Refactoring

12 files changed, 104 insertions, 76 deletions

diff --git a/src/eval/template.rs b/src/eval/template.rs
index 6c1223cb..7801dc79 100644
--- a/src/eval/template.rs
+++ b/src/eval/template.rs
@@ -9,7 +9,7 @@ use crate::diag::StrResult;
 use crate::geom::{Align, Dir, GenAxis, Length, Linear, Sides, Size};
 use crate::layout::{Layout, PackedNode};
 use crate::library::{
-    Decoration, DocumentNode, FlowChild, FlowNode, PadNode, PageNode, ParChild, ParNode,
+    Decoration, DocumentNode, FlowChild, FlowNode, PageNode, ParChild, ParNode,
     PlacedNode, Spacing,
 };
 use crate::style::Style;
@@ -400,7 +400,7 @@ impl PageBuilder {
         let Self { size, padding, hard } = self;
         (!child.children.is_empty() || (keep && hard)).then(|| PageNode {
             size,
-            child: PadNode { padding, child: child.pack() }.pack(),
+            child: child.pack().padded(padding),
         })
     }
 }
diff --git a/src/frame.rs b/src/frame.rs
index 94234ae9..9feb6959 100644
--- a/src/frame.rs
+++ b/src/frame.rs
@@ -64,6 +64,13 @@ impl Frame {
         }
     }
 
+    /// Move all elements in the frame by an offset.
+    pub fn translate(&mut self, offset: Point) {
+        for (point, _) in &mut self.elements {
+            *point += offset;
+        }
+    }
+
     /// An iterator over all non-frame elements in this and nested frames.
     pub fn elements(&self) -> Elements {
         Elements { stack: vec![(0, Point::zero(), self)] }
diff --git a/src/geom/spec.rs b/src/geom/spec.rs
index 3b49b54a..82bedf9e 100644
--- a/src/geom/spec.rs
+++ b/src/geom/spec.rs
@@ -23,11 +23,6 @@ impl<T> Spec<T> {
         Self { x: v.clone(), y: v }
     }
 
-    /// Borrows the individual fields.
-    pub fn as_ref(&self) -> Spec<&T> {
-        Spec { x: &self.x, y: &self.y }
-    }
-
     /// Maps the individual fields with `f`.
     pub fn map<F, U>(self, mut f: F) -> Spec<U>
     where
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index 3ac32722..8f46c049 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -17,9 +17,9 @@ use std::rc::Rc;
 
 use crate::font::FontStore;
 use crate::frame::Frame;
-use crate::geom::{Align, Linear, Spec};
+use crate::geom::{Align, Linear, Sides, Spec};
 use crate::image::ImageStore;
-use crate::library::{AlignNode, DocumentNode, MoveNode, SizedNode};
+use crate::library::{AlignNode, DocumentNode, MoveNode, PadNode, SizedNode};
 use crate::Context;
 
 /// Layout a document node into a collection of frames.
@@ -129,6 +129,19 @@ impl PackedNode {
             self
         }
     }
+
+    /// Pad this node at the sides.
+    pub fn padded(self, padding: Sides<Linear>) -> Self {
+        if !padding.left.is_zero()
+            || !padding.top.is_zero()
+            || !padding.right.is_zero()
+            || !padding.bottom.is_zero()
+        {
+            PadNode { child: self, padding }.pack()
+        } else {
+            self
+        }
+    }
 }
 
 impl Layout for PackedNode {
diff --git a/src/library/align.rs b/src/library/align.rs
index 19c52f98..5aeef543 100644
--- a/src/library/align.rs
+++ b/src/library/align.rs
@@ -49,7 +49,6 @@ impl Layout for AlignNode {
         pod.expand.y &= self.aligns.y.is_none();
 
         let mut frames = self.child.layout(ctx, &pod);
-
         for (Constrained { item: frame, cts }, (current, _)) in
             frames.iter_mut().zip(regions.iter())
         {
@@ -67,10 +66,7 @@ impl Layout for AlignNode {
             let frame = Rc::make_mut(frame);
             frame.size = canvas;
             frame.baseline += offset.y;
-
-            for (point, _) in &mut frame.elements {
-                *point += offset;
-            }
+            frame.translate(offset);
 
             cts.expand = regions.expand;
             cts.exact = current.to_spec().map(Some);
diff --git a/src/library/flow.rs b/src/library/flow.rs
index 185e60bb..5271eca9 100644
--- a/src/library/flow.rs
+++ b/src/library/flow.rs
@@ -61,7 +61,7 @@ impl Layout for FlowNode {
 pub enum FlowChild {
     /// Vertical spacing between other children.
     Spacing(Spacing),
-    /// A node and how to align it in the flow.
+    /// An arbitrary node.
     Node(PackedNode),
 }
 
diff --git a/src/library/grid.rs b/src/library/grid.rs
index 347132e1..6bd72388 100644
--- a/src/library/grid.rs
+++ b/src/library/grid.rs
@@ -288,17 +288,17 @@ impl<'a> GridLayouter<'a> {
             for y in 0 .. self.rows.len() {
                 if let Some(node) = self.cell(x, y) {
                     let size = Size::new(available, self.regions.base.h);
-                    let mut regions =
+                    let mut pod =
                         Regions::one(size, self.regions.base, Spec::splat(false));
 
                     // For linear rows, we can already resolve the correct
                     // base, for auto it's already correct and for fr we could
                     // only guess anyway.
                     if let TrackSizing::Linear(v) = self.rows[y] {
-                        regions.base.h = v.resolve(self.regions.base.h);
+                        pod.base.h = v.resolve(self.regions.base.h);
                     }
 
-                    let frame = node.layout(ctx, &regions).remove(0).item;
+                    let frame = node.layout(ctx, &pod).remove(0).item;
                     resolved.set_max(frame.size.w);
                 }
             }
@@ -376,17 +376,17 @@ impl<'a> GridLayouter<'a> {
         // Determine the size for each region of the row.
         for (x, &rcol) in self.rcols.iter().enumerate() {
             if let Some(node) = self.cell(x, y) {
-                let mut regions = self.regions.clone();
-                regions.mutate(|size| size.w = rcol);
+                let mut pod = self.regions.clone();
+                pod.mutate(|size| size.w = rcol);
 
                 // Set the horizontal base back to the parent region's base for
                 // auto columns.
                 if self.cols[x] == TrackSizing::Auto {
-                    regions.base.w = self.regions.base.w;
+                    pod.base.w = self.regions.base.w;
                 }
 
                 let mut sizes =
-                    node.layout(ctx, &regions).into_iter().map(|frame| frame.item.size.h);
+                    node.layout(ctx, &pod).into_iter().map(|frame| frame.item.size.h);
 
                 for (target, size) in resolved.iter_mut().zip(&mut sizes) {
                     target.set_max(size);
@@ -475,8 +475,8 @@ impl<'a> GridLayouter<'a> {
                     base.h = size.h;
                 }
 
-                let regions = Regions::one(size, base, Spec::splat(true));
-                let frame = node.layout(ctx, &regions).remove(0);
+                let pod = Regions::one(size, base, Spec::splat(true));
+                let frame = node.layout(ctx, &pod).remove(0);
                 output.push_frame(pos, frame.item);
             }
 
@@ -501,8 +501,8 @@ impl<'a> GridLayouter<'a> {
 
         // Prepare regions.
         let size = Size::new(self.used.w, resolved[0]);
-        let mut regions = Regions::one(size, self.regions.base, Spec::splat(true));
-        regions.backlog = resolved[1 ..]
+        let mut pod = Regions::one(size, self.regions.base, Spec::splat(true));
+        pod.backlog = resolved[1 ..]
             .iter()
             .map(|&h| Size::new(self.used.w, h))
             .collect::<Vec<_>>()
@@ -512,16 +512,16 @@ impl<'a> GridLayouter<'a> {
         let mut pos = Point::zero();
         for (x, &rcol) in self.rcols.iter().enumerate() {
             if let Some(node) = self.cell(x, y) {
-                regions.mutate(|size| size.w = rcol);
+                pod.mutate(|size| size.w = rcol);
 
                 // Set the horizontal base back to the parent region's base for
                 // auto columns.
                 if self.cols[x] == TrackSizing::Auto {
-                    regions.base.w = self.regions.base.w;
+                    pod.base.w = self.regions.base.w;
                 }
 
                 // Push the layouted frames into the individual output frames.
-                let frames = node.layout(ctx, &regions);
+                let frames = node.layout(ctx, &pod);
                 for (output, frame) in outputs.iter_mut().zip(frames) {
                     output.push_frame(pos, frame.item);
                 }
diff --git a/src/library/pad.rs b/src/library/pad.rs
index a1c8c6f9..829272cc 100644
--- a/src/library/pad.rs
+++ b/src/library/pad.rs
@@ -8,7 +8,6 @@ pub fn pad(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
     let right = args.named("right")?;
     let bottom = args.named("bottom")?;
     let body: Template = args.expect("body")?;
-
     let padding = Sides::new(
         left.or(all).unwrap_or_default(),
         top.or(all).unwrap_or_default(),
@@ -17,17 +16,17 @@ pub fn pad(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
     );
 
     Ok(Value::Template(Template::from_inline(move |style| {
-        PadNode { padding, child: body.pack(style) }
+        body.pack(style).padded(padding)
     })))
 }
 
 /// A node that adds padding to its child.
 #[derive(Debug, Hash)]
 pub struct PadNode {
-    /// The amount of padding.
-    pub padding: Sides<Linear>,
     /// The child node whose sides to pad.
     pub child: PackedNode,
+    /// The amount of padding.
+    pub padding: Sides<Linear>,
 }
 
 impl Layout for PadNode {
@@ -37,43 +36,23 @@ impl Layout for PadNode {
         regions: &Regions,
     ) -> Vec<Constrained<Rc<Frame>>> {
         // Layout child into padded regions.
-        let mut frames = self.child.layout(
-            ctx,
-            &regions.map(|size| size - self.padding.resolve(size).size()),
-        );
+        let pod = regions.map(|size| shrink(size, self.padding));
+        let mut frames = self.child.layout(ctx, &pod);
 
         for (Constrained { item: frame, cts }, (current, base)) in
             frames.iter_mut().zip(regions.iter())
         {
-            fn solve_axis(length: Length, padding: Linear) -> Length {
-                (length + padding.abs).safe_div(1.0 - padding.rel.get())
-            }
-
-            // Solve for the size `padded` that satisfies (approximately):
-            // `padded - padding.resolve(padded).size() == size`
-            let padded = Size::new(
-                solve_axis(frame.size.w, self.padding.left + self.padding.right),
-                solve_axis(frame.size.h, self.padding.top + self.padding.bottom),
-            );
-
+            // Apply the padding inversely such that the grown size padded
+            // yields the frame's size.
+            let padded = grow(frame.size, self.padding);
             let padding = self.padding.resolve(padded);
-            let origin = Point::new(padding.left, padding.top);
-
-            // Create a new larger frame and place the child's frame inside it.
-            let empty = Frame::new(padded, frame.baseline + origin.y);
-            let prev = std::mem::replace(frame, Rc::new(empty));
-            let new = Rc::make_mut(frame);
-            new.push_frame(origin, prev);
+            let offset = Point::new(padding.left, padding.top);
 
-            // Inflate min and max contraints by the padding.
-            for spec in [&mut cts.min, &mut cts.max] {
-                if let Some(x) = spec.x.as_mut() {
-                    *x += padding.size().w;
-                }
-                if let Some(y) = spec.y.as_mut() {
-                    *y += padding.size().h;
-                }
-            }
+            // Grow the frame and translate everything in the frame inwards.
+            let frame = Rc::make_mut(frame);
+            frame.size = padded;
+            frame.baseline += offset.y;
+            frame.translate(offset);
 
             // Set exact and base constraints if the child had them.
             cts.exact.x.and_set(Some(current.w));
@@ -89,8 +68,53 @@ impl Layout for PadNode {
             if self.padding.top.is_relative() || self.padding.bottom.is_relative() {
                 cts.base.y = Some(base.h);
             }
+
+            // Inflate min and max contraints by the padding.
+            for spec in [&mut cts.min, &mut cts.max] {
+                if let Some(x) = spec.x.as_mut() {
+                    *x += padding.size().w;
+                }
+                if let Some(y) = spec.y.as_mut() {
+                    *y += padding.size().h;
+                }
+            }
         }
 
         frames
     }
 }
+
+/// Shrink a size by padding relative to the size itself.
+fn shrink(size: Size, padding: Sides<Linear>) -> Size {
+    size - padding.resolve(size).size()
+}
+
+/// Grow a size by padding relative to the grown size.
+/// This is the inverse operation to `shrink()`.
+///
+/// For the horizontal axis the derivation looks as follows.
+/// (Vertical axis is analogous.)
+///
+/// Let w be the grown target width,
+///     s be given width,
+///     l be the left padding,
+///     r be the right padding,
+///     p = l + r.
+///
+/// We want that: w - l.resolve(w) - r.resolve(w) = s
+///
+/// Thus: w - l.resolve(w) - r.resolve(w) = s
+///   <=> w - p.resolve(w) = s
+///   <=> w - p.rel * w - p.abs = s
+///   <=> (1 - p.rel) * w = s + p.abs
+///   <=> w = (s + p.abs) / (1 - p.rel)
+fn grow(size: Size, padding: Sides<Linear>) -> Size {
+    fn solve_axis(length: Length, padding: Linear) -> Length {
+        (length + padding.abs).safe_div(1.0 - padding.rel.get())
+    }
+
+    Size::new(
+        solve_axis(size.w, padding.left + padding.right),
+        solve_axis(size.h, padding.top + padding.bottom),
+    )
+}
diff --git a/src/library/shape.rs b/src/library/shape.rs
index 5d9b4152..7c543958 100644
--- a/src/library/shape.rs
+++ b/src/library/shape.rs
@@ -1,7 +1,6 @@
 use std::f64::consts::SQRT_2;
 
 use super::prelude::*;
-use super::PadNode;
 use crate::util::RcExt;
 
 /// `rect`: A rectangle with optional content.
@@ -113,10 +112,8 @@ impl Layout for ShapeNode {
             if matches!(self.kind, ShapeKind::Circle | ShapeKind::Ellipse) {
                 // Padding with this ratio ensures that a rectangular child fits
                 // perfectly into a circle / an ellipse.
-                storage = PadNode {
-                    padding: Sides::splat(Relative::new(0.5 - SQRT_2 / 4.0).into()),
-                    child: child.clone(),
-                };
+                let ratio = Relative::new(0.5 - SQRT_2 / 4.0);
+                storage = child.clone().padded(Sides::splat(ratio.into()));
                 node = &storage;
             }
 
diff --git a/src/library/stack.rs b/src/library/stack.rs
index cc02592f..3d91bec7 100644
--- a/src/library/stack.rs
+++ b/src/library/stack.rs
@@ -75,7 +75,7 @@ impl Layout for StackNode {
 pub enum StackChild {
     /// Spacing between other nodes.
     Spacing(Spacing),
-    /// Any block node and how to align it in the stack.
+    /// An arbitrary node.
     Node(PackedNode),
 }
 
diff --git a/src/library/transform.rs b/src/library/transform.rs
index ef9caf2e..10752358 100644
--- a/src/library/transform.rs
+++ b/src/library/transform.rs
@@ -30,14 +30,10 @@ impl Layout for MoveNode {
         for (Constrained { item: frame, .. }, (_, base)) in
             frames.iter_mut().zip(regions.iter())
         {
-            let offset = Point::new(
+            Rc::make_mut(frame).translate(Point::new(
                 self.offset.x.map(|x| x.resolve(base.w)).unwrap_or_default(),
                 self.offset.y.map(|y| y.resolve(base.h)).unwrap_or_default(),
-            );
-
-            for (point, _) in &mut Rc::make_mut(frame).elements {
-                *point += offset;
-            }
+            ));
         }
 
         frames
diff --git a/tests/ref/coma.png b/tests/ref/coma.png
index 04356991..d4c6c3de 100644
--- a/tests/ref/coma.png
+++ b/tests/ref/coma.png