Fix overflow on wrong scroll region setting

Fixes #2822.

4 files changed, 25 insertions, 19 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f47a0135..fd802b39 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -48,6 +48,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Wayland primary selection clipboard not storing text when selection is stopped outside of the window
 - Block URL highlight while a selection is active
 - Bindings for Alt + F1-F12
+- Discard scrolling region escape with bottom above top
 
 ### Removed
 
diff --git a/alacritty_terminal/src/ansi.rs b/alacritty_terminal/src/ansi.rs
index f95dc356..69391617 100644
--- a/alacritty_terminal/src/ansi.rs
+++ b/alacritty_terminal/src/ansi.rs
@@ -14,7 +14,6 @@
 //
 //! ANSI Terminal Stream Parsing
 use std::io;
-use std::ops::Range;
 use std::str;
 
 use crate::index::{Column, Contains, Line};
@@ -296,7 +295,7 @@ pub trait Handler {
     fn unset_mode(&mut self, _: Mode) {}
 
     /// DECSTBM - Set the terminal scrolling region
-    fn set_scrolling_region(&mut self, _: Range<Line>) {}
+    fn set_scrolling_region(&mut self, _top: usize, _bottom: usize) {}
 
     /// DECKPAM - Set keypad to applications mode (ESCape instead of digits)
     fn set_keypad_application_mode(&mut self) {}
@@ -1079,16 +1078,10 @@ where
                 handler.set_cursor_style(style);
             },
             ('r', None) => {
-                let arg0 = arg_or_default!(idx: 0, default: 1) as usize;
-                let top = Line(arg0 - 1);
-                // Bottom should be included in the range, but range end is not
-                // usually included.  One option would be to use an inclusive
-                // range, but instead we just let the open range end be 1
-                // higher.
-                let arg1 = arg_or_default!(idx: 1, default: handler.lines().0 as _) as usize;
-                let bottom = Line(arg1);
-
-                handler.set_scrolling_region(top..bottom);
+                let top = arg_or_default!(idx: 0, default: 1) as usize;
+                let bottom = arg_or_default!(idx: 1, default: handler.lines().0 as _) as usize;
+
+                handler.set_scrolling_region(top, bottom);
             },
             ('s', None) => handler.save_cursor_position(),
             ('u', None) => handler.restore_cursor_position(),
diff --git a/alacritty_terminal/src/term/mod.rs b/alacritty_terminal/src/term/mod.rs
index 11e0af45..6829c7d0 100644
--- a/alacritty_terminal/src/term/mod.rs
+++ b/alacritty_terminal/src/term/mod.rs
@@ -1260,8 +1260,7 @@ impl Term {
     fn deccolm(&mut self) {
         // Setting 132 column font makes no sense, but run the other side effects
         // Clear scrolling region
-        let scroll_region = Line(0)..self.grid.num_lines();
-        self.set_scrolling_region(scroll_region);
+        self.set_scrolling_region(1, self.grid.num_lines().0);
 
         // Clear grid
         let template = self.cursor.template;
@@ -2118,10 +2117,23 @@ impl ansi::Handler for Term {
     }
 
     #[inline]
-    fn set_scrolling_region(&mut self, region: Range<Line>) {
-        trace!("Setting scrolling region: {:?}", region);
-        self.scroll_region.start = min(region.start, self.grid.num_lines());
-        self.scroll_region.end = min(region.end, self.grid.num_lines());
+    fn set_scrolling_region(&mut self, top: usize, bottom: usize) {
+        if top >= bottom {
+            debug!("Invalid scrolling region: ({};{})", top, bottom);
+            return;
+        }
+
+        // Bottom should be included in the range, but range end is not
+        // usually included. One option would be to use an inclusive
+        // range, but instead we just let the open range end be 1
+        // higher.
+        let start = Line(top - 1);
+        let end = Line(bottom);
+
+        trace!("Setting scrolling region: ({};{})", start, end);
+
+        self.scroll_region.start = min(start, self.grid.num_lines());
+        self.scroll_region.end = min(end, self.grid.num_lines());
         self.goto(Line(0), Column(0));
     }
 
diff --git a/alacritty_terminal/src/window.rs b/alacritty_terminal/src/window.rs
index 3e3f47f7..f18fda3a 100644
--- a/alacritty_terminal/src/window.rs
+++ b/alacritty_terminal/src/window.rs
@@ -32,7 +32,7 @@ use glutin::{
 #[cfg(not(target_os = "macos"))]
 use image::ImageFormat;
 #[cfg(not(any(target_os = "macos", windows)))]
-use x11_dl::xlib::{Xlib, Display as XDisplay, PropModeReplace, XErrorEvent};
+use x11_dl::xlib::{Display as XDisplay, PropModeReplace, XErrorEvent, Xlib};
 
 use crate::config::{Config, Decorations, StartupMode, WindowConfig};
 use crate::gl;