Read the odd startup option from org-mode files.

src/context/global_settings.rs

@@ -22,6 +22,11 @@ pub struct GlobalSettings<'g, 's> {
     ///
     /// Corresponds to the tab-width elisp variable.
     pub tab_width: IndentationLevel,
+
+    /// Whether to only allow odd headline levels.
+    ///
+    /// Corresponds to org-odd-levels-only elisp variable.
+    pub odd_levels_only: HeadlineLevelFilter,
 }
 
 impl<'g, 's> GlobalSettings<'g, 's> {
@@ -35,6 +40,7 @@ impl<'g, 's> GlobalSettings<'g, 's> {
             complete_todo_keywords: BTreeSet::new(),
             org_list_allow_alphabetical: false,
             tab_width: 8,
+            odd_levels_only: HeadlineLevelFilter::OddEven,
         }
     }
 }
@@ -44,3 +50,9 @@ impl<'g, 's> Default for GlobalSettings<'g, 's> {
         GlobalSettings::new()
     }
 }
+
+#[derive(Debug, Clone)]
+pub enum HeadlineLevelFilter {
+    Odd,
+    OddEven,
+}

src/context/mod.rs

@@ -25,5 +25,6 @@ pub(crate) use exiting::ExitClass;
 pub use file_access_interface::FileAccessInterface;
 pub use file_access_interface::LocalFileAccessInterface;
 pub use global_settings::GlobalSettings;
+pub use global_settings::HeadlineLevelFilter;
 pub(crate) use list::List;
 pub(crate) use parser_with_context::parser_with_context;

src/parser/in_buffer_settings.rs

@@ -1,13 +1,17 @@
 use nom::branch::alt;
+use nom::bytes::complete::is_not;
 use nom::bytes::complete::tag_no_case;
 use nom::character::complete::anychar;
+use nom::character::complete::space1;
 use nom::combinator::map;
 use nom::multi::many0;
 use nom::multi::many_till;
+use nom::multi::separated_list0;
 
 use super::keyword::filtered_keyword;
 use super::keyword_todo::todo_keywords;
 use super::OrgSource;
+use crate::context::HeadlineLevelFilter;
 use crate::error::Res;
 use crate::types::Keyword;
 use crate::GlobalSettings;
@@ -50,6 +54,7 @@ pub(crate) fn apply_in_buffer_settings<'g, 's, 'sf>(
 ) -> Result<GlobalSettings<'g, 's>, String> {
     let mut new_settings = original_settings.clone();
 
+    // Todo Keywords
     for kw in keywords.iter().filter(|kw| {
         kw.key.eq_ignore_ascii_case("todo")
             || kw.key.eq_ignore_ascii_case("seq_todo")
@@ -65,5 +70,18 @@ pub(crate) fn apply_in_buffer_settings<'g, 's, 'sf>(
             .extend(complete_words.into_iter().map(str::to_string));
     }
 
+    // Startup settings
+    for kw in keywords
+        .iter()
+        .filter(|kw| kw.key.eq_ignore_ascii_case("startup"))
+    {
+        let (_remaining, settings) =
+            separated_list0(space1::<&str, nom::error::Error<_>>, is_not(" \t"))(kw.value)
+                .map_err(|err: nom::Err<_>| err.to_string())?;
+        if settings.contains(&"odd") {
+            new_settings.odd_levels_only = HeadlineLevelFilter::Odd;
+        }
+    }
+
     Ok(new_settings)
 }