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use super::*;
/// Layouts syntax trees into boxes.
pub fn layout_tree(tree: &SyntaxTree, ctx: LayoutContext) -> LayoutResult<MultiLayout> {
let mut layouter = TreeLayouter::new(ctx);
layouter.layout(tree)?;
layouter.finish()
}
#[derive(Debug, Clone)]
struct TreeLayouter<'a, 'p> {
ctx: LayoutContext<'a, 'p>,
stack: StackLayouter,
flex: FlexLayouter,
style: Cow<'a, TextStyle>,
alignment: Alignment,
set_newline: bool,
}
impl<'a, 'p> TreeLayouter<'a, 'p> {
/// Create a new layouter.
fn new(ctx: LayoutContext<'a, 'p>) -> TreeLayouter<'a, 'p> {
TreeLayouter {
ctx,
stack: StackLayouter::new(StackContext::from_layout_ctx(ctx)),
flex: FlexLayouter::new(FlexContext {
space: ctx.space.usable_space(),
followup_spaces: ctx.followup_spaces.map(|s| s.usable_space()),
shrink_to_fit: true,
.. FlexContext::from_layout_ctx(ctx, flex_spacing(&ctx.style))
}),
style: Cow::Borrowed(ctx.style),
alignment: ctx.alignment,
set_newline: false,
}
}
/// Layout the tree into a box.
fn layout(&mut self, tree: &SyntaxTree) -> LayoutResult<()> {
for node in &tree.nodes {
match node {
Node::Text(text) => {
let layout = self.layout_text(text)?;
self.flex.add(layout);
self.set_newline = true;
}
Node::Space => {
// Only add a space if there was any content before.
if !self.flex.is_empty() {
let layout = self.layout_text(" ")?;
self.flex.add_glue(layout.dimensions);
}
}
// Finish the current flex layouting process.
Node::Newline => {
self.finish_flex()?;
if self.set_newline {
let space = paragraph_spacing(&self.style);
self.stack.add_space(space)?;
self.set_newline = false;
}
self.start_new_flex();
}
// Toggle the text styles.
Node::ToggleItalics => self.style.to_mut().toggle_class(FontClass::Italic),
Node::ToggleBold => self.style.to_mut().toggle_class(FontClass::Bold),
Node::ToggleMonospace => self.style.to_mut().toggle_class(FontClass::Monospace),
Node::Func(func) => self.layout_func(func)?,
}
}
Ok(())
}
/// Finish the layout.
fn finish(mut self) -> LayoutResult<MultiLayout> {
self.finish_flex()?;
self.stack.finish()
}
/// 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.flow = Flow::Vertical;
ctx.shrink_to_fit = true;
ctx.space.dimensions = remaining;
ctx.space.padding = SizeBox::zero();
if let Some(space) = ctx.followup_spaces.as_mut() {
*space = space.usable_space();
}
let commands = func.body.layout(ctx)?;
for command in commands {
match command {
Command::Layout(tree) => self.layout(tree)?,
Command::Add(layout) => {
self.finish_flex()?;
self.stack.add(layout)?;
self.set_newline = true;
self.start_new_flex();
}
Command::AddMany(layouts) => {
self.finish_flex()?;
self.stack.add_many(layouts)?;
self.set_newline = true;
self.start_new_flex();
}
Command::AddFlex(layout) => self.flex.add(layout),
Command::SetAlignment(alignment) => {
self.finish_flex()?;
self.alignment = alignment;
self.start_new_flex();
}
Command::SetStyle(style) => *self.style.to_mut() = style,
Command::FinishLayout => {
self.finish_flex()?;
self.stack.finish_layout(true)?;
self.start_new_flex();
}
Command::FinishFlexRun => self.flex.add_break(),
}
}
Ok(())
}
/// Add text to the flex layout. If `glue` is true, the text will be a glue
/// part in the flex layouter. For details, see [`FlexLayouter`].
fn layout_text(&mut self, text: &str) -> LayoutResult<Layout> {
let ctx = TextContext {
loader: &self.ctx.loader,
style: &self.style,
};
layout_text(text, ctx)
}
/// Finish the current flex layout and add it the stack.
fn finish_flex(&mut self) -> LayoutResult<()> {
if self.flex.is_empty() {
return Ok(());
}
let layouts = self.flex.finish()?;
self.stack.add_many(layouts)?;
Ok(())
}
/// Start a new flex layout.
fn start_new_flex(&mut self) {
let mut ctx = self.flex.ctx();
ctx.space.dimensions = self.stack.remaining();
ctx.alignment = self.alignment;
ctx.flex_spacing = flex_spacing(&self.style);
self.flex = FlexLayouter::new(ctx);
}
}
fn flex_spacing(style: &TextStyle) -> Size {
(style.line_spacing - 1.0) * Size::pt(style.font_size)
}
fn paragraph_spacing(style: &TextStyle) -> Size {
let line_height = Size::pt(style.font_size);
let space_factor = style.line_spacing * style.paragraph_spacing - 1.0;
line_height * space_factor
}
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