feat(editor): add support for trailing whitespace rendering

helix-term/src/ui/document.rs

@@ -8,13 +8,15 @@ use helix_core::syntax::HighlightEvent;
 use helix_core::text_annotations::TextAnnotations;
 use helix_core::{visual_offset_from_block, Position, RopeSlice};
 use helix_stdx::rope::RopeSliceExt;
-use helix_view::editor::{WhitespaceConfig, WhitespaceRenderValue};
+use helix_view::editor::WhitespaceFeature;
 use helix_view::graphics::Rect;
 use helix_view::theme::Style;
 use helix_view::view::ViewPosition;
 use helix_view::{Document, Theme};
 use tui::buffer::Buffer as Surface;
 
+use super::trailing_whitespace::{TrailingWhitespaceTracker, WhitespaceKind};
+
 use crate::ui::text_decorations::DecorationManager;
 
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
@@ -254,6 +256,7 @@ pub struct TextRenderer<'a> {
     surface: &'a mut Surface,
     pub text_style: Style,
     pub whitespace_style: Style,
+    pub trailing_whitespace_style: Style,
     pub indent_guide_char: String,
     pub indent_guide_style: Style,
     pub newline: String,
@@ -267,6 +270,7 @@ pub struct TextRenderer<'a> {
     pub draw_indent_guides: bool,
     pub viewport: Rect,
     pub offset: Position,
+    pub trailing_whitespace_tracker: TrailingWhitespaceTracker,
 }
 
 pub struct GraphemeStyle {
@@ -283,56 +287,27 @@ impl<'a> TextRenderer<'a> {
         viewport: Rect,
     ) -> TextRenderer<'a> {
         let editor_config = doc.config.load();
-        let WhitespaceConfig {
-            render: ws_render,
-            characters: ws_chars,
-        } = &editor_config.whitespace;
 
         let tab_width = doc.tab_width();
-        let tab = if ws_render.tab() == WhitespaceRenderValue::All {
-            std::iter::once(ws_chars.tab)
-                .chain(std::iter::repeat(ws_chars.tabpad).take(tab_width - 1))
-                .collect()
-        } else {
-            " ".repeat(tab_width)
-        };
-        let virtual_tab = " ".repeat(tab_width);
-        let newline = if ws_render.newline() == WhitespaceRenderValue::All {
-            ws_chars.newline.into()
-        } else {
-            " ".to_owned()
-        };
-
-        let space = if ws_render.space() == WhitespaceRenderValue::All {
-            ws_chars.space.into()
-        } else {
-            " ".to_owned()
-        };
-        let nbsp = if ws_render.nbsp() == WhitespaceRenderValue::All {
-            ws_chars.nbsp.into()
-        } else {
-            " ".to_owned()
-        };
-        let nnbsp = if ws_render.nnbsp() == WhitespaceRenderValue::All {
-            ws_chars.nnbsp.into()
-        } else {
-            " ".to_owned()
-        };
-
         let text_style = theme.get("ui.text");
-
         let indent_width = doc.indent_style.indent_width(tab_width) as u16;
 
+        let ws = &editor_config.whitespace;
+        let regular_ws = WhitespaceFeature::Regular.palette(ws, tab_width);
+        let trailing_ws = WhitespaceFeature::Trailing.palette(ws, tab_width);
+        let trailing_whitespace_tracker = TrailingWhitespaceTracker::new(ws.render, trailing_ws);
+
         TextRenderer {
             surface,
             indent_guide_char: editor_config.indent_guides.character.into(),
-            newline,
-            nbsp,
-            nnbsp,
-            space,
-            tab,
-            virtual_tab,
+            newline: regular_ws.newline,
+            nbsp: regular_ws.nbsp,
+            nnbsp: regular_ws.nnbsp,
+            space: regular_ws.space,
+            tab: regular_ws.tab,
+            virtual_tab: regular_ws.virtual_tab,
             whitespace_style: theme.get("ui.virtual.whitespace"),
+            trailing_whitespace_style: theme.get("ui.virtual.trailing_whitespace"),
             indent_width,
             starting_indent: offset.col / indent_width as usize
                 + (offset.col % indent_width as usize != 0) as usize
@@ -346,6 +321,7 @@ impl<'a> TextRenderer<'a> {
             draw_indent_guides: editor_config.indent_guides.render,
             viewport,
             offset,
+            trailing_whitespace_tracker,
         }
     }
     /// Draws a single `grapheme` at the current render position with a specified `style`.
@@ -420,28 +396,61 @@ impl<'a> TextRenderer<'a> {
         } else {
             &self.tab
         };
+        let mut whitespace_kind = WhitespaceKind::None;
         let grapheme = match grapheme {
             Grapheme::Tab { width } => {
+                whitespace_kind = WhitespaceKind::Tab;
                 let grapheme_tab_width = char_to_byte_idx(tab, width);
                 &tab[..grapheme_tab_width]
             }
             // TODO special rendering for other whitespaces?
-            Grapheme::Other { ref g } if g == " " => space,
-            Grapheme::Other { ref g } if g == "\u{00A0}" => nbsp,
-            Grapheme::Other { ref g } if g == "\u{202F}" => nnbsp,
+            Grapheme::Other { ref g } if g == " " => {
+                whitespace_kind = WhitespaceKind::Space;
+                space
+            }
+            Grapheme::Other { ref g } if g == "\u{00A0}" => {
+                whitespace_kind = WhitespaceKind::NonBreakingSpace;
+                nbsp
+            }
+            Grapheme::Other { ref g } if g == "\u{202F}" => {
+                whitespace_kind = WhitespaceKind::NarrowNonBreakingSpace;
+                nnbsp
+            }
             Grapheme::Other { ref g } => g,
-            Grapheme::Newline => &self.newline,
+            Grapheme::Newline => {
+                whitespace_kind = WhitespaceKind::Newline;
+                &self.newline
+            }
         };
 
+        let viewport_right_edge = self.viewport.width as usize + self.offset.col - 1;
         let in_bounds = self.column_in_bounds(position.col, width);
 
         if in_bounds {
+            let in_bounds_col = position.col - self.offset.col;
             self.surface.set_string(
-                self.viewport.x + (position.col - self.offset.col) as u16,
+                self.viewport.x + in_bounds_col as u16,
                 self.viewport.y + position.row as u16,
                 grapheme,
                 style,
             );
+
+            if self
+                .trailing_whitespace_tracker
+                .track(in_bounds_col, whitespace_kind)
+                || position.col == viewport_right_edge
+            {
+                self.trailing_whitespace_tracker.render(
+                    &mut |trailing_whitespace: &str, from: usize| {
+                        self.surface.set_string(
+                            self.viewport.x + from as u16,
+                            self.viewport.y + position.row as u16,
+                            trailing_whitespace,
+                            style.patch(self.trailing_whitespace_style),
+                        );
+                    },
+                );
+            }
         } else if cut_off_start != 0 && cut_off_start < width {
             // partially on screen
             let rect = Rect::new(

helix-term/src/ui/mod.rs

@@ -13,6 +13,7 @@ mod spinner;
 mod statusline;
 mod text;
 mod text_decorations;
+mod trailing_whitespace;
 
 use crate::compositor::Compositor;
 use crate::filter_picker_entry;

helix-term/src/ui/trailing_whitespace.rs

@@ -0,0 +1,173 @@
+use helix_core::str_utils::char_to_byte_idx;
+use helix_view::editor::{WhitespacePalette, WhitespaceRender, WhitespaceRenderValue};
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub enum WhitespaceKind {
+    None,
+    Space,
+    NonBreakingSpace,
+    NarrowNonBreakingSpace,
+    Tab,
+    Newline,
+}
+
+impl WhitespaceKind {
+    pub fn to_str(self, palette: &WhitespacePalette) -> &str {
+        match self {
+            WhitespaceKind::Space => &palette.space,
+            WhitespaceKind::NonBreakingSpace => &palette.nbsp,
+            WhitespaceKind::NarrowNonBreakingSpace => &palette.nnbsp,
+            WhitespaceKind::Tab => {
+                let grapheme_tab_width = char_to_byte_idx(&palette.tab, palette.tab.len());
+                &palette.tab[..grapheme_tab_width]
+            }
+            WhitespaceKind::Newline | WhitespaceKind::None => "",
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct TrailingWhitespaceTracker {
+    enabled: bool,
+    palette: WhitespacePalette,
+    tracking_from: usize,
+    tracking_content: Vec<(WhitespaceKind, usize)>,
+}
+
+impl TrailingWhitespaceTracker {
+    pub fn new(render: WhitespaceRender, palette: WhitespacePalette) -> Self {
+        Self {
+            palette,
+            enabled: render.any(WhitespaceRenderValue::Trailing),
+            tracking_from: 0,
+            tracking_content: vec![],
+        }
+    }
+
+    // Tracks the whitespace and returns wether [`render`] should be called right after
+    // to display the trailing whitespace.
+    pub fn track(&mut self, from: usize, kind: WhitespaceKind) -> bool {
+        if !self.enabled || kind == WhitespaceKind::None {
+            self.tracking_content.clear();
+            return false;
+        }
+        if kind == WhitespaceKind::Newline {
+            return true;
+        }
+        if self.tracking_content.is_empty() {
+            self.tracking_from = from;
+        }
+        self.compress(kind);
+        false
+    }
+
+    pub fn render(&mut self, callback: &mut impl FnMut(&str, usize)) {
+        if self.tracking_content.is_empty() {
+            return;
+        }
+        let mut offset = self.tracking_from;
+        self.tracking_content.iter().for_each(|(kind, n)| {
+            let ws = kind.to_str(&self.palette).repeat(*n);
+            callback(&ws, offset);
+            offset += n;
+        });
+        self.tracking_content.clear();
+    }
+
+    fn compress(&mut self, kind: WhitespaceKind) {
+        if let Some((last_kind, n)) = self.tracking_content.last_mut() {
+            if *last_kind == kind {
+                *n += 1;
+                return;
+            }
+        }
+        self.tracking_content.push((kind, 1));
+    }
+}
+
+#[cfg(test)]
+mod tests {
+
+    use super::*;
+
+    use helix_view::editor::WhitespaceRender;
+
+    fn palette() -> WhitespacePalette {
+        WhitespacePalette {
+            space: "S".into(),
+            nbsp: "N".into(),
+            nnbsp: "M".into(),
+            tab: "<TAB>".into(),
+            virtual_tab: "V".into(),
+            newline: "L".into(),
+        }
+    }
+
+    fn capture(sut: &mut TrailingWhitespaceTracker) -> (String, usize, usize) {
+        let mut captured_content = String::new();
+        let mut from: usize = 0;
+        let mut to: usize = 0;
+
+        sut.render(&mut |content: &str, pos: usize| {
+            captured_content.push_str(content);
+            if from == 0 {
+                from = pos;
+            }
+            to = pos;
+        });
+
+        (captured_content, from, to)
+    }
+
+    #[test]
+    fn test_trailing_whitespace_tracker_correctly_tracks_sequences() {
+        let ws_render = WhitespaceRender::Basic(WhitespaceRenderValue::Trailing);
+
+        let mut sut = TrailingWhitespaceTracker::new(ws_render, palette());
+
+        sut.track(5, WhitespaceKind::Space);
+        sut.track(6, WhitespaceKind::NonBreakingSpace);
+        sut.track(7, WhitespaceKind::NarrowNonBreakingSpace);
+        sut.track(8, WhitespaceKind::Tab);
+
+        let (content, from, to) = capture(&mut sut);
+
+        assert_eq!(5, from);
+        assert_eq!(8, to);
+        assert_eq!("SNM<TAB>", content);
+
+        // Now we break the sequence
+        sut.track(6, WhitespaceKind::None);
+
+        let (content, from, to) = capture(&mut sut);
+        assert_eq!(0, from);
+        assert_eq!(0, to);
+        assert_eq!("", content);
+
+        sut.track(10, WhitespaceKind::Tab);
+        sut.track(11, WhitespaceKind::NonBreakingSpace);
+        sut.track(12, WhitespaceKind::NarrowNonBreakingSpace);
+        sut.track(13, WhitespaceKind::Space);
+
+        let (content, from, to) = capture(&mut sut);
+        assert_eq!(10, from);
+        assert_eq!(13, to);
+        assert_eq!("<TAB>NMS", content);
+
+        // Verify compression works
+        sut.track(20, WhitespaceKind::Space);
+        sut.track(21, WhitespaceKind::Space);
+        sut.track(22, WhitespaceKind::NonBreakingSpace);
+        sut.track(23, WhitespaceKind::NonBreakingSpace);
+        sut.track(24, WhitespaceKind::NarrowNonBreakingSpace);
+        sut.track(25, WhitespaceKind::NarrowNonBreakingSpace);
+        sut.track(26, WhitespaceKind::Tab);
+        sut.track(27, WhitespaceKind::Tab);
+        sut.track(28, WhitespaceKind::Tab);
+
+        let (content, from, to) = capture(&mut sut);
+        assert_eq!(20, from);
+        assert_eq!(26, to); // Compression means last tracked token is on 26 instead of 28
+        assert_eq!("SSNNMM<TAB><TAB><TAB>", content);
+    }
+}