xi-core-lib 0.3.0

// Copyright 2017 The xi-editor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Handles syntax highlighting and other styling.
//!
//! Plugins provide syntax highlighting information in the form of 'scopes'.
//! Scope information originating from any number of plugins can be resolved
//! into styles using a theme, augmented with additional style definitions.

use std::collections::{BTreeMap, HashMap, HashSet};
use syntect::highlighting::StyleModifier;
use syntect::parsing::Scope;

use xi_rope::spans::{Spans, SpansBuilder};
use xi_rope::{Interval, RopeDelta};
use xi_trace::trace_block;

use crate::plugins::PluginPid;
use crate::styles::{Style, ThemeStyleMap};

/// A collection of layers containing scope information.
#[derive(Default)]
pub struct Layers {
    layers: BTreeMap<PluginPid, ScopeLayer>,
    deleted: HashSet<PluginPid>,
    merged: Spans<Style>,
}

/// A collection of scope spans from a single source.
pub struct ScopeLayer {
    stack_lookup: Vec<Vec<Scope>>,
    style_lookup: Vec<Style>,
    // TODO: this might be efficient (in memory at least) if we use
    // a prefix tree.
    /// style state of existing scope spans, so we can more efficiently
    /// compute styles of child spans.
    style_cache: HashMap<Vec<Scope>, StyleModifier>,
    /// Human readable scope names, for debugging
    scope_spans: Spans<u32>,
    style_spans: Spans<Style>,
}

impl Layers {
    pub fn get_merged(&self) -> &Spans<Style> {
        &self.merged
    }

    /// Adds the provided scopes to the layer's lookup table.
    pub fn add_scopes(
        &mut self,
        layer: PluginPid,
        scopes: Vec<Vec<String>>,
        style_map: &ThemeStyleMap,
    ) {
        let _t = trace_block("Layers::AddScopes", &["core"]);
        if self.create_if_missing(layer).is_err() {
            return;
        }
        self.layers.get_mut(&layer).unwrap().add_scopes(scopes, style_map);
    }

    /// Applies the delta to all layers, inserting empty intervals
    /// for any regions inserted in the delta.
    ///
    /// This is useful for clearing spans, and for updating spans
    /// as edits occur.
    pub fn update_all(&mut self, delta: &RopeDelta) {
        self.merged.apply_shape(delta);

        for layer in self.layers.values_mut() {
            layer.blank_scopes(delta);
        }
        let (iv, _len) = delta.summary();
        self.resolve_styles(iv);
    }

    /// Updates the scope spans for a given layer.
    pub fn update_layer(&mut self, layer: PluginPid, iv: Interval, spans: Spans<u32>) {
        if self.create_if_missing(layer).is_err() {
            return;
        }
        self.layers.get_mut(&layer).unwrap().update_scopes(iv, &spans);
        self.resolve_styles(iv);
    }

    /// Removes a given layer. This will remove all styles derived from
    /// that layer's scopes.
    pub fn remove_layer(&mut self, layer: PluginPid) -> Option<ScopeLayer> {
        self.deleted.insert(layer);
        let layer = self.layers.remove(&layer);
        if layer.is_some() {
            let iv_all = Interval::new(0, self.merged.len());
            //TODO: should Spans<T> have a clear() method?
            self.merged = SpansBuilder::new(self.merged.len()).build();
            self.resolve_styles(iv_all);
        }
        layer
    }

    pub fn theme_changed(&mut self, style_map: &ThemeStyleMap) {
        for layer in self.layers.values_mut() {
            layer.theme_changed(style_map);
        }
        self.merged = SpansBuilder::new(self.merged.len()).build();
        let iv_all = Interval::new(0, self.merged.len());
        self.resolve_styles(iv_all);
    }

    /// Resolves styles from all layers for the given interval, updating
    /// the master style spans.
    fn resolve_styles(&mut self, iv: Interval) {
        if self.layers.is_empty() {
            return;
        }
        let mut layer_iter = self.layers.values();
        let mut resolved = layer_iter.next().unwrap().style_spans.subseq(iv);

        for other in layer_iter {
            let spans = other.style_spans.subseq(iv);
            assert_eq!(resolved.len(), spans.len());
            resolved = resolved.merge(&spans, |a, b| match b {
                Some(b) => a.merge(b),
                None => a.to_owned(),
            });
        }
        self.merged.edit(iv, resolved);
    }

    /// Prints scopes and style information for the given `Interval`.
    pub fn debug_print_spans(&self, iv: Interval) {
        for (id, layer) in &self.layers {
            let spans = layer.scope_spans.subseq(iv);
            let styles = layer.style_spans.subseq(iv);
            if spans.iter().next().is_some() {
                info!("scopes for layer {:?}:", id);
                for (iv, val) in spans.iter() {
                    info!("{}: {:?}", iv, layer.stack_lookup[*val as usize]);
                }
                info!("styles:");
                for (iv, val) in styles.iter() {
                    info!("{}: {:?}", iv, val);
                }
            }
        }
    }

    /// Returns an `Err` if this layer has been deleted; the caller should return.
    fn create_if_missing(&mut self, layer_id: PluginPid) -> Result<(), ()> {
        if self.deleted.contains(&layer_id) {
            return Err(());
        }
        if !self.layers.contains_key(&layer_id) {
            self.layers.insert(layer_id, ScopeLayer::new(self.merged.len()));
        }
        Ok(())
    }
}

impl Default for ScopeLayer {
    fn default() -> Self {
        ScopeLayer {
            stack_lookup: Vec::new(),
            style_lookup: Vec::new(),
            style_cache: HashMap::new(),
            scope_spans: Spans::default(),
            style_spans: Spans::default(),
        }
    }
}

impl ScopeLayer {
    pub fn new(len: usize) -> Self {
        ScopeLayer {
            stack_lookup: Vec::new(),
            style_lookup: Vec::new(),
            style_cache: HashMap::new(),
            scope_spans: SpansBuilder::new(len).build(),
            style_spans: SpansBuilder::new(len).build(),
        }
    }

    fn theme_changed(&mut self, style_map: &ThemeStyleMap) {
        // recompute styles with the new theme
        let cur_stacks = self.stack_lookup.clone();
        self.style_lookup = self.styles_for_stacks(&cur_stacks, style_map);
        let iv_all = Interval::new(0, self.style_spans.len());
        self.style_spans = SpansBuilder::new(self.style_spans.len()).build();
        // this feels unnecessary but we can't pass in a reference to self
        // and I don't want to get fancy unless there's an actual perf problem
        let scopes = self.scope_spans.clone();
        self.update_styles(iv_all, &scopes)
    }

    fn add_scopes(&mut self, scopes: Vec<Vec<String>>, style_map: &ThemeStyleMap) {
        let mut stacks = Vec::with_capacity(scopes.len());
        for stack in scopes {
            let scopes = stack
                .iter()
                .map(|s| Scope::new(&s))
                .filter(|result| match *result {
                    Err(ref err) => {
                        warn!("failed to resolve scope {}\nErr: {:?}", &stack.join(" "), err);
                        false
                    }
                    _ => true,
                })
                .map(|s| s.unwrap())
                .collect::<Vec<_>>();
            stacks.push(scopes);
        }

        let mut new_styles = self.styles_for_stacks(stacks.as_slice(), style_map);
        self.stack_lookup.append(&mut stacks);
        self.style_lookup.append(&mut new_styles);
    }

    fn styles_for_stacks(
        &mut self,
        stacks: &[Vec<Scope>],
        style_map: &ThemeStyleMap,
    ) -> Vec<Style> {
        //let style_map = style_map.borrow();
        let highlighter = style_map.get_highlighter();
        let mut new_styles = Vec::new();

        for stack in stacks {
            let mut last_style: Option<StyleModifier> = None;
            let mut upper_bound_of_last = stack.len() as usize;

            // walk backwards through stack to see if we have an existing
            // style for any child stacks.
            for i in 0..stack.len() - 1 {
                let prev_range = 0..stack.len() - (i + 1);
                if let Some(s) = self.style_cache.get(&stack[prev_range]) {
                    last_style = Some(*s);
                    upper_bound_of_last = stack.len() - (i + 1);
                    break;
                }
            }
            let mut base_style_mod = last_style.unwrap_or_default();

            // apply the stack, generating children as needed.
            for i in upper_bound_of_last..stack.len() {
                let style_mod = highlighter.style_mod_for_stack(&stack[0..=i]);
                base_style_mod = base_style_mod.apply(style_mod);
            }

            let style = Style::from_syntect_style_mod(&base_style_mod);
            self.style_cache.insert(stack.clone(), base_style_mod);

            new_styles.push(style);
        }
        new_styles
    }

    fn update_scopes(&mut self, iv: Interval, spans: &Spans<u32>) {
        self.scope_spans.edit(iv, spans.to_owned());
        self.update_styles(iv, spans);
    }

    /// Applies `delta`, which is presumed to contain empty spans.
    /// This is only used when we receive an edit, to adjust current span
    /// positions.
    fn blank_scopes(&mut self, delta: &RopeDelta) {
        self.style_spans.apply_shape(delta);
        self.scope_spans.apply_shape(delta);
    }

    /// Updates `self.style_spans`, mapping scopes to styles and combining
    /// adjacent and equal spans.
    fn update_styles(&mut self, iv: Interval, spans: &Spans<u32>) {
        // NOTE: This is a tradeoff. Keeping both u32 and Style spans for each
        // layer makes debugging simpler and reduces the total number of spans
        // on the wire (because we combine spans that resolve to the same style)
        // but it does require additional computation + memory up front.
        let mut sb = SpansBuilder::new(spans.len());
        let mut spans_iter = spans.iter();
        let mut prev = spans_iter.next();
        {
            // distinct adjacent scopes can often resolve to the same style,
            // so we combine them when building the styles.
            let style_eq = |i1: &u32, i2: &u32| {
                self.style_lookup[*i1 as usize] == self.style_lookup[*i2 as usize]
            };

            while let Some((p_iv, p_val)) = prev {
                match spans_iter.next() {
                    Some((n_iv, n_val)) if n_iv.start() == p_iv.end() && style_eq(p_val, n_val) => {
                        prev = Some((p_iv.union(n_iv), p_val));
                    }
                    other => {
                        sb.add_span(p_iv, self.style_lookup[*p_val as usize].to_owned());
                        prev = other;
                    }
                }
            }
        }
        self.style_spans.edit(iv, sb.build());
    }
}