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, 2 insertions, 1 deletions

diff --git a/alacritty/src/main.rs b/alacritty/src/main.rs
index 30eff73d..0914aee4 100644
--- a/alacritty/src/main.rs
+++ b/alacritty/src/main.rs
@@ -25,6 +25,7 @@ use log::{error, info};
 use winapi::um::wincon::{AttachConsole, FreeConsole, ATTACH_PARENT_PROCESS};
 
 use alacritty_terminal::event_loop::{self, EventLoop, Msg};
+use alacritty_terminal::grid::Dimensions;
 use alacritty_terminal::sync::FairMutex;
 use alacritty_terminal::term::Term;
 use alacritty_terminal::tty;
@@ -139,7 +140,7 @@ fn run(
     info!(
         "PTY dimensions: {:?} x {:?}",
         display.size_info.screen_lines(),
-        display.size_info.cols()
+        display.size_info.columns()
     );
 
     // Create the terminal.