WIP: document some items in theme.rs.

Quite unsure about several of those.

src/theme.rs

@@ -626,8 +626,11 @@ impl Theme for ColorfulTheme {
 pub(crate) struct TermThemeRenderer<'a> {
     term: &'a Term,
     theme: &'a dyn Theme,
+    /// Number of lines of input in the current theme.
     height: usize,
+    /// Height of the current prompt string in the current theme.
     prompt_height: usize,
+    /// TODO what's this?
     prompts_reset_height: bool,
 }
 
@@ -850,13 +853,17 @@ impl<'a> TermThemeRenderer<'a> {
         })
     }
 
+    /// Clear the current theme.
+    ///
+    /// Position the cursor at the beginning of the current line.
     pub fn clear(&mut self) -> io::Result<()> {
         self.term
             .clear_last_lines(self.height + self.prompt_height)?;
         self.height = 0;
         Ok(())
     }
 
+    /// Clear the current theme no idea about prompt!
     pub fn clear_preserve_prompt(&mut self, size_vec: &[usize]) -> io::Result<()> {
         let mut new_height = self.height;
         // Check each item size, increment on finding an overflow