Add current-file word counter to the status bar

Shows a live word count for the open file plus the net words added or
removed since this session started. Per-file baselines are snapshotted
when the workspace opens (session_start_counts) and follow renames.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -73,6 +73,10 @@ Terminal=false
    document. Each file becomes a chapter headed by its title, optionally followed
    by a caption from its `# Slug:` line.
 
+The status bar shows a live **word count** for the current file, plus the net
+words added (or removed) to it since the current session started. The count
+updates as you type, including unsaved edits.
+
 ## Header stripping on export
 
 Manuscript files often carry editorial notes and metadata above the prose that

src/app.rs

@@ -30,6 +30,9 @@ pub struct App {
     show_log: bool,
     git_log: String,
     is_repo: bool,
+    /// Each file's word count captured when the workspace was opened, used as the
+    /// per-file baseline for the "this session" delta.
+    session_start_counts: HashMap<String, usize>,
 }
 
 impl App {
@@ -52,6 +55,7 @@ impl App {
             show_log: false,
             git_log: String::new(),
             is_repo: false,
+            session_start_counts: HashMap::new(),
         };
         app.open_workspace();
         app
@@ -78,6 +82,7 @@ impl App {
         self.buffer.clear();
         self.dirty = false;
         self.pending_delete = false;
+        self.session_start_counts = self.snapshot_counts();
         if !self.files.is_empty() {
             self.select(0);
         }
@@ -85,6 +90,17 @@ impl App {
         self.status = format!("{} file(s) in {}", self.files.len(), ws.display());
     }
 
+    /// Read every file and return its current on-disk word count.
+    fn snapshot_counts(&self) -> HashMap<String, usize> {
+        self.files
+            .iter()
+            .map(|name| {
+                let text = std::fs::read_to_string(self.path_for(name)).unwrap_or_default();
+                (name.clone(), count_words(&text))
+            })
+            .collect()
+    }
+
     fn persist_order(&self) {
         let _ = order::write_order(self.workspace(), &self.files);
     }
@@ -189,6 +205,7 @@ impl App {
                     Ok(_) => {
                         self.files.remove(idx);
                         self.titles.remove(&name);
+                        self.session_start_counts.remove(&name);
                         self.persist_titles();
                         self.persist_order();
                         self.selected = None;
@@ -237,6 +254,9 @@ impl App {
                     self.titles.insert(new_name.clone(), title);
                     self.persist_titles();
                 }
+                if let Some(words) = self.session_start_counts.remove(&old_name) {
+                    self.session_start_counts.insert(new_name.clone(), words);
+                }
                 self.persist_order();
                 self.status = format!("Renamed to {new_name}");
             }
@@ -411,6 +431,28 @@ impl App {
             ui.horizontal(|ui| {
                 let dirty = if self.dirty { " • unsaved" } else { "" };
                 ui.label(format!("{}{dirty}", self.status));
+
+                ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), |ui| {
+                    if let Some(idx) = self.selected {
+                        let name = &self.files[idx];
+                        let total = count_words(&self.buffer);
+                        let baseline =
+                            self.session_start_counts.get(name).copied().unwrap_or(0);
+                        let delta = total as i64 - baseline as i64;
+                        let sign = if delta < 0 { "-" } else { "+" };
+                        ui.label(
+                            egui::RichText::new(format!(
+                                "{} words · {sign}{} this session",
+                                thousands(total),
+                                thousands(delta.unsigned_abs() as usize),
+                            ))
+                            .weak(),
+                        )
+                        .on_hover_text(
+                            "Words in the current file · net change since this session opened",
+                        );
+                    }
+                });
             });
             ui.add_space(2.0);
         });
@@ -751,6 +793,25 @@ fn split_title(markdown: &str, filename: &str) -> (String, String) {
     (stem, markdown.to_string())
 }
 
+/// Count words in a string: runs of non-whitespace separated by whitespace.
+fn count_words(s: &str) -> usize {
+    s.split_whitespace().count()
+}
+
+/// Format a non-negative integer with comma thousands separators (e.g. 12345 -> "12,345").
+fn thousands(n: usize) -> String {
+    let digits = n.to_string();
+    let len = digits.len();
+    let mut out = String::with_capacity(len + len / 3);
+    for (i, ch) in digits.chars().enumerate() {
+        if i > 0 && (len - i) % 3 == 0 {
+            out.push(',');
+        }
+        out.push(ch);
+    }
+    out
+}
+
 /// A dependency-free timestamp for commit messages (UTC seconds since epoch).
 fn chrono_like_timestamp() -> String {
     use std::time::{SystemTime, UNIX_EPOCH};
@@ -760,3 +821,27 @@ fn chrono_like_timestamp() -> String {
         .unwrap_or(0);
     format!("@{secs}")
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn counts_words_across_whitespace() {
+        assert_eq!(count_words(""), 0);
+        assert_eq!(count_words("   \n\t  "), 0);
+        assert_eq!(count_words("one"), 1);
+        assert_eq!(count_words("one two three"), 3);
+        assert_eq!(count_words("  spread \n over\tlines  "), 3);
+    }
+
+    #[test]
+    fn formats_thousands_separators() {
+        assert_eq!(thousands(0), "0");
+        assert_eq!(thousands(42), "42");
+        assert_eq!(thousands(999), "999");
+        assert_eq!(thousands(1_000), "1,000");
+        assert_eq!(thousands(12_345), "12,345");
+        assert_eq!(thousands(1_234_567), "1,234,567");
+    }
+}