support insert register in prompt

book/src/keymap.md

@@ -367,6 +367,7 @@ Keys to use within prompt, Remapping currently not supported.
 | `Ctrl-s`                | Insert a word under doc cursor, may be changed to Ctrl-r Ctrl-w later   |
 | `Ctrl-p`, `Up`          | Select previous history                                                 |
 | `Ctrl-n`, `Down`        | Select next history                                                     |
+| `Ctrl-r`                | Insert the content of the register selected by following input char     |
 | `Tab`                   | Select next completion item                                             |
 | `BackTab`               | Select previous completion item                                         |
 | `Enter`                 | Open selected                                                           |

helix-term/src/ui/prompt.rs

@@ -16,6 +16,7 @@ use helix_view::{
 };
 
 pub type Completion = (RangeFrom<usize>, Cow<'static, str>);
+type PromptCharHandler = Box<dyn Fn(&mut Prompt, char, &Context)>;
 
 pub struct Prompt {
     prompt: Cow<'static, str>,
@@ -28,6 +29,7 @@ pub struct Prompt {
     completion_fn: Box<dyn FnMut(&Editor, &str) -> Vec<Completion>>,
     callback_fn: Box<dyn FnMut(&mut Context, &str, PromptEvent)>,
     pub doc_fn: Box<dyn Fn(&str) -> Option<Cow<str>>>,
+    next_char_handler: Option<PromptCharHandler>,
 }
 
 #[derive(Clone, Copy, PartialEq)]
@@ -78,6 +80,7 @@ impl Prompt {
             completion_fn: Box::new(completion_fn),
             callback_fn: Box::new(callback_fn),
             doc_fn: Box::new(|_| None),
+            next_char_handler: None,
         }
     }
 
@@ -191,6 +194,13 @@ impl Prompt {
     }
 
     pub fn insert_char(&mut self, c: char, cx: &Context) {
+        if let Some(handler) = &self.next_char_handler.take() {
+            handler(self, c, cx);
+
+            self.next_char_handler = None;
+            return;
+        }
+
         self.line.insert(self.cursor, c);
         let mut cursor = GraphemeCursor::new(self.cursor, self.line.len(), false);
         if let Ok(Some(pos)) = cursor.next_boundary(&self.line, 0) {
@@ -538,6 +548,36 @@ impl Component for Prompt {
                 (self.callback_fn)(cx, &self.line, PromptEvent::Update)
             }
             ctrl!('q') => self.exit_selection(),
+            ctrl!('r') => {
+                self.completion = cx
+                    .editor
+                    .registers
+                    .inner()
+                    .iter()
+                    .map(|(ch, reg)| {
+                        let content = reg
+                            .read()
+                            .get(0)
+                            .and_then(|s| s.lines().next())
+                            .map(String::from)
+                            .unwrap_or_default();
+                        (0.., format!("{} {}", ch, &content).into())
+                    })
+                    .collect();
+                self.next_char_handler = Some(Box::new(|prompt, c, context| {
+                    prompt.insert_str(
+                        context
+                            .editor
+                            .registers
+                            .read(c)
+                            .and_then(|r| r.first())
+                            .map_or("", |r| r.as_str()),
+                    );
+                    prompt.recalculate_completion(context.editor);
+                }));
+                (self.callback_fn)(cx, &self.line, PromptEvent::Update);
+                return EventResult::Consumed(None);
+            }
             // any char event that's not mapped to any other combo
             KeyEvent {
                 code: KeyCode::Char(c),