Clear selection on clear line/screen escapes

Selection is now cleared if clear line or clear screen escape sequences
are clearing content behind it.

4 files changed, 78 insertions, 6 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 65cc94e9..1af19d7d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -40,6 +40,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Set IUTF8 termios flag for improved UTF8 input support
 - Dragging files into terminal now adds a space after each path
 - Default binding replacement conditions
+- Adjusted selection clearing granularity to more accurately match content
 
 ### Fixed
 
diff --git a/alacritty_terminal/src/grid/mod.rs b/alacritty_terminal/src/grid/mod.rs
index 5178ed99..fd555d1b 100644
--- a/alacritty_terminal/src/grid/mod.rs
+++ b/alacritty_terminal/src/grid/mod.rs
@@ -187,6 +187,11 @@ impl<T: GridCell + Default + PartialEq + Copy> Grid<T> {
         Point { line: self.lines.0 + self.display_offset - point.line.0 - 1, col: point.col }
     }
 
+    /// Return the cursor position in buffer coordinates.
+    pub fn cursor_buffer_point(&self) -> Point<usize> {
+        Point { line: self.lines.0 - self.cursor.point.line.0 - 1, col: self.cursor.point.col }
+    }
+
     /// Update the size of the scrollback history.
     pub fn update_history(&mut self, history_size: usize) {
         let current_history_size = self.history_size();
diff --git a/alacritty_terminal/src/selection.rs b/alacritty_terminal/src/selection.rs
index 7e1e108e..dbd11592 100644
--- a/alacritty_terminal/src/selection.rs
+++ b/alacritty_terminal/src/selection.rs
@@ -7,7 +7,7 @@
 
 use std::convert::TryFrom;
 use std::mem;
-use std::ops::Range;
+use std::ops::{Bound, Range, RangeBounds};
 
 use crate::index::{Column, Line, Point, Side};
 use crate::term::{Search, Term};
@@ -193,6 +193,30 @@ impl Selection {
         }
     }
 
+    /// Check whether selection contains any point in a given range.
+    pub fn intersects_range<R: RangeBounds<usize>>(&self, range: R) -> bool {
+        let mut start = self.region.start.point.line;
+        let mut end = self.region.end.point.line;
+
+        if Self::points_need_swap(self.region.start.point, self.region.end.point) {
+            mem::swap(&mut start, &mut end);
+        }
+
+        let range_start = match range.start_bound() {
+            Bound::Included(&range_start) => range_start,
+            Bound::Excluded(&range_start) => range_start.saturating_add(1),
+            Bound::Unbounded => 0,
+        };
+
+        let range_end = match range.end_bound() {
+            Bound::Included(&range_end) => range_end,
+            Bound::Excluded(&range_end) => range_end.saturating_sub(1),
+            Bound::Unbounded => usize::max_value(),
+        };
+
+        range_start <= start && range_end >= end
+    }
+
     /// Expand selection sides to include all cells.
     pub fn include_all(&mut self) {
         let (start, end) = (self.region.start.point, self.region.end.point);
@@ -217,7 +241,9 @@ impl Selection {
         let num_cols = grid.num_cols();
 
         // Order start above the end.
-        let (mut start, mut end) = (self.region.start, self.region.end);
+        let mut start = self.region.start;
+        let mut end = self.region.end;
+
         if Self::points_need_swap(start.point, end.point) {
             mem::swap(&mut start, &mut end);
         }
@@ -643,4 +669,21 @@ mod tests {
             is_block: true,
         });
     }
+
+    #[test]
+    fn range_intersection() {
+        let mut selection =
+            Selection::new(SelectionType::Lines, Point::new(6, Column(1)), Side::Left);
+        selection.update(Point::new(3, Column(1)), Side::Right);
+
+        assert!(selection.intersects_range(..));
+        assert!(selection.intersects_range(2..));
+        assert!(selection.intersects_range(2..=4));
+        assert!(selection.intersects_range(2..=7));
+        assert!(selection.intersects_range(4..=5));
+        assert!(selection.intersects_range(5..8));
+
+        assert!(!selection.intersects_range(..=2));
+        assert!(!selection.intersects_range(7..=8));
+    }
 }
diff --git a/alacritty_terminal/src/term/mod.rs b/alacritty_terminal/src/term/mod.rs
index 33d2e14e..77ad826a 100644
--- a/alacritty_terminal/src/term/mod.rs
+++ b/alacritty_terminal/src/term/mod.rs
@@ -1763,6 +1763,12 @@ impl<T: EventListener> Handler for Term<T> {
                 }
             },
         }
+
+        let cursor_buffer_line = self.grid.cursor_buffer_point().line;
+        self.selection = self
+            .selection
+            .take()
+            .filter(|s| !s.intersects_range(cursor_buffer_line..=cursor_buffer_line));
     }
 
     /// Set the indexed color value.
@@ -1840,8 +1846,8 @@ impl<T: EventListener> Handler for Term<T> {
         trace!("Clearing screen: {:?}", mode);
         let template = self.grid.cursor.template;
 
-        // Remove active selections.
-        self.selection = None;
+        let num_lines = self.grid.num_lines().0;
+        let cursor_buffer_line = self.grid.cursor_buffer_point().line;
 
         match mode {
             ansi::ClearMode::Above => {
@@ -1858,15 +1864,24 @@ impl<T: EventListener> Handler for Term<T> {
                 for cell in &mut self.grid[cursor.line][..end] {
                     cell.reset(&template);
                 }
+
+                self.selection = self
+                    .selection
+                    .take()
+                    .filter(|s| !s.intersects_range(cursor_buffer_line..num_lines));
             },
             ansi::ClearMode::Below => {
                 let cursor = self.grid.cursor.point;
                 for cell in &mut self.grid[cursor.line][cursor.col..] {
                     cell.reset(&template);
                 }
-                if cursor.line < self.grid.num_lines() - 1 {
+
+                if cursor.line.0 < num_lines - 1 {
                     self.grid.region_mut((cursor.line + 1)..).each(|cell| cell.reset(&template));
                 }
+
+                self.selection =
+                    self.selection.take().filter(|s| !s.intersects_range(..=cursor_buffer_line));
             },
             ansi::ClearMode::All => {
                 if self.mode.contains(TermMode::ALT_SCREEN) {
@@ -1875,8 +1890,16 @@ impl<T: EventListener> Handler for Term<T> {
                     let template = Cell { bg: template.bg, ..Cell::default() };
                     self.grid.clear_viewport(template);
                 }
+
+                self.selection = self.selection.take().filter(|s| !s.intersects_range(..num_lines));
+            },
+            ansi::ClearMode::Saved if self.grid.history_size() > 0 => {
+                self.grid.clear_history();
+
+                self.selection = self.selection.take().filter(|s| !s.intersects_range(num_lines..));
             },
-            ansi::ClearMode::Saved => self.grid.clear_history(),
+            // We have no history to clear.
+            ansi::ClearMode::Saved => (),
         }
     }