Allow measure to accept available size (#4264)

crates/typst/src/layout/measure.rs

@@ -2,17 +2,19 @@ use comemo::Tracked;
 
 use crate::diag::{At, SourceResult};
 use crate::engine::Engine;
-use crate::foundations::{dict, func, Content, Context, Dict, StyleChain, Styles};
-use crate::layout::{Abs, Axes, LayoutMultiple, Regions, Size};
+use crate::foundations::{
+    dict, func, Content, Context, Dict, Resolve, Smart, StyleChain, Styles,
+};
+use crate::layout::{Abs, Axes, LayoutMultiple, Length, Regions, Size};
 use crate::syntax::Span;
 
 /// Measures the layouted size of content.
 ///
-/// The `measure` function lets you determine the layouted size of content. Note
-/// that an infinite space is assumed, therefore the measured height/width may
-/// not necessarily match the final height/width of the measured content. If you
-/// want to measure in the current layout dimensions, you can combine `measure`
-/// and [`layout`].
+/// The `measure` function lets you determine the layouted size of content.
+/// By default an infinite space is assumed, so the measured dimensions may
+/// not necessarily match the final dimensions of the content.
+/// If you want to measure in the current layout dimensions, you can combine
+/// `measure` and [`layout`].
 ///
 /// # Example
 /// The same content can have a different size depending on the [context] that
@@ -48,6 +50,29 @@ pub fn measure(
     context: Tracked<Context>,
     /// The callsite span.
     span: Span,
+    /// The width available to layout the content.
+    ///
+    /// Defaults to `{auto}`, which denotes an infinite width.
+    ///
+    /// Using the `width` and `height` parameters of this function is
+    /// different from measuring a [`box`] containing the content;
+    /// the former will get the dimensions of the inner content
+    /// instead of the dimensions of the box:
+    ///
+    /// ```example
+    /// #context measure(lorem(100), width: 400pt)
+    ///
+    /// #context measure(block(lorem(100), width: 400pt))
+    /// ```
+    #[named]
+    #[default(Smart::Auto)]
+    width: Smart<Length>,
+    /// The height available to layout the content.
+    ///
+    /// Defaults to `{auto}`, which denotes an infinite height.
+    #[named]
+    #[default(Smart::Auto)]
+    height: Smart<Length>,
     /// The content whose size to measure.
     content: Content,
     /// _Compatibility:_ This argument only exists for compatibility with
@@ -60,7 +85,12 @@ pub fn measure(
         None => context.styles().at(span)?,
     };
 
-    let pod = Regions::one(Axes::splat(Abs::inf()), Axes::splat(false));
+    let available = Axes::new(
+        width.resolve(styles).unwrap_or(Abs::inf()),
+        height.resolve(styles).unwrap_or(Abs::inf()),
+    );
+
+    let pod = Regions::one(available, Axes::splat(false));
     let frame = content.measure(engine, styles, pod)?.into_frame();
     let Size { x, y } = frame.size();
     Ok(dict! { "width" => x, "height" => y })

tests/suite/layout/measure.typ

@@ -7,3 +7,16 @@
 }
 #text(10pt, f(6pt, 8pt))
 #text(20pt, f(13pt, 14pt))
+
+--- measure-given-area ---
+// Test `measure` given an area.
+#let text = lorem(100)
+
+#context {
+  let d1 = measure(text)
+  assert(d1.width > 2000pt)
+  assert(d1.height < 10pt)
+  let d2 = measure(width: 400pt, height: auto, text)
+  assert(d2.width < 400pt)
+  assert(d2.height > 50pt)
+}