Ensure line wrapping uses the same length on both sides

Closes #421

CHANGELOG.md

@@ -18,6 +18,9 @@ distinct from file content.
 Fixed an issue with inline display discarding newlines when color is
 disabled, leading to broken display.
 
+Two column display now ensures that both columns have the same width,
+so line wrapping is at the same point on both sides.
+
 ## 0.37 (released 14th October 2022)
 
 ### Manual

sample_files/compare.expected

@@ -1,5 +1,5 @@
 sample_files/b2_math_before.h sample_files/b2_math_after.h
-ec0854e630def8d7e6ce04cbcf1358f3  -
+ccbd784fa7df5d317fce588ac477956a  -
 
 sample_files/bad_combine_before.rs sample_files/bad_combine_after.rs
 affa06f407f8e07bc025c24e96d01298  -
@@ -68,7 +68,7 @@ sample_files/html_simple_before.html sample_files/html_simple_after.html
 ce3bfa12bc21d0eb5528766e18387e86  -
 
 sample_files/huge_cpp_before.cpp sample_files/huge_cpp_after.cpp
-d948c1835eac1cdf4019edb6eed6bcaa  -
+94a49575858e6400ac95b80e5bc52dfe  -
 
 sample_files/identical_before.scala sample_files/identical_after.scala
 9c7319f61833e46a0a8cb6c01cc997c9  -
@@ -104,7 +104,7 @@ sample_files/lua_before.lua sample_files/lua_after.lua
 9886d61f459cdf566be9c42f7fa61a12  -
 
 sample_files/metadata_before.clj sample_files/metadata_after.clj
-a23d575010ed8d902740e7fa9ef6d15b  -
+8464059b3e1bb3b7109020386fc2985b  -
 
 sample_files/modules_before.ml sample_files/modules_after.ml
 7e578048e01b2c9eccf26c055c0eb9fd  -
@@ -116,7 +116,7 @@ sample_files/multiline_string_before.ml sample_files/multiline_string_after.ml
 ba135b1451962f563ce8c2f449a904bf  -
 
 sample_files/nest_before.rs sample_files/nest_after.rs
-e51eac2420b5bd0a6e156dc0bae28e4c  -
+a8d0454af5275807d425cdfa2d08dce8  -
 
 sample_files/nested_slider_before.rs sample_files/nested_slider_after.rs
 5c3dc3d870cdf182658da6a29650d911  -
@@ -155,7 +155,7 @@ sample_files/scala_before.scala sample_files/scala_after.scala
 dc36b671167f2b16c7800808d07197ee  -
 
 sample_files/Session_before.kt sample_files/Session_after.kt
-75db3872d74834ab70358bc50c50b072  -
+9def134da4bbc423a1fde93001618776  -
 
 sample_files/simple_before.js sample_files/simple_after.js
 43feeac1f3afe2c0c0b862009770f27a  -
@@ -170,7 +170,7 @@ sample_files/slider_before.rs sample_files/slider_after.rs
 52e0f2e690d11ef6f38704b8cee84d36  -
 
 sample_files/slow_before.rs sample_files/slow_after.rs
-0dba9e3e733237733a050435f0d741fc  -
+f67aeacbc7164dd076a9a6d6fe0413be  -
 
 sample_files/small_before.js sample_files/small_after.js
 b4300bfc0203acd8f2603b504b859dc8  -

src/display/side_by_side.rs

@@ -2,7 +2,10 @@
 
 use owo_colors::{OwoColorize, Style};
 use rustc_hash::FxHashMap;
-use std::{cmp::max, collections::HashSet};
+use std::{
+    cmp::{max, min},
+    collections::HashSet,
+};
 
 use crate::{
     constants::Side,
@@ -147,11 +150,18 @@ fn display_line_nums(
 // Sizes used when displaying a hunk.
 #[derive(Debug)]
 struct SourceDimensions {
-    lhs_content_width: usize,
-    rhs_content_width: usize,
+    /// The number of characters used to display source lines. Any
+    /// line that exceeds this length will be wrapped.
+    content_width: usize,
+    /// The number of characters required to display line numbers on
+    /// the LHS.
     lhs_line_nums_width: usize,
+    /// The number of characters required to display line numbers on
+    /// the RHS.
     rhs_line_nums_width: usize,
+    /// The highest line number in the LHS source.
     lhs_max_line: LineNumber,
+    /// The highest line number in the RHS source.
     rhs_max_line: LineNumber,
 }
 
@@ -206,9 +216,13 @@ impl SourceDimensions {
                 - rhs_line_nums_width as isize,
         ) as usize;
 
+        // We want the content width to be the same on both
+        // sides. This ensures that line wrapping splits lines at the
+        // same point on both sides.
+        let content_width = min(lhs_content_width, rhs_content_width);
+
         Self {
-            lhs_content_width,
-            rhs_content_width,
+            content_width,
             lhs_line_nums_width,
             rhs_line_nums_width,
             lhs_max_line,
@@ -493,17 +507,17 @@ pub fn print(
                 let lhs_line = match lhs_line_num {
                     Some(lhs_line_num) => split_and_apply(
                         lhs_lines[lhs_line_num.as_usize()],
-                        source_dims.lhs_content_width,
+                        source_dims.content_width,
                         display_options.use_color,
                         lhs_highlights.get(lhs_line_num).unwrap_or(&vec![]),
                         Side::Left,
                     ),
-                    None => vec![" ".repeat(source_dims.lhs_content_width)],
+                    None => vec![" ".repeat(source_dims.content_width)],
                 };
                 let rhs_line = match rhs_line_num {
                     Some(rhs_line_num) => split_and_apply(
                         rhs_lines[rhs_line_num.as_usize()],
-                        source_dims.rhs_content_width,
+                        source_dims.content_width,
                         display_options.use_color,
                         rhs_highlights.get(rhs_line_num).unwrap_or(&vec![]),
                         Side::Right,
@@ -516,7 +530,7 @@ pub fn print(
                     .enumerate()
                 {
                     let lhs_line =
-                        lhs_line.unwrap_or_else(|| " ".repeat(source_dims.lhs_content_width));
+                        lhs_line.unwrap_or_else(|| " ".repeat(source_dims.content_width));
                     let rhs_line = rhs_line.unwrap_or_else(|| "".into());
                     let lhs_num: String = if i == 0 {
                         display_lhs_line_num.clone()