Add pagebreak function ⏭

src/func.rs

@@ -35,6 +35,35 @@ impl PartialEq for dyn Function {
     }
 }
 
+/// A helper trait that describes requirements for types that can implement
+/// [`Function`].
+///
+/// Automatically implemented for all types which fulfill to the bounds `Debug +
+/// PartialEq + 'static`. There should be no need to implement this manually.
+pub trait FunctionBounds: Debug {
+    /// Cast self into `Any`.
+    fn help_cast_as_any(&self) -> &dyn Any;
+
+    /// Compare self with another function.
+    fn help_eq(&self, other: &dyn Function) -> bool;
+}
+
+impl<T> FunctionBounds for T
+where T: Debug + PartialEq + 'static
+{
+    fn help_cast_as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn help_eq(&self, other: &dyn Function) -> bool {
+        if let Some(other) = other.help_cast_as_any().downcast_ref::<Self>() {
+            self == other
+        } else {
+            false
+        }
+    }
+}
+
 /// A sequence of commands requested for execution by a function.
 #[derive(Debug)]
 pub struct CommandList<'a> {
@@ -47,6 +76,11 @@ impl<'a> CommandList<'a> {
         CommandList { commands: vec![] }
     }
 
+    /// Create a command list with commands from a vector.
+    pub fn from_vec(commands: Vec<Command<'a>>) -> CommandList<'a> {
+        CommandList { commands }
+    }
+
     /// Add a command to the sequence.
     pub fn add(&mut self, command: Command<'a>) {
         self.commands.push(command);
@@ -84,35 +118,13 @@ pub enum Command<'a> {
     AddMany(MultiLayout),
     SetAlignment(Alignment),
     SetStyle(TextStyle),
+    FinishLayout,
 }
 
-/// A helper trait that describes requirements for types that can implement
-/// [`Function`].
-///
-/// Automatically implemented for all types which fulfill to the bounds `Debug +
-/// PartialEq + 'static`. There should be no need to implement this manually.
-pub trait FunctionBounds: Debug {
-    /// Cast self into `Any`.
-    fn help_cast_as_any(&self) -> &dyn Any;
-
-    /// Compare self with another function.
-    fn help_eq(&self, other: &dyn Function) -> bool;
-}
-
-impl<T> FunctionBounds for T
-where T: Debug + PartialEq + 'static
-{
-    fn help_cast_as_any(&self) -> &dyn Any {
-        self
-    }
-
-    fn help_eq(&self, other: &dyn Function) -> bool {
-        if let Some(other) = other.help_cast_as_any().downcast_ref::<Self>() {
-            self == other
-        } else {
-            false
-        }
-    }
+macro_rules! commands {
+    ($($x:expr),*$(,)*) => ({
+        $crate::func::CommandList::from_vec(vec![$($x,)*])
+    });
 }
 
 /// A map from identifiers to functions.

src/layout/flex.rs

@@ -17,6 +17,7 @@ use super::*;
 /// flows into a new line. A _glue_ layout is typically used for a space character
 /// since it prevents a space from appearing in the beginning or end of a line.
 /// However, it can be any layout.
+#[derive(Debug, Clone)]
 pub struct FlexLayouter {
     ctx: FlexContext,
     units: Vec<FlexUnit>,
@@ -64,6 +65,7 @@ impl FlexContext {
     }
 }
 
+#[derive(Debug, Clone)]
 enum FlexUnit {
     /// A content unit to be arranged flexibly.
     Boxed(Layout),
@@ -73,6 +75,7 @@ enum FlexUnit {
     Glue(Size2D),
 }
 
+#[derive(Debug, Clone)]
 struct FlexRun {
     content: Vec<(Size, Layout)>,
     size: Size2D,
@@ -168,7 +171,6 @@ impl FlexLayouter {
     }
 
     fn layout_glue(&mut self, glue: Size2D) {
-        self.flush_glue();
         self.cached_glue = Some(glue);
     }
 

src/layout/stacked.rs

@@ -3,6 +3,7 @@ use super::*;
 /// Layouts boxes stack-like.
 ///
 /// The boxes are arranged vertically, each layout gettings it's own "line".
+#[derive(Debug, Clone)]
 pub struct StackLayouter {
     ctx: StackContext,
     layouts: MultiLayout,

src/layout/tree.rs

@@ -7,6 +7,7 @@ pub fn layout_tree(tree: &SyntaxTree, ctx: LayoutContext) -> LayoutResult<MultiL
     layouter.finish()
 }
 
+#[derive(Debug, Clone)]
 struct TreeLayouter<'a, 'p> {
     ctx: LayoutContext<'a, 'p>,
     stack: StackLayouter,
@@ -85,13 +86,18 @@ impl<'a, 'p> TreeLayouter<'a, 'p> {
 
     /// Layout a function.
     fn layout_func(&mut self, func: &FuncCall) -> LayoutResult<()> {
+        // Finish the current flex layout on a copy to find out how
+        // much space would be remaining if we finished.
+        let mut lookahead_stack = self.stack.clone();
+        let layouts = self.flex.clone().finish()?;
+        lookahead_stack.add_many(layouts)?;
+        let remaining = lookahead_stack.remaining();
+
         let mut ctx = self.ctx;
         ctx.style = &self.style;
         ctx.shrink_to_fit = true;
-
-        ctx.space.dimensions = self.stack.remaining();
+        ctx.space.dimensions = remaining;
         ctx.space.padding = SizeBox::zero();
-
         if let Some(space) = ctx.followup_spaces.as_mut() {
             *space = space.usable_space();
         }
@@ -127,6 +133,12 @@ impl<'a, 'p> TreeLayouter<'a, 'p> {
                 Command::SetStyle(style) => {
                     *self.style.to_mut() = style;
                 }
+
+                Command::FinishLayout => {
+                    self.finish_flex()?;
+                    self.stack.finish_layout(true)?;
+                    self.start_new_flex();
+                }
             }
         }
 

src/lib.rs

@@ -29,6 +29,7 @@ use crate::syntax::SyntaxTree;
 #[macro_use]
 mod macros;
 pub mod export;
+#[macro_use]
 pub mod func;
 pub mod layout;
 pub mod library;

src/library/align.rs

@@ -12,7 +12,7 @@ impl Function for AlignFunc {
     fn parse(header: &FuncHeader, body: Option<&str>, ctx: ParseContext) -> ParseResult<Self>
     where Self: Sized {
         if header.args.len() != 1 || !header.kwargs.is_empty() {
-            return err("expected exactly one positional argument specifying the alignment");
+            return err("align: expected exactly one positional argument");
         }
 
         let alignment = if let Expression::Ident(ident) = &header.args[0] {
@@ -29,11 +29,7 @@ impl Function for AlignFunc {
             ));
         };
 
-        let body = if let Some(body) = body {
-            Some(parse(body, ctx)?)
-        } else {
-            None
-        };
+        let body = parse_maybe_body(body, ctx)?;
 
         Ok(AlignFunc { alignment, body })
     }
@@ -45,14 +41,9 @@ impl Function for AlignFunc {
                 .. ctx
             })?;
 
-            let mut commands = CommandList::new();
-            commands.add(Command::AddMany(layouts));
-            Ok(commands)
+            Ok(commands![Command::AddMany(layouts)])
         } else {
-            let mut commands = CommandList::new();
-            commands.add(Command::SetAlignment(self.alignment));
-
-            Ok(commands)
+            Ok(commands![Command::SetAlignment(self.alignment)])
         }
     }
 }

src/library/breaks.rs

@@ -0,0 +1,24 @@
+use super::prelude::*;
+
+/// Ends the current page.
+#[derive(Debug, PartialEq)]
+pub struct PagebreakFunc;
+
+impl Function for PagebreakFunc {
+    fn parse(header: &FuncHeader, body: Option<&str>, _: ParseContext) -> ParseResult<Self>
+    where Self: Sized {
+        if has_arguments(header) {
+            return err("pagebreak: expected no arguments");
+        }
+
+        if body.is_some() {
+            return err("pagebreak: expected no body");
+        }
+
+        Ok(PagebreakFunc)
+    }
+
+    fn layout(&self, _: LayoutContext) -> LayoutResult<CommandList> {
+        Ok(commands![Command::FinishLayout])
+    }
+}

src/library/mod.rs

@@ -4,6 +4,7 @@ use crate::func::Scope;
 
 mod align;
 mod styles;
+mod breaks;
 
 /// Useful imports for creating your own functions.
 pub mod prelude {
@@ -12,13 +13,11 @@ pub mod prelude {
     pub use crate::layout::{LayoutError, LayoutResult};
     pub use crate::parsing::{parse, ParseContext, ParseError, ParseResult};
     pub use crate::syntax::{Expression, FuncHeader, SyntaxTree};
-
-    pub fn err<S: Into<String>, T>(message: S) -> ParseResult<T> {
-        Err(ParseError::new(message))
-    }
+    pub use super::helpers::*;
 }
 
 pub use align::AlignFunc;
+pub use breaks::PagebreakFunc;
 pub use styles::{BoldFunc, ItalicFunc, MonospaceFunc};
 
 /// Create a scope with all standard functions.
@@ -28,5 +27,26 @@ pub fn std() -> Scope {
     std.add::<ItalicFunc>("italic");
     std.add::<MonospaceFunc>("mono");
     std.add::<AlignFunc>("align");
+    std.add::<PagebreakFunc>("pagebreak");
     std
 }
+
+pub mod helpers {
+    use super::prelude::*;
+
+    pub fn has_arguments(header: &FuncHeader) -> bool {
+        !header.args.is_empty() || !header.kwargs.is_empty()
+    }
+
+    pub fn parse_maybe_body(body: Option<&str>, ctx: ParseContext) -> ParseResult<Option<SyntaxTree>> {
+        if let Some(body) = body {
+            Ok(Some(parse(body, ctx)?))
+        } else {
+            Ok(None)
+        }
+    }
+
+    pub fn err<S: Into<String>, T>(message: S) -> ParseResult<T> {
+        Err(ParseError::new(message))
+    }
+}

src/library/styles.rs

@@ -10,35 +10,37 @@ macro_rules! style_func {
     ) => {
         $(#[$outer])*
         #[derive(Debug, PartialEq)]
-        pub struct $struct { body: SyntaxTree }
+        pub struct $struct {
+            body: Option<SyntaxTree>
+        }
 
         impl Function for $struct {
             fn parse(header: &FuncHeader, body: Option<&str>, ctx: ParseContext)
                 -> ParseResult<Self> where Self: Sized {
                 // Accept only invocations without arguments and with body.
-                if header.args.is_empty() && header.kwargs.is_empty() {
-                    if let Some(body) = body {
-                        Ok($struct { body: parse(body, ctx)? })
-                    } else {
-                        Err(ParseError::new(format!("expected body for function `{}`", $name)))
-                    }
-                } else {
-                    Err(ParseError::new(format!("unexpected arguments to function `{}`", $name)))
+                if has_arguments(header) {
+                    return err(format!("{}: expected no arguments", $name));
                 }
+
+                let body = parse_maybe_body(body, ctx)?;
+
+                Ok($struct { body })
             }
 
             fn layout(&self, ctx: LayoutContext) -> LayoutResult<CommandList> {
-                let mut commands = CommandList::new();
-
-                let saved_style = ctx.style.clone();
                 let mut new_style = ctx.style.clone();
                 new_style.toggle_class(FontClass::$class);
 
-                commands.add(Command::SetStyle(new_style));
-                commands.add(Command::Layout(&self.body));
-                commands.add(Command::SetStyle(saved_style));
-
-                Ok(commands)
+                if let Some(body) = &self.body {
+                    let saved_style = ctx.style.clone();
+                    Ok(commands![
+                        Command::SetStyle(new_style),
+                        Command::Layout(body),
+                        Command::SetStyle(saved_style),
+                    ])
+                } else {
+                    Ok(commands![Command::SetStyle(new_style)])
+                }
             }
         }
     };

tests/layouts/align.typ

@@ -1,25 +1,33 @@
-{size:150pt*208pt}
+{size:150pt*215pt}
 
-// Without newline in between
+// ---------------------------------- //
+// Without newline in between.
 [align: left][Left: {lorem:20}]
 [align: right][Right: {lorem:20}]
 
-// With newline in between
+// Over three pages.
 [align: center][Center: {lorem:80}]
 
-[align: left][Left: {lorem:20}]
+// Over multiple pages after the pervious 3-page run.
+[align: left][Left: {lorem:80}]
 
-// Context-modifying align
+[pagebreak]
+
+// ---------------------------------- //
+// Context-modifying align.
 [align: right]
 
-New Right: {lorem:30}
+Context Right: {lorem:10}
 
-[align: left][Inside Left: {lorem:10}]
+[align: left][In-between Left: {lorem:10}]
 
 Right Again: {lorem:10}
 
-// Reset context-modifier
+// Reset context-modifier.
 [align: left]
 
-// All in one line
-{lorem:25} [align: right][{lorem:50}] {lorem:15}
+[pagebreak]
+
+// ---------------------------------- //
+// All in one line.
+All in one line: {lorem:25} [align: right][{lorem:50}] {lorem:15}

tests/layouts/pagebreaks.typ

@@ -1,2 +1,10 @@
-{size:200pt*200pt}
-{lorem:300}
+{size:150pt*200pt}
+{lorem:100}
+
+[pagebreak]
+[pagebreak]
+
+{lorem:20}
+[pagebreak]
+
+{lorem:150}

tests/layouts/styles.typ

@@ -1,5 +1,4 @@
-_Multiline:_
-{lorem:45}
+{size:250pt*500pt}
 
 _Emoji:_ Hello World! 🌍
 
@@ -8,3 +7,13 @@ built-in syntax!
 
 _Styles with functions:_ This [bold][word] is made bold and [italic][that] italic
 using the standard library functions `bold` and `italic`!
+
+[italic]
+Styles can also be changed through [bold] context modification.
+This works basically in the same way as the built-in syntax.
+_
+
+This is not italic anymore, but still bold.
+[bold]
+
+This is completely reset. 😀