Add selectable Pixel clock styling and widget font controls

shell/ferese-settings/src/fonts.rs

@@ -0,0 +1,34 @@
+use std::{process::Command, sync::OnceLock};
+
+pub fn families() -> &'static [String] {
+    static FAMILIES: OnceLock<Vec<String>> = OnceLock::new();
+
+    FAMILIES.get_or_init(|| {
+        let output = Command::new("fc-list")
+            .args(["--format", "%{family}\\n"])
+            .output()
+            .ok()
+            .filter(|output| output.status.success());
+        let mut families: Vec<String> = output
+            .as_ref()
+            .map(|output| String::from_utf8_lossy(&output.stdout))
+            .unwrap_or_default()
+            .lines()
+            .flat_map(|line| line.split(','))
+            .map(str::trim)
+            .filter(|family| !family.is_empty() && family.len() <= 128)
+            .map(str::to_owned)
+            .collect();
+
+        families.extend([
+            "Comfortaa".into(),
+            "sans-serif".into(),
+            "serif".into(),
+            "monospace".into(),
+        ]);
+        families.sort_unstable_by_key(|family| family.to_lowercase());
+        families.dedup();
+        families.insert(0, "Default font".into());
+        families
+    })
+}