Fix regional scrolling leaking into history

This fixes an issue where a scrolling region that does not start at the
top of the screen would still rotate lines into history when scrolling
the content "upwards".

CHANGELOG.md

@@ -22,6 +22,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - C0 and C1 codes being emitted in associated text when using kitty keyboard
 - Occasional hang on startup with some Wayland compositors
 - Missing key for `NumpadDecimal` in key bindings
+- Scrolling content upwards moving lines into history when it shouldn't
 
 ### Changed
 

alacritty_terminal/src/grid/mod.rs

@@ -268,6 +268,8 @@ impl<T: GridCell + Default + PartialEq + Clone> Grid<T> {
             self.display_offset = min(self.display_offset + positions, self.max_scroll_limit);
         }
 
+        // Only rotate the entire history if the active region starts at the top.
+        if region.start == 0 {
             // Create scrollback for the new lines.
             self.increase_scroll_limit(positions);
 
@@ -277,8 +279,8 @@ impl<T: GridCell + Default + PartialEq + Clone> Grid<T> {
             // know that the position of the fixed lines before the rotation must already be
             // visible.
             //
-        // We need to start from the bottom, to make sure the fixed lines aren't swapped with each
+            // We need to start from the bottom, to make sure the fixed lines aren't swapped with
-        // other.
+            // each other.
             for i in (0..region.start.0).rev().map(Line::from) {
                 self.raw.swap(i, i + positions);
             }
@@ -286,15 +288,21 @@ impl<T: GridCell + Default + PartialEq + Clone> Grid<T> {
             // Rotate the entire line buffer upward.
             self.raw.rotate(-(positions as isize));
 
-        // Ensure all new lines are fully cleared.
+            // Swap the fixed lines at the bottom back into position.
-        let screen_lines = self.screen_lines();
+            let screen_lines = self.screen_lines() as i32;
-        for i in ((screen_lines - positions)..screen_lines).map(Line::from) {
+            for i in (region.end.0..screen_lines).rev().map(Line::from) {
-            self.raw[i].reset(&self.cursor.template);
+                self.raw.swap(i, i - positions);
+            }
+        } else {
+            // Rotate lines without moving anything into history.
+            for i in (region.start.0..region.end.0 - positions as i32).map(Line::from) {
+                self.raw.swap(i, i + positions);
+            }
         }
 
-        // Swap the fixed lines at the bottom back into position.
+        // Ensure all new lines are fully cleared.
-        for i in (region.end.0..(screen_lines as i32)).rev().map(Line::from) {
+        for i in (region.end.0 - positions as i32..region.end.0).map(Line::from) {
-            self.raw.swap(i, i - positions);
+            self.raw[i].reset(&self.cursor.template);
         }
     }
 

alacritty_terminal/tests/ref.rs

@@ -71,6 +71,7 @@ ref_tests! {
     zerowidth
     zsh_tab_completion
     erase_in_line
+    scroll_in_region_up_preserves_history
 }
 
 fn read_u8<P>(path: P) -> Vec<u8>

alacritty_terminal/tests/ref/scroll_in_region_up_preserves_history/alacritty.recording

@@ -0,0 +1,91 @@
+]0;undeadleech@archhq:~/programming/alacritty/alacritty[?2004h[undeadleech@archhq alacritty]$ ls -lah
+[?2004l
total 464K
+drwxr-xr-x 13 undeadleech undeadleech 4.0K Feb 12 20:50 .
+drwxr-xr-x 15 undeadleech undeadleech 4.0K Dec  9 18:42 ..
+drwxr-xr-x  5 undeadleech undeadleech 4.0K Feb 10 09:04 alacritty
+drwxr-xr-x  3 undeadleech undeadleech 4.0K Feb 10 09:04 alacritty_config
+drwxr-xr-x  4 undeadleech undeadleech 4.0K Feb 10 09:04 alacritty_config_derive
+-rw-r--r--  1 undeadleech undeadleech  115 Feb 12 20:51 alacritty.recording
+drwxr-xr-x  4 undeadleech undeadleech 4.0K Feb 10 09:04 alacritty_terminal
+drwxr-xr-x  2 undeadleech undeadleech 4.0K Jan  8 23:30 .builds
+-rw-r--r--  1 undeadleech undeadleech  62K Feb 12 18:19 Cargo.lock
+-rw-r--r--  1 undeadleech undeadleech  201 Jan  8 23:29 Cargo.toml
+-rw-r--r--  1 undeadleech undeadleech  56K Feb 10 09:04 CHANGELOG.md
+-rw-r--r--  1 undeadleech undeadleech   18 Feb 12 20:50 config.json
+-rw-r--r--  1 undeadleech undeadleech 7.9K Feb 10 09:04 CONTRIBUTING.md
+drwxr-xr-x  2 undeadleech undeadleech 4.0K Feb 10 09:04 docs
+-rw-r--r--  1 undeadleech undeadleech  240 Jan  8 23:29 .editorconfig
+drwxr-xr-x  8 undeadleech undeadleech 4.0K Feb 10 09:04 extra
+drwxr-xr-x  8 undeadleech undeadleech 4.0K Feb 12 20:50 .git
+drwxr-xr-x  3 undeadleech undeadleech 4.0K Oct 14  2022 .github
+-rw-r--r--  1 undeadleech undeadleech    7 Oct 14  2022 .gitignore
+-rw-r--r--  1 undeadleech undeadleech 212K Feb 12 20:50 grid.json
+-rw-r--r--  1 undeadleech undeadleech  11K Jan  8 23:29 INSTALL.md
+-rw-r--r--  1 undeadleech undeadleech  11K Sep  1  2022 LICENSE-APACHE
+-rw-r--r--  1 undeadleech undeadleech 1023 Jan 15  2023 LICENSE-MIT
+-rw-r--r--  1 undeadleech undeadleech 3.2K Jan  8 23:29 Makefile
+-rw-r--r--  1 undeadleech undeadleech 4.2K Feb 10 09:04 README.md
+-rw-r--r--  1 undeadleech undeadleech  421 Oct 14  2022 rustfmt.toml
+drwxr-xr-x  2 undeadleech undeadleech 4.0K Sep  1  2022 scripts
+-rw-r--r--  1 undeadleech undeadleech   32 Feb 12 20:50 size.json
+drwxr-xr-x  6 undeadleech undeadleech 4.0K Feb 12 18:19 target
+-rw-r--r--  1 undeadleech undeadleech   27 Apr  9  2023 TODO
+]0;undeadleech@archhq:~/programming/alacritty/alacritty[?2004h[undeadleech@archhq alacritty]$ echo -e "\e[12r"
+[?2004l

+]0;undeadleech@archhq:~/programming/alacritty/alacritty[?2004h[undeadleech@archhq alacritty]$ ls
+[?2004l
alacritty		 Cargo.toml	  grid.json	  rustfmt.toml
+alacritty_config	 CHANGELOG.md	  INSTALL.md	  scripts
+alacritty_config_derive  config.json	  LICENSE-APACHE  size.json
+alacritty.recording	 CONTRIBUTING.md  LICENSE-MIT	  target
+alacritty_terminal	 docs		  Makefile	  TODO
+Cargo.lock		 extra		  README.md
+]0;undeadleech@archhq:~/programming/alacritty/alacritty[?2004h[undeadleech@archhq alacritty]$ ls
+[?2004l
alacritty		 Cargo.toml	  grid.json	  rustfmt.toml
+alacritty_config	 CHANGELOG.md	  INSTALL.md	  scripts
+alacritty_config_derive  config.json	  LICENSE-APACHE  size.json
+alacritty.recording	 CONTRIBUTING.md  LICENSE-MIT	  target
+alacritty_terminal	 docs		  Makefile	  TODO
+Cargo.lock		 extra		  README.md
+]0;undeadleech@archhq:~/programming/alacritty/alacritty[?2004h[undeadleech@archhq alacritty]$ ls
+[?2004l
alacritty		 Cargo.toml	  grid.json	  rustfmt.toml
+alacritty_config	 CHANGELOG.md	  INSTALL.md	  scripts
+alacritty_config_derive  config.json	  LICENSE-APACHE  size.json
+alacritty.recording	 CONTRIBUTING.md  LICENSE-MIT	  target
+alacritty_terminal	 docs		  Makefile	  TODO
+Cargo.lock		 extra		  README.md
+]0;undeadleech@archhq:~/programming/alacritty/alacritty[?2004h[undeadleech@archhq alacritty]$ ls
+[?2004l
alacritty		 Cargo.toml	  grid.json	  rustfmt.toml
+alacritty_config	 CHANGELOG.md	  INSTALL.md	  scripts
+alacritty_config_derive  config.json	  LICENSE-APACHE  size.json
+alacritty.recording	 CONTRIBUTING.md  LICENSE-MIT	  target
+alacritty_terminal	 docs		  Makefile	  TODO
+Cargo.lock		 extra		  README.md
+]0;undeadleech@archhq:~/programming/alacritty/alacritty[?2004h[undeadleech@archhq alacritty]$ ls
+[?2004l
alacritty		 Cargo.toml	  grid.json	  rustfmt.toml
+alacritty_config	 CHANGELOG.md	  INSTALL.md	  scripts
+alacritty_config_derive  config.json	  LICENSE-APACHE  size.json
+alacritty.recording	 CONTRIBUTING.md  LICENSE-MIT	  target
+alacritty_terminal	 docs		  Makefile	  TODO
+Cargo.lock		 extra		  README.md
+]0;undeadleech@archhq:~/programming/alacritty/alacritty[?2004h[undeadleech@archhq alacritty]$ ls
+[?2004l
alacritty		 Cargo.toml	  grid.json	  rustfmt.toml
+alacritty_config	 CHANGELOG.md	  INSTALL.md	  scripts
+alacritty_config_derive  config.json	  LICENSE-APACHE  size.json
+alacritty.recording	 CONTRIBUTING.md  LICENSE-MIT	  target
+alacritty_terminal	 docs		  Makefile	  TODO
+Cargo.lock		 extra		  README.md
+]0;undeadleech@archhq:~/programming/alacritty/alacritty[?2004h[undeadleech@archhq alacritty]$ ls
+[?2004l
alacritty		 Cargo.toml	  grid.json	  rustfmt.toml
+alacritty_config	 CHANGELOG.md	  INSTALL.md	  scripts
+alacritty_config_derive  config.json	  LICENSE-APACHE  size.json
+alacritty.recording	 CONTRIBUTING.md  LICENSE-MIT	  target
+alacritty_terminal	 docs		  Makefile	  TODO
+Cargo.lock		 extra		  README.md
+]0;undeadleech@archhq:~/programming/alacritty/alacritty[?2004h[undeadleech@archhq alacritty]$ ls
+[?2004l
alacritty		 Cargo.toml	  grid.json	  rustfmt.toml
+alacritty_config	 CHANGELOG.md	  INSTALL.md	  scripts
+alacritty_config_derive  config.json	  LICENSE-APACHE  size.json
+alacritty.recording	 CONTRIBUTING.md  LICENSE-MIT	  target
+alacritty_terminal	 docs		  Makefile	  TODO
+Cargo.lock		 extra		  README.md
+]0;undeadleech@archhq:~/programming/alacritty/alacritty[?2004h[undeadleech@archhq alacritty]$ 

alacritty_terminal/tests/ref/scroll_in_region_up_preserves_history/config.json

@@ -0,0 +1 @@
+{"history_size":10}

alacritty_terminal/tests/ref/scroll_in_region_up_preserves_history/size.json

@@ -0,0 +1 @@
+{"columns":80,"screen_lines":30}