From 72214b7db969634dcb2e19e99ef0c826ddca44bb Mon Sep 17 00:00:00 2001
From: Wez Furlong <wez@wezfurlong.org>
Date: Mon, 28 Mar 2022 19:32:00 -0700
Subject: [PATCH] Disable ligatures for Menlo and Monaco

refs: https://github.com/wez/wezterm/issues/1736
refs: https://github.com/wez/wezterm/issues/1786
---
 config/src/lua.rs | 92 +++++++++++++++++++++++++++++------------------
 docs/changelog.md |  1 +
 2 files changed, 59 insertions(+), 34 deletions(-)

diff --git a/config/src/lua.rs b/config/src/lua.rs
index 80096b18f..9c6ce5146 100644
--- a/config/src/lua.rs
+++ b/config/src/lua.rs
@@ -529,6 +529,24 @@ impl<'lua> FromLua<'lua> for LuaFontAttributes {
     }
 }
 
+/// On macOS, both Menlo and Monaco fonts have ligatures for `fi` that
+/// take effect for words like `find` and which are a source of
+/// confusion/annoyance and issues filed on Github.
+/// Let's default to disabling ligatures for these fonts unless
+/// the user has explicitly specified harfbuzz_features.
+/// <https://github.com/wez/wezterm/issues/1736>
+/// <https://github.com/wez/wezterm/issues/1786>
+fn disable_ligatures_for_menlo_or_monaco(mut attrs: FontAttributes) -> FontAttributes {
+    if attrs.harfbuzz_features.is_none() && (attrs.family == "Menlo" || attrs.family == "Monaco") {
+        attrs.harfbuzz_features = Some(vec![
+            "kern".to_string(),
+            "clig".to_string(),
+            "liga=0".to_string(),
+        ]);
+    }
+    attrs
+}
+
 /// Given a simple font family name, returns a text style instance.
 /// The second optional argument is a list of the other TextStyle
 /// fields, which at the time of writing includes only the
@@ -556,22 +574,26 @@ fn font<'lua>(
         text_style.foreground = map_defaults.foreground;
     }
 
-    text_style.font.push(FontAttributes {
-        family: attrs.family,
-        stretch: attrs.stretch,
-        weight: attrs.weight,
-        style: attrs.style,
-        is_fallback: false,
-        is_synthetic: false,
-        harfbuzz_features: attrs.harfbuzz_features,
-        freetype_load_target: attrs.freetype_load_target,
-        freetype_render_target: attrs.freetype_render_target,
-        freetype_load_flags: match attrs.freetype_load_flags {
-            Some(flags) => Some(TryFrom::try_from(flags).map_err(|e| mlua::Error::external(e))?),
-            None => None,
-        },
-        scale: attrs.scale,
-    });
+    text_style
+        .font
+        .push(disable_ligatures_for_menlo_or_monaco(FontAttributes {
+            family: attrs.family,
+            stretch: attrs.stretch,
+            weight: attrs.weight,
+            style: attrs.style,
+            is_fallback: false,
+            is_synthetic: false,
+            harfbuzz_features: attrs.harfbuzz_features,
+            freetype_load_target: attrs.freetype_load_target,
+            freetype_render_target: attrs.freetype_render_target,
+            freetype_load_flags: match attrs.freetype_load_flags {
+                Some(flags) => {
+                    Some(TryFrom::try_from(flags).map_err(|e| mlua::Error::external(e))?)
+                }
+                None => None,
+            },
+            scale: attrs.scale,
+        }));
 
     Ok(text_style)
 }
@@ -602,24 +624,26 @@ fn font_with_fallback<'lua>(
             text_style.foreground = map_defaults.foreground;
         }
 
-        text_style.font.push(FontAttributes {
-            family: attrs.family,
-            stretch: attrs.stretch,
-            weight: attrs.weight,
-            style: attrs.style,
-            is_fallback: idx != 0,
-            is_synthetic: false,
-            harfbuzz_features: attrs.harfbuzz_features,
-            freetype_load_target: attrs.freetype_load_target,
-            freetype_render_target: attrs.freetype_render_target,
-            freetype_load_flags: match attrs.freetype_load_flags {
-                Some(flags) => {
-                    Some(TryFrom::try_from(flags).map_err(|e| mlua::Error::external(e))?)
-                }
-                None => None,
-            },
-            scale: attrs.scale,
-        });
+        text_style
+            .font
+            .push(disable_ligatures_for_menlo_or_monaco(FontAttributes {
+                family: attrs.family,
+                stretch: attrs.stretch,
+                weight: attrs.weight,
+                style: attrs.style,
+                is_fallback: idx != 0,
+                is_synthetic: false,
+                harfbuzz_features: attrs.harfbuzz_features,
+                freetype_load_target: attrs.freetype_load_target,
+                freetype_render_target: attrs.freetype_render_target,
+                freetype_load_flags: match attrs.freetype_load_flags {
+                    Some(flags) => {
+                        Some(TryFrom::try_from(flags).map_err(|e| mlua::Error::external(e))?)
+                    }
+                    None => None,
+                },
+                scale: attrs.scale,
+            }));
     }
 
     Ok(text_style)
diff --git a/docs/changelog.md b/docs/changelog.md
index 3aca7d8b5..a6fd44fc4 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -13,6 +13,7 @@ As features stabilize some brief notes about them will accumulate here.
 
 #### New
 #### Changed
+* Disabled ligatures for `"Monaco"` and `"Menlo"` fonts, as those ligatures match even for words such as `find`. [#1786](https://github.com/wez/wezterm/issues/1786) [#1736](https://github.com/wez/wezterm/issues/1736)
 #### Updated and Improved
 * Bundled harfbuzz to 4.1.0
 * On macOS, non-native fullscreen mode now attempts to avoid the notch on systems that have one. [#1737](https://github.com/wez/wezterm/issues/1737)