implement scrolling back

5 files changed, 175 insertions, 38 deletions

diff --git a/src/grid.rs b/src/grid.rs
index 5a53c6e..db96326 100644
--- a/src/grid.rs
+++ b/src/grid.rs
@@ -12,8 +12,9 @@ pub struct Grid {
     scroll_bottom: u16,
     origin_mode: bool,
     saved_origin_mode: bool,
-    scrollback: std::collections::VecDeque<(usize, crate::row::Row)>,
+    scrollback: std::collections::VecDeque<crate::row::Row>,
     scrollback_len: usize,
+    scrollback_offset: usize,
 }
 
 impl Grid {
@@ -29,9 +30,18 @@ impl Grid {
             saved_origin_mode: false,
             scrollback: std::collections::VecDeque::new(),
             scrollback_len,
+            scrollback_offset: 0,
         }
     }
 
+    pub fn scrollback(&self) -> usize {
+        self.scrollback_offset
+    }
+
+    pub fn set_scrollback(&mut self, rows: usize) {
+        self.scrollback_offset = rows.min(self.scrollback.len());
+    }
+
     fn new_row(&self) -> crate::row::Row {
         crate::row::Row::new(self.size.cols)
     }
@@ -39,7 +49,7 @@ impl Grid {
     pub fn clear(&mut self) {
         self.pos = Pos::default();
         self.saved_pos = Pos::default();
-        for row in self.rows_mut() {
+        for row in self.drawing_rows_mut() {
             row.clear(crate::attrs::Color::Default);
         }
         self.scroll_top = 0;
@@ -97,37 +107,58 @@ impl Grid {
         self.origin_mode = self.saved_origin_mode;
     }
 
-    pub fn rows(&self) -> impl Iterator<Item = &crate::row::Row> {
+    pub fn visible_rows(&self) -> impl Iterator<Item = &crate::row::Row> {
+        let scrollback_len = self.scrollback.len();
+        let rows_len = self.rows.len();
+        self.scrollback
+            .iter()
+            .skip(scrollback_len - self.scrollback_offset)
+            .chain(self.rows.iter().take(rows_len - self.scrollback_offset))
+    }
+
+    pub fn drawing_rows(&self) -> impl Iterator<Item = &crate::row::Row> {
         self.rows.iter()
     }
 
-    pub fn rows_mut(&mut self) -> impl Iterator<Item = &mut crate::row::Row> {
+    pub fn drawing_rows_mut(
+        &mut self,
+    ) -> impl Iterator<Item = &mut crate::row::Row> {
         self.rows.iter_mut()
     }
 
-    pub fn row(&self, pos: Pos) -> Option<&crate::row::Row> {
-        self.rows.get(pos.row as usize)
+    pub fn visible_row(&self, pos: Pos) -> Option<&crate::row::Row> {
+        self.visible_rows().nth(pos.row as usize)
+    }
+
+    pub fn drawing_row(&self, pos: Pos) -> Option<&crate::row::Row> {
+        self.drawing_rows().nth(pos.row as usize)
     }
 
-    pub fn row_mut(&mut self, pos: Pos) -> Option<&mut crate::row::Row> {
-        self.rows.get_mut(pos.row as usize)
+    pub fn drawing_row_mut(
+        &mut self,
+        pos: Pos,
+    ) -> Option<&mut crate::row::Row> {
+        self.drawing_rows_mut().nth(pos.row as usize)
     }
 
     pub fn current_row_mut(&mut self) -> &mut crate::row::Row {
-        self.row_mut(self.pos)
+        self.drawing_row_mut(self.pos)
             .expect("cursor not pointing to a cell")
     }
 
-    pub fn cell(&self, pos: Pos) -> Option<&crate::cell::Cell> {
-        self.row(pos).and_then(|r| r.get(pos.col))
+    pub fn visible_cell(&self, pos: Pos) -> Option<&crate::cell::Cell> {
+        self.visible_row(pos).and_then(|r| r.get(pos.col))
     }
 
-    pub fn cell_mut(&mut self, pos: Pos) -> Option<&mut crate::cell::Cell> {
-        self.row_mut(pos).and_then(|r| r.get_mut(pos.col))
+    pub fn drawing_cell_mut(
+        &mut self,
+        pos: Pos,
+    ) -> Option<&mut crate::cell::Cell> {
+        self.drawing_row_mut(pos).and_then(|r| r.get_mut(pos.col))
     }
 
     pub fn current_cell_mut(&mut self) -> &mut crate::cell::Cell {
-        self.cell_mut(self.pos)
+        self.drawing_cell_mut(self.pos)
             .expect("cursor not pointing to a cell")
     }
 
@@ -136,7 +167,7 @@ impl Grid {
     }
 
     pub fn write_contents(&self, contents: &mut String) {
-        for row in self.rows() {
+        for row in self.visible_rows() {
             row.write_contents(contents, 0, self.size.cols);
             if !row.wrapped() {
                 writeln!(contents).unwrap();
@@ -159,7 +190,7 @@ impl Grid {
 
         let mut prev_attrs = crate::attrs::Attrs::default();
         let mut final_col = 0;
-        for row in self.rows() {
+        for row in self.visible_rows() {
             let (new_attrs, new_col) = row.write_contents_formatted(
                 contents,
                 0,
@@ -192,7 +223,8 @@ impl Grid {
         let mut prev_attrs = crate::attrs::Attrs::default();
         let mut final_row = prev.pos.row;
         let mut final_col = prev.pos.col;
-        for (idx, (row, prev_row)) in self.rows().zip(prev.rows()).enumerate()
+        for (idx, (row, prev_row)) in
+            self.visible_rows().zip(prev.visible_rows()).enumerate()
         {
             let idx = idx.try_into().unwrap();
             let (new_attrs, new_col) = row.write_contents_diff(
@@ -224,14 +256,14 @@ impl Grid {
     }
 
     pub fn erase_all(&mut self, bgcolor: crate::attrs::Color) {
-        for row in self.rows_mut() {
+        for row in self.drawing_rows_mut() {
             row.clear(bgcolor);
         }
     }
 
     pub fn erase_all_forward(&mut self, bgcolor: crate::attrs::Color) {
         let pos = self.pos;
-        for row in self.rows_mut().skip(pos.row as usize + 1) {
+        for row in self.drawing_rows_mut().skip(pos.row as usize + 1) {
             row.clear(bgcolor);
         }
 
@@ -240,7 +272,7 @@ impl Grid {
 
     pub fn erase_all_backward(&mut self, bgcolor: crate::attrs::Color) {
         let pos = self.pos;
-        for row in self.rows_mut().take(pos.row as usize) {
+        for row in self.drawing_rows_mut().take(pos.row as usize) {
             row.clear(bgcolor);
         }
 
@@ -319,11 +351,14 @@ impl Grid {
                 .insert(self.scroll_bottom as usize + 1, self.new_row());
             let removed = self.rows.remove(self.scroll_top as usize);
             if self.scrollback_len > 0 && !self.scroll_region_active() {
-                let idx = self.scrollback.back().map_or(0, |r| r.0 + 1);
-                self.scrollback.push_back((idx, removed));
+                self.scrollback.push_back(removed);
                 while self.scrollback.len() > self.scrollback_len {
                     self.scrollback.pop_front();
                 }
+                if self.scrollback_offset > 0 {
+                    self.scrollback_offset =
+                        self.scrollback.len().min(self.scrollback_offset + 1);
+                }
             }
         }
     }
diff --git a/src/lib.rs b/src/lib.rs
index 9424fb9..d14b78f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -12,7 +12,7 @@
 //! # Synopsis
 //!
 //! ```
-//! let mut parser = vt100::Parser::new(24, 80);
+//! let mut parser = vt100::Parser::new(24, 80, 0);
 //! parser.process(b"this text is \x1b[31mRED\x1b[m");
 //! assert_eq!(
 //!     parser.screen().cell(0, 13).unwrap().fgcolor(),
diff --git a/src/parser.rs b/src/parser.rs
index 0cabb1a..a18f7e8 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -36,4 +36,12 @@ impl Parser {
     pub fn screen_mut(&mut self) -> &mut crate::screen::Screen {
         &mut self.screen
     }
+
+    pub fn scroll_pos(&self) -> usize {
+        self.screen.scrollback()
+    }
+
+    pub fn scroll_to(&mut self, idx: usize) {
+        self.screen.set_scrollback(idx);
+    }
 }
diff --git a/src/screen.rs b/src/screen.rs
index f3fdf6a..5150e3a 100644
--- a/src/screen.rs
+++ b/src/screen.rs
@@ -112,6 +112,14 @@ impl Screen {
         }
     }
 
+    pub fn scrollback(&self) -> usize {
+        self.grid().scrollback()
+    }
+
+    pub fn set_scrollback(&mut self, rows: usize) {
+        self.grid_mut().set_scrollback(rows);
+    }
+
     /// Resizes the terminal.
     pub fn set_size(&mut self, rows: u16, cols: u16) {
         self.grid.set_size(crate::grid::Size { rows, cols });
@@ -153,7 +161,7 @@ impl Screen {
         start: u16,
         width: u16,
     ) -> impl Iterator<Item = String> + '_ {
-        self.grid().rows().map(move |row| {
+        self.grid().visible_rows().map(move |row| {
             let mut contents = String::new();
             row.write_contents(&mut contents, start, width);
             contents
@@ -199,7 +207,7 @@ impl Screen {
         start: u16,
         width: u16,
     ) -> impl Iterator<Item = Vec<u8>> + '_ {
-        self.grid().rows().map(move |row| {
+        self.grid().visible_rows().map(move |row| {
             let mut contents = vec![];
             row.write_contents_formatted(
                 &mut contents,
@@ -252,8 +260,10 @@ impl Screen {
         start: u16,
         width: u16,
     ) -> impl Iterator<Item = Vec<u8>> + 'a {
-        self.grid().rows().zip(prev.grid().rows()).map(
-            move |(row, prev_row)| {
+        self.grid()
+            .visible_rows()
+            .zip(prev.grid().visible_rows())
+            .map(move |(row, prev_row)| {
                 let mut contents = vec![];
                 row.write_contents_diff(
                     &mut contents,
@@ -264,14 +274,13 @@ impl Screen {
                     crate::attrs::Attrs::default(),
                 );
                 contents
-            },
-        )
+            })
     }
 
     /// Returns the `Cell` object at the given location in the terminal, if it
     /// exists.
     pub fn cell(&self, row: u16, col: u16) -> Option<&crate::cell::Cell> {
-        self.grid().cell(crate::grid::Pos { row, col })
+        self.grid().visible_cell(crate::grid::Pos { row, col })
     }
 
     /// Returns the current cursor position of the terminal.
@@ -350,15 +359,15 @@ impl Screen {
         }
     }
 
-    fn row(&self, pos: crate::grid::Pos) -> Option<&crate::row::Row> {
-        self.grid().row(pos)
+    fn drawing_row(&self, pos: crate::grid::Pos) -> Option<&crate::row::Row> {
+        self.grid().drawing_row(pos)
     }
 
-    fn cell_mut(
+    fn drawing_cell_mut(
         &mut self,
         pos: crate::grid::Pos,
     ) -> Option<&mut crate::cell::Cell> {
-        self.grid_mut().cell_mut(pos)
+        self.grid_mut().drawing_cell_mut(pos)
     }
 
     fn current_cell_mut(&mut self) -> &mut crate::cell::Cell {
@@ -366,6 +375,7 @@ impl Screen {
     }
 
     fn enter_alternate_grid(&mut self) {
+        self.grid_mut().set_scrollback(0);
         self.set_mode(Mode::AlternateScreen);
     }
 
@@ -436,7 +446,7 @@ impl Screen {
         if pos.col > 0 {
             let bgcolor = self.attrs.bgcolor;
             let prev_cell = self
-                .cell_mut(crate::grid::Pos {
+                .drawing_cell_mut(crate::grid::Pos {
                     row: pos.row,
                     col: pos.col - 1,
                 })
@@ -455,7 +465,7 @@ impl Screen {
         if width == 0 {
             if pos.col > 0 {
                 let prev_cell = self
-                    .cell_mut(crate::grid::Pos {
+                    .drawing_cell_mut(crate::grid::Pos {
                         row: pos.row,
                         col: pos.col - 1,
                     })
@@ -463,14 +473,14 @@ impl Screen {
                 prev_cell.append(c);
             } else if pos.row > 0 {
                 let prev_row = self
-                    .row(crate::grid::Pos {
+                    .drawing_row(crate::grid::Pos {
                         row: pos.row - 1,
                         col: 0,
                     })
                     .unwrap();
                 if prev_row.wrapped() {
                     let prev_cell = self
-                        .cell_mut(crate::grid::Pos {
+                        .drawing_cell_mut(crate::grid::Pos {
                             row: pos.row - 1,
                             col: self.grid().size().cols - 1,
                         })
diff --git a/tests/scroll.rs b/tests/scroll.rs
index 2881da6..4bbe1e9 100644
--- a/tests/scroll.rs
+++ b/tests/scroll.rs
@@ -69,3 +69,87 @@ fn origin_mode() {
     parser.process(b"\x1b[?47l\x1b[H");
     assert_eq!(parser.screen().cursor_position(), (4, 0));
 }
+
+#[allow(clippy::cognitive_complexity)]
+#[test]
+fn scrollback() {
+    let mut parser = vt100::Parser::new(24, 80, 10);
+
+    parser.process(b"1\r\n2\r\n3\r\n4\r\n5\r\n6\r\n7\r\n8\r\n9\r\n10\r\n11\r\n12\r\n13\r\n14\r\n15\r\n16\r\n17\r\n18\r\n19\r\n20\r\n21\r\n22\r\n23\r\n24");
+    assert_eq!(parser.screen().contents(), "1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24");
+
+    parser.process(b"\r\n25\r\n26\r\n27\r\n28\r\n29\r\n30");
+    assert_eq!(parser.screen().contents(), "7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27\n28\n29\n30");
+
+    parser.scroll_to(0);
+    assert_eq!(parser.scroll_pos(), 0);
+    assert_eq!(parser.screen().contents(), "7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27\n28\n29\n30");
+
+    parser.scroll_to(1);
+    assert_eq!(parser.scroll_pos(), 1);
+    assert_eq!(parser.screen().contents(), "6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27\n28\n29");
+
+    parser.scroll_to(3);
+    assert_eq!(parser.scroll_pos(), 3);
+    assert_eq!(parser.screen().contents(), "4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27");
+
+    parser.scroll_to(6);
+    assert_eq!(parser.scroll_pos(), 6);
+    assert_eq!(parser.screen().contents(), "1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24");
+
+    parser.scroll_to(7);
+    assert_eq!(parser.scroll_pos(), 6);
+    assert_eq!(parser.screen().contents(), "1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24");
+
+    parser.scroll_to(0);
+    assert_eq!(parser.scroll_pos(), 0);
+    assert_eq!(parser.screen().contents(), "7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27\n28\n29\n30");
+
+    parser.scroll_to(7);
+    assert_eq!(parser.scroll_pos(), 6);
+    assert_eq!(parser.screen().contents(), "1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24");
+
+    parser.process(b"\r\n31");
+    assert_eq!(parser.scroll_pos(), 7);
+    assert_eq!(parser.screen().contents(), "1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24");
+
+    parser.process(b"\r\n32");
+    assert_eq!(parser.scroll_pos(), 8);
+    assert_eq!(parser.screen().contents(), "1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24");
+
+    parser.process(b"\r\n33");
+    assert_eq!(parser.scroll_pos(), 9);
+    assert_eq!(parser.screen().contents(), "1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24");
+
+    parser.process(b"\r\n34");
+    assert_eq!(parser.scroll_pos(), 10);
+    assert_eq!(parser.screen().contents(), "1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24");
+
+    parser.process(b"\r\n35");
+    assert_eq!(parser.scroll_pos(), 10);
+    assert_eq!(parser.screen().contents(), "2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25");
+
+    parser.process(b"\r\n36");
+    assert_eq!(parser.scroll_pos(), 10);
+    assert_eq!(parser.screen().contents(), "3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26");
+
+    parser.scroll_to(12);
+    assert_eq!(parser.scroll_pos(), 10);
+    assert_eq!(parser.screen().contents(), "3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26");
+
+    parser.scroll_to(0);
+    assert_eq!(parser.scroll_pos(), 0);
+    assert_eq!(parser.screen().contents(), "13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27\n28\n29\n30\n31\n32\n33\n34\n35\n36");
+
+    parser.process(b"\r\n37\r\n38");
+    assert_eq!(parser.scroll_pos(), 0);
+    assert_eq!(parser.screen().contents(), "15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27\n28\n29\n30\n31\n32\n33\n34\n35\n36\n37\n38");
+
+    parser.scroll_to(5);
+    assert_eq!(parser.scroll_pos(), 5);
+    assert_eq!(parser.screen().contents(), "10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27\n28\n29\n30\n31\n32\n33");
+
+    parser.process(b"\r\n39\r\n40");
+    assert_eq!(parser.scroll_pos(), 7);
+    assert_eq!(parser.screen().contents(), "10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27\n28\n29\n30\n31\n32\n33");
+}