Unify the grid line indexing types

Previously Alacritty was using two different ways to reference lines in
the terminal. Either a `usize`, or a `Line(usize)`. These indexing
systems both served different purposes, but made it difficult to reason
about logic involving these systems because of its inconsistency.

To resolve this issue, a single new `Line(i32)` type has been
introduced.  All existing references to lines and points now rely on
this definition of a line.

The indexing starts at the top of the terminal region with the line 0,
which matches the line 1 used by escape sequences. Each line in the
history becomes increasingly negative and the bottommost line is equal
to the number of visible lines minus one.

Having a system which goes into the negatives allows following the
escape sequence's indexing system closely, while at the same time making
it trivial to implement `Ord` for points.

The Alacritty UI crate is the only place which has a different indexing
system, since rendering and input puts the zero line at the top of the
viewport, rather than the top of the terminal region.

All instances which refer to a number of lines/columns instead of just a
single Line/Column have also been changed to use a `usize` instead. This
way a Line/Column will always refer to a specific place in the grid and
no confusion is created by having a count of lines as a possible index
into the grid storage.

1 files changed, 1 insertions, 3 deletions

diff --git a/alacritty/src/display/hint.rs b/alacritty/src/display/hint.rs
index 6499a959..fe107139 100644
--- a/alacritty/src/display/hint.rs
+++ b/alacritty/src/display/hint.rs
@@ -118,9 +118,7 @@ impl HintState {
         if label.len() == 1 {
             // Get text for the hint's regex match.
             let hint_match = &self.matches[index];
-            let start = term.visible_to_buffer(*hint_match.start());
-            let end = term.visible_to_buffer(*hint_match.end());
-            let text = term.bounds_to_string(start, end);
+            let text = term.bounds_to_string(*hint_match.start(), *hint_match.end());
 
             // Append text as last argument and launch command.
             let program = hint.command.program();