Refined expansion model 🔛

4 files changed, 190 insertions, 158 deletions

diff --git a/src/layout/flex.rs b/src/layout/flex.rs
index 4985fed2..64d48c7d 100644
--- a/src/layout/flex.rs
+++ b/src/layout/flex.rs
@@ -43,7 +43,7 @@ struct PartialLine {
     usable: Size,
     content: Vec<(Size, Layout)>,
     dimensions: Size2D,
-    space: Option<(Size, bool)>,
+    space: Option<Size>,
 }
 
 impl PartialLine {
@@ -64,7 +64,7 @@ impl PartialLine {
 pub struct FlexContext {
     pub spaces: LayoutSpaces,
     pub axes: LayoutAxes,
-    pub shrink_to_fit: bool,
+    pub expand: bool,
     pub flex_spacing: Size,
 }
 
@@ -74,10 +74,11 @@ impl FlexLayouter {
         let stack = StackLayouter::new(StackContext {
             spaces: ctx.spaces,
             axes: ctx.axes,
-            shrink_to_fit: ctx.shrink_to_fit,
+            expand: ctx.expand,
         });
 
         let usable = stack.primary_usable();
+
         FlexLayouter {
             stack,
 
@@ -107,9 +108,11 @@ impl FlexLayouter {
         self.units.push(FlexUnit::Space(space, soft));
     }
 
-    pub fn add_secondary_space(&mut self, space: Size) -> LayoutResult<()> {
-        self.finish_run()?;
-        Ok(self.stack.add_space(space))
+    pub fn add_secondary_space(&mut self, space: Size, soft: bool) -> LayoutResult<()> {
+        if !self.run_is_empty() {
+            self.finish_run()?;
+        }
+        Ok(self.stack.add_space(space, soft))
     }
 
     pub fn set_axes(&mut self, axes: LayoutAxes) {
@@ -120,28 +123,26 @@ impl FlexLayouter {
         if replace_empty && self.run_is_empty() && self.stack.space_is_empty() {
             self.stack.set_spaces(spaces, true);
             self.start_run();
-
-            // let usable = self.stack.primary_usable();
-            // self.line = FlexLine::new(usable);
-
-            // // self.total_usable = self.stack.primary_usable();
-            // // self.usable = self.total_usable;
-            // // self.space = None;
         } else {
             self.stack.set_spaces(spaces, false);
         }
     }
 
-    pub fn remaining(&self) -> LayoutResult<(LayoutSpaces, LayoutSpaces)> {
-        let mut future = self.clone();
-        future.finish_run()?;
+    pub fn remaining(&self) -> LayoutResult<(LayoutSpaces, Option<LayoutSpaces>)> {
+        if self.run_is_empty() {
+            Ok((self.stack.remaining(), None))
+        } else {
+            let mut future = self.clone();
+            let remaining_run = future.finish_run()?;
+
+            let stack_spaces = future.stack.remaining();
+            let mut flex_spaces = stack_spaces.clone();
+            flex_spaces[0].dimensions.x = remaining_run.x;
+            flex_spaces[0].dimensions.y += remaining_run.y;
 
-        let stack_spaces = future.stack.remaining();
-        let mut flex_spaces = stack_spaces.clone();
-        flex_spaces[0].dimensions.x = future.last_run_remaining.x;
-        flex_spaces[0].dimensions.y += future.last_run_remaining.y;
+            Ok((flex_spaces, Some(stack_spaces)))
+        }
 
-        Ok((flex_spaces, stack_spaces))
     }
 
     pub fn run_is_empty(&self) -> bool {
@@ -149,7 +150,7 @@ impl FlexLayouter {
     }
 
     pub fn run_last_is_space(&self) -> bool {
-        matches!(self.units.last(), Some(FlexUnit::Space(_)))
+        matches!(self.units.last(), Some(FlexUnit::Space(_, _)))
     }
 
     pub fn finish(mut self) -> LayoutResult<MultiLayout> {
@@ -158,32 +159,65 @@ impl FlexLayouter {
     }
 
     pub fn finish_space(&mut self, hard: bool) -> LayoutResult<()> {
-        self.finish_run()?;
+        if !self.run_is_empty() {
+            self.finish_run()?;
+        }
         Ok(self.stack.finish_space(hard))
     }
 
-    pub fn finish_run(&mut self) -> LayoutResult<()> {
+    pub fn finish_run(&mut self) -> LayoutResult<Size2D> {
         let units = std::mem::replace(&mut self.units, vec![]);
         for unit in units {
             match unit {
                 FlexUnit::Boxed(boxed) => self.layout_box(boxed)?,
-                FlexUnit::Space(space, soft) => {
-                    self.layout_space();
-                    self.space = Some(space);
-                }
-
-                FlexUnit::Break => {
-                    self.space = None;
-                    self.finish_line()?;
-                },
-
+                FlexUnit::Space(space, soft) => self.layout_space(space, soft),
                 FlexUnit::SetAxes(axes) => self.layout_set_axes(axes),
+                FlexUnit::Break => self.layout_break(),
             }
         }
 
-        self.finish_line()?;
+        self.finish_line()
+    }
 
-        Ok(())
+    fn finish_line(&mut self) -> LayoutResult<Size2D> {
+        self.finish_partial_line();
+
+        self.stack.add(Layout {
+            dimensions: self.axes.specialize(self.line.combined_dimensions),
+            actions: self.line.actions.into_vec(),
+            debug_render: false,
+        })?;
+
+        let remaining = self.axes.specialize(Size2D {
+            x: self.line.usable - self.line.combined_dimensions.x,
+            y: self.line.combined_dimensions.y,
+        });
+
+        self.line = FlexLine::new(self.stack.primary_usable());
+
+        Ok(remaining)
+    }
+
+    fn finish_partial_line(&mut self) {
+        let part = self.line.part;
+
+        let factor = self.axes.primary.axis.factor();
+        let anchor =
+            self.axes.primary.anchor(self.line.usable)
+            - self.axes.primary.anchor(part.dimensions.x);
+
+        for (offset, layout) in part.content {
+            let pos = self.axes.specialize(Size2D::with_x(anchor + factor * offset));
+            self.line.actions.add_layout(pos, layout);
+        }
+
+        self.line.combined_dimensions.x.max_eq(part.dimensions.x);
+        self.line.part = PartialLine::new(self.line.usable - part.dimensions.x);
+    }
+
+    fn start_run(&mut self) {
+        let usable = self.stack.primary_usable();
+        self.line = FlexLine::new(usable);
     }
 
     fn layout_box(&mut self, boxed: Layout) -> LayoutResult<()> {
@@ -215,7 +249,7 @@ impl FlexLayouter {
         Ok(())
     }
 
-    fn layout_space(&mut self) {
+    fn layout_space(&mut self, space: Size, soft: bool) {
         if let Some(space) = self.space.take() {
             if self.run.size.x > Size::zero() && self.run.size.x + space <= self.usable {
                 self.run.size.x += space;
@@ -227,19 +261,19 @@ impl FlexLayouter {
         if axes.primary != self.axes.primary {
             self.finish_partial_line();
 
-            self.usable = match axes.primary.alignment {
-                Alignment::Origin =>
-                    if self.max_extent == Size::zero() {
-                        self.total_usable
-                    } else {
-                        Size::zero()
-                    },
-                Alignment::Center => crate::size::max(
-                    self.total_usable - 2 * self.max_extent,
-                    Size::zero()
-                ),
-                Alignment::End => self.total_usable - self.max_extent,
-            };
+            // self.usable = match axes.primary.alignment {
+            //     Alignment::Origin =>
+            //         if self.max_extent == Size::zero() {
+            //             self.total_usable
+            //         } else {
+            //             Size::zero()
+            //         },
+            //     Alignment::Center => crate::size::max(
+            //         self.total_usable - 2 * self.max_extent,
+            //         Size::zero()
+            //     ),
+            //     Alignment::End => self.total_usable - self.max_extent,
+            // };
         }
 
         if axes.secondary != self.axes.secondary {
@@ -249,57 +283,8 @@ impl FlexLayouter {
         self.axes = axes;
     }
 
-    fn finish_line(&mut self) -> LayoutResult<()> {
-        self.finish_partial_line();
-
-        if self.merged_dimensions.y == Size::zero() {
-            return Ok(());
-        }
-
-        let actions = std::mem::replace(&mut self.merged_actions, LayoutActionList::new());
-        self.stack.add(Layout {
-            dimensions: self.axes.specialize(self.merged_dimensions),
-            actions: actions.into_vec(),
-            debug_render: false,
-        })?;
-
-        self.merged_dimensions = Size2D::zero();
-        self.max_extent = Size::zero();
-        self.usable = self.total_usable;
-
-        Ok(())
-    }
-
-    fn finish_partial_line(&mut self) {
-        if self.run.content.is_empty() {
-            return;
-        }
-
-        let factor = if self.axes.primary.axis.is_positive() { 1 } else { -1 };
-        let anchor = self.axes.primary.anchor(self.total_usable)
-                     - self.axes.primary.anchor(self.run.size.x);
-
-        self.max_extent = crate::size::max(self.max_extent, anchor + factor * self.run.size.x);
-
-        for (offset, layout) in self.run.content.drain(..) {
-            let general_position = Size2D::with_x(anchor + factor * offset);
-            let position = self.axes.specialize(general_position);
-
-            self.merged_actions.add_layout(position, layout);
-        }
-
-        self.merged_dimensions.x = match self.axes.primary.alignment {
-            Alignment::Origin => self.run.size.x,
-            Alignment::Center | Alignment::End => self.total_usable,
-        };
-
-        self.merged_dimensions.y = crate::size::max(
-            self.merged_dimensions.y,
-            self.run.size.y + self.flex_spacing,
-        );
+    fn layout_break(&mut self) {
 
-        self.last_run_remaining = Size2D::new(self.size_left(), self.merged_dimensions.y);
-        self.run.size = Size2D::zero();
     }
 
     fn size_left(&self) -> Size {
diff --git a/src/layout/mod.rs b/src/layout/mod.rs
index 13b63568..2c725e1d 100644
--- a/src/layout/mod.rs
+++ b/src/layout/mod.rs
@@ -147,9 +147,9 @@ pub struct LayoutContext<'a, 'p> {
     /// The axes to flow on.
     pub axes: LayoutAxes,
 
-    /// Whether to shrink the spaces to fit the content or to keep
-    /// the original dimensions.
-    pub shrink_to_fit: bool,
+    /// Whether layouts should expand to the full dimensions of the space
+    /// they lie on or whether should tightly fit the content.
+    pub expand: bool,
 }
 
 /// A possibly stack-allocated vector of layout spaces.
@@ -219,6 +219,14 @@ impl LayoutAxes {
     pub fn anchor(&self, space: Size2D) -> Size2D {
         Size2D::new(self.primary.anchor(space.x), self.secondary.anchor(space.y))
     }
+
+    /// This axes with `expand` set to the given value for both axes.
+    pub fn expanding(&self, expand: bool) -> LayoutAxes {
+        LayoutAxes {
+            primary: self.primary.expanding(expand),
+            secondary: self.secondary.expanding(expand),
+        }
+    }
 }
 
 /// An axis with an alignment.
@@ -226,17 +234,13 @@ impl LayoutAxes {
 pub struct AlignedAxis {
     pub axis: Axis,
     pub alignment: Alignment,
+    pub expand: bool,
 }
 
 impl AlignedAxis {
-    /// Returns an aligned axis if the alignment is compatible with the axis.
-    pub fn new(axis: Axis, alignment: Alignment) -> AlignedAxis {
-        AlignedAxis { axis, alignment }
-    }
-
-    /// The pair of axis and alignment.
-    pub fn pair(&self) -> (Axis, Alignment) {
-        (self.axis, self.alignment)
+    /// Creates an aligned axis from its three components.
+    pub fn new(axis: Axis, alignment: Alignment, expand: bool) -> AlignedAxis {
+        AlignedAxis { axis, alignment, expand }
     }
 
     /// The position of the anchor specified by this axis on the given line.
@@ -248,6 +252,16 @@ impl AlignedAxis {
             (true, End) | (false, Origin) => line,
         }
     }
+
+    /// This axis with `expand` set to the given value.
+    pub fn expanding(&self, expand: bool) -> AlignedAxis {
+        AlignedAxis { expand, ..*self }
+    }
+
+    /// Whether this axis needs expansion.
+    pub fn needs_expansion(&self) -> bool {
+        self.expand || self.alignment != Alignment::Origin
+    }
 }
 
 /// Where to put content.
diff --git a/src/layout/stacked.rs b/src/layout/stacked.rs
index b2d07382..cdc35580 100644
--- a/src/layout/stacked.rs
+++ b/src/layout/stacked.rs
@@ -8,28 +8,31 @@ pub struct StackLayouter {
 
     space: usize,
     hard: bool,
-    start: Size2D,
     actions: LayoutActionList,
-    combined_dimensions: Size2D,
+    combined_dimensions: Size2D, // <- specialized
 
     sub: Subspace,
 }
 
 #[derive(Debug, Clone)]
 struct Subspace {
+    origin: Size2D, // <- specialized
     usable: Size2D,
-    anchor: Size2D,
+    anchor: Size2D, // <- generic
     factor: i32,
-    dimensions: Size2D,
+    dimensions: Size2D, // <- generic
+    space: Option<Size>,
 }
 
 impl Subspace {
-    fn new(usable: Size2D, axes: LayoutAxes) -> Subspace {
+    fn new(origin: Size2D, usable: Size2D, axes: LayoutAxes) -> Subspace {
         Subspace {
-            usable,
+            origin,
+            usable: axes.generalize(usable),
             anchor: axes.anchor(usable),
             factor: axes.secondary.axis.factor(),
             dimensions: Size2D::zero(),
+            space: None,
         }
     }
 }
@@ -41,7 +44,7 @@ impl Subspace {
 pub struct StackContext {
     pub spaces: LayoutSpaces,
     pub axes: LayoutAxes,
-    pub shrink_to_fit: bool,
+    pub expand: bool,
 }
 
 impl StackLayouter {
@@ -49,7 +52,6 @@ impl StackLayouter {
     pub fn new(ctx: StackContext) -> StackLayouter {
         let axes = ctx.axes;
         let space = ctx.spaces[0];
-        let usable = ctx.axes.generalize(space.usable());
 
         StackLayouter {
             ctx,
@@ -57,15 +59,16 @@ impl StackLayouter {
 
             space: 0,
             hard: true,
-            start: space.start(),
             actions: LayoutActionList::new(),
             combined_dimensions: Size2D::zero(),
 
-            sub: Subspace::new(usable, axes),
+            sub: Subspace::new(space.start(), space.usable(), axes),
         }
     }
 
     pub fn add(&mut self, layout: Layout) -> LayoutResult<()> {
+        self.layout_space();
+
         let size = self.ctx.axes.generalize(layout.dimensions);
         let mut new_dimensions = merge(self.sub.dimensions, size);
 
@@ -81,10 +84,9 @@ impl StackLayouter {
         let offset = self.sub.dimensions.y;
         let anchor = self.ctx.axes.anchor(size);
 
-        let pos = self.ctx.axes.specialize(
-            self.start
-                + (self.sub.anchor - anchor)
-                + Size2D::with_y(self.combined_dimensions.y + self.sub.factor * offset)
+        let pos = self.sub.origin + self.ctx.axes.specialize(
+            (self.sub.anchor - anchor)
+            + Size2D::with_y(self.combined_dimensions.y + self.sub.factor * offset)
         );
 
         self.actions.add_layout(pos, layout);
@@ -100,19 +102,16 @@ impl StackLayouter {
         Ok(())
     }
 
-    pub fn add_space(&mut self, space: Size) {
-        if self.sub.dimensions.y + space > self.sub.usable.y {
-            self.finish_space(false);
-        } else {
-            self.sub.dimensions.y += space;
+    pub fn add_space(&mut self, space: Size, soft: bool) {
+        self.sub.space = Some(space);
+        if !soft {
+            self.layout_space();
         }
     }
 
     pub fn set_axes(&mut self, axes: LayoutAxes) {
         if axes != self.ctx.axes {
-            self.finish_subspace();
-            self.ctx.axes = axes;
-            self.sub = Subspace::new(self.remaining_subspace(), axes);
+            self.finish_subspace(axes);
         }
     }
 
@@ -128,7 +127,7 @@ impl StackLayouter {
 
     pub fn remaining(&self) -> LayoutSpaces {
         let mut spaces = smallvec![LayoutSpace {
-            dimensions: self.ctx.axes.specialize(self.remaining_subspace()),
+            dimensions: self.remaining_subspace().1,
             padding: SizeBox::zero(),
         }];
 
@@ -161,13 +160,13 @@ impl StackLayouter {
     }
 
     pub fn finish_space(&mut self, hard: bool) {
-        self.finish_subspace();
+        self.finish_subspace(self.ctx.axes);
 
         let space = self.ctx.spaces[self.space];
         let actions = std::mem::replace(&mut self.actions, LayoutActionList::new());
 
         self.layouts.add(Layout {
-            dimensions: match self.ctx.shrink_to_fit {
+            dimensions: match self.ctx.expand {
                 true => self.combined_dimensions.padded(space.padding),
                 false => space.dimensions,
             },
@@ -180,27 +179,60 @@ impl StackLayouter {
 
     fn start_space(&mut self, space: usize, hard: bool) {
         self.space = space;
-
         let space = self.ctx.spaces[space];
-        let usable = self.ctx.axes.generalize(space.usable());
 
         self.hard = hard;
-        self.start = space.start();
         self.combined_dimensions = Size2D::zero();
-        self.sub = Subspace::new(usable, self.ctx.axes);
+        self.sub = Subspace::new(space.start(), space.usable(), self.ctx.axes);
     }
 
     fn next_space(&self) -> usize {
         (self.space + 1).min(self.ctx.spaces.len() - 1)
     }
 
-    fn finish_subspace(&mut self) {
-        let dims = self.ctx.axes.specialize(self.sub.dimensions);
-        self.combined_dimensions = merge(self.combined_dimensions, dims);
+    fn finish_subspace(&mut self, new_axes: LayoutAxes) {
+        if self.ctx.axes.primary.needs_expansion() {
+            self.sub.dimensions.x = self.sub.usable.x;
+        }
+
+        if self.ctx.axes.secondary.needs_expansion() {
+            self.sub.dimensions.y = self.sub.usable.y;
+        }
+
+        let (new_origin, new_usable) = self.remaining_subspace();
+
+        let origin = self.sub.origin;
+        let dimensions = self.ctx.axes.specialize(self.sub.dimensions);
+        let space = self.ctx.spaces[self.space];
+        self.combined_dimensions.max_eq(origin - space.start() + dimensions);
+
+        self.ctx.axes = new_axes;
+        self.sub = Subspace::new(new_origin, new_usable, new_axes);
     }
 
-    fn remaining_subspace(&self) -> Size2D {
-        Size2D::new(self.sub.usable.x, self.sub.usable.y - self.sub.dimensions.y)
+    fn remaining_subspace(&self) -> (Size2D, Size2D) {
+        let used = self.ctx.axes.specialize(self.sub.usable);
+        let dimensions = self.ctx.axes.specialize(self.sub.dimensions);
+
+        let new_usable = self.ctx.axes.specialize(Size2D {
+            x: self.sub.usable.x,
+            y: self.sub.usable.y - self.sub.dimensions.y,
+        });
+
+        let new_origin = self.sub.origin
+            + Size2D::with_y(self.ctx.axes.specialize(self.sub.dimensions).y);
+
+        (new_origin, new_usable)
+    }
+
+    fn layout_space(&mut self) {
+        if let Some(space) = self.sub.space.take() {
+            if self.sub.dimensions.y + space > self.sub.usable.y {
+                self.finish_space(false);
+            } else {
+                self.sub.dimensions.y += space;
+            }
+        }
     }
 }
 
diff --git a/src/layout/tree.rs b/src/layout/tree.rs
index f7526500..d9f15618 100644
--- a/src/layout/tree.rs
+++ b/src/layout/tree.rs
@@ -23,7 +23,7 @@ impl<'a, 'p> TreeLayouter<'a, 'p> {
                 flex_spacing: flex_spacing(&ctx.text_style),
                 spaces: ctx.spaces.clone(),
                 axes: ctx.axes,
-                shrink_to_fit: ctx.shrink_to_fit,
+                expand: ctx.expand,
             }),
             style: ctx.text_style.clone(),
             ctx,
@@ -66,24 +66,25 @@ impl<'a, 'p> TreeLayouter<'a, 'p> {
 
     /// Layout a function.
     fn layout_func(&mut self, func: &FuncCall) -> LayoutResult<()> {
-        let (flex_spaces, stack_spaces) = self.flex.remaining()?;
+        let (first, second) = self.flex.remaining()?;
 
         let ctx = |spaces| LayoutContext {
+            loader: self.ctx.loader,
             top_level: false,
             text_style: &self.style,
+            page_style: self.ctx.page_style,
             spaces,
-            shrink_to_fit: true,
-            .. self.ctx
+            axes: self.ctx.axes.expanding(false),
+            expand: false,
         };
 
-        // Try putting it in the flex space first, but if that is not enough
-        // space, use the other space.
-        let commands = match func.body.val.layout(ctx(flex_spaces)) {
+        let commands = match func.body.val.layout(ctx(first)) {
             Ok(c) => c,
-            Err(LayoutError::NotEnoughSpace(_)) => {
-                func.body.val.layout(ctx(stack_spaces))?
+            Err(e) => match (e, second) {
+                (LayoutError::NotEnoughSpace(_), Some(space))
+                    => func.body.val.layout(ctx(space))?,
+                _ => Err(e)?,
             },
-            e => e?,
         };
 
         for command in commands {
@@ -101,10 +102,10 @@ impl<'a, 'p> TreeLayouter<'a, 'p> {
             Command::AddMultiple(layouts) => self.flex.add_multiple(layouts),
 
             Command::AddPrimarySpace(space) => self.flex.add_primary_space(space, false),
-            Command::AddSecondarySpace(space) => self.flex.add_secondary_space(space)?,
+            Command::AddSecondarySpace(space) => self.flex.add_secondary_space(space, false)?,
 
             Command::FinishLine => self.flex.add_break(),
-            Command::FinishRun => self.flex.finish_run()?,
+            Command::FinishRun => { self.flex.finish_run()?; },
             Command::FinishSpace => self.flex.finish_space(true)?,
 
             Command::BreakParagraph => self.break_paragraph()?,
@@ -140,7 +141,7 @@ impl<'a, 'p> TreeLayouter<'a, 'p> {
 
     /// Finish the current flex layout and add space after it.
     fn break_paragraph(&mut self) -> LayoutResult<()> {
-        self.flex.add_secondary_space(paragraph_spacing(&self.style))
+        self.flex.add_secondary_space(paragraph_spacing(&self.style), true)
     }
 }