eui_core/

measure.rs

//! The host MEASURE contract. The VAPP-4 verdict: never one FFI upcall per
//! taffy measure call (taffy asks a leaf 10–15 times per pass). The core
//! batches: ONE upcall for the intrinsic widths of every dirty leaf (with the
//! resolved text style, so Compose can pick the font before its first pass),
//! taffy runs against a Rust-side memo, ONE upcall for the heights at the
//! widths taffy decided, and a third round only when a height changed a width
//! decision (counted in `LayoutOutput::measure_rounds`). In-process painters
//! (gpui) may answer per request through [`DirectMeasure`]; nothing crosses
//! an FFI there.

use std::collections::HashMap;

use serde::{Deserialize, Serialize};
use serde_json::{Map, Value};

/// Typography a measured leaf is laid out with (the theme's resolved recipe).
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct TextStyle {
    pub font_size: f32,
    pub font_weight: u16,
    pub line_height: f32,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub font_family: Option<String>,
    /// `fontStyle` (`italic`), `textTransform` and `letterSpacing` (px):
    /// they change the shaped width, so the measurer needs them too.
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub font_style: Option<String>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub text_transform: Option<String>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub letter_spacing: Option<f32>,
}

impl Default for TextStyle {
    fn default() -> Self {
        TextStyle { font_size: 14.0, font_weight: 400, line_height: 20.0, font_family: None, font_style: None, text_transform: None, letter_spacing: None }
    }
}

/// The control box a leaf's recipe fixes (padding inside the measured size,
/// definite sizes taffy already knows). The measurer adds the padding around
/// the content it shapes and honours `min_*`. `padding_horizontal` /
/// `padding_vertical` are the AVERAGES of the two sides (a measurer adding
/// `2 × padding` gets the exact total); `padding` has every side.
#[derive(Debug, Clone, Copy, PartialEq, Default, Serialize, Deserialize)]
pub struct ControlBox {
    pub padding_horizontal: f32,
    pub padding_vertical: f32,
    /// `[top, right, bottom, left]`, logical keys resolved by the direction.
    #[serde(default)]
    pub padding: [f32; 4],
    pub border_width: f32,
    pub gap: f32,
    pub min_width: Option<f32>,
    pub min_height: Option<f32>,
    pub width: Option<f32>,
    pub height: Option<f32>,
}

/// One leaf the host must measure. `index` names the layout node; the host
/// keys its own caches on it. `lines` = the `Text` prop (truncate to N lines).
#[derive(Debug, Clone)]
pub struct LeafRequest<'a> {
    pub index: u32,
    pub id: &'a str,
    /// The native kind (`Text`, `Button`, `Input`, `Extension`…).
    pub component: &'a str,
    /// The synthetic part of a native when the leaf is one (`Tabs/tab`).
    pub part: Option<&'a str>,
    /// The component that owns the part (`Tabs` for `Tabs/tab`; `None` for
    /// a plain node): a part's chrome (an icon, a check) depends on it.
    pub owner_component: Option<&'a str>,
    pub props: &'a Map<String, Value>,
    pub text_style: &'a TextStyle,
    pub control: ControlBox,
    pub lines: Option<u32>,
}

impl LeafRequest<'_> {
    /// The text a textual leaf shows.
    pub fn text(&self) -> &str {
        self.props
            .get("text")
            .or_else(|| self.props.get("label"))
            .or_else(|| self.props.get("title"))
            .or_else(|| self.props.get("content"))
            .or_else(|| self.props.get("placeholder"))
            .and_then(Value::as_str)
            .unwrap_or("")
    }

    /// [`Self::text`] for a painter: the same prop, and a number or boolean
    /// in it shows as its [`crate::format::display_string`] (`412`, `1.5`,
    /// `true`), the rule the build applies to bound text props. An FFI host
    /// gets this as `FfiLeaf.text`.
    pub fn display_text(&self) -> std::borrow::Cow<'_, str> {
        let v = ["text", "label", "title", "content", "placeholder"].iter().find_map(|k| self.props.get(*k));
        match v {
            Some(Value::String(s)) => std::borrow::Cow::Borrowed(s.as_str()),
            Some(v @ (Value::Number(_) | Value::Bool(_))) => std::borrow::Cow::Owned(crate::format::display_string(v)),
            _ => std::borrow::Cow::Borrowed(""),
        }
    }
}

/// What the host answers for one leaf: the width it needs with every line
/// break taken (`min_content`), with none (`max_content`), the height at
/// `max_content` width (one line for text) and the FIRST BASELINE from the
/// top of the border box (`alignItems: baseline`; it does not move with the
/// width: the first line stays the first line). `None` = no baseline (an
/// icon, a box): the bottom edge stands in, like CSS. Controls with a fixed
/// box return it in both widths.
#[derive(Debug, Clone, Copy, PartialEq, Default, Serialize, Deserialize)]
pub struct Intrinsics {
    pub min_content_width: f32,
    pub max_content_width: f32,
    pub height_at_max_content: f32,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub baseline: Option<f32>,
}

impl Intrinsics {
    /// R8 F53: a host measurer's answer with every NaN or infinite number
    /// replaced (0; a baseline that is not finite = none) and the widths
    /// ordered (`min_content_width <= max_content_width`): the memo clamps
    /// against them (`f32::clamp` panics on NaN) and taffy sizes by them.
    /// Non-negative too: a negative width or height is 0.
    pub fn sanitised(self) -> Intrinsics {
        let min = finite_or_zero(self.min_content_width);
        let max = finite_or_zero(self.max_content_width);
        Intrinsics {
            min_content_width: min.min(max),
            max_content_width: max.max(min),
            height_at_max_content: finite_or_zero(self.height_at_max_content),
            baseline: self.baseline.filter(|b| b.is_finite()),
        }
    }
}

/// `v` when finite and non-negative, else 0 (R8 F53: a host's NaN, ±inf or
/// negative size never reaches the memo or taffy).
pub fn finite_or_zero(v: f32) -> f32 {
    if v.is_finite() && v > 0.0 {
        v
    } else {
        0.0
    }
}

/// Second phase: the height of leaf `index` when laid out `width` wide.
#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
pub struct HeightRequest {
    pub index: u32,
    pub width: f32,
}

/// Implemented by the host. Both calls receive batches; the core never calls
/// them per taffy request.
pub trait Measure {
    /// Identity of this measurer (font scale, Dynamic Type state…). Two
    /// consecutive passes with different ids invalidate every memo.
    fn measure_id(&self) -> u64 {
        2
    }
    fn measure_intrinsics(&mut self, leaves: &[LeafRequest]) -> Vec<Intrinsics>;
    fn measure_heights(&mut self, leaves: &[LeafRequest], requests: &[HeightRequest]) -> Vec<f32>;
}

/// The per-request form for in-process painters (gpui): one closure that
/// answers `(leaf, wrap_width)` with a size. `None` = unconstrained
/// (max-content); `Some(0.0)` = min-content. No baselines (see
/// [`DirectMeasureWithBaseline`]).
pub struct DirectMeasure<F>(pub F, pub u64);

/// [`DirectMeasure`] whose closure also answers the first baseline:
/// `(leaf, wrap_width) → (width, height, baseline)`.
pub struct DirectMeasureWithBaseline<F>(pub F, pub u64);

impl<F: FnMut(&LeafRequest, Option<f32>) -> (f32, f32, Option<f32>)> Measure for DirectMeasureWithBaseline<F> {
    fn measure_id(&self) -> u64 {
        self.1
    }

    fn measure_intrinsics(&mut self, leaves: &[LeafRequest]) -> Vec<Intrinsics> {
        leaves
            .iter()
            .map(|leaf| {
                let (max_w, h, baseline) = (self.0)(leaf, None);
                let (min_w, _, _) = (self.0)(leaf, Some(0.0));
                Intrinsics { min_content_width: min_w, max_content_width: max_w, height_at_max_content: h, baseline }
            })
            .collect()
    }

    fn measure_heights(&mut self, leaves: &[LeafRequest], requests: &[HeightRequest]) -> Vec<f32> {
        requests.iter().map(|r| leaves.iter().find(|l| l.index == r.index).map(|leaf| (self.0)(leaf, Some(r.width)).1).unwrap_or(0.0)).collect()
    }
}

impl<F: FnMut(&LeafRequest, Option<f32>) -> (f32, f32)> Measure for DirectMeasure<F> {
    fn measure_id(&self) -> u64 {
        self.1
    }

    fn measure_intrinsics(&mut self, leaves: &[LeafRequest]) -> Vec<Intrinsics> {
        leaves
            .iter()
            .map(|leaf| {
                let (max_w, h) = (self.0)(leaf, None);
                let (min_w, _) = (self.0)(leaf, Some(0.0));
                Intrinsics { min_content_width: min_w, max_content_width: max_w, height_at_max_content: h, baseline: None }
            })
            .collect()
    }

    fn measure_heights(&mut self, leaves: &[LeafRequest], requests: &[HeightRequest]) -> Vec<f32> {
        requests
            .iter()
            .map(|r| leaves.iter().find(|l| l.index == r.index).map(|leaf| (self.0)(leaf, Some(r.width)).1).unwrap_or(0.0))
            .collect()
    }
}

pub const FIXED_CHAR_WIDTH: f32 = 8.0;
pub const FIXED_LINE_HEIGHT: f32 = 20.0;
/// The fixed measure's ascent: a 20 px line's baseline sits 15 px down.
pub const FIXED_ASCENT: f32 = 15.0;

/// The geometry-test measure every platform reproduces exactly: 8 px per
/// character on ONE 20 px line (no wrapping), fixed boxes per control, or an
/// explicit size per node id (`fixtures/layout-geometry.json` `measures`).
#[derive(Debug, Clone, Default)]
pub struct FixedMeasure {
    pub sizes: HashMap<String, (f32, f32)>,
    /// When true, text leaves WRAP at 8 px per character (for the list and
    /// overlay tests); the geometry fixture keeps it off.
    pub wrap: bool,
}

impl FixedMeasure {
    pub fn with_sizes(sizes: HashMap<String, (f32, f32)>) -> FixedMeasure {
        FixedMeasure { sizes, wrap: false }
    }

    fn chars(s: &str) -> f32 {
        s.chars().count() as f32
    }

    /// The intrinsic size of a leaf by kind (the spike's table).
    pub fn intrinsic(&self, leaf: &LeafRequest) -> (f32, f32) {
        if let Some(size) = self.sizes.get(leaf.id) {
            return *size;
        }
        let text = leaf.text();
        let str_prop = |k: &str| leaf.props.get(k).and_then(Value::as_str).unwrap_or("");
        let c = leaf.control;
        let (w, h) = match leaf.component {
            // A host text field inside a control (NumberField/ChipInput
            // `input`, Select `search`): one line of its text or placeholder.
            _ if matches!(leaf.part, Some("input") | Some("search")) => {
                let shown = Self::chars(text).max(Self::chars(str_prop("placeholder")));
                (FIXED_CHAR_WIDTH * shown, c.height.unwrap_or(FIXED_LINE_HEIGHT))
            }
            "Text" | "Link" if text.contains('\n') => {
                let lines = text.split('\n').count() as f32;
                let widest = text.split('\n').map(Self::chars).fold(0.0, f32::max);
                (FIXED_CHAR_WIDTH * widest, leaf.text_style.line_height.max(FIXED_LINE_HEIGHT) * lines)
            }
            "Text" | "Link" => (FIXED_CHAR_WIDTH * Self::chars(text), leaf.text_style.line_height.max(FIXED_LINE_HEIGHT)),
            "Markdown" => {
                let lines = text.lines().count().max(1) as f32;
                let widest = text.lines().map(Self::chars).fold(0.0, f32::max);
                (FIXED_CHAR_WIDTH * widest, FIXED_LINE_HEIGHT * lines)
            }
            // EXP-1259: a loading Button never shrinks below its idle width
            // and grows to fit `pendingLabel`.
            "Button" if leaf.props.get("loading").and_then(Value::as_bool) == Some(true) => {
                let chars = Self::chars(str_prop("label")).max(Self::chars(str_prop("pendingLabel")));
                (FIXED_CHAR_WIDTH * chars + 24.0, c.height.unwrap_or(36.0))
            }
            "Button" | "Toggle" => (FIXED_CHAR_WIDTH * Self::chars(str_prop("label")) + 24.0, c.height.unwrap_or(36.0)),
            "SearchList" if leaf.part.is_none() => (240.0, 40.0 + FIXED_LINE_HEIGHT * leaf.props.get("items").and_then(Value::as_array).map_or(0, Vec::len).min(8) as f32),
            "Input" | "Select" | "DatePicker" => (160.0, c.height.unwrap_or(36.0)),
            "Textarea" if leaf.part.is_none() || leaf.part == Some("field") => (160.0, c.height.unwrap_or_else(|| Self::textarea_height(leaf))),
            "Textarea" | "Composer" => (160.0, c.height.unwrap_or(72.0)),
            "NumberField" | "TimePicker" | "DateRangePicker" | "ChipInput" if leaf.part.is_none() => (160.0, c.height.unwrap_or(36.0)),
            "CodeBlock" if leaf.part.is_none() => {
                let code = str_prop("code");
                let lines = code.split('\n').count().max(1) as f32;
                let widest = code.split('\n').map(Self::chars).fold(0.0, f32::max);
                (FIXED_CHAR_WIDTH * widest, FIXED_LINE_HEIGHT * lines)
            }
            "Chart" => (320.0, leaf.props.get("height").and_then(Value::as_f64).unwrap_or(200.0) as f32),
            // EXP-1280: an unexpanded ChoiceTiles (geometry mode) = its grid
            // of tiles at 320 px: per row a picture (when any option has
            // one, 1.6 : 1) over two lines, 8 px padding, 8 px gaps.
            "ChoiceTiles" if leaf.part.is_none() => {
                let options = leaf.props.get("options").and_then(Value::as_array);
                let n = options.map_or(0, Vec::len) as f32;
                let cols = leaf.props.get("columns").and_then(Value::as_f64).unwrap_or(2.0).round().clamp(1.0, 4.0) as f32;
                let rows = (n / cols).ceil();
                let pictures = options.is_some_and(|o| o.iter().any(|o| o.get("image").and_then(Value::as_str).is_some_and(|s| !s.is_empty())));
                let tile_w = (320.0 - 8.0 * (cols - 1.0)) / cols - 18.0;
                let tile_h = if pictures { tile_w / 1.6 + 4.0 } else { 0.0 } + 2.0 * FIXED_LINE_HEIGHT + 4.0 + 18.0;
                (320.0, (rows * tile_h + (rows - 1.0).max(0.0) * 8.0).max(0.0))
            }
            "Switch" => (44.0, 24.0),
            "Checkbox" | "Radio" => (16.0, 16.0),
            "Avatar" => {
                let s = c.width.unwrap_or(32.0);
                (s, s)
            }
            "Icon" => (c.width.unwrap_or(16.0), c.height.unwrap_or(16.0)),
            "Image" | "Video" => (320.0, 180.0),
            // EXP-1604: the composition's px size (a `src` animation: none).
            "Motion" => crate::layout_tree::motion_size(&leaf.props).map_or((0.0, 0.0), |(w, h)| (w as f32, h as f32)),
            "Slider" => (160.0, 16.0),
            "Spinner" | "Ring" => (c.width.unwrap_or(20.0), c.height.unwrap_or(20.0)),
            "Skeleton" => (
                leaf.props.get("width").and_then(Value::as_f64).unwrap_or(120.0) as f32,
                leaf.props.get("height").and_then(Value::as_f64).unwrap_or(16.0) as f32,
            ),
            _ => (c.width.unwrap_or(0.0), c.height.unwrap_or(0.0)),
        };
        (c.width.unwrap_or(w).max(c.min_width.unwrap_or(0.0)), c.height.unwrap_or(h).max(c.min_height.unwrap_or(0.0)))
    }

    /// `rows` lines (autosize: the value's lines clamped to `rows..maxRows`)
    /// of 20 px plus the vertical padding.
    fn textarea_height(leaf: &LeafRequest) -> f32 {
        let rows = leaf.props.get("rows").and_then(Value::as_f64).unwrap_or(3.0).max(1.0) as f32;
        let mut lines = rows;
        if leaf.props.get("autosize").and_then(Value::as_bool) == Some(true) {
            let value = leaf.props.get("value").and_then(Value::as_str).unwrap_or("");
            let typed = value.split('\n').count() as f32;
            let max = leaf.props.get("maxRows").and_then(Value::as_f64).map(|m| m as f32).unwrap_or(f32::INFINITY);
            lines = typed.max(rows).min(max.max(rows));
        }
        lines * FIXED_LINE_HEIGHT + leaf.control.padding[0] + leaf.control.padding[2]
    }

    /// The fixed baseline: the first 20 px line's ascent, centred in a
    /// control's box; none for boxes without text.
    pub fn baseline(&self, leaf: &LeafRequest, height: f32) -> Option<f32> {
        match leaf.component {
            "Text" | "Link" | "Markdown" | "CodeBlock" => Some(leaf.control.padding[0] + FIXED_ASCENT),
            "Checkbox" | "Radio" | "Switch" | "Avatar" | "Icon" | "Image" | "Video" | "Slider" | "Spinner" | "Ring" | "Skeleton" | "Chart" | "Motion" => None,
            _ if leaf.text().is_empty() => None,
            _ => Some(((height - FIXED_LINE_HEIGHT) / 2.0).max(0.0) + FIXED_ASCENT),
        }
    }

    fn wraps(&self, leaf: &LeafRequest) -> bool {
        self.wrap && !self.sizes.contains_key(leaf.id) && matches!(leaf.component, "Text" | "Markdown")
    }
}

impl Measure for FixedMeasure {
    fn measure_id(&self) -> u64 {
        1
    }

    fn measure_intrinsics(&mut self, leaves: &[LeafRequest]) -> Vec<Intrinsics> {
        leaves
            .iter()
            .map(|leaf| {
                let (w, h) = self.intrinsic(leaf);
                let min = if self.wraps(leaf) {
                    leaf.text().split_whitespace().map(Self::chars).fold(0.0, f32::max) * FIXED_CHAR_WIDTH
                } else {
                    w
                };
                let baseline = if self.sizes.contains_key(leaf.id) { None } else { self.baseline(leaf, h) };
                Intrinsics { min_content_width: min, max_content_width: w, height_at_max_content: h, baseline }
            })
            .collect()
    }

    fn measure_heights(&mut self, leaves: &[LeafRequest], requests: &[HeightRequest]) -> Vec<f32> {
        requests
            .iter()
            .map(|r| {
                let Some(leaf) = leaves.iter().find(|l| l.index == r.index) else { return 0.0 };
                let (w, h) = self.intrinsic(leaf);
                if !self.wraps(leaf) || r.width >= w || r.width <= 0.0 {
                    return h;
                }
                let per_line = (r.width / FIXED_CHAR_WIDTH).floor().max(1.0);
                let lines = (Self::chars(leaf.text()) / per_line).ceil().max(1.0);
                let lines = match leaf.lines {
                    Some(n) if n > 0 => lines.min(n as f32),
                    _ => lines,
                };
                lines * FIXED_LINE_HEIGHT
            })
            .collect()
    }
}

/// The Rust-side memo taffy's measure closure answers from. Keyed by layout
/// node index; `content_version` bumps clear a leaf's entries.
#[derive(Debug, Default, Clone)]
pub struct MeasureMemo {
    pub intrinsics: HashMap<u32, Intrinsics>,
    /// index → (width in 1/64 px, height) pairs. VAPP-132: by index, so
    /// forgetting a leaf costs its own entries, not every leaf's (a
    /// 10,000-item rebind forgot 10,000 leaves one full scan each).
    heights: HashMap<u32, Vec<(i64, f32)>>,
}

impl MeasureMemo {
    pub fn width_key(width: f32) -> i64 {
        (width * 64.0).round() as i64
    }

    pub fn clear(&mut self) {
        self.intrinsics.clear();
        self.heights.clear();
    }

    pub fn forget(&mut self, index: u32) {
        self.intrinsics.remove(&index);
        self.heights.remove(&index);
    }

    pub fn height_at(&self, index: u32, width: f32) -> Option<f32> {
        let key = Self::width_key(width);
        self.heights.get(&index)?.iter().find(|(w, _)| *w == key).map(|(_, h)| *h)
    }

    /// Remember the height at a width key ([`Self::width_key`]).
    pub fn insert_height(&mut self, index: u32, width_key: i64, height: f32) {
        let at = self.heights.entry(index).or_default();
        match at.iter_mut().find(|(w, _)| *w == width_key) {
            Some(entry) => entry.1 = height,
            None => at.push((width_key, height)),
        }
    }

    /// Every (width key, height) remembered for a leaf.
    pub fn heights_of(&self, index: u32) -> &[(i64, f32)] {
        self.heights.get(&index).map(Vec::as_slice).unwrap_or(&[])
    }
}

/// A measured leaf's answer for one taffy request, from the memo. `width`
/// taffy already knows wins; else the available space picks min/max content;
/// a definite available width clamps max-content (text wraps).
#[derive(Debug, Clone, Copy)]
pub struct MeasureRequest {
    pub index: u32,
    pub known_width: Option<f32>,
    pub known_height: Option<f32>,
    pub available_width: taffy::AvailableSpace,
    pub available_height: taffy::AvailableSpace,
}

impl MeasureMemo {
    /// Answer from the memo. The second value says whether the HEIGHT was a
    /// guess (the max-content height at a narrower width), i.e. a second
    /// phase must ask the host for it; the third is the leaf's first
    /// baseline (`Intrinsics::baseline`).
    pub fn answer(&self, req: &MeasureRequest) -> (taffy::geometry::Size<f32>, bool, Option<f32>) {
        let Some(i) = self.intrinsics.get(&req.index) else {
            return (taffy::geometry::Size { width: req.known_width.unwrap_or(0.0), height: req.known_height.unwrap_or(0.0) }, false, None);
        };
        let width = req.known_width.unwrap_or(match req.available_width {
            // CSS: a definite available width shrinks the content down to its
            // min-content and no further (the box overflows instead).
            taffy::AvailableSpace::Definite(w) => w.clamp(i.min_content_width.min(i.max_content_width), i.max_content_width),
            taffy::AvailableSpace::MinContent => i.min_content_width,
            taffy::AvailableSpace::MaxContent => i.max_content_width,
        });
        if let Some(h) = req.known_height {
            return (taffy::geometry::Size { width, height: h }, false, i.baseline);
        }
        // No line-break opportunity (min == max) = the height never changes
        // with the width: no second phase.
        if width + 0.01 >= i.max_content_width || (i.max_content_width - i.min_content_width).abs() < 0.01 {
            return (taffy::geometry::Size { width, height: i.height_at_max_content }, false, i.baseline);
        }
        match self.height_at(req.index, width) {
            Some(h) => (taffy::geometry::Size { width, height: h }, false, i.baseline),
            None => (taffy::geometry::Size { width, height: i.height_at_max_content }, true, i.baseline),
        }
    }
}