From 8518ade58230503e2261e2ba51046be6a42bfbe3 Mon Sep 17 00:00:00 2001
From: KnottyDyes <47539659+KnottyDyes@users.noreply.github.com>
Date: Sat, 10 Oct 2026 20:21:31 -0600
Subject: [PATCH] Fonts: discover Linux user fonts in XDG_DATA_HOME

Linux font discovery ignored XDG_DATA_HOME and always scanned ~/.local/share/fonts.

Use XDG_DATA_HOME/fonts when the base path is absolute, otherwise keep the default. Preserve ~/.fonts and system directories, with environment-independent regression tests for directory selection.
---
 crates/fonts/src/fontdb.rs         | 18 +++++++---
 crates/fonts/src/tests_sysfonts.rs | 58 ++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+), 5 deletions(-)

diff --git a/crates/fonts/src/fontdb.rs b/crates/fonts/src/fontdb.rs
index 14441e14..390669ab 100644
--- a/crates/fonts/src/fontdb.rs
+++ b/crates/fonts/src/fontdb.rs
@@ -608,15 +608,23 @@ pub fn system_font_dirs() -> Vec<std::path::PathBuf> {
             dirs.push(std::path::PathBuf::from(l).join("Microsoft\\Windows\\Fonts"));
         }
     } else {
-        dirs.extend(["/usr/share/fonts", "/usr/local/share/fonts"].map(Into::into));
-        if let Some(h) = &home {
-            dirs.push(h.join(".fonts"));
-            dirs.push(h.join(".local/share/fonts"));
-        }
+        let xdg_data_home = std::env::var_os("XDG_DATA_HOME").map(std::path::PathBuf::from);
+        dirs.extend(unix_font_dirs(home.as_deref(), xdg_data_home.as_deref()));
     }
     dirs
 }
 
+fn unix_font_dirs(home: Option<&std::path::Path>, xdg_data_home: Option<&std::path::Path>) -> Vec<std::path::PathBuf> {
+    let mut dirs: Vec<std::path::PathBuf> = ["/usr/share/fonts", "/usr/local/share/fonts"].map(Into::into).into();
+    if let Some(home) = home {
+        dirs.push(home.join(".fonts"));
+    }
+    let data_home =
+        xdg_data_home.filter(|path| path.is_absolute()).map(std::path::Path::to_path_buf).or_else(|| home.map(|path| path.join(".local/share")));
+    dirs.extend(data_home.map(|path| path.join("fonts")));
+    dirs
+}
+
 /// One face found in a font file: index, family, style and (variable fonts) the named instance's
 /// axis settings.
 type Found = (u32, String, String, Vec<([u8; 4], f32)>);
diff --git a/crates/fonts/src/tests_sysfonts.rs b/crates/fonts/src/tests_sysfonts.rs
index a9cda7cd..a05be10e 100644
--- a/crates/fonts/src/tests_sysfonts.rs
+++ b/crates/fonts/src/tests_sysfonts.rs
@@ -6,6 +6,64 @@ use super::*;
 
 const FAMILY: &str = "Sysfont Sans3";
 
+#[cfg(not(any(target_os = "macos", windows)))]
+mod user_font_dirs {
+    use super::*;
+
+    #[test]
+    fn user_font_dirs_when_xdg_is_absolute() {
+        let home = Path::new("/home/font-user");
+        let xdg = Path::new("/custom/data");
+        let dirs = unix_font_dirs(Some(home), Some(xdg));
+        assert_eq!(dirs, ["/usr/share/fonts", "/usr/local/share/fonts", "/home/font-user/.fonts", "/custom/data/fonts"].map(PathBuf::from));
+    }
+
+    #[test]
+    fn user_font_dirs_when_xdg_is_unset() {
+        let home = Path::new("/home/font-user");
+        let dirs = unix_font_dirs(Some(home), None);
+        assert_eq!(
+            dirs,
+            ["/usr/share/fonts", "/usr/local/share/fonts", "/home/font-user/.fonts", "/home/font-user/.local/share/fonts"].map(PathBuf::from)
+        );
+    }
+
+    #[test]
+    fn user_font_dirs_when_xdg_is_relative() {
+        let home = Path::new("/home/font-user");
+        let xdg = Path::new("relative/data");
+        let dirs = unix_font_dirs(Some(home), Some(xdg));
+        assert_eq!(
+            dirs,
+            ["/usr/share/fonts", "/usr/local/share/fonts", "/home/font-user/.fonts", "/home/font-user/.local/share/fonts"].map(PathBuf::from)
+        );
+    }
+
+    #[test]
+    fn user_font_dirs_when_xdg_is_empty() {
+        let home = Path::new("/home/font-user");
+        let xdg = Path::new("");
+        let dirs = unix_font_dirs(Some(home), Some(xdg));
+        assert_eq!(
+            dirs,
+            ["/usr/share/fonts", "/usr/local/share/fonts", "/home/font-user/.fonts", "/home/font-user/.local/share/fonts"].map(PathBuf::from)
+        );
+    }
+
+    #[test]
+    fn user_font_dirs_when_home_is_unset_and_xdg_is_absolute() {
+        let xdg = Path::new("/custom/data");
+        let dirs = unix_font_dirs(None, Some(xdg));
+        assert_eq!(dirs, ["/usr/share/fonts", "/usr/local/share/fonts", "/custom/data/fonts"].map(PathBuf::from));
+    }
+
+    #[test]
+    fn user_font_dirs_when_home_and_xdg_are_unset() {
+        let dirs = unix_font_dirs(None, None);
+        assert_eq!(dirs, ["/usr/share/fonts", "/usr/local/share/fonts"].map(PathBuf::from));
+    }
+}
+
 /// A bundled Source Sans 3 file renamed [`FAMILY`] (as long as the original name).
 fn renamed(file: &str) -> Vec<u8> {
     let mut data = std::fs::read(Path::new(env!("CARGO_MANIFEST_DIR")).join("../../assets/fonts").join(file)).unwrap();