Simplify selection rendering by injecting highlight scopes

3 files changed, 240 insertions, 143 deletions

diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
index 78cca5c7..c737b3ce 100644
--- a/helix-term/src/ui/editor.rs
+++ b/helix-term/src/ui/editor.rs
@@ -9,7 +9,7 @@ use crate::{
 use helix_core::{
     coords_at_pos,
     graphemes::ensure_grapheme_boundary,
-    syntax::{self, HighlightEvent},
+    syntax::{self, Highlight, HighlightEvent},
     LineEnding, Position, Range,
 };
 use helix_lsp::LspProgressMap;
@@ -44,6 +44,124 @@ impl Default for EditorView {
     }
 }
 
+struct Merge<I> {
+    iter: I,
+    spans: Box<dyn Iterator<Item = (usize, std::ops::Range<usize>)>>,
+
+    next_event: Option<HighlightEvent>,
+    next_span: Option<(usize, std::ops::Range<usize>)>,
+
+    queue: Vec<HighlightEvent>,
+}
+
+fn merge<I: Iterator<Item = HighlightEvent>>(
+    iter: I,
+    spans: Vec<(usize, std::ops::Range<usize>)>,
+) -> impl Iterator<Item = HighlightEvent> {
+    let spans = Box::new(spans.into_iter());
+    let mut merge = Merge {
+        iter,
+        spans,
+        next_event: None,
+        next_span: None,
+        queue: Vec::new(),
+    };
+    merge.next_event = merge.iter.next();
+    merge.next_span = merge.spans.next();
+    merge
+}
+
+impl<I: Iterator<Item = HighlightEvent>> Iterator for Merge<I> {
+    type Item = HighlightEvent;
+    fn next(&mut self) -> Option<Self::Item> {
+        use HighlightEvent::*;
+        if let Some(event) = self.queue.pop() {
+            return Some(event);
+        }
+
+        loop {
+            match (self.next_event, &self.next_span) {
+                // this happens when range is partially or fully offscreen
+                (Some(Source { start, end }), Some((span, range))) if start > range.start => {
+                    if start > range.end {
+                        self.next_span = self.spans.next();
+                    } else {
+                        self.next_span = Some((*span, start..range.end));
+                    };
+                }
+                _ => break,
+            }
+        }
+
+        match (self.next_event, &self.next_span) {
+            (Some(HighlightStart(i)), _) => {
+                self.next_event = self.iter.next();
+                return Some(HighlightStart(i));
+            }
+            (Some(HighlightEnd), _) => {
+                self.next_event = self.iter.next();
+                return Some(HighlightEnd);
+            }
+            (Some(Source { start, end }), Some((span, range))) if start < range.start => {
+                let intersect = range.start.min(end);
+                let event = Source {
+                    start,
+                    end: intersect,
+                };
+
+                if end == intersect {
+                    // the event is complete
+                    self.next_event = self.iter.next();
+                } else {
+                    // subslice the event
+                    self.next_event = Some(Source {
+                        start: intersect,
+                        end,
+                    });
+                };
+
+                Some(event)
+            }
+            (Some(Source { start, end }), Some((span, range))) if start == range.start => {
+                let intersect = range.end.min(end);
+                let event = HighlightStart(Highlight(*span));
+
+                // enqueue in reverse order
+                self.queue.push(HighlightEnd);
+                self.queue.push(Source {
+                    start,
+                    end: intersect,
+                });
+
+                if end == intersect {
+                    // the event is complete
+                    self.next_event = self.iter.next();
+                } else {
+                    // subslice the event
+                    self.next_event = Some(Source {
+                        start: intersect,
+                        end,
+                    });
+                };
+
+                if intersect == range.end {
+                    self.next_span = self.spans.next();
+                } else {
+                    self.next_span = Some((*span, intersect..range.end));
+                }
+
+                Some(event)
+            }
+            (Some(event), None) => {
+                self.next_event = self.iter.next();
+                return Some(event);
+            }
+            (None, None) => return None,
+            e => unreachable!("{:?}", e),
+        }
+    }
+}
+
 impl EditorView {
     pub fn new(keymaps: Keymaps) -> Self {
         Self {
@@ -140,9 +258,91 @@ impl EditorView {
         let mut line = 0u16;
         let tab_width = doc.tab_width();
 
+        let highlights = highlights.into_iter().map(|event| match event.unwrap() {
+            // convert byte offsets to char offset
+            HighlightEvent::Source { start, end } => {
+                let start = ensure_grapheme_boundary(text, text.byte_to_char(start));
+                let end = ensure_grapheme_boundary(text, text.byte_to_char(end));
+                HighlightEvent::Source { start, end }
+            }
+            event => event,
+        });
+
+        let selections = doc.selection(view.id);
+        let primary_idx = selections.primary_index();
+
+        let selection_scope = theme
+            .find_scope_index("ui.selection")
+            .expect("no selection scope found!");
+
+        let base_cursor_scope = theme
+            .find_scope_index("ui.cursor")
+            .unwrap_or(selection_scope);
+
+        let cursor_scope = match doc.mode() {
+            Mode::Insert => theme.find_scope_index("ui.cursor.insert"),
+            Mode::Select => theme.find_scope_index("ui.cursor.select"),
+            Mode::Normal => Some(base_cursor_scope),
+        }
+        .unwrap_or(base_cursor_scope);
+
+        let primary_selection_scope = theme
+            .find_scope_index("ui.selection.primary")
+            .unwrap_or(selection_scope);
+
+        // TODO: primary + insert mode patching
+        // let primary_cursor_style = theme
+        //     .try_get("ui.cursor.primary")
+        //     .map(|style| {
+        //         if mode != Mode::Normal {
+        //             // we want to make sure that the insert and select highlights
+        //             // also affect the primary cursor if set
+        //             style.patch(cursor_style)
+        //         } else {
+        //             style
+        //         }
+        //     })
+        //     .unwrap_or(cursor_style);
+
+        let primary_cursor_scope = theme
+            .find_scope_index("ui.cursor.primary")
+            .unwrap_or(cursor_scope);
+
+        let highlights: Box<dyn Iterator<Item = HighlightEvent>> = if is_focused {
+            // inject selections as highlight scopes
+            let mut spans_: Vec<(usize, std::ops::Range<usize>)> = Vec::new();
+
+            for (i, range) in selections.iter().enumerate() {
+                let (cursor_scope, selection_scope) = if i == primary_idx {
+                    (primary_cursor_scope, primary_selection_scope)
+                } else {
+                    (cursor_scope, selection_scope)
+                };
+
+                if range.head == range.anchor {
+                    spans_.push((cursor_scope, range.head..range.head + 1));
+                    continue;
+                }
+
+                let reverse = range.head < range.anchor;
+
+                if reverse {
+                    spans_.push((cursor_scope, range.head..range.head + 1));
+                    spans_.push((selection_scope, range.head + 1..range.anchor + 1));
+                } else {
+                    spans_.push((selection_scope, range.anchor..range.head));
+                    spans_.push((cursor_scope, range.head..range.head + 1));
+                }
+            }
+
+            Box::new(merge(highlights, spans_))
+        } else {
+            Box::new(highlights)
+        };
+
         'outer: for event in highlights {
-            match event.unwrap() {
-                HighlightEvent::HighlightStart(mut span) => {
+            match event {
+                HighlightEvent::HighlightStart(span) => {
                     spans.push(span);
                 }
                 HighlightEvent::HighlightEnd => {
@@ -150,29 +350,14 @@ impl EditorView {
                 }
                 HighlightEvent::Source { start, end } => {
                     // TODO: filter out spans out of viewport for now..
-
-                    // TODO: do these before iterating
-                    let start = ensure_grapheme_boundary(text, text.byte_to_char(start));
-                    let end = ensure_grapheme_boundary(text, text.byte_to_char(end));
-
                     let text = text.slice(start..end);
 
                     use helix_core::graphemes::{grapheme_width, RopeGraphemes};
 
-                    // TODO: scope matching: biggest union match? [string] & [html, string], [string, html] & [ string, html]
-                    // can do this by sorting our theme matches based on array len (longest first) then stopping at the
-                    // first rule that matches (rule.all(|scope| scopes.contains(scope)))
-                    // log::info!(
-                    //     "scopes: {:?}",
-                    //     spans
-                    //         .iter()
-                    //         .map(|span| theme.scopes()[span.0].as_str())
-                    //         .collect::<Vec<_>>()
-                    // );
-                    let style = match spans.first() {
-                        Some(span) => theme.get(theme.scopes()[span.0].as_str()),
-                        None => theme.get("ui.text"),
-                    };
+                    let style = spans.iter().fold(theme.get("ui.text"), |acc, span| {
+                        let style = theme.get(theme.scopes()[span.0].as_str());
+                        acc.patch(style)
+                    });
 
                     // TODO: we could render the text to a surface, then cache that, that
                     // way if only the selection/cursor changes we can copy from cache
@@ -183,7 +368,19 @@ impl EditorView {
 
                     // iterate over range char by char
                     for grapheme in RopeGraphemes::new(text) {
+                        let out_of_bounds = visual_x < view.first_col as u16
+                            || visual_x >= viewport.width + view.first_col as u16;
                         if LineEnding::from_rope_slice(&grapheme).is_some() {
+                            if !out_of_bounds {
+                                // we still want to render an empty cell with the style
+                                surface.set_string(
+                                    viewport.x + visual_x - view.first_col as u16,
+                                    viewport.y + line,
+                                    " ",
+                                    style,
+                                );
+                            }
+
                             visual_x = 0;
                             line += 1;
 
@@ -192,11 +389,18 @@ impl EditorView {
                                 break 'outer;
                             }
                         } else if grapheme == "\t" {
+                            if !out_of_bounds {
+                                // we still want to render an empty cell with the style
+                                surface.set_string(
+                                    viewport.x + visual_x - view.first_col as u16,
+                                    viewport.y + line,
+                                    " ".repeat(tab_width),
+                                    style,
+                                );
+                            }
+
                             visual_x = visual_x.saturating_add(tab_width as u16);
                         } else {
-                            let out_of_bounds = visual_x < view.first_col as u16
-                                || visual_x >= viewport.width + view.first_col as u16;
-
                             // Cow will prevent allocations if span contained in a single slice
                             // which should really be the majority case
                             let grapheme = Cow::from(grapheme);
@@ -283,126 +487,11 @@ impl EditorView {
                 Range::new(start, end)
             };
 
-            let mode = doc.mode();
-            let base_cursor_style = theme
-                .try_get("ui.cursor")
-                .unwrap_or_else(|| Style::default().add_modifier(Modifier::REVERSED));
-            let cursor_style = match mode {
-                Mode::Insert => theme.try_get("ui.cursor.insert"),
-                Mode::Select => theme.try_get("ui.cursor.select"),
-                Mode::Normal => Some(base_cursor_style),
-            }
-            .unwrap_or(base_cursor_style);
-            let primary_cursor_style = theme
-                .try_get("ui.cursor.primary")
-                .map(|style| {
-                    if mode != Mode::Normal {
-                        // we want to make sure that the insert and select highlights
-                        // also affect the primary cursor if set
-                        style.patch(cursor_style)
-                    } else {
-                        style
-                    }
-                })
-                .unwrap_or(cursor_style);
-
-            let selection_style = theme.get("ui.selection");
-            let primary_selection_style = theme
-                .try_get("ui.selection.primary")
-                .unwrap_or(selection_style);
-
             let selection = doc.selection(view.id);
-            let primary_idx = selection.primary_index();
-
-            for (i, selection) in selection
-                .iter()
-                .enumerate()
-                .filter(|(_, range)| range.overlaps(&screen))
-            {
-                // TODO: render also if only one of the ranges is in viewport
-                let mut start = view.screen_coords_at_pos(doc, text, selection.anchor);
-                let mut end = view.screen_coords_at_pos(doc, text, selection.head);
-
-                let (cursor_style, selection_style) = if i == primary_idx {
-                    (primary_cursor_style, primary_selection_style)
-                } else {
-                    (cursor_style, selection_style)
-                };
-
-                let head = end;
 
-                if selection.head < selection.anchor {
-                    std::mem::swap(&mut start, &mut end);
-                }
-                let start = start.unwrap_or_else(|| Position::new(0, 0));
-                let end = end.unwrap_or_else(|| {
-                    Position::new(viewport.height as usize, viewport.width as usize)
-                });
-
-                if start.row == end.row {
-                    surface.set_style(
-                        Rect::new(
-                            viewport.x + start.col as u16,
-                            viewport.y + start.row as u16,
-                            // .min is important, because set_style does a
-                            // for i in area.left()..area.right() and
-                            // area.right = x + width !!! which shouldn't be > then surface.area.right()
-                            // This is checked by a debug_assert! in Buffer::index_of
-                            ((end.col - start.col) as u16 + 1).min(
-                                surface
-                                    .area
-                                    .width
-                                    .saturating_sub(viewport.x + start.col as u16),
-                            ),
-                            1,
-                        ),
-                        selection_style,
-                    );
-                } else {
-                    surface.set_style(
-                        Rect::new(
-                            viewport.x + start.col as u16,
-                            viewport.y + start.row as u16,
-                            // text.line(view.first_line).len_chars() as u16 - start.col as u16,
-                            viewport.width.saturating_sub(start.col as u16),
-                            1,
-                        ),
-                        selection_style,
-                    );
-                    for i in start.row + 1..end.row {
-                        surface.set_style(
-                            Rect::new(
-                                viewport.x,
-                                viewport.y + i as u16,
-                                // text.line(view.first_line + i).len_chars() as u16,
-                                viewport.width,
-                                1,
-                            ),
-                            selection_style,
-                        );
-                    }
-                    surface.set_style(
-                        Rect::new(
-                            viewport.x,
-                            viewport.y + end.row as u16,
-                            (end.col as u16).min(viewport.width),
-                            1,
-                        ),
-                        selection_style,
-                    );
-                }
-
-                // cursor
+            for selection in selection.iter().filter(|range| range.overlaps(&screen)) {
+                let head = view.screen_coords_at_pos(doc, text, selection.head);
                 if let Some(head) = head {
-                    surface.set_style(
-                        Rect::new(
-                            viewport.x + head.col as u16,
-                            viewport.y + head.row as u16,
-                            1,
-                            1,
-                        ),
-                        cursor_style,
-                    );
                     surface.set_stringn(
                         viewport.x + 1 - OFFSET,
                         viewport.y + head.row as u16,
@@ -410,6 +499,7 @@ impl EditorView {
                         5,
                         linenr_select,
                     );
+
                     // TODO: set cursor position for IME
                     if let Some(syntax) = doc.syntax() {
                         use helix_core::match_brackets;
diff --git a/helix-view/src/theme.rs b/helix-view/src/theme.rs
index 947c6ee0..ece4fe9a 100644
--- a/helix-view/src/theme.rs
+++ b/helix-view/src/theme.rs
@@ -215,6 +215,10 @@ impl Theme {
     pub fn scopes(&self) -> &[String] {
         &self.scopes
     }
+
+    pub fn find_scope_index(&self, scope: &str) -> Option<usize> {
+        self.scopes().iter().position(|s| s == scope)
+    }
 }
 
 #[test]
diff --git a/theme.toml b/theme.toml
index e7e79313..bf99fb7a 100644
--- a/theme.toml
+++ b/theme.toml
@@ -52,9 +52,12 @@
 
 "ui.selection" = { bg = "#540099" }
 "ui.selection.primary" = { bg = "#540099" }
+# TODO: namespace ui.cursor as ui.selection.cursor?
 "ui.cursor.select" = { bg = "#6F44F0" }
-"ui.cursor.insert" = { bg = "#802F00" }
+"ui.cursor.insert" = { bg = "#ffffff" }
 "ui.cursor.match" = { fg = "#212121", bg = "#6C6999" }
+"ui.cursor" = { modifiers = ["reversed"] }
+
 "ui.menu.selected" = { fg = "#281733", bg = "#ffffff" } # revolver
 
 "warning" = "#ffcd1c"