::text::Span;
+use std::sync::OnceLock;
+use tree_sitter_highlight::Highlight;
+use tree_sitter_highlight::HighlightConfiguration;
+use tree_sitter_highlight::HighlightEvent;
+use tree_sitter_highlight::Highlighter;
+
+// Ref: https://github.com/tree-sitter/tree-sitter-bash/blob/master/queries/highlights.scm
+#[derive(Copy, Clone)]
+enum BashHighlight {
+    Comment,
+    Constant,
+    Embedded,
+    Function,
+    Keyword,
+    Number,
+    Operator,
+    Property,
+    String,
+}
+
+impl BashHighlight {
+    const ALL: [Self; 9] = [
+        Self::Comment,
+        Self::Constant,
+        Self::Embedded,
+        Self::Function,
+        Self::Keyword,
+        Self::Number,
+        Self::Operator,
+        Self::Property,
+        Self::String,
+    ];
+
+    const fn as_str(self) -> &'static str {
+        match self {
+            Self::Comment => "comment",
+            Self::Constant => "constant",
+            Self::Embedded => "embedded",
+            Self::Function => "function",
+            Self::Keyword => "keyword",
+            Self::Number => "number",
+            Self::Operator => "operator",
+            Self::Property => "property",
+            Self::String => "string",
+        }
+    }
+
+    fn style(self) -> Style {
+        match self {
+            Self::Comment | Self::Operator | Self::String => Style::default().dim(),
+            _ => Style::default(),
+        }
+    }
+}
+
+static HIGHLIGHT_CONFIG: OnceLock<HighlightConfiguration> = OnceLock::new();
+
+fn highlight_names() -> &'static [&'static str] {
+    static NAMES: OnceLock<[&'static str; BashHighlight::ALL.len()]> = OnceLock::new();
+    NAMES
+        .get_or_init(|| BashHighlight::ALL.map(BashHighlight::as_str))
+        .as_slice()
+}
+
+fn highlight_config() -> &'static HighlightConfiguration {
+    HIGHLIGHT_CONFIG.get_or_init(|| {
+        let language = tree_sitter_bash::LANGUAGE.into();
+        #[expect(clippy::expect_used)]
+        let mut config = HighlightConfiguration::new(
+            language,
+            "bash",
+            tree_sitter_bash::HIGHLIGHT_QUERY,
+            "",
+            "",
+        )
+        .expect("load bash highlight query");
+        config.configure(highlight_names());
+        config
+    })
+}
+
+fn highlight_for(highlight: Highlight) -> BashHighlight {
+    BashHighlight::ALL[highlight.0]
+}
+
+fn push_segment(lines: &mut Vec<Line<'static>>, segment: &str, style: Option<Style>) {
+    for (i, part) in segment.split('\n').enumerate() {
+        if i > 0 {
+            lines.push(Line::from(""));
+        }
+        if part.is_empty() {
+            continue;
+        }
+        let span = match style {
+            Some(style) => Span::styled(part.to_string(), style),
+            None => part.to_string().into(),
+        };
+        if let Some(last) = lines.last_mut() {
+            last.spans.push(span);
+        }
+    }
+}
+
+/// Convert a bash script into per-line styled content using tree-sitter's
+/// bash highlight query. The highlighter is streamed so multi-line content is
+/// split into `Line`s while preserving style boundaries.
+pub(crate) fn highlight_bash_to_lines(script: &str) -> Vec<Line<'static>> {
+    let mut highlighter = Highlighter::new();
+    let iterator =
+        match highlighter.highlight(highlight_config(), script.as_bytes(), None, |_| None) {
+            Ok(iter) => iter,
+            Err(_) => return vec![script.to_string().into()],
+        };
+
+    let mut lines: Vec<Line<'static>> = vec![Line::from("")];
+    let mut highlight_stack: Vec<Highlight> = Vec::new();
+
+    for event in iterator {
+        match event {
+            Ok(HighlightEvent::HighlightStart(highlight)) => highlight_stack.push(highlight),
+            Ok(HighlightEvent::HighlightEnd) => {
+                highlight_stack.pop();
+            }
+            Ok(HighlightEvent::Source { start, end }) => {
+                if start == end {
+                    continue;
+                }
+                let style = highlight_stack.last().map(|h| highlight_for(*h).style());
+                push_segment(&mut lines, &script[start..end], style);
+            }
+            Err(_) => return vec![script.to_string().into()],
+        }
+    }
+
+    if lines.is_empty() {
+        vec![Line::from("")]
+    } else {
+        lines
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+    use ratatui::style::Modifier;
+
+    fn reconstructed(lines: &[Line<'static>]) -> String {
+        lines
+            .iter()
+            .map(|l| {
+                l.spans
+                    .iter()
+                    .map(|sp| sp.content.clone())
+                    .collect::<String>()
+            })
+            .collect::<Vec<_>>()
+            .join("\n")
+    }
+
+    fn dimmed_tokens(lines: &[Line<'static>]) -> Vec<String> {
+        lines
+            .iter()
+            .flat_map(|l| l.spans.iter())
+            .filter(|sp| sp.style.add_modifier.contains(Modifier::DIM))
+            .map(|sp| sp.content.clone().into_owned())
+            .map(|token| token.trim().to_string())
+            .filter(|token| !token.is_empty())
+            .collect()
+    }
+
+    #[test]
+    fn dims_expected_bash_operators() {
+        let s = "echo foo && bar || baz | qux & (echo hi)";
+        let lines = highlight_bash_to_lines(s);
+        assert_eq!(reconstructed(&lines), s);
+
+        let dimmed = dimmed_tokens(&lines);
+        assert!(dimmed.contains(&"&&".to_string()));
+        assert!(dimmed.contains(&"|".to_string()));
+        assert!(!dimmed.contains(&"echo".to_string()));
+    }
+
+    #[test]
+    fn dims_redirects_and_strings() {
+        let s = "echo \"hi\" > out.txt; echo 'ok'";
+        let lines = highlight_bash_to_lines(s);
+        assert_eq!(reconstructed(&lines), s);
+
+        let dimmed = dimmed_tokens(&lines);
+        assert!(dimmed.contains(&">".to_string()));
+        assert!(dimmed.contains(&"\"hi\"".to_string()));
+        assert!(dimmed.contains(&"'ok'".to_string()));
+    }
+
+    #[test]
+    fn highlights_command_and_strings() {
+        let s = "echo \"hi\"";
+        let lines = highlight_bash_to_lines(s);
+        let mut echo_style = None;
+        let mut string_style = None;
+        for span in &lines[0].spans {
+            let text = span.content.as_ref();
+            if text == "echo" {
+                echo_style = Some(span.style);
+            }
+            if text == "\"hi\"" {
+                string_style = Some(span.style);
+            }
+        }
+        let echo_style = echo_style.expect("echo span missing");
+        let string_style = string_style.expect("string span missing");
+        assert!(echo_style.fg.is_none());
+        assert!(!echo_style.add_modifier.contains(Modifier::DIM));
+        assert!(string_style.add_modifier.contains(Modifier::DIM));
+    }
+
+    #[test]
+    fn highlights_heredoc_body_as_string() {
+        let s = "cat <<EOF\nheredoc body\nEOF";
+        let lines = highlight_bash_to_lines(s);
+        let body_line = &lines[1];
+        let mut body_style = None;
+        for span in &body_line.spans {
+            if span.content.as_ref() == "heredoc body" {
+                body_style = Some(span.style);
+            }
+        }
+        let body_style = body_style.expect("missing heredoc span");
+        assert!(body_style.add_modifier.contains(Modifier::DIM));
+    }
+}

codex-rs/tui2/src/render/line_utils.rs

@@ -0,0 +1,59 @@
+use ratatui::text::Line;
+use ratatui::text::Span;
+
+/// Clone a borrowed ratatui `Line` into an owned `'static` line.
+pub fn line_to_static(line: &Line<'_>) -> Line<'static> {
+    Line {
+        style: line.style,
+        alignment: line.alignment,
+        spans: line
+            .spans
+            .iter()
+            .map(|s| Span {
+                style: s.style,
+                content: std::borrow::Cow::Owned(s.content.to_string()),
+            })
+            .collect(),
+    }
+}
+
+/// Append owned copies of borrowed lines to `out`.
+pub fn push_owned_lines<'a>(src: &[Line<'a>], out: &mut Vec<Line<'static>>) {
+    for l in src {
+        out.push(line_to_static(l));
+    }
+}
+
+/// Consider a line blank if it has no spans or only spans whose contents are
+/// empty or consist solely of spaces (no tabs/newlines).
+pub fn is_blank_line_spaces_only(line: &Line<'_>) -> bool {
+    if line.spans.is_empty() {
+        return true;
+    }
+    line.spans
+        .iter()
+        .all(|s| s.content.is_empty() || s.content.chars().all(|c| c == ' '))
+}
+
+/// Prefix each line with `initial_prefix` for the first line and
+/// `subsequent_prefix` for following lines. Returns a new Vec of owned lines.
+pub fn prefix_lines(
+    lines: Vec<Line<'static>>,
+    initial_prefix: Span<'static>,
+    subsequent_prefix: Span<'static>,
+) -> Vec<Line<'static>> {
+    lines
+        .into_iter()
+        .enumerate()
+        .map(|(i, l)| {
+            let mut spans = Vec::with_capacity(l.spans.len() + 1);
+            spans.push(if i == 0 {
+                initial_prefix.clone()
+            } else {
+                subsequent_prefix.clone()
+            });
+            spans.extend(l.spans);
+            Line::from(spans).style(l.style)
+        })
+        .collect()
+}

codex-rs/tui2/src/render/mod.rs

@@ -0,0 +1,50 @@
+use ratatui::layout::Rect;
+
+pub mod highlight;
+pub mod line_utils;
+pub mod renderable;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Insets {
+    left: u16,
+    top: u16,
+    right: u16,
+    bottom: u16,
+}
+
+impl Insets {
+    pub fn tlbr(top: u16, left: u16, bottom: u16, right: u16) -> Self {
+        Self {
+            top,
+            left,
+            bottom,
+            right,
+        }
+    }
+
+    pub fn vh(v: u16, h: u16) -> Self {
+        Self {
+            top: v,
+            left: h,
+            bottom: v,
+            right: h,
+        }
+    }
+}
+
+pub trait RectExt {
+    fn inset(&self, insets: Insets) -> Rect;
+}
+
+impl RectExt for Rect {
+    fn inset(&self, insets: Insets) -> Rect {
+        let horizontal = insets.left.saturating_add(insets.right);
+        let vertical = insets.top.saturating_add(insets.bottom);
+        Rect {
+            x: self.x.saturating_add(insets.left),
+            y: self.y.saturating_add(insets.top),
+            width: self.width.saturating_sub(horizontal),
+            height: self.height.saturating_sub(vertical),
+        }
+    }
+}

codex-rs/tui2/src/render/renderable.rs

@@ -0,0 +1,431 @@
+use std::sync::Arc;
+
+use ratatui::buffer::Buffer;
+use ratatui::layout::Rect;
+use ratatui::text::Line;
+use ratatui::text::Span;
+use ratatui::widgets::Paragraph;
+use ratatui::widgets::WidgetRef;
+
+use crate::render::Insets;
+use crate::render::RectExt as _;
+
+pub trait Renderable {
+    fn render(&self, area: Rect, buf: &mut Buffer);
+    fn desired_height(&self, width: u16) -> u16;
+    fn cursor_pos(&self, _area: Rect) -> Option<(u16, u16)> {
+        None
+    }
+}
+
+pub enum RenderableItem<'a> {
+    Owned(Box<dyn Renderable + 'a>),
+    Borrowed(&'a dyn Renderable),
+}
+
+impl<'a> Renderable for RenderableItem<'a> {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        match self {
+            RenderableItem::Owned(child) => child.render(area, buf),
+            RenderableItem::Borrowed(child) => child.render(area, buf),
+        }
+    }
+
+    fn desired_height(&self, width: u16) -> u16 {
+        match self {
+            RenderableItem::Owned(child) => child.desired_height(width),
+            RenderableItem::Borrowed(child) => child.desired_height(width),
+        }
+    }
+
+    fn cursor_pos(&self, area: Rect) -> Option<(u16, u16)> {
+        match self {
+            RenderableItem::Owned(child) => child.cursor_pos(area),
+            RenderableItem::Borrowed(child) => child.cursor_pos(area),
+        }
+    }
+}
+
+impl<'a> From<Box<dyn Renderable + 'a>> for RenderableItem<'a> {
+    fn from(value: Box<dyn Renderable + 'a>) -> Self {
+        RenderableItem::Owned(value)
+    }
+}
+
+impl<'a, R> From<R> for Box<dyn Renderable + 'a>
+where
+    R: Renderable + 'a,
+{
+    fn from(value: R) -> Self {
+        Box::new(value)
+    }
+}
+
+impl Renderable for () {
+    fn render(&self, _area: Rect, _buf: &mut Buffer) {}
+    fn desired_height(&self, _width: u16) -> u16 {
+        0
+    }
+}
+
+impl Renderable for &str {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        self.render_ref(area, buf);
+    }
+    fn desired_height(&self, _width: u16) -> u16 {
+        1
+    }
+}
+
+impl Renderable for String {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        self.render_ref(area, buf);
+    }
+    fn desired_height(&self, _width: u16) -> u16 {
+        1
+    }
+}
+
+impl<'a> Renderable for Span<'a> {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        self.render_ref(area, buf);
+    }
+    fn desired_height(&self, _width: u16) -> u16 {
+        1
+    }
+}
+
+impl<'a> Renderable for Line<'a> {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        WidgetRef::render_ref(self, area, buf);
+    }
+    fn desired_height(&self, _width: u16) -> u16 {
+        1
+    }
+}
+
+impl<'a> Renderable for Paragraph<'a> {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        self.render_ref(area, buf);
+    }
+    fn desired_height(&self, width: u16) -> u16 {
+        self.line_count(width) as u16
+    }
+}
+
+impl<R: Renderable> Renderable for Option<R> {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        if let Some(renderable) = self {
+            renderable.render(area, buf);
+        }
+    }
+
+    fn desired_height(&self, width: u16) -> u16 {
+        if let Some(renderable) = self {
+            renderable.desired_height(width)
+        } else {
+            0
+        }
+    }
+}
+
+impl<R: Renderable> Renderable for Arc<R> {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        self.as_ref().render(area, buf);
+    }
+    fn desired_height(&self, width: u16) -> u16 {
+        self.as_ref().desired_height(width)
+    }
+}
+
+pub struct ColumnRenderable<'a> {
+    children: Vec<RenderableItem<'a>>,
+}
+
+impl Renderable for ColumnRenderable<'_> {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        let mut y = area.y;
+        for child in &self.children {
+            let child_area = Rect::new(area.x, y, area.width, child.desired_height(area.width))
+                .intersection(area);
+            if !child_area.is_empty() {
+                child.render(child_area, buf);
+            }
+            y += child_area.height;
+        }
+    }
+
+    fn desired_height(&self, width: u16) -> u16 {
+        self.children
+            .iter()
+            .map(|child| child.desired_height(width))
+            .sum()
+    }
+
+    /// Returns the cursor position of the first child that has a cursor position, offset by the
+    /// child's position in the column.
+    ///
+    /// It is generally assumed that either zero or one child will have a cursor position.
+    fn cursor_pos(&self, area: Rect) -> Option<(u16, u16)> {
+        let mut y = area.y;
+        for child in &self.children {
+            let child_area = Rect::new(area.x, y, area.width, child.desired_height(area.width))
+                .intersection(area);
+            if !child_area.is_empty()
+                && let Some((px, py)) = child.cursor_pos(child_area)
+            {
+                return Some((px, py));
+            }
+            y += child_area.height;
+        }
+        None
+    }
+}
+
+impl<'a> ColumnRenderable<'a> {
+    pub fn new() -> Self {
+        Self { children: vec![] }
+    }
+
+    pub fn with<I, T>(children: I) -> Self
+    where
+        I: IntoIterator<Item = T>,
+        T: Into<RenderableItem<'a>>,
+    {
+        Self {
+            children: children.into_iter().map(Into::into).collect(),
+        }
+    }
+
+    pub fn push(&mut self, child: impl Into<Box<dyn Renderable + 'a>>) {
+        self.children.push(RenderableItem::Owned(child.into()));
+    }
+
+    #[allow(dead_code)]
+    pub fn push_ref<R>(&mut self, child: &'a R)
+    where
+        R: Renderable + 'a,
+    {
+        self.children
+            .push(RenderableItem::Borrowed(child as &'a dyn Renderable));
+    }
+}
+
+pub struct FlexChild<'a> {
+    flex: i32,
+    child: RenderableItem<'a>,
+}
+
+pub struct FlexRenderable<'a> {
+    children: Vec<FlexChild<'a>>,
+}
+
+/// Lays out children in a column, with the ability to specify a flex factor for each child.
+///
+/// Children with flex factor > 0 will be allocated the remaining space after the non-flex children,
+/// proportional to the flex factor.
+impl<'a> FlexRenderable<'a> {
+    pub fn new() -> Self {
+        Self { children: vec![] }
+    }
+
+    pub fn push(&mut self, flex: i32, child: impl Into<RenderableItem<'a>>) {
+        self.children.push(FlexChild {
+            flex,
+            child: child.into(),
+        });
+    }
+
+    /// Loosely inspired by Flutter's Flex widget.
+    ///
+    /// Ref https://github.com/flutter/flutter/blob/3fd81edbf1e015221e143c92b2664f4371bdc04a/packages/flutter/lib/src/rendering/flex.dart#L1205-L1209
+    fn allocate(&self, area: Rect) -> Vec<Rect> {
+        let mut allocated_rects = Vec::with_capacity(self.children.len());
+        let mut child_sizes = vec![0; self.children.len()];
+        let mut allocated_size = 0;
+        let mut total_flex = 0;
+
+        // 1. Allocate space to non-flex children.
+        let max_size = area.height;
+        let mut last_flex_child_idx = 0;
+        for (i, FlexChild { flex, child }) in self.children.iter().enumerate() {
+            if *flex > 0 {
+                total_flex += flex;
+                last_flex_child_idx = i;
+            } else {
+                child_sizes[i] = child
+                    .desired_height(area.width)
+                    .min(max_size.saturating_sub(allocated_size));
+                allocated_size += child_sizes[i];
+            }
+        }
+        let free_space = max_size.saturating_sub(allocated_size);
+        // 2. Allocate space to flex children, proportional to their flex factor.
+        let mut allocated_flex_space = 0;
+        if total_flex > 0 {
+            let space_per_flex = free_space / total_flex as u16;
+            for (i, FlexChild { flex, child }) in self.children.iter().enumerate() {
+                if *flex > 0 {
+                    // Last flex child gets all the remaining space, to prevent a rounding error
+                    // from not allocating all the space.
+                    let max_child_extent = if i == last_flex_child_idx {
+                        free_space - allocated_flex_space
+                    } else {
+                        space_per_flex * *flex as u16
+                    };
+                    let child_size = child.desired_height(area.width).min(max_child_extent);
+                    child_sizes[i] = child_size;
+                    allocated_size += child_size;
+                    allocated_flex_space += child_size;
+                }
+            }
+        }
+
+        let mut y = area.y;
+        for size in child_sizes {
+            let child_area = Rect::new(area.x, y, area.width, size);
+            allocated_rects.push(child_area);
+            y += child_area.height;
+        }
+        allocated_rects
+    }
+}
+
+impl<'a> Renderable for FlexRenderable<'a> {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        self.allocate(area)
+            .into_iter()
+            .zip(self.children.iter())
+            .for_each(|(rect, child)| {
+                child.child.render(rect, buf);
+            });
+    }
+
+    fn desired_height(&self, width: u16) -> u16 {
+        self.allocate(Rect::new(0, 0, width, u16::MAX))
+            .last()
+            .map(|rect| rect.bottom())
+            .unwrap_or(0)
+    }
+
+    fn cursor_pos(&self, area: Rect) -> Option<(u16, u16)> {
+        self.allocate(area)
+            .into_iter()
+            .zip(self.children.iter())
+            .find_map(|(rect, child)| child.child.cursor_pos(rect))
+    }
+}
+
+pub struct RowRenderable<'a> {
+    children: Vec<(u16, RenderableItem<'a>)>,
+}
+
+impl Renderable for RowRenderable<'_> {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        let mut x = area.x;
+        for (width, child) in &self.children {
+            let available_width = area.width.saturating_sub(x - area.x);
+            let child_area = Rect::new(x, area.y, (*width).min(available_width), area.height);
+            if child_area.is_empty() {
+                break;
+            }
+            child.render(child_area, buf);
+            x = x.saturating_add(*width);
+        }
+    }
+    fn desired_height(&self, width: u16) -> u16 {
+        let mut max_height = 0;
+        let mut width_remaining = width;
+        for (child_width, child) in &self.children {
+            let w = (*child_width).min(width_remaining);
+            if w == 0 {
+                break;
+            }
+            let height = child.desired_height(w);
+            if height > max_height {
+                max_height = height;
+            }
+            width_remaining = width_remaining.saturating_sub(w);
+        }
+        max_height
+    }
+
+    fn cursor_pos(&self, area: Rect) -> Option<(u16, u16)> {
+        let mut x = area.x;
+        for (width, child) in &self.children {
+            let available_width = area.width.saturating_sub(x - area.x);
+            let child_area = Rect::new(x, area.y, (*width).min(available_width), area.height);
+            if !child_area.is_empty()
+                && let Some(pos) = child.cursor_pos(child_area)
+            {
+                return Some(pos);
+            }
+            x = x.saturating_add(*width);
+        }
+        None
+    }
+}
+
+impl<'a> RowRenderable<'a> {
+    pub fn new() -> Self {
+        Self { children: vec![] }
+    }
+
+    pub fn push(&mut self, width: u16, child: impl Into<Box<dyn Renderable>>) {
+        self.children
+            .push((width, RenderableItem::Owned(child.into())));
+    }
+
+    #[allow(dead_code)]
+    pub fn push_ref<R>(&mut self, width: u16, child: &'a R)
+    where
+        R: Renderable + 'a,
+    {
+        self.children
+            .push((width, RenderableItem::Borrowed(child as &'a dyn Renderable)));
+    }
+}
+
+pub struct InsetRenderable<'a> {
+    child: RenderableItem<'a>,
+    insets: Insets,
+}
+
+impl<'a> Renderable for InsetRenderable<'a> {
+    fn render(&self, area: Rect, buf: &mut Buffer) {
+        self.child.render(area.inset(self.insets), buf);
+    }
+    fn desired_height(&self, width: u16) -> u16 {
+        self.child
+            .desired_height(width - self.insets.left - self.insets.right)
+            + self.insets.top
+            + self.insets.bottom
+    }
+    fn cursor_pos(&self, area: Rect) -> Option<(u16, u16)> {
+        self.child.cursor_pos(area.inset(self.insets))
+    }
+}
+
+impl<'a> InsetRenderable<'a> {
+    pub fn new(child: impl Into<RenderableItem<'a>>, insets: Insets) -> Self {
+        Self {
+            child: child.into(),
+            insets,
+        }
+    }
+}
+
+pub trait RenderableExt<'a> {
+    fn inset(self, insets: Insets) -> RenderableItem<'a>;
+}
+
+impl<'a, R> RenderableExt<'a> for R
+where
+    R: Renderable + 'a,
+{
+    fn inset(self, insets: Insets) -> RenderableItem<'a> {
+        let child: RenderableItem<'a> =
+            RenderableItem::Owned(Box::new(self) as Box<dyn Renderable + 'a>);
+        RenderableItem::Owned(Box::new(InsetRenderable { child, insets }))
+    }
+}