Add filter ability to picker

Inspired by doom emacs. Able to filter picker options multiple times.

book/src/keymap.md

@@ -169,3 +169,17 @@ This layer is a kludge of mappings I had under leader key in neovim.
 | s   | Open symbol picker (current document)|
 | w   | Enter window mode |
 | space   | Keep primary selection TODO: it's here because space mode replaced it |
+
+# Picker
+
+Keys to use within picker.
+
+| Key | Description |
+|-----|-------------|
+| up, ctrl-p | Previous entry |
+| down, ctrl-n | Next entry |
+| ctrl-space | Filter options |
+| enter | Open selected |
+| ctrl-h | Open horizontally |
+| ctrl-v | Open vertically |
+| escape, ctrl-c | Close picker |

helix-term/src/ui/picker.rs

@@ -23,6 +23,8 @@ pub struct Picker<T> {
     matcher: Box<Matcher>,
     /// (index, score)
     matches: Vec<(usize, i64)>,
+    /// Filter over original options.
+    filters: Vec<usize>, // could be optimized into bit but not worth it now
 
     cursor: usize,
     // pattern: String,
@@ -50,6 +52,7 @@ impl<T> Picker<T> {
             options,
             matcher: Box::new(Matcher::default()),
             matches: Vec::new(),
+            filters: Vec::new(),
             cursor: 0,
             prompt,
             format_fn: Box::new(format_fn),
@@ -68,6 +71,7 @@ impl<T> Picker<T> {
             ref mut options,
             ref mut matcher,
             ref mut matches,
+            ref filters,
             ref format_fn,
             ..
         } = *self;
@@ -81,6 +85,10 @@ impl<T> Picker<T> {
                 .iter()
                 .enumerate()
                 .filter_map(|(index, option)| {
+                    // filter options first before matching
+                    if !filters.is_empty() {
+                        filters.binary_search(&index).ok()?;
+                    }
                     // TODO: maybe using format_fn isn't the best idea here
                     let text = (format_fn)(option);
                     // TODO: using fuzzy_indices could give us the char idx for match highlighting
@@ -114,6 +122,14 @@ impl<T> Picker<T> {
             .get(self.cursor)
             .map(|(index, _score)| &self.options[*index])
     }
+
+    pub fn save_filter(&mut self) {
+        self.filters.clear();
+        self.filters
+            .extend(self.matches.iter().map(|(index, _)| *index));
+        self.filters.sort_unstable(); // used for binary search later
+        self.prompt.clear();
+    }
 }
 
 // process:
@@ -205,6 +221,12 @@ impl<T: 'static> Component for Picker<T> {
                 }
                 return close_fn;
             }
+            KeyEvent {
+                code: KeyCode::Char(' '),
+                modifiers: KeyModifiers::CONTROL,
+            } => {
+                self.save_filter();
+            }
             _ => {
                 if let EventResult::Consumed(_) = self.prompt.handle_event(event, cx) {
                     // TODO: recalculate only if pattern changed

helix-term/src/ui/prompt.rs

@@ -106,6 +106,13 @@ impl Prompt {
         self.exit_selection();
     }
 
+    pub fn clear(&mut self) {
+        self.line.clear();
+        self.cursor = 0;
+        self.completion = (self.completion_fn)(&self.line);
+        self.exit_selection();
+    }
+
     pub fn change_completion_selection(&mut self, direction: CompletionDirection) {
         if self.completion.is_empty() {
             return;