diff --git a/src/frame.rs b/src/frame.rs
index 908872a..eef783e 100644
--- a/src/frame.rs
+++ b/src/frame.rs
@@ -1,3 +1,5 @@
+//! Rendering the next frame.
+
 use crossterm::style::ContentStyle;
 
 use crate::buffer::Buffer;
diff --git a/src/terminal.rs b/src/terminal.rs
index 5f4e320..2f2b35f 100644
--- a/src/terminal.rs
+++ b/src/terminal.rs
@@ -1,3 +1,5 @@
+//! Displaying frames on a terminal.
+
 use std::io::Write;
 use std::{io, mem};
 
diff --git a/src/widthdb.rs b/src/widthdb.rs
index f9da5f9..e3605c3 100644
--- a/src/widthdb.rs
+++ b/src/widthdb.rs
@@ -8,6 +8,7 @@ use crossterm::QueueableCommand;
 use unicode_segmentation::UnicodeSegmentation;
 use unicode_width::UnicodeWidthStr;
 
+/// Measures and stores the with (in terminal coordinates) of graphemes.
 #[derive(Debug, Default)]
 pub struct WidthDB {
     known: HashMap<String, u8>,
@@ -15,6 +16,10 @@ pub struct WidthDB {
 }
 
 impl WidthDB {
+    /// Determine the width of a string based on its graphemes.
+    ///
+    /// If the width of a grapheme has not been measured yet, it is estimated
+    /// using the Unicode Standard Annex #11.
     pub fn width(&mut self, s: &str) -> u8 {
         let mut total = 0;
         for grapheme in s.graphemes(true) {
@@ -28,10 +33,18 @@ impl WidthDB {
         total
     }
 
+    /// Whether any new graphemes have been seen since the last time
+    /// [`Self::measure_widths`] was called.
     pub fn measuring_required(&self) -> bool {
         !self.requested.is_empty()
     }
 
+    /// Measure the width of all new graphemes that have been seen since the
+    /// last time this function was called.
+    ///
+    /// This function measures the actual width of graphemes by writing them to
+    /// the terminal. After it finishes, the terminal's contents should be
+    /// assumed to be garbage and a full redraw should be performed.
     pub fn measure_widths(&mut self, out: &mut impl Write) -> io::Result<()> {
         for grapheme in self.requested.drain() {
             out.queue(Clear(ClearType::All))?