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, 4 insertions, 2 deletions

diff --git a/alacritty/src/message_bar.rs b/alacritty/src/message_bar.rs
index 609af55d..72e6f354 100644
--- a/alacritty/src/message_bar.rs
+++ b/alacritty/src/message_bar.rs
@@ -1,8 +1,10 @@
 use std::collections::VecDeque;
 
-use alacritty_terminal::term::SizeInfo;
 use unicode_width::UnicodeWidthChar;
 
+use alacritty_terminal::grid::Dimensions;
+use alacritty_terminal::term::SizeInfo;
+
 pub const CLOSE_BUTTON_TEXT: &str = "[X]";
 const CLOSE_BUTTON_PADDING: usize = 1;
 const MIN_FREE_LINES: usize = 3;
@@ -34,7 +36,7 @@ impl Message {
 
     /// Formatted message text lines.
     pub fn text(&self, size_info: &SizeInfo) -> Vec<String> {
-        let num_cols = size_info.cols().0;
+        let num_cols = size_info.columns();
         let total_lines =
             (size_info.height() - 2. * size_info.padding_y()) / size_info.cell_height();
         let max_lines = (total_lines as usize).saturating_sub(MIN_FREE_LINES);