Add visual selection effect

src/core_editor/editor.rs

@@ -533,6 +533,18 @@ impl Editor {
     fn reset_selection(&mut self) {
         self.selection_anchor = None;
     }
+
+    /// If a selection is active returns the selected range, otherwise None.
+    /// The range is guaranteed to be ascending.
+    pub fn get_selection(&self) -> Option<(usize, usize)> {
+        self.selection_anchor.map(|selection_anchor| {
+            if self.insertion_point() > selection_anchor {
+                (selection_anchor, self.insertion_point())
+            } else {
+                (self.insertion_point(), selection_anchor)
+            }
+        })
+    }
 }
 
 #[cfg(test)]

src/engine.rs

@@ -1,6 +1,7 @@
 use std::path::PathBuf;
 
 use itertools::Itertools;
+use nu_ansi_term::{Color, Style};
 
 use crate::{enums::ReedlineRawEvent, CursorConfig};
 #[cfg(feature = "bashisms")]
@@ -127,6 +128,9 @@ pub struct Reedline {
     // Highlight the edit buffer
     highlighter: Box<dyn Highlighter>,
 
+    // Style used for visual selection
+    visual_selection_style: Style,
+
     // Showcase hints based on various strategies (history, language-completion, spellcheck, etc)
     hinter: Option<Box<dyn Hinter>>,
     hide_hints: bool,
@@ -183,6 +187,7 @@ impl Reedline {
         let history = Box::<FileBackedHistory>::default();
         let painter = Painter::new(std::io::BufWriter::new(std::io::stderr()));
         let buffer_highlighter = Box::<ExampleHighlighter>::default();
+        let visual_selection_style = Style::new().on(Color::LightGray);
         let completer = Box::<DefaultCompleter>::default();
         let hinter = None;
         let validator = None;
@@ -209,6 +214,7 @@ impl Reedline {
             quick_completions: false,
             partial_completions: false,
             highlighter: buffer_highlighter,
+            visual_selection_style,
             hinter,
             hide_hints: false,
             validator,
@@ -371,6 +377,13 @@ impl Reedline {
         self
     }
 
+    /// A builder that configures the style used for visual selection
+    #[must_use]
+    pub fn with_visual_selection_style(mut self, style: Style) -> Self {
+        self.visual_selection_style = style;
+        self
+    }
+
     /// A builder which configures the history for your instance of the Reedline engine
     /// # Example
     /// ```rust,no_run
@@ -1638,14 +1651,18 @@ impl Reedline {
         let cursor_position_in_buffer = self.editor.insertion_point();
         let buffer_to_paint = self.editor.get_buffer();
 
-        let (before_cursor, after_cursor) = self
+        let mut styled_text = self
             .highlighter
-            .highlight(buffer_to_paint, cursor_position_in_buffer)
-            .render_around_insertion_point(
-                cursor_position_in_buffer,
-                prompt,
-                self.use_ansi_coloring,
-            );
+            .highlight(buffer_to_paint, cursor_position_in_buffer);
+        if let Some((from, to)) = self.editor.get_selection() {
+            styled_text.style_range(from, to, self.visual_selection_style);
+        }
+
+        let (before_cursor, after_cursor) = styled_text.render_around_insertion_point(
+            cursor_position_in_buffer,
+            prompt,
+            self.use_ansi_coloring,
+        );
 
         let hint: String = if self.hints_active() {
             self.hinter.as_mut().map_or_else(String::new, |hinter| {

src/painting/styled_text.rs

@@ -5,6 +5,7 @@ use crate::Prompt;
 use super::utils::strip_ansi;
 
 /// A representation of a buffer with styling, used for doing syntax highlighting
+#[derive(Clone)]
 pub struct StyledText {
     /// The component, styled parts of the text
     pub buffer: Vec<(Style, String)>,
@@ -27,6 +28,67 @@ impl StyledText {
         self.buffer.push(styled_string);
     }
 
+    /// Style range with the provided style
+    pub fn style_range(&mut self, from: usize, to: usize, new_style: Style) {
+        let (from, to) = if from > to { (to, from) } else { (from, to) };
+        let mut current_idx = 0;
+        let mut pair_idx = 0;
+        while pair_idx < self.buffer.len() {
+            let pair = &mut self.buffer[pair_idx];
+            let end_idx = current_idx + pair.1.len();
+            enum Position {
+                Before,
+                In,
+                After,
+            }
+            let start_position = if current_idx < from {
+                Position::Before
+            } else if current_idx >= to {
+                Position::After
+            } else {
+                Position::In
+            };
+            let end_position = if end_idx < from {
+                Position::Before
+            } else if end_idx > to {
+                Position::After
+            } else {
+                Position::In
+            };
+            match (start_position, end_position) {
+                (Position::Before, Position::After) => {
+                    let mut in_range = pair.1.split_off(from - current_idx);
+                    let after_range = in_range.split_off(to - current_idx - from);
+                    let in_range = (new_style, in_range);
+                    let after_range = (pair.0, after_range);
+                    self.buffer.insert(pair_idx + 1, in_range);
+                    self.buffer.insert(pair_idx + 2, after_range);
+                    break;
+                }
+                (Position::Before, Position::In) => {
+                    let in_range = pair.1.split_off(from - current_idx);
+                    pair_idx += 1; // Additional increment for the split pair, since the new insertion is already correctly styled and can be skipped next iteration
+                    self.buffer.insert(pair_idx, (new_style, in_range));
+                }
+                (Position::In, Position::After) => {
+                    let after_range = pair.1.split_off(to - current_idx);
+                    let old_style = pair.0;
+                    pair.0 = new_style;
+                    if !after_range.is_empty() {
+                        self.buffer.insert(pair_idx + 1, (old_style, after_range));
+                    }
+                    break;
+                }
+                (Position::In, Position::In) => pair.0 = new_style,
+
+                (Position::After, _) => break,
+                _ => (),
+            }
+            current_idx = end_idx;
+            pair_idx += 1;
+        }
+    }
+
     /// Render the styled string. We use the insertion point to render around so that
     /// we can properly write out the styled string to the screen and find the correct
     /// place to put the cursor. This assumes a logic that prints the first part of the
@@ -109,3 +171,88 @@ fn render_as_string(
     }
     rendered
 }
+
+#[cfg(test)]
+mod test {
+    use nu_ansi_term::{Color, Style};
+
+    use crate::StyledText;
+
+    fn get_styled_text_template() -> (super::StyledText, Style, Style) {
+        let before_style = Style::new().on(Color::Black);
+        let after_style = Style::new().on(Color::Red);
+        (
+            super::StyledText {
+                buffer: vec![
+                    (before_style, "aaa".into()),
+                    (before_style, "bbb".into()),
+                    (before_style, "ccc".into()),
+                ],
+            },
+            before_style,
+            after_style,
+        )
+    }
+    #[test]
+    fn style_range_partial_update_one_part() {
+        let (styled_text_template, before_style, after_style) = get_styled_text_template();
+        let mut styled_text = styled_text_template.clone();
+        styled_text.style_range(0, 1, after_style);
+        assert_eq!(styled_text.buffer[0], (after_style, "a".into()));
+        assert_eq!(styled_text.buffer[1], (before_style, "aa".into()));
+        assert_eq!(styled_text.buffer[2], (before_style, "bbb".into()));
+        assert_eq!(styled_text.buffer[3], (before_style, "ccc".into()));
+    }
+    #[test]
+    fn style_range_complete_update_one_part() {
+        let (styled_text_template, before_style, after_style) = get_styled_text_template();
+        let mut styled_text = styled_text_template.clone();
+        styled_text.style_range(0, 3, after_style);
+        assert_eq!(styled_text.buffer[0], (after_style, "aaa".into()));
+        assert_eq!(styled_text.buffer[1], (before_style, "bbb".into()));
+        assert_eq!(styled_text.buffer[2], (before_style, "ccc".into()));
+        assert_eq!(styled_text.buffer.len(), 3);
+    }
+    #[test]
+    fn style_range_update_over_boundary() {
+        let (styled_text_template, before_style, after_style) = get_styled_text_template();
+        let mut styled_text = styled_text_template;
+        styled_text.style_range(0, 5, after_style);
+        assert_eq!(styled_text.buffer[0], (after_style, "aaa".into()));
+        assert_eq!(styled_text.buffer[1], (after_style, "bb".into()));
+        assert_eq!(styled_text.buffer[2], (before_style, "b".into()));
+        assert_eq!(styled_text.buffer[3], (before_style, "ccc".into()));
+    }
+    #[test]
+    fn style_range_update_over_part() {
+        let (styled_text_template, before_style, after_style) = get_styled_text_template();
+        let mut styled_text = styled_text_template;
+        styled_text.style_range(1, 7, after_style);
+        assert_eq!(styled_text.buffer[0], (before_style, "a".into()));
+        assert_eq!(styled_text.buffer[1], (after_style, "aa".into()));
+        assert_eq!(styled_text.buffer[2], (after_style, "bbb".into()));
+        assert_eq!(styled_text.buffer[3], (after_style, "c".into()));
+        assert_eq!(styled_text.buffer[4], (before_style, "cc".into()));
+    }
+    #[test]
+    fn style_range_last_letter() {
+        let (_, before_style, after_style) = get_styled_text_template();
+        let mut styled_text = StyledText {
+            buffer: vec![(before_style, "asdf".into())],
+        };
+        styled_text.style_range(3, 4, after_style);
+        assert_eq!(styled_text.buffer[0], (before_style, "asd".into()));
+        assert_eq!(styled_text.buffer[1], (after_style, "f".into()));
+    }
+    #[test]
+    fn style_range_from_second_to_last() {
+        let (_, before_style, after_style) = get_styled_text_template();
+        let mut styled_text = StyledText {
+            buffer: vec![(before_style, "asdf".into())],
+        };
+        styled_text.style_range(2, 3, after_style);
+        assert_eq!(styled_text.buffer[0], (before_style, "as".into()));
+        assert_eq!(styled_text.buffer[1], (after_style, "d".into()));
+        assert_eq!(styled_text.buffer[2], (before_style, "f".into()));
+    }
+}