Fix colored row reset performance

This fixes a bug where a row would always get reset completely if its
background does not equal the default terminal background. This leads to
big performance bottlenecks when running commands like `echo "\e[41m" &&
yes`.

Instead of resetting the entire row whenever the template cell is not
empty, the template cell is now compared to the last cell in the row.
The last cell will always be equal to the previous template cell when
`row.occ < row.inner.len()` and if `occ` is equal to the row's length,
the entire row is always reset anyways.

Fixes #2989.

1 files changed, 4 insertions, 0 deletions

diff --git a/alacritty_terminal/src/grid/tests.rs b/alacritty_terminal/src/grid/tests.rs
index d28e7833..f3480b14 100644
--- a/alacritty_terminal/src/grid/tests.rs
+++ b/alacritty_terminal/src/grid/tests.rs
@@ -29,6 +29,10 @@ impl GridCell for usize {
     }
 
     fn set_wrap(&mut self, _wrap: bool) {}
+
+    fn fast_eq(&self, other: Self) -> bool {
+        self == &other
+    }
 }
 
 // Scroll up moves lines upwards